[external/binutils.git] / gdb / mips-tdep.c

/* Target-dependent code for the MIPS architecture, for GDB, the GNU Debugger.

   Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
   1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software
   Foundation, Inc.

   Contributed by Alessandro Forin(af@cs.cmu.edu) at CMU
   and by Per Bothner(bothner@cs.wisc.edu) at U.Wisconsin.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "gdb_string.h"
#include "gdb_assert.h"
#include "frame.h"
#include "inferior.h"
#include "symtab.h"
#include "value.h"
#include "gdbcmd.h"
#include "language.h"
#include "gdbcore.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbtypes.h"
#include "target.h"
#include "arch-utils.h"
#include "regcache.h"
#include "osabi.h"
#include "mips-tdep.h"
#include "block.h"
#include "reggroups.h"
#include "opcode/mips.h"
#include "elf/mips.h"
#include "elf-bfd.h"
#include "symcat.h"
#include "sim-regno.h"
#include "dis-asm.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "trad-frame.h"
#include "infcall.h"
#include "floatformat.h"

static const struct objfile_data *mips_pdr_data;

static struct type *mips_register_type (struct gdbarch *gdbarch, int regnum);

/* A useful bit in the CP0 status register (MIPS_PS_REGNUM).  */
/* This bit is set if we are emulating 32-bit FPRs on a 64-bit chip.  */
#define ST0_FR (1 << 26)

/* The sizes of floating point registers.  */

enum
{
  MIPS_FPU_SINGLE_REGSIZE = 4,
  MIPS_FPU_DOUBLE_REGSIZE = 8
};


static const char *mips_abi_string;

static const char *mips_abi_strings[] = {
  "auto",
  "n32",
  "o32",
  "n64",
  "o64",
  "eabi32",
  "eabi64",
  NULL
};

/* Various MIPS ISA options (related to stack analysis) can be
   overridden dynamically.  Establish an enum/array for managing
   them. */

static const char size_auto[] = "auto";
static const char size_32[] = "32";
static const char size_64[] = "64";

static const char *size_enums[] = {
  size_auto,
  size_32,
  size_64,
  0
};

/* Some MIPS boards don't support floating point while others only
   support single-precision floating-point operations.  */

enum mips_fpu_type
{
  MIPS_FPU_DOUBLE,              /* Full double precision floating point.  */
  MIPS_FPU_SINGLE,              /* Single precision floating point (R4650).  */
  MIPS_FPU_NONE                 /* No floating point.  */
};

#ifndef MIPS_DEFAULT_FPU_TYPE
#define MIPS_DEFAULT_FPU_TYPE MIPS_FPU_DOUBLE
#endif
static int mips_fpu_type_auto = 1;
static enum mips_fpu_type mips_fpu_type = MIPS_DEFAULT_FPU_TYPE;

static int mips_debug = 0;

/* MIPS specific per-architecture information */
struct gdbarch_tdep
{
  /* from the elf header */
  int elf_flags;

  /* mips options */
  enum mips_abi mips_abi;
  enum mips_abi found_abi;
  enum mips_fpu_type mips_fpu_type;
  int mips_last_arg_regnum;
  int mips_last_fp_arg_regnum;
  int default_mask_address_p;
  /* Is the target using 64-bit raw integer registers but only
     storing a left-aligned 32-bit value in each?  */
  int mips64_transfers_32bit_regs_p;
  /* Indexes for various registers.  IRIX and embedded have
     different values.  This contains the "public" fields.  Don't
     add any that do not need to be public.  */
  const struct mips_regnum *regnum;
  /* Register names table for the current register set.  */
  const char **mips_processor_reg_names;
};

static int
n32n64_floatformat_always_valid (const struct floatformat *fmt,
                                 const char *from)
{
  return 1;
}

/* FIXME: brobecker/2004-08-08: Long Double values are 128 bit long.
   They are implemented as a pair of 64bit doubles where the high
   part holds the result of the operation rounded to double, and
   the low double holds the difference between the exact result and
   the rounded result.  So "high" + "low" contains the result with
   added precision.  Unfortunately, the floatformat structure used
   by GDB is not powerful enough to describe this format.  As a temporary
   measure, we define a 128bit floatformat that only uses the high part.
   We lose a bit of precision but that's probably the best we can do
   for now with the current infrastructure.  */

static const struct floatformat floatformat_n32n64_long_double_big =
{
  floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52,
  floatformat_intbit_no,
  "floatformat_ieee_double_big",
  n32n64_floatformat_always_valid
};

const struct mips_regnum *
mips_regnum (struct gdbarch *gdbarch)
{
  return gdbarch_tdep (gdbarch)->regnum;
}

static int
mips_fpa0_regnum (struct gdbarch *gdbarch)
{
  return mips_regnum (gdbarch)->fp0 + 12;
}

#define MIPS_EABI (gdbarch_tdep (current_gdbarch)->mips_abi == MIPS_ABI_EABI32 \
                   || gdbarch_tdep (current_gdbarch)->mips_abi == MIPS_ABI_EABI64)

#define MIPS_LAST_FP_ARG_REGNUM (gdbarch_tdep (current_gdbarch)->mips_last_fp_arg_regnum)

#define MIPS_LAST_ARG_REGNUM (gdbarch_tdep (current_gdbarch)->mips_last_arg_regnum)

#define MIPS_FPU_TYPE (gdbarch_tdep (current_gdbarch)->mips_fpu_type)

/* MIPS16 function addresses are odd (bit 0 is set).  Here are some
   functions to test, set, or clear bit 0 of addresses.  */

static CORE_ADDR
is_mips16_addr (CORE_ADDR addr)
{
  return ((addr) & 1);
}

static CORE_ADDR
unmake_mips16_addr (CORE_ADDR addr)
{
  return ((addr) & ~1);
}

/* Return the contents of register REGNUM as a signed integer.  */

static LONGEST
read_signed_register (int regnum)
{
  LONGEST val;
  regcache_cooked_read_signed (current_regcache, regnum, &val);
  return val;
}

static LONGEST
read_signed_register_pid (int regnum, ptid_t ptid)
{
  ptid_t save_ptid;
  LONGEST retval;

  if (ptid_equal (ptid, inferior_ptid))
    return read_signed_register (regnum);

  save_ptid = inferior_ptid;

  inferior_ptid = ptid;

  retval = read_signed_register (regnum);

  inferior_ptid = save_ptid;

  return retval;
}

/* Return the MIPS ABI associated with GDBARCH.  */
enum mips_abi
mips_abi (struct gdbarch *gdbarch)
{
  return gdbarch_tdep (gdbarch)->mips_abi;
}

int
mips_isa_regsize (struct gdbarch *gdbarch)
{
  return (gdbarch_bfd_arch_info (gdbarch)->bits_per_word
          / gdbarch_bfd_arch_info (gdbarch)->bits_per_byte);
}

/* Return the currently configured (or set) saved register size. */

static const char *mips_abi_regsize_string = size_auto;

unsigned int
mips_abi_regsize (struct gdbarch *gdbarch)
{
  if (mips_abi_regsize_string == size_auto)
    switch (mips_abi (gdbarch))
      {
      case MIPS_ABI_EABI32:
      case MIPS_ABI_O32:
        return 4;
      case MIPS_ABI_N32:
      case MIPS_ABI_N64:
      case MIPS_ABI_O64:
      case MIPS_ABI_EABI64:
        return 8;
      case MIPS_ABI_UNKNOWN:
      case MIPS_ABI_LAST:
      default:
        internal_error (__FILE__, __LINE__, "bad switch");
      }
  else if (mips_abi_regsize_string == size_64)
    return 8;
  else                          /* if (mips_abi_regsize_string == size_32) */
    return 4;
}

/* Functions for setting and testing a bit in a minimal symbol that
   marks it as 16-bit function.  The MSB of the minimal symbol's
   "info" field is used for this purpose.

   ELF_MAKE_MSYMBOL_SPECIAL tests whether an ELF symbol is "special",
   i.e. refers to a 16-bit function, and sets a "special" bit in a
   minimal symbol to mark it as a 16-bit function

   MSYMBOL_IS_SPECIAL   tests the "special" bit in a minimal symbol  */

static void
mips_elf_make_msymbol_special (asymbol * sym, struct minimal_symbol *msym)
{
  if (((elf_symbol_type *) (sym))->internal_elf_sym.st_other == STO_MIPS16)
    {
      MSYMBOL_INFO (msym) = (char *)
        (((long) MSYMBOL_INFO (msym)) | 0x80000000);
      SYMBOL_VALUE_ADDRESS (msym) |= 1;
    }
}

static int
msymbol_is_special (struct minimal_symbol *msym)
{
  return (((long) MSYMBOL_INFO (msym) & 0x80000000) != 0);
}

/* XFER a value from the big/little/left end of the register.
   Depending on the size of the value it might occupy the entire
   register or just part of it.  Make an allowance for this, aligning
   things accordingly.  */

static void
mips_xfer_register (struct regcache *regcache, int reg_num, int length,
                    enum bfd_endian endian, bfd_byte * in,
                    const bfd_byte * out, int buf_offset)
{
  int reg_offset = 0;
  gdb_assert (reg_num >= NUM_REGS);
  /* Need to transfer the left or right part of the register, based on
     the targets byte order.  */
  switch (endian)
    {
    case BFD_ENDIAN_BIG:
      reg_offset = register_size (current_gdbarch, reg_num) - length;
      break;
    case BFD_ENDIAN_LITTLE:
      reg_offset = 0;
      break;
    case BFD_ENDIAN_UNKNOWN:    /* Indicates no alignment.  */
      reg_offset = 0;
      break;
    default:
      internal_error (__FILE__, __LINE__, "bad switch");
    }
  if (mips_debug)
    fprintf_unfiltered (gdb_stderr,
                        "xfer $%d, reg offset %d, buf offset %d, length %d, ",
                        reg_num, reg_offset, buf_offset, length);
  if (mips_debug && out != NULL)
    {
      int i;
      fprintf_unfiltered (gdb_stdlog, "out ");
      for (i = 0; i < length; i++)
        fprintf_unfiltered (gdb_stdlog, "%02x", out[buf_offset + i]);
    }
  if (in != NULL)
    regcache_cooked_read_part (regcache, reg_num, reg_offset, length,
                               in + buf_offset);
  if (out != NULL)
    regcache_cooked_write_part (regcache, reg_num, reg_offset, length,
                                out + buf_offset);
  if (mips_debug && in != NULL)
    {
      int i;
      fprintf_unfiltered (gdb_stdlog, "in ");
      for (i = 0; i < length; i++)
        fprintf_unfiltered (gdb_stdlog, "%02x", in[buf_offset + i]);
    }
  if (mips_debug)
    fprintf_unfiltered (gdb_stdlog, "\n");
}

/* Determine if a MIPS3 or later cpu is operating in MIPS{1,2} FPU
   compatiblity mode.  A return value of 1 means that we have
   physical 64-bit registers, but should treat them as 32-bit registers.  */

static int
mips2_fp_compat (void)
{
  /* MIPS1 and MIPS2 have only 32 bit FPRs, and the FR bit is not
     meaningful.  */
  if (register_size (current_gdbarch, mips_regnum (current_gdbarch)->fp0) ==
      4)
    return 0;

#if 0
  /* FIXME drow 2002-03-10: This is disabled until we can do it consistently,
     in all the places we deal with FP registers.  PR gdb/413.  */
  /* Otherwise check the FR bit in the status register - it controls
     the FP compatiblity mode.  If it is clear we are in compatibility
     mode.  */
  if ((read_register (MIPS_PS_REGNUM) & ST0_FR) == 0)
    return 1;
#endif

  return 0;
}

/* The amount of space reserved on the stack for registers. This is
   different to MIPS_ABI_REGSIZE as it determines the alignment of
   data allocated after the registers have run out. */

static const char *mips_stack_argsize_string = size_auto;

static unsigned int
mips_stack_argsize (struct gdbarch *gdbarch)
{
  if (mips_stack_argsize_string == size_auto)
    return mips_abi_regsize (gdbarch);
  else if (mips_stack_argsize_string == size_64)
    return 8;
  else                          /* if (mips_stack_argsize_string == size_32) */
    return 4;
}

#define VM_MIN_ADDRESS (CORE_ADDR)0x400000

static CORE_ADDR heuristic_proc_start (CORE_ADDR);

static CORE_ADDR read_next_frame_reg (struct frame_info *, int);

static void reinit_frame_cache_sfunc (char *, int, struct cmd_list_element *);

static struct type *mips_float_register_type (void);
static struct type *mips_double_register_type (void);

/* The list of available "set mips " and "show mips " commands */

static struct cmd_list_element *setmipscmdlist = NULL;
static struct cmd_list_element *showmipscmdlist = NULL;

/* Integer registers 0 thru 31 are handled explicitly by
   mips_register_name().  Processor specific registers 32 and above
   are listed in the followign tables.  */

enum
{ NUM_MIPS_PROCESSOR_REGS = (90 - 32) };

/* Generic MIPS.  */

static const char *mips_generic_reg_names[NUM_MIPS_PROCESSOR_REGS] = {
  "sr", "lo", "hi", "bad", "cause", "pc",
  "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",
  "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",
  "f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",
  "f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",
  "fsr", "fir", "" /*"fp" */ , "",
  "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "",
};

/* Names of IDT R3041 registers.  */

static const char *mips_r3041_reg_names[] = {
  "sr", "lo", "hi", "bad", "cause", "pc",
  "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",
  "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",
  "f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",
  "f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",
  "fsr", "fir", "", /*"fp" */ "",
  "", "", "bus", "ccfg", "", "", "", "",
  "", "", "port", "cmp", "", "", "epc", "prid",
};

/* Names of tx39 registers.  */

static const char *mips_tx39_reg_names[NUM_MIPS_PROCESSOR_REGS] = {
  "sr", "lo", "hi", "bad", "cause", "pc",
  "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "",
  "", "", "", "",
  "", "", "", "", "", "", "", "",
  "", "", "config", "cache", "debug", "depc", "epc", ""
};

/* Names of IRIX registers.  */
static const char *mips_irix_reg_names[NUM_MIPS_PROCESSOR_REGS] = {
  "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7",
  "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15",
  "f16", "f17", "f18", "f19", "f20", "f21", "f22", "f23",
  "f24", "f25", "f26", "f27", "f28", "f29", "f30", "f31",
  "pc", "cause", "bad", "hi", "lo", "fsr", "fir"
};


/* Return the name of the register corresponding to REGNO.  */
static const char *
mips_register_name (int regno)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  /* GPR names for all ABIs other than n32/n64.  */
  static char *mips_gpr_names[] = {
    "zero", "at", "v0", "v1", "a0", "a1", "a2", "a3",
    "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7",
    "s0", "s1", "s2", "s3", "s4", "s5", "s6", "s7",
    "t8", "t9", "k0", "k1", "gp", "sp", "s8", "ra",
  };

  /* GPR names for n32 and n64 ABIs.  */
  static char *mips_n32_n64_gpr_names[] = {
    "zero", "at", "v0", "v1", "a0", "a1", "a2", "a3",
    "a4", "a5", "a6", "a7", "t0", "t1", "t2", "t3",
    "s0", "s1", "s2", "s3", "s4", "s5", "s6", "s7",
    "t8", "t9", "k0", "k1", "gp", "sp", "s8", "ra"
  };

  enum mips_abi abi = mips_abi (current_gdbarch);

  /* Map [NUM_REGS .. 2*NUM_REGS) onto the raw registers, but then
     don't make the raw register names visible.  */
  int rawnum = regno % NUM_REGS;
  if (regno < NUM_REGS)
    return "";

  /* The MIPS integer registers are always mapped from 0 to 31.  The
     names of the registers (which reflects the conventions regarding
     register use) vary depending on the ABI.  */
  if (0 <= rawnum && rawnum < 32)
    {
      if (abi == MIPS_ABI_N32 || abi == MIPS_ABI_N64)
        return mips_n32_n64_gpr_names[rawnum];
      else
        return mips_gpr_names[rawnum];
    }
  else if (32 <= rawnum && rawnum < NUM_REGS)
    {
      gdb_assert (rawnum - 32 < NUM_MIPS_PROCESSOR_REGS);
      return tdep->mips_processor_reg_names[rawnum - 32];
    }
  else
    internal_error (__FILE__, __LINE__,
                    "mips_register_name: bad register number %d", rawnum);
}

/* Return the groups that a MIPS register can be categorised into.  */

static int
mips_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
                          struct reggroup *reggroup)
{
  int vector_p;
  int float_p;
  int raw_p;
  int rawnum = regnum % NUM_REGS;
  int pseudo = regnum / NUM_REGS;
  if (reggroup == all_reggroup)
    return pseudo;
  vector_p = TYPE_VECTOR (register_type (gdbarch, regnum));
  float_p = TYPE_CODE (register_type (gdbarch, regnum)) == TYPE_CODE_FLT;
  /* FIXME: cagney/2003-04-13: Can't yet use gdbarch_num_regs
     (gdbarch), as not all architectures are multi-arch.  */
  raw_p = rawnum < NUM_REGS;
  if (REGISTER_NAME (regnum) == NULL || REGISTER_NAME (regnum)[0] == '\0')
    return 0;
  if (reggroup == float_reggroup)
    return float_p && pseudo;
  if (reggroup == vector_reggroup)
    return vector_p && pseudo;
  if (reggroup == general_reggroup)
    return (!vector_p && !float_p) && pseudo;
  /* Save the pseudo registers.  Need to make certain that any code
     extracting register values from a saved register cache also uses
     pseudo registers.  */
  if (reggroup == save_reggroup)
    return raw_p && pseudo;
  /* Restore the same pseudo register.  */
  if (reggroup == restore_reggroup)
    return raw_p && pseudo;
  return 0;
}

/* Map the symbol table registers which live in the range [1 *
   NUM_REGS .. 2 * NUM_REGS) back onto the corresponding raw
   registers.  Take care of alignment and size problems.  */

static void
mips_pseudo_register_read (struct gdbarch *gdbarch, struct regcache *regcache,
                           int cookednum, void *buf)
{
  int rawnum = cookednum % NUM_REGS;
  gdb_assert (cookednum >= NUM_REGS && cookednum < 2 * NUM_REGS);
  if (register_size (gdbarch, rawnum) == register_size (gdbarch, cookednum))
    regcache_raw_read (regcache, rawnum, buf);
  else if (register_size (gdbarch, rawnum) >
           register_size (gdbarch, cookednum))
    {
      if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p
          || TARGET_BYTE_ORDER == BFD_ENDIAN_LITTLE)
        regcache_raw_read_part (regcache, rawnum, 0, 4, buf);
      else
        regcache_raw_read_part (regcache, rawnum, 4, 4, buf);
    }
  else
    internal_error (__FILE__, __LINE__, "bad register size");
}

static void
mips_pseudo_register_write (struct gdbarch *gdbarch,
                            struct regcache *regcache, int cookednum,
                            const void *buf)
{
  int rawnum = cookednum % NUM_REGS;
  gdb_assert (cookednum >= NUM_REGS && cookednum < 2 * NUM_REGS);
  if (register_size (gdbarch, rawnum) == register_size (gdbarch, cookednum))
    regcache_raw_write (regcache, rawnum, buf);
  else if (register_size (gdbarch, rawnum) >
           register_size (gdbarch, cookednum))
    {
      if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p
          || TARGET_BYTE_ORDER == BFD_ENDIAN_LITTLE)
        regcache_raw_write_part (regcache, rawnum, 0, 4, buf);
      else
        regcache_raw_write_part (regcache, rawnum, 4, 4, buf);
    }
  else
    internal_error (__FILE__, __LINE__, "bad register size");
}

/* Table to translate MIPS16 register field to actual register number.  */
static int mips16_to_32_reg[8] = { 16, 17, 2, 3, 4, 5, 6, 7 };

/* Heuristic_proc_start may hunt through the text section for a long
   time across a 2400 baud serial line.  Allows the user to limit this
   search.  */

static unsigned int heuristic_fence_post = 0;

/* Number of bytes of storage in the actual machine representation for
   register N.  NOTE: This defines the pseudo register type so need to
   rebuild the architecture vector.  */

static int mips64_transfers_32bit_regs_p = 0;

static void
set_mips64_transfers_32bit_regs (char *args, int from_tty,
                                 struct cmd_list_element *c)
{
  struct gdbarch_info info;
  gdbarch_info_init (&info);
  /* FIXME: cagney/2003-11-15: Should be setting a field in "info"
     instead of relying on globals.  Doing that would let generic code
     handle the search for this specific architecture.  */
  if (!gdbarch_update_p (info))
    {
      mips64_transfers_32bit_regs_p = 0;
      error ("32-bit compatibility mode not supported");
    }
}

/* Convert to/from a register and the corresponding memory value.  */

static int
mips_convert_register_p (int regnum, struct type *type)
{
  return (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
          && register_size (current_gdbarch, regnum) == 4
          && (regnum % NUM_REGS) >= mips_regnum (current_gdbarch)->fp0
          && (regnum % NUM_REGS) < mips_regnum (current_gdbarch)->fp0 + 32
          && TYPE_CODE (type) == TYPE_CODE_FLT && TYPE_LENGTH (type) == 8);
}

static void
mips_register_to_value (struct frame_info *frame, int regnum,
                        struct type *type, void *to)
{
  get_frame_register (frame, regnum + 0, (char *) to + 4);
  get_frame_register (frame, regnum + 1, (char *) to + 0);
}

static void
mips_value_to_register (struct frame_info *frame, int regnum,
                        struct type *type, const void *from)
{
  put_frame_register (frame, regnum + 0, (const char *) from + 4);
  put_frame_register (frame, regnum + 1, (const char *) from + 0);
}

/* Return the GDB type object for the "standard" data type of data in
   register REG.  */

static struct type *
mips_register_type (struct gdbarch *gdbarch, int regnum)
{
  gdb_assert (regnum >= 0 && regnum < 2 * NUM_REGS);
  if ((regnum % NUM_REGS) >= mips_regnum (current_gdbarch)->fp0
      && (regnum % NUM_REGS) < mips_regnum (current_gdbarch)->fp0 + 32)
    {
      /* The floating-point registers raw, or cooked, always match
         mips_isa_regsize(), and also map 1:1, byte for byte.  */
      switch (gdbarch_byte_order (gdbarch))
        {
        case BFD_ENDIAN_BIG:
          if (mips_isa_regsize (gdbarch) == 4)
            return builtin_type_ieee_single_big;
          else
            return builtin_type_ieee_double_big;
        case BFD_ENDIAN_LITTLE:
          if (mips_isa_regsize (gdbarch) == 4)
            return builtin_type_ieee_single_little;
          else
            return builtin_type_ieee_double_little;
        case BFD_ENDIAN_UNKNOWN:
        default:
          internal_error (__FILE__, __LINE__, "bad switch");
        }
    }
  else if (regnum < NUM_REGS)
    {
      /* The raw or ISA registers.  These are all sized according to
         the ISA regsize.  */
      if (mips_isa_regsize (gdbarch) == 4)
        return builtin_type_int32;
      else
        return builtin_type_int64;
    }
  else
    {
      /* The cooked or ABI registers.  These are sized according to
         the ABI (with a few complications).  */
      if (regnum >= (NUM_REGS
                     + mips_regnum (current_gdbarch)->fp_control_status)
          && regnum <= NUM_REGS + MIPS_LAST_EMBED_REGNUM)
        /* The pseudo/cooked view of the embedded registers is always
           32-bit.  The raw view is handled below.  */
        return builtin_type_int32;
      else if (gdbarch_tdep (gdbarch)->mips64_transfers_32bit_regs_p)
        /* The target, while possibly using a 64-bit register buffer,
           is only transfering 32-bits of each integer register.
           Reflect this in the cooked/pseudo (ABI) register value.  */
        return builtin_type_int32;
      else if (mips_abi_regsize (gdbarch) == 4)
        /* The ABI is restricted to 32-bit registers (the ISA could be
           32- or 64-bit).  */
        return builtin_type_int32;
      else
        /* 64-bit ABI.  */
        return builtin_type_int64;
    }
}

/* TARGET_READ_SP -- Remove useless bits from the stack pointer.  */

static CORE_ADDR
mips_read_sp (void)
{
  return read_signed_register (MIPS_SP_REGNUM);
}

/* Should the upper word of 64-bit addresses be zeroed? */
enum auto_boolean mask_address_var = AUTO_BOOLEAN_AUTO;

static int
mips_mask_address_p (struct gdbarch_tdep *tdep)
{
  switch (mask_address_var)
    {
    case AUTO_BOOLEAN_TRUE:
      return 1;
    case AUTO_BOOLEAN_FALSE:
      return 0;
      break;
    case AUTO_BOOLEAN_AUTO:
      return tdep->default_mask_address_p;
    default:
      internal_error (__FILE__, __LINE__, "mips_mask_address_p: bad switch");
      return -1;
    }
}

static void
show_mask_address (char *cmd, int from_tty, struct cmd_list_element *c)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  switch (mask_address_var)
    {
    case AUTO_BOOLEAN_TRUE:
      printf_filtered ("The 32 bit mips address mask is enabled\n");
      break;
    case AUTO_BOOLEAN_FALSE:
      printf_filtered ("The 32 bit mips address mask is disabled\n");
      break;
    case AUTO_BOOLEAN_AUTO:
      printf_filtered
        ("The 32 bit address mask is set automatically.  Currently %s\n",
         mips_mask_address_p (tdep) ? "enabled" : "disabled");
      break;
    default:
      internal_error (__FILE__, __LINE__, "show_mask_address: bad switch");
      break;
    }
}

/* Tell if the program counter value in MEMADDR is in a MIPS16 function.  */

int
mips_pc_is_mips16 (CORE_ADDR memaddr)
{
  struct minimal_symbol *sym;

  /* If bit 0 of the address is set, assume this is a MIPS16 address. */
  if (is_mips16_addr (memaddr))
    return 1;

  /* A flag indicating that this is a MIPS16 function is stored by elfread.c in
     the high bit of the info field.  Use this to decide if the function is
     MIPS16 or normal MIPS.  */
  sym = lookup_minimal_symbol_by_pc (memaddr);
  if (sym)
    return msymbol_is_special (sym);
  else
    return 0;
}

/* MIPS believes that the PC has a sign extended value.  Perhaps the
   all registers should be sign extended for simplicity? */

static CORE_ADDR
mips_read_pc (ptid_t ptid)
{
  return read_signed_register_pid (mips_regnum (current_gdbarch)->pc, ptid);
}

static CORE_ADDR
mips_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  return frame_unwind_register_signed (next_frame,
                                       NUM_REGS + mips_regnum (gdbarch)->pc);
}

/* Assuming NEXT_FRAME->prev is a dummy, return the frame ID of that
   dummy frame.  The frame ID's base needs to match the TOS value
   saved by save_dummy_frame_tos(), and the PC match the dummy frame's
   breakpoint.  */

static struct frame_id
mips_unwind_dummy_id (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  return frame_id_build (frame_unwind_register_signed (next_frame, NUM_REGS + MIPS_SP_REGNUM),
                         frame_pc_unwind (next_frame));
}

static void
mips_write_pc (CORE_ADDR pc, ptid_t ptid)
{
  write_register_pid (mips_regnum (current_gdbarch)->pc, pc, ptid);
}

/* Fetch and return instruction from the specified location.  If the PC
   is odd, assume it's a MIPS16 instruction; otherwise MIPS32.  */

static ULONGEST
mips_fetch_instruction (CORE_ADDR addr)
{
  char buf[MIPS_INSN32_SIZE];
  int instlen;
  int status;

  if (mips_pc_is_mips16 (addr))
    {
      instlen = MIPS_INSN16_SIZE;
      addr = unmake_mips16_addr (addr);
    }
  else
    instlen = MIPS_INSN32_SIZE;
  status = deprecated_read_memory_nobpt (addr, buf, instlen);
  if (status)
    memory_error (status, addr);
  return extract_unsigned_integer (buf, instlen);
}

/* These the fields of 32 bit mips instructions */
#define mips32_op(x) (x >> 26)
#define itype_op(x) (x >> 26)
#define itype_rs(x) ((x >> 21) & 0x1f)
#define itype_rt(x) ((x >> 16) & 0x1f)
#define itype_immediate(x) (x & 0xffff)

#define jtype_op(x) (x >> 26)
#define jtype_target(x) (x & 0x03ffffff)

#define rtype_op(x) (x >> 26)
#define rtype_rs(x) ((x >> 21) & 0x1f)
#define rtype_rt(x) ((x >> 16) & 0x1f)
#define rtype_rd(x) ((x >> 11) & 0x1f)
#define rtype_shamt(x) ((x >> 6) & 0x1f)
#define rtype_funct(x) (x & 0x3f)

static LONGEST
mips32_relative_offset (ULONGEST inst)
{
  return ((itype_immediate (inst) ^ 0x8000) - 0x8000) << 2;
}

/* Determine whate to set a single step breakpoint while considering
   branch prediction */
static CORE_ADDR
mips32_next_pc (CORE_ADDR pc)
{
  unsigned long inst;
  int op;
  inst = mips_fetch_instruction (pc);
  if ((inst & 0xe0000000) != 0) /* Not a special, jump or branch instruction */
    {
      if (itype_op (inst) >> 2 == 5)
        /* BEQL, BNEL, BLEZL, BGTZL: bits 0101xx */
        {
          op = (itype_op (inst) & 0x03);
          switch (op)
            {
            case 0:             /* BEQL */
              goto equal_branch;
            case 1:             /* BNEL */
              goto neq_branch;
            case 2:             /* BLEZL */
              goto less_branch;
            case 3:             /* BGTZ */
              goto greater_branch;
            default:
              pc += 4;
            }
        }
      else if (itype_op (inst) == 17 && itype_rs (inst) == 8)
        /* BC1F, BC1FL, BC1T, BC1TL: 010001 01000 */
        {
          int tf = itype_rt (inst) & 0x01;
          int cnum = itype_rt (inst) >> 2;
          int fcrcs =
            read_signed_register (mips_regnum (current_gdbarch)->
                                  fp_control_status);
          int cond = ((fcrcs >> 24) & 0x0e) | ((fcrcs >> 23) & 0x01);

          if (((cond >> cnum) & 0x01) == tf)
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
        }
      else
        pc += 4;                /* Not a branch, next instruction is easy */
    }
  else
    {                           /* This gets way messy */

      /* Further subdivide into SPECIAL, REGIMM and other */
      switch (op = itype_op (inst) & 0x07)      /* extract bits 28,27,26 */
        {
        case 0:         /* SPECIAL */
          op = rtype_funct (inst);
          switch (op)
            {
            case 8:             /* JR */
            case 9:             /* JALR */
              /* Set PC to that address */
              pc = read_signed_register (rtype_rs (inst));
              break;
            default:
              pc += 4;
            }

          break;                /* end SPECIAL */
        case 1:         /* REGIMM */
          {
            op = itype_rt (inst);       /* branch condition */
            switch (op)
              {
              case 0:           /* BLTZ */
              case 2:           /* BLTZL */
              case 16:          /* BLTZAL */
              case 18:          /* BLTZALL */
              less_branch:
                if (read_signed_register (itype_rs (inst)) < 0)
                  pc += mips32_relative_offset (inst) + 4;
                else
                  pc += 8;      /* after the delay slot */
                break;
              case 1:           /* BGEZ */
              case 3:           /* BGEZL */
              case 17:          /* BGEZAL */
              case 19:          /* BGEZALL */
                if (read_signed_register (itype_rs (inst)) >= 0)
                  pc += mips32_relative_offset (inst) + 4;
                else
                  pc += 8;      /* after the delay slot */
                break;
                /* All of the other instructions in the REGIMM category */
              default:
                pc += 4;
              }
          }
          break;                /* end REGIMM */
        case 2:         /* J */
        case 3:         /* JAL */
          {
            unsigned long reg;
            reg = jtype_target (inst) << 2;
            /* Upper four bits get never changed... */
            pc = reg + ((pc + 4) & 0xf0000000);
          }
          break;
          /* FIXME case JALX : */
          {
            unsigned long reg;
            reg = jtype_target (inst) << 2;
            pc = reg + ((pc + 4) & 0xf0000000) + 1;     /* yes, +1 */
            /* Add 1 to indicate 16 bit mode - Invert ISA mode */
          }
          break;                /* The new PC will be alternate mode */
        case 4:         /* BEQ, BEQL */
        equal_branch:
          if (read_signed_register (itype_rs (inst)) ==
              read_signed_register (itype_rt (inst)))
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        case 5:         /* BNE, BNEL */
        neq_branch:
          if (read_signed_register (itype_rs (inst)) !=
              read_signed_register (itype_rt (inst)))
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        case 6:         /* BLEZ, BLEZL */
          if (read_signed_register (itype_rs (inst)) <= 0)
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        case 7:
        default:
        greater_branch: /* BGTZ, BGTZL */
          if (read_signed_register (itype_rs (inst)) > 0)
            pc += mips32_relative_offset (inst) + 4;
          else
            pc += 8;
          break;
        }                       /* switch */
    }                           /* else */
  return pc;
}                               /* mips32_next_pc */

/* Decoding the next place to set a breakpoint is irregular for the
   mips 16 variant, but fortunately, there fewer instructions. We have to cope
   ith extensions for 16 bit instructions and a pair of actual 32 bit instructions.
   We dont want to set a single step instruction on the extend instruction
   either.
 */

/* Lots of mips16 instruction formats */
/* Predicting jumps requires itype,ritype,i8type
   and their extensions      extItype,extritype,extI8type
 */
enum mips16_inst_fmts
{
  itype,                        /* 0  immediate 5,10 */
  ritype,                       /* 1   5,3,8 */
  rrtype,                       /* 2   5,3,3,5 */
  rritype,                      /* 3   5,3,3,5 */
  rrrtype,                      /* 4   5,3,3,3,2 */
  rriatype,                     /* 5   5,3,3,1,4 */
  shifttype,                    /* 6   5,3,3,3,2 */
  i8type,                       /* 7   5,3,8 */
  i8movtype,                    /* 8   5,3,3,5 */
  i8mov32rtype,                 /* 9   5,3,5,3 */
  i64type,                      /* 10  5,3,8 */
  ri64type,                     /* 11  5,3,3,5 */
  jalxtype,                     /* 12  5,1,5,5,16 - a 32 bit instruction */
  exiItype,                     /* 13  5,6,5,5,1,1,1,1,1,1,5 */
  extRitype,                    /* 14  5,6,5,5,3,1,1,1,5 */
  extRRItype,                   /* 15  5,5,5,5,3,3,5 */
  extRRIAtype,                  /* 16  5,7,4,5,3,3,1,4 */
  EXTshifttype,                 /* 17  5,5,1,1,1,1,1,1,5,3,3,1,1,1,2 */
  extI8type,                    /* 18  5,6,5,5,3,1,1,1,5 */
  extI64type,                   /* 19  5,6,5,5,3,1,1,1,5 */
  extRi64type,                  /* 20  5,6,5,5,3,3,5 */
  extshift64type                /* 21  5,5,1,1,1,1,1,1,5,1,1,1,3,5 */
};
/* I am heaping all the fields of the formats into one structure and
   then, only the fields which are involved in instruction extension */
struct upk_mips16
{
  CORE_ADDR offset;
  unsigned int regx;            /* Function in i8 type */
  unsigned int regy;
};


/* The EXT-I, EXT-ri nad EXT-I8 instructions all have the same format
   for the bits which make up the immediatate extension.  */

static CORE_ADDR
extended_offset (unsigned int extension)
{
  CORE_ADDR value;
  value = (extension >> 21) & 0x3f;     /* * extract 15:11 */
  value = value << 6;
  value |= (extension >> 16) & 0x1f;    /* extrace 10:5 */
  value = value << 5;
  value |= extension & 0x01f;   /* extract 4:0 */
  return value;
}

/* Only call this function if you know that this is an extendable
   instruction, It wont malfunction, but why make excess remote memory references?
   If the immediate operands get sign extended or somthing, do it after
   the extension is performed.
 */
/* FIXME: Every one of these cases needs to worry about sign extension
   when the offset is to be used in relative addressing */


static unsigned int
fetch_mips_16 (CORE_ADDR pc)
{
  char buf[8];
  pc &= 0xfffffffe;             /* clear the low order bit */
  target_read_memory (pc, buf, 2);
  return extract_unsigned_integer (buf, 2);
}

static void
unpack_mips16 (CORE_ADDR pc,
               unsigned int extension,
               unsigned int inst,
               enum mips16_inst_fmts insn_format, struct upk_mips16 *upk)
{
  CORE_ADDR offset;
  int regx;
  int regy;
  switch (insn_format)
    {
    case itype:
      {
        CORE_ADDR value;
        if (extension)
          {
            value = extended_offset (extension);
            value = value << 11;        /* rom for the original value */
            value |= inst & 0x7ff;      /* eleven bits from instruction */
          }
        else
          {
            value = inst & 0x7ff;
            /* FIXME : Consider sign extension */
          }
        offset = value;
        regx = -1;
        regy = -1;
      }
      break;
    case ritype:
    case i8type:
      {                         /* A register identifier and an offset */
        /* Most of the fields are the same as I type but the
           immediate value is of a different length */
        CORE_ADDR value;
        if (extension)
          {
            value = extended_offset (extension);
            value = value << 8; /* from the original instruction */
            value |= inst & 0xff;       /* eleven bits from instruction */
            regx = (extension >> 8) & 0x07;     /* or i8 funct */
            if (value & 0x4000) /* test the sign bit , bit 26 */
              {
                value &= ~0x3fff;       /* remove the sign bit */
                value = -value;
              }
          }
        else
          {
            value = inst & 0xff;        /* 8 bits */
            regx = (inst >> 8) & 0x07;  /* or i8 funct */
            /* FIXME: Do sign extension , this format needs it */
            if (value & 0x80)   /* THIS CONFUSES ME */
              {
                value &= 0xef;  /* remove the sign bit */
                value = -value;
              }
          }
        offset = value;
        regy = -1;
        break;
      }
    case jalxtype:
      {
        unsigned long value;
        unsigned int nexthalf;
        value = ((inst & 0x1f) << 5) | ((inst >> 5) & 0x1f);
        value = value << 16;
        nexthalf = mips_fetch_instruction (pc + 2);     /* low bit still set */
        value |= nexthalf;
        offset = value;
        regx = -1;
        regy = -1;
        break;
      }
    default:
      internal_error (__FILE__, __LINE__, "bad switch");
    }
  upk->offset = offset;
  upk->regx = regx;
  upk->regy = regy;
}


static CORE_ADDR
add_offset_16 (CORE_ADDR pc, int offset)
{
  return ((offset << 2) | ((pc + 2) & (0xf0000000)));
}

static CORE_ADDR
extended_mips16_next_pc (CORE_ADDR pc,
                         unsigned int extension, unsigned int insn)
{
  int op = (insn >> 11);
  switch (op)
    {
    case 2:                     /* Branch */
      {
        CORE_ADDR offset;
        struct upk_mips16 upk;
        unpack_mips16 (pc, extension, insn, itype, &upk);
        offset = upk.offset;
        if (offset & 0x800)
          {
            offset &= 0xeff;
            offset = -offset;
          }
        pc += (offset << 1) + 2;
        break;
      }
    case 3:                     /* JAL , JALX - Watch out, these are 32 bit instruction */
      {
        struct upk_mips16 upk;
        unpack_mips16 (pc, extension, insn, jalxtype, &upk);
        pc = add_offset_16 (pc, upk.offset);
        if ((insn >> 10) & 0x01)        /* Exchange mode */
          pc = pc & ~0x01;      /* Clear low bit, indicate 32 bit mode */
        else
          pc |= 0x01;
        break;
      }
    case 4:                     /* beqz */
      {
        struct upk_mips16 upk;
        int reg;
        unpack_mips16 (pc, extension, insn, ritype, &upk);
        reg = read_signed_register (upk.regx);
        if (reg == 0)
          pc += (upk.offset << 1) + 2;
        else
          pc += 2;
        break;
      }
    case 5:                     /* bnez */
      {
        struct upk_mips16 upk;
        int reg;
        unpack_mips16 (pc, extension, insn, ritype, &upk);
        reg = read_signed_register (upk.regx);
        if (reg != 0)
          pc += (upk.offset << 1) + 2;
        else
          pc += 2;
        break;
      }
    case 12:                    /* I8 Formats btez btnez */
      {
        struct upk_mips16 upk;
        int reg;
        unpack_mips16 (pc, extension, insn, i8type, &upk);
        /* upk.regx contains the opcode */
        reg = read_signed_register (24);        /* Test register is 24 */
        if (((upk.regx == 0) && (reg == 0))     /* BTEZ */
            || ((upk.regx == 1) && (reg != 0))) /* BTNEZ */
          /* pc = add_offset_16(pc,upk.offset) ; */
          pc += (upk.offset << 1) + 2;
        else
          pc += 2;
        break;
      }
    case 29:                    /* RR Formats JR, JALR, JALR-RA */
      {
        struct upk_mips16 upk;
        /* upk.fmt = rrtype; */
        op = insn & 0x1f;
        if (op == 0)
          {
            int reg;
            upk.regx = (insn >> 8) & 0x07;
            upk.regy = (insn >> 5) & 0x07;
            switch (upk.regy)
              {
              case 0:
                reg = upk.regx;
                break;
              case 1:
                reg = 31;
                break;          /* Function return instruction */
              case 2:
                reg = upk.regx;
                break;
              default:
                reg = 31;
                break;          /* BOGUS Guess */
              }
            pc = read_signed_register (reg);
          }
        else
          pc += 2;
        break;
      }
    case 30:
      /* This is an instruction extension.  Fetch the real instruction
         (which follows the extension) and decode things based on
         that. */
      {
        pc += 2;
        pc = extended_mips16_next_pc (pc, insn, fetch_mips_16 (pc));
        break;
      }
    default:
      {
        pc += 2;
        break;
      }
    }
  return pc;
}

static CORE_ADDR
mips16_next_pc (CORE_ADDR pc)
{
  unsigned int insn = fetch_mips_16 (pc);
  return extended_mips16_next_pc (pc, 0, insn);
}

/* The mips_next_pc function supports single_step when the remote
   target monitor or stub is not developed enough to do a single_step.
   It works by decoding the current instruction and predicting where a
   branch will go. This isnt hard because all the data is available.
   The MIPS32 and MIPS16 variants are quite different */
CORE_ADDR
mips_next_pc (CORE_ADDR pc)
{
  if (pc & 0x01)
    return mips16_next_pc (pc);
  else
    return mips32_next_pc (pc);
}

struct mips_frame_cache
{
  CORE_ADDR base;
  struct trad_frame_saved_reg *saved_regs;
};

/* Set a register's saved stack address in temp_saved_regs.  If an
   address has already been set for this register, do nothing; this
   way we will only recognize the first save of a given register in a
   function prologue.

   For simplicity, save the address in both [0 .. NUM_REGS) and
   [NUM_REGS .. 2*NUM_REGS).  Strictly speaking, only the second range
   is used as it is only second range (the ABI instead of ISA
   registers) that comes into play when finding saved registers in a
   frame.  */

static void
set_reg_offset (struct mips_frame_cache *this_cache, int regnum,
                CORE_ADDR offset)
{
  if (this_cache != NULL
      && this_cache->saved_regs[regnum].addr == -1)
    {
      this_cache->saved_regs[regnum + 0 * NUM_REGS].addr = offset;
      this_cache->saved_regs[regnum + 1 * NUM_REGS].addr = offset;
    }
}


/* Fetch the immediate value from a MIPS16 instruction.
   If the previous instruction was an EXTEND, use it to extend
   the upper bits of the immediate value.  This is a helper function
   for mips16_scan_prologue.  */

static int
mips16_get_imm (unsigned short prev_inst,       /* previous instruction */
                unsigned short inst,    /* current instruction */
                int nbits,      /* number of bits in imm field */
                int scale,      /* scale factor to be applied to imm */
                int is_signed)  /* is the imm field signed? */
{
  int offset;

  if ((prev_inst & 0xf800) == 0xf000)   /* prev instruction was EXTEND? */
    {
      offset = ((prev_inst & 0x1f) << 11) | (prev_inst & 0x7e0);
      if (offset & 0x8000)      /* check for negative extend */
        offset = 0 - (0x10000 - (offset & 0xffff));
      return offset | (inst & 0x1f);
    }
  else
    {
      int max_imm = 1 << nbits;
      int mask = max_imm - 1;
      int sign_bit = max_imm >> 1;

      offset = inst & mask;
      if (is_signed && (offset & sign_bit))
        offset = 0 - (max_imm - offset);
      return offset * scale;
    }
}


/* Analyze the function prologue from START_PC to LIMIT_PC. Builds
   the associated FRAME_CACHE if not null.
   Return the address of the first instruction past the prologue.  */

static CORE_ADDR
mips16_scan_prologue (CORE_ADDR start_pc, CORE_ADDR limit_pc,
                      struct frame_info *next_frame,
                      struct mips_frame_cache *this_cache)
{
  CORE_ADDR cur_pc;
  CORE_ADDR frame_addr = 0;     /* Value of $r17, used as frame pointer */
  CORE_ADDR sp;
  long frame_offset = 0;        /* Size of stack frame.  */
  long frame_adjust = 0;        /* Offset of FP from SP.  */
  int frame_reg = MIPS_SP_REGNUM;
  unsigned short prev_inst = 0; /* saved copy of previous instruction */
  unsigned inst = 0;            /* current instruction */
  unsigned entry_inst = 0;      /* the entry instruction */
  int reg, offset;

  int extend_bytes = 0;
  int prev_extend_bytes;
  CORE_ADDR end_prologue_addr = 0;

  /* Can be called when there's no process, and hence when there's no
     NEXT_FRAME.  */
  if (next_frame != NULL)
    sp = read_next_frame_reg (next_frame, NUM_REGS + MIPS_SP_REGNUM);
  else
    sp = 0;

  if (limit_pc > start_pc + 200)
    limit_pc = start_pc + 200;

  for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += MIPS_INSN16_SIZE)
    {
      /* Save the previous instruction.  If it's an EXTEND, we'll extract
         the immediate offset extension from it in mips16_get_imm.  */
      prev_inst = inst;

      /* Fetch and decode the instruction.   */
      inst = (unsigned short) mips_fetch_instruction (cur_pc);

      /* Normally we ignore extend instructions.  However, if it is
         not followed by a valid prologue instruction, then this
         instruction is not part of the prologue either.  We must
         remember in this case to adjust the end_prologue_addr back
         over the extend.  */
      if ((inst & 0xf800) == 0xf000)    /* extend */
        {
          extend_bytes = MIPS_INSN16_SIZE;
          continue;
        }

      prev_extend_bytes = extend_bytes;
      extend_bytes = 0;

      if ((inst & 0xff00) == 0x6300     /* addiu sp */
          || (inst & 0xff00) == 0xfb00) /* daddiu sp */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 8, 1);
          if (offset < 0)       /* negative stack adjustment? */
            frame_offset -= offset;
          else
            /* Exit loop if a positive stack adjustment is found, which
               usually means that the stack cleanup code in the function
               epilogue is reached.  */
            break;
        }
      else if ((inst & 0xf800) == 0xd000)       /* sw reg,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 4, 0);
          reg = mips16_to_32_reg[(inst & 0x700) >> 8];
          set_reg_offset (this_cache, reg, sp + offset);
        }
      else if ((inst & 0xff00) == 0xf900)       /* sd reg,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 5, 8, 0);
          reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
          set_reg_offset (this_cache, reg, sp + offset);
        }
      else if ((inst & 0xff00) == 0x6200)       /* sw $ra,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 4, 0);
          set_reg_offset (this_cache, MIPS_RA_REGNUM, sp + offset);
        }
      else if ((inst & 0xff00) == 0xfa00)       /* sd $ra,n($sp) */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 8, 0);
          set_reg_offset (this_cache, MIPS_RA_REGNUM, sp + offset);
        }
      else if (inst == 0x673d)  /* move $s1, $sp */
        {
          frame_addr = sp;
          frame_reg = 17;
        }
      else if ((inst & 0xff00) == 0x0100)       /* addiu $s1,sp,n */
        {
          offset = mips16_get_imm (prev_inst, inst, 8, 4, 0);
          frame_addr = sp + offset;
          frame_reg = 17;
          frame_adjust = offset;
        }
      else if ((inst & 0xFF00) == 0xd900)       /* sw reg,offset($s1) */
        {
          offset = mips16_get_imm (prev_inst, inst, 5, 4, 0);
          reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
          set_reg_offset (this_cache, reg, frame_addr + offset);
        }
      else if ((inst & 0xFF00) == 0x7900)       /* sd reg,offset($s1) */
        {
          offset = mips16_get_imm (prev_inst, inst, 5, 8, 0);
          reg = mips16_to_32_reg[(inst & 0xe0) >> 5];
          set_reg_offset (this_cache, reg, frame_addr + offset);
        }
      else if ((inst & 0xf81f) == 0xe809
               && (inst & 0x700) != 0x700)      /* entry */
        entry_inst = inst;      /* save for later processing */
      else if ((inst & 0xf800) == 0x1800)       /* jal(x) */
        cur_pc += MIPS_INSN16_SIZE;     /* 32-bit instruction */
      else if ((inst & 0xff1c) == 0x6704)       /* move reg,$a0-$a3 */
        {
          /* This instruction is part of the prologue, but we don't
             need to do anything special to handle it.  */
        }
      else
        {
          /* This instruction is not an instruction typically found
             in a prologue, so we must have reached the end of the
             prologue.  */
          if (end_prologue_addr == 0)
            end_prologue_addr = cur_pc - prev_extend_bytes;
        }
    }

  /* The entry instruction is typically the first instruction in a function,
     and it stores registers at offsets relative to the value of the old SP
     (before the prologue).  But the value of the sp parameter to this
     function is the new SP (after the prologue has been executed).  So we
     can't calculate those offsets until we've seen the entire prologue,
     and can calculate what the old SP must have been. */
  if (entry_inst != 0)
    {
      int areg_count = (entry_inst >> 8) & 7;
      int sreg_count = (entry_inst >> 6) & 3;

      /* The entry instruction always subtracts 32 from the SP.  */
      frame_offset += 32;

      /* Now we can calculate what the SP must have been at the
         start of the function prologue.  */
      sp += frame_offset;

      /* Check if a0-a3 were saved in the caller's argument save area.  */
      for (reg = 4, offset = 0; reg < areg_count + 4; reg++)
        {
          set_reg_offset (this_cache, reg, sp + offset);
          offset += mips_abi_regsize (current_gdbarch);
        }

      /* Check if the ra register was pushed on the stack.  */
      offset = -4;
      if (entry_inst & 0x20)
        {
          set_reg_offset (this_cache, MIPS_RA_REGNUM, sp + offset);
          offset -= mips_abi_regsize (current_gdbarch);
        }

      /* Check if the s0 and s1 registers were pushed on the stack.  */
      for (reg = 16; reg < sreg_count + 16; reg++)
        {
          set_reg_offset (this_cache, reg, sp + offset);
          offset -= mips_abi_regsize (current_gdbarch);
        }
    }

  if (this_cache != NULL)
    {
      this_cache->base =
        (frame_unwind_register_signed (next_frame, NUM_REGS + frame_reg)
         + frame_offset - frame_adjust);
      /* FIXME: brobecker/2004-10-10: Just as in the mips32 case, we should
         be able to get rid of the assignment below, evetually. But it's
         still needed for now.  */
      this_cache->saved_regs[NUM_REGS + mips_regnum (current_gdbarch)->pc]
        = this_cache->saved_regs[NUM_REGS + MIPS_RA_REGNUM];
    }

  /* If we didn't reach the end of the prologue when scanning the function
     instructions, then set end_prologue_addr to the address of the
     instruction immediately after the last one we scanned.  */
  if (end_prologue_addr == 0)
    end_prologue_addr = cur_pc;

  return end_prologue_addr;
}

/* Heuristic unwinder for 16-bit MIPS instruction set (aka MIPS16).
   Procedures that use the 32-bit instruction set are handled by the
   mips_insn32 unwinder.  */

static struct mips_frame_cache *
mips_insn16_frame_cache (struct frame_info *next_frame, void **this_cache)
{
  struct mips_frame_cache *cache;

  if ((*this_cache) != NULL)
    return (*this_cache);
  cache = FRAME_OBSTACK_ZALLOC (struct mips_frame_cache);
  (*this_cache) = cache;
  cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);

  /* Analyze the function prologue.  */
  {
    const CORE_ADDR pc = frame_pc_unwind (next_frame);
    CORE_ADDR start_addr;

    find_pc_partial_function (pc, NULL, &start_addr, NULL);
    if (start_addr == 0)
      start_addr = heuristic_proc_start (pc);
    /* We can't analyze the prologue if we couldn't find the begining
       of the function.  */
    if (start_addr == 0)
      return cache;

    mips16_scan_prologue (start_addr, pc, next_frame, *this_cache);
  }
  
  /* SP_REGNUM, contains the value and not the address.  */
  trad_frame_set_value (cache->saved_regs, NUM_REGS + MIPS_SP_REGNUM, cache->base);

  return (*this_cache);
}

static void
mips_insn16_frame_this_id (struct frame_info *next_frame, void **this_cache,
                           struct frame_id *this_id)
{
  struct mips_frame_cache *info = mips_insn16_frame_cache (next_frame,
                                                           this_cache);
  (*this_id) = frame_id_build (info->base, frame_func_unwind (next_frame));
}

static void
mips_insn16_frame_prev_register (struct frame_info *next_frame,
                                 void **this_cache,
                                 int regnum, int *optimizedp,
                                 enum lval_type *lvalp, CORE_ADDR *addrp,
                                 int *realnump, void *valuep)
{
  struct mips_frame_cache *info = mips_insn16_frame_cache (next_frame,
                                                           this_cache);
  trad_frame_get_prev_register (next_frame, info->saved_regs, regnum,
                                optimizedp, lvalp, addrp, realnump, valuep);
}

static const struct frame_unwind mips_insn16_frame_unwind =
{
  NORMAL_FRAME,
  mips_insn16_frame_this_id,
  mips_insn16_frame_prev_register
};

static const struct frame_unwind *
mips_insn16_frame_sniffer (struct frame_info *next_frame)
{
  CORE_ADDR pc = frame_pc_unwind (next_frame);
  if (mips_pc_is_mips16 (pc))
    return &mips_insn16_frame_unwind;
  return NULL;
}

static CORE_ADDR
mips_insn16_frame_base_address (struct frame_info *next_frame,
                                void **this_cache)
{
  struct mips_frame_cache *info = mips_insn16_frame_cache (next_frame,
                                                           this_cache);
  return info->base;
}

static const struct frame_base mips_insn16_frame_base =
{
  &mips_insn16_frame_unwind,
  mips_insn16_frame_base_address,
  mips_insn16_frame_base_address,
  mips_insn16_frame_base_address
};

static const struct frame_base *
mips_insn16_frame_base_sniffer (struct frame_info *next_frame)
{
  if (mips_insn16_frame_sniffer (next_frame) != NULL)
    return &mips_insn16_frame_base;
  else
    return NULL;
}

/* Mark all the registers as unset in the saved_regs array
   of THIS_CACHE.  Do nothing if THIS_CACHE is null.  */

void
reset_saved_regs (struct mips_frame_cache *this_cache)
{
  if (this_cache == NULL || this_cache->saved_regs == NULL)
    return;

  {
    const int num_regs = NUM_REGS;
    int i;

    for (i = 0; i < num_regs; i++)
      {
        this_cache->saved_regs[i].addr = -1;
      }
  }
}

/* Analyze the function prologue from START_PC to LIMIT_PC. Builds
   the associated FRAME_CACHE if not null.  
   Return the address of the first instruction past the prologue.  */

static CORE_ADDR
mips32_scan_prologue (CORE_ADDR start_pc, CORE_ADDR limit_pc,
                      struct frame_info *next_frame,
                      struct mips_frame_cache *this_cache)
{
  CORE_ADDR cur_pc;
  CORE_ADDR frame_addr = 0; /* Value of $r30. Used by gcc for frame-pointer */
  CORE_ADDR sp;
  long frame_offset;
  int  frame_reg = MIPS_SP_REGNUM;

  CORE_ADDR end_prologue_addr = 0;
  int seen_sp_adjust = 0;
  int load_immediate_bytes = 0;

  /* Can be called when there's no process, and hence when there's no
     NEXT_FRAME.  */
  if (next_frame != NULL)
    sp = read_next_frame_reg (next_frame, NUM_REGS + MIPS_SP_REGNUM);
  else
    sp = 0;

  if (limit_pc > start_pc + 200)
    limit_pc = start_pc + 200;

restart:

  frame_offset = 0;
  for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += MIPS_INSN32_SIZE)
    {
      unsigned long inst, high_word, low_word;
      int reg;

      /* Fetch the instruction.   */
      inst = (unsigned long) mips_fetch_instruction (cur_pc);

      /* Save some code by pre-extracting some useful fields.  */
      high_word = (inst >> 16) & 0xffff;
      low_word = inst & 0xffff;
      reg = high_word & 0x1f;

      if (high_word == 0x27bd   /* addiu $sp,$sp,-i */
          || high_word == 0x23bd        /* addi $sp,$sp,-i */
          || high_word == 0x67bd)       /* daddiu $sp,$sp,-i */
        {
          if (low_word & 0x8000)        /* negative stack adjustment? */
            frame_offset += 0x10000 - low_word;
          else
            /* Exit loop if a positive stack adjustment is found, which
               usually means that the stack cleanup code in the function
               epilogue is reached.  */
            break;
          seen_sp_adjust = 1;
        }
      else if ((high_word & 0xFFE0) == 0xafa0)  /* sw reg,offset($sp) */
        {
          set_reg_offset (this_cache, reg, sp + low_word);
        }
      else if ((high_word & 0xFFE0) == 0xffa0)  /* sd reg,offset($sp) */
        {
          /* Irix 6.2 N32 ABI uses sd instructions for saving $gp and $ra.  */
          set_reg_offset (this_cache, reg, sp + low_word);
        }
      else if (high_word == 0x27be)     /* addiu $30,$sp,size */
        {
          /* Old gcc frame, r30 is virtual frame pointer.  */
          if ((long) low_word != frame_offset)
            frame_addr = sp + low_word;
          else if (frame_reg == MIPS_SP_REGNUM)
            {
              unsigned alloca_adjust;

              frame_reg = 30;
              frame_addr = read_next_frame_reg (next_frame, NUM_REGS + 30);
              alloca_adjust = (unsigned) (frame_addr - (sp + low_word));
              if (alloca_adjust > 0)
                {
                  /* FP > SP + frame_size. This may be because of
                     an alloca or somethings similar.  Fix sp to
                     "pre-alloca" value, and try again.  */
                  sp += alloca_adjust;
                  /* Need to reset the status of all registers.  Otherwise,
                     we will hit a guard that prevents the new address
                     for each register to be recomputed during the second
                     pass.  */
                  reset_saved_regs (this_cache);
                  goto restart;
                }
            }
        }
      /* move $30,$sp.  With different versions of gas this will be either
         `addu $30,$sp,$zero' or `or $30,$sp,$zero' or `daddu 30,sp,$0'.
         Accept any one of these.  */
      else if (inst == 0x03A0F021 || inst == 0x03a0f025 || inst == 0x03a0f02d)
        {
          /* New gcc frame, virtual frame pointer is at r30 + frame_size.  */
          if (frame_reg == MIPS_SP_REGNUM)
            {
              unsigned alloca_adjust;

              frame_reg = 30;
              frame_addr = read_next_frame_reg (next_frame, NUM_REGS + 30);
              alloca_adjust = (unsigned) (frame_addr - sp);
              if (alloca_adjust > 0)
                {
                  /* FP > SP + frame_size. This may be because of
                     an alloca or somethings similar.  Fix sp to
                     "pre-alloca" value, and try again.  */
                  sp = frame_addr;
                  /* Need to reset the status of all registers.  Otherwise,
                     we will hit a guard that prevents the new address
                     for each register to be recomputed during the second
                     pass.  */
                  reset_saved_regs (this_cache);
                  goto restart;
                }
            }
        }
      else if ((high_word & 0xFFE0) == 0xafc0)  /* sw reg,offset($30) */
        {
          set_reg_offset (this_cache, reg, frame_addr + low_word);
        }
      else if ((high_word & 0xFFE0) == 0xE7A0 /* swc1 freg,n($sp) */
               || (high_word & 0xF3E0) == 0xA3C0 /* sx reg,n($s8) */
               || (inst & 0xFF9F07FF) == 0x00800021 /* move reg,$a0-$a3 */
               || high_word == 0x3c1c /* lui $gp,n */
               || high_word == 0x279c /* addiu $gp,$gp,n */
               || inst == 0x0399e021 /* addu $gp,$gp,$t9 */
               || inst == 0x033ce021 /* addu $gp,$t9,$gp */
              )
       {
         /* These instructions are part of the prologue, but we don't
            need to do anything special to handle them.  */
       }
      /* The instructions below load $at or $t0 with an immediate
         value in preparation for a stack adjustment via
         subu $sp,$sp,[$at,$t0]. These instructions could also
         initialize a local variable, so we accept them only before
         a stack adjustment instruction was seen.  */
      else if (!seen_sp_adjust
               && (high_word == 0x3c01 /* lui $at,n */
                   || high_word == 0x3c08 /* lui $t0,n */
                   || high_word == 0x3421 /* ori $at,$at,n */
                   || high_word == 0x3508 /* ori $t0,$t0,n */
                   || high_word == 0x3401 /* ori $at,$zero,n */
                   || high_word == 0x3408 /* ori $t0,$zero,n */
                  ))
       {
          load_immediate_bytes += MIPS_INSN32_SIZE;             /* FIXME!  */
       }
      else
       {
         /* This instruction is not an instruction typically found
            in a prologue, so we must have reached the end of the
            prologue.  */
         /* FIXME: brobecker/2004-10-10: Can't we just break out of this
            loop now?  Why would we need to continue scanning the function
            instructions?  */
         if (end_prologue_addr == 0)
           end_prologue_addr = cur_pc;
       }
    }

  if (this_cache != NULL)
    {
      this_cache->base = 
        (frame_unwind_register_signed (next_frame, NUM_REGS + frame_reg)
         + frame_offset);
      /* FIXME: brobecker/2004-09-15: We should be able to get rid of
         this assignment below, eventually.  But it's still needed
         for now.  */
      this_cache->saved_regs[NUM_REGS + mips_regnum (current_gdbarch)->pc]
        = this_cache->saved_regs[NUM_REGS + MIPS_RA_REGNUM];
    }

  /* If we didn't reach the end of the prologue when scanning the function
     instructions, then set end_prologue_addr to the address of the
     instruction immediately after the last one we scanned.  */
  /* brobecker/2004-10-10: I don't think this would ever happen, but
     we may as well be careful and do our best if we have a null
     end_prologue_addr.  */
  if (end_prologue_addr == 0)
    end_prologue_addr = cur_pc;
     
  /* In a frameless function, we might have incorrectly
     skipped some load immediate instructions. Undo the skipping
     if the load immediate was not followed by a stack adjustment.  */
  if (load_immediate_bytes && !seen_sp_adjust)
    end_prologue_addr -= load_immediate_bytes;

  return end_prologue_addr;
}

/* Heuristic unwinder for procedures using 32-bit instructions (covers
   both 32-bit and 64-bit MIPS ISAs).  Procedures using 16-bit
   instructions (a.k.a. MIPS16) are handled by the mips_insn16
   unwinder.  */

static struct mips_frame_cache *
mips_insn32_frame_cache (struct frame_info *next_frame, void **this_cache)
{
  struct mips_frame_cache *cache;

  if ((*this_cache) != NULL)
    return (*this_cache);

  cache = FRAME_OBSTACK_ZALLOC (struct mips_frame_cache);
  (*this_cache) = cache;
  cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);

  /* Analyze the function prologue.  */
  {
    const CORE_ADDR pc = frame_pc_unwind (next_frame);
    CORE_ADDR start_addr;

    find_pc_partial_function (pc, NULL, &start_addr, NULL);
    if (start_addr == 0)
      start_addr = heuristic_proc_start (pc);
    /* We can't analyze the prologue if we couldn't find the begining
       of the function.  */
    if (start_addr == 0)
      return cache;

    mips32_scan_prologue (start_addr, pc, next_frame, *this_cache);
  }
  
  /* SP_REGNUM, contains the value and not the address.  */
  trad_frame_set_value (cache->saved_regs, NUM_REGS + MIPS_SP_REGNUM, cache->base);

  return (*this_cache);
}

static void
mips_insn32_frame_this_id (struct frame_info *next_frame, void **this_cache,
                           struct frame_id *this_id)
{
  struct mips_frame_cache *info = mips_insn32_frame_cache (next_frame,
                                                           this_cache);
  (*this_id) = frame_id_build (info->base, frame_func_unwind (next_frame));
}

static void
mips_insn32_frame_prev_register (struct frame_info *next_frame,
                                 void **this_cache,
                                 int regnum, int *optimizedp,
                                 enum lval_type *lvalp, CORE_ADDR *addrp,
                                 int *realnump, void *valuep)
{
  struct mips_frame_cache *info = mips_insn32_frame_cache (next_frame,
                                                           this_cache);
  trad_frame_get_prev_register (next_frame, info->saved_regs, regnum,
                                optimizedp, lvalp, addrp, realnump, valuep);
}

static const struct frame_unwind mips_insn32_frame_unwind =
{
  NORMAL_FRAME,
  mips_insn32_frame_this_id,
  mips_insn32_frame_prev_register
};

static const struct frame_unwind *
mips_insn32_frame_sniffer (struct frame_info *next_frame)
{
  CORE_ADDR pc = frame_pc_unwind (next_frame);
  if (! mips_pc_is_mips16 (pc))
    return &mips_insn32_frame_unwind;
  return NULL;
}

static CORE_ADDR
mips_insn32_frame_base_address (struct frame_info *next_frame,
                                void **this_cache)
{
  struct mips_frame_cache *info = mips_insn32_frame_cache (next_frame,
                                                           this_cache);
  return info->base;
}

static const struct frame_base mips_insn32_frame_base =
{
  &mips_insn32_frame_unwind,
  mips_insn32_frame_base_address,
  mips_insn32_frame_base_address,
  mips_insn32_frame_base_address
};

static const struct frame_base *
mips_insn32_frame_base_sniffer (struct frame_info *next_frame)
{
  if (mips_insn32_frame_sniffer (next_frame) != NULL)
    return &mips_insn32_frame_base;
  else
    return NULL;
}

static struct trad_frame_cache *
mips_stub_frame_cache (struct frame_info *next_frame, void **this_cache)
{
  CORE_ADDR pc;
  CORE_ADDR start_addr;
  CORE_ADDR stack_addr;
  struct trad_frame_cache *this_trad_cache;

  if ((*this_cache) != NULL)
    return (*this_cache);
  this_trad_cache = trad_frame_cache_zalloc (next_frame);
  (*this_cache) = this_trad_cache;

  /* The return address is in the link register.  */
  trad_frame_set_reg_realreg (this_trad_cache, PC_REGNUM, MIPS_RA_REGNUM);

  /* Frame ID, since it's a frameless / stackless function, no stack
     space is allocated and SP on entry is the current SP.  */
  pc = frame_pc_unwind (next_frame);
  find_pc_partial_function (pc, NULL, &start_addr, NULL);
  stack_addr = frame_unwind_register_signed (next_frame, MIPS_SP_REGNUM);
  trad_frame_set_id (this_trad_cache, frame_id_build (start_addr, stack_addr));

  /* Assume that the frame's base is the same as the
     stack-pointer.  */
  trad_frame_set_this_base (this_trad_cache, stack_addr);

  return this_trad_cache;
}

static void
mips_stub_frame_this_id (struct frame_info *next_frame, void **this_cache,
                         struct frame_id *this_id)
{
  struct trad_frame_cache *this_trad_cache
    = mips_stub_frame_cache (next_frame, this_cache);
  trad_frame_get_id (this_trad_cache, this_id);
}

static void
mips_stub_frame_prev_register (struct frame_info *next_frame,
                                 void **this_cache,
                                 int regnum, int *optimizedp,
                                 enum lval_type *lvalp, CORE_ADDR *addrp,
                                 int *realnump, void *valuep)
{
  struct trad_frame_cache *this_trad_cache
    = mips_stub_frame_cache (next_frame, this_cache);
  trad_frame_get_register (this_trad_cache, next_frame, regnum, optimizedp,
                           lvalp, addrp, realnump, valuep);
}

static const struct frame_unwind mips_stub_frame_unwind =
{
  NORMAL_FRAME,
  mips_stub_frame_this_id,
  mips_stub_frame_prev_register
};

static const struct frame_unwind *
mips_stub_frame_sniffer (struct frame_info *next_frame)
{
  CORE_ADDR pc = frame_pc_unwind (next_frame);
  if (in_plt_section (pc, NULL))
    return &mips_stub_frame_unwind;
  else
    return NULL;
}

static CORE_ADDR
mips_stub_frame_base_address (struct frame_info *next_frame,
                              void **this_cache)
{
  struct trad_frame_cache *this_trad_cache
    = mips_stub_frame_cache (next_frame, this_cache);
  return trad_frame_get_this_base (this_trad_cache);
}

static const struct frame_base mips_stub_frame_base =
{
  &mips_stub_frame_unwind,
  mips_stub_frame_base_address,
  mips_stub_frame_base_address,
  mips_stub_frame_base_address
};

static const struct frame_base *
mips_stub_frame_base_sniffer (struct frame_info *next_frame)
{
  if (mips_stub_frame_sniffer (next_frame) != NULL)
    return &mips_stub_frame_base;
  else
    return NULL;
}

static CORE_ADDR
read_next_frame_reg (struct frame_info *fi, int regno)
{
  /* Always a pseudo.  */
  gdb_assert (regno >= NUM_REGS);
  if (fi == NULL)
    {
      LONGEST val;
      regcache_cooked_read_signed (current_regcache, regno, &val);
      return val;
    }
  else
    return frame_unwind_register_signed (fi, regno);

}

/* mips_addr_bits_remove - remove useless address bits  */

static CORE_ADDR
mips_addr_bits_remove (CORE_ADDR addr)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  if (mips_mask_address_p (tdep) && (((ULONGEST) addr) >> 32 == 0xffffffffUL))
    /* This hack is a work-around for existing boards using PMON, the
       simulator, and any other 64-bit targets that doesn't have true
       64-bit addressing.  On these targets, the upper 32 bits of
       addresses are ignored by the hardware.  Thus, the PC or SP are
       likely to have been sign extended to all 1s by instruction
       sequences that load 32-bit addresses.  For example, a typical
       piece of code that loads an address is this:

       lui $r2, <upper 16 bits>
       ori $r2, <lower 16 bits>

       But the lui sign-extends the value such that the upper 32 bits
       may be all 1s.  The workaround is simply to mask off these
       bits.  In the future, gcc may be changed to support true 64-bit
       addressing, and this masking will have to be disabled.  */
    return addr &= 0xffffffffUL;
  else
    return addr;
}

/* mips_software_single_step() is called just before we want to resume
   the inferior, if we want to single-step it but there is no hardware
   or kernel single-step support (MIPS on GNU/Linux for example).  We find
   the target of the coming instruction and breakpoint it.

   single_step is also called just after the inferior stops.  If we had
   set up a simulated single-step, we undo our damage.  */

void
mips_software_single_step (enum target_signal sig, int insert_breakpoints_p)
{
  static CORE_ADDR next_pc;
  typedef char binsn_quantum[BREAKPOINT_MAX];
  static binsn_quantum break_mem;
  CORE_ADDR pc;

  if (insert_breakpoints_p)
    {
      pc = read_register (mips_regnum (current_gdbarch)->pc);
      next_pc = mips_next_pc (pc);

      target_insert_breakpoint (next_pc, break_mem);
    }
  else
    target_remove_breakpoint (next_pc, break_mem);
}

/* Test whether the PC points to the return instruction at the
   end of a function. */

static int
mips_about_to_return (CORE_ADDR pc)
{
  if (mips_pc_is_mips16 (pc))
    /* This mips16 case isn't necessarily reliable.  Sometimes the compiler
       generates a "jr $ra"; other times it generates code to load
       the return address from the stack to an accessible register (such
       as $a3), then a "jr" using that register.  This second case
       is almost impossible to distinguish from an indirect jump
       used for switch statements, so we don't even try.  */
    return mips_fetch_instruction (pc) == 0xe820;       /* jr $ra */
  else
    return mips_fetch_instruction (pc) == 0x3e00008;    /* jr $ra */
}


/* This fencepost looks highly suspicious to me.  Removing it also
   seems suspicious as it could affect remote debugging across serial
   lines.  */

static CORE_ADDR
heuristic_proc_start (CORE_ADDR pc)
{
  CORE_ADDR start_pc;
  CORE_ADDR fence;
  int instlen;
  int seen_adjsp = 0;

  pc = ADDR_BITS_REMOVE (pc);
  start_pc = pc;
  fence = start_pc - heuristic_fence_post;
  if (start_pc == 0)
    return 0;

  if (heuristic_fence_post == UINT_MAX || fence < VM_MIN_ADDRESS)
    fence = VM_MIN_ADDRESS;

  instlen = mips_pc_is_mips16 (pc) ? MIPS_INSN16_SIZE : MIPS_INSN32_SIZE;

  /* search back for previous return */
  for (start_pc -= instlen;; start_pc -= instlen)
    if (start_pc < fence)
      {
        /* It's not clear to me why we reach this point when
           stop_soon, but with this test, at least we
           don't print out warnings for every child forked (eg, on
           decstation).  22apr93 rich@cygnus.com.  */
        if (stop_soon == NO_STOP_QUIETLY)
          {
            static int blurb_printed = 0;

            warning ("GDB can't find the start of the function at 0x%s.",
                     paddr_nz (pc));

            if (!blurb_printed)
              {
                /* This actually happens frequently in embedded
                   development, when you first connect to a board
                   and your stack pointer and pc are nowhere in
                   particular.  This message needs to give people
                   in that situation enough information to
                   determine that it's no big deal.  */
                printf_filtered ("\n\
    GDB is unable to find the start of the function at 0x%s\n\
and thus can't determine the size of that function's stack frame.\n\
This means that GDB may be unable to access that stack frame, or\n\
the frames below it.\n\
    This problem is most likely caused by an invalid program counter or\n\
stack pointer.\n\
    However, if you think GDB should simply search farther back\n\
from 0x%s for code which looks like the beginning of a\n\
function, you can increase the range of the search using the `set\n\
heuristic-fence-post' command.\n", paddr_nz (pc), paddr_nz (pc));
                blurb_printed = 1;
              }
          }

        return 0;
      }
    else if (mips_pc_is_mips16 (start_pc))
      {
        unsigned short inst;

        /* On MIPS16, any one of the following is likely to be the
           start of a function:
           entry
           addiu sp,-n
           daddiu sp,-n
           extend -n followed by 'addiu sp,+n' or 'daddiu sp,+n'  */
        inst = mips_fetch_instruction (start_pc);
        if (((inst & 0xf81f) == 0xe809 && (inst & 0x700) != 0x700)      /* entry */
            || (inst & 0xff80) == 0x6380        /* addiu sp,-n */
            || (inst & 0xff80) == 0xfb80        /* daddiu sp,-n */
            || ((inst & 0xf810) == 0xf010 && seen_adjsp))       /* extend -n */
          break;
        else if ((inst & 0xff00) == 0x6300      /* addiu sp */
                 || (inst & 0xff00) == 0xfb00)  /* daddiu sp */
          seen_adjsp = 1;
        else
          seen_adjsp = 0;
      }
    else if (mips_about_to_return (start_pc))
      {
        /* Skip return and its delay slot.  */
        start_pc += 2 * MIPS_INSN32_SIZE;
        break;
      }

  return start_pc;
}

struct mips_objfile_private
{
  bfd_size_type size;
  char *contents;
};

/* According to the current ABI, should the type be passed in a
   floating-point register (assuming that there is space)?  When there
   is no FPU, FP are not even considered as possibile candidates for
   FP registers and, consequently this returns false - forces FP
   arguments into integer registers. */

static int
fp_register_arg_p (enum type_code typecode, struct type *arg_type)
{
  return ((typecode == TYPE_CODE_FLT
           || (MIPS_EABI
               && (typecode == TYPE_CODE_STRUCT
                   || typecode == TYPE_CODE_UNION)
               && TYPE_NFIELDS (arg_type) == 1
               && TYPE_CODE (TYPE_FIELD_TYPE (arg_type, 0)) == TYPE_CODE_FLT))
          && MIPS_FPU_TYPE != MIPS_FPU_NONE);
}

/* On o32, argument passing in GPRs depends on the alignment of the type being
   passed.  Return 1 if this type must be aligned to a doubleword boundary. */

static int
mips_type_needs_double_align (struct type *type)
{
  enum type_code typecode = TYPE_CODE (type);

  if (typecode == TYPE_CODE_FLT && TYPE_LENGTH (type) == 8)
    return 1;
  else if (typecode == TYPE_CODE_STRUCT)
    {
      if (TYPE_NFIELDS (type) < 1)
        return 0;
      return mips_type_needs_double_align (TYPE_FIELD_TYPE (type, 0));
    }
  else if (typecode == TYPE_CODE_UNION)
    {
      int i, n;

      n = TYPE_NFIELDS (type);
      for (i = 0; i < n; i++)
        if (mips_type_needs_double_align (TYPE_FIELD_TYPE (type, i)))
          return 1;
      return 0;
    }
  return 0;
}

/* Adjust the address downward (direction of stack growth) so that it
   is correctly aligned for a new stack frame.  */
static CORE_ADDR
mips_frame_align (struct gdbarch *gdbarch, CORE_ADDR addr)
{
  return align_down (addr, 16);
}

static CORE_ADDR
mips_eabi_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
                           struct regcache *regcache, CORE_ADDR bp_addr,
                           int nargs, struct value **args, CORE_ADDR sp,
                           int struct_return, CORE_ADDR struct_addr)
{
  int argreg;
  int float_argreg;
  int argnum;
  int len = 0;
  int stack_offset = 0;
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  CORE_ADDR func_addr = find_function_addr (function, NULL);

  /* For shared libraries, "t9" needs to point at the function
     address.  */
  regcache_cooked_write_signed (regcache, MIPS_T9_REGNUM, func_addr);

  /* Set the return address register to point to the entry point of
     the program, where a breakpoint lies in wait.  */
  regcache_cooked_write_signed (regcache, MIPS_RA_REGNUM, bp_addr);

  /* First ensure that the stack and structure return address (if any)
     are properly aligned.  The stack has to be at least 64-bit
     aligned even on 32-bit machines, because doubles must be 64-bit
     aligned.  For n32 and n64, stack frames need to be 128-bit
     aligned, so we round to this widest known alignment.  */

  sp = align_down (sp, 16);
  struct_addr = align_down (struct_addr, 16);

  /* Now make space on the stack for the args.  We allocate more
     than necessary for EABI, because the first few arguments are
     passed in registers, but that's OK.  */
  for (argnum = 0; argnum < nargs; argnum++)
    len += align_up (TYPE_LENGTH (value_type (args[argnum])),
                     mips_stack_argsize (gdbarch));
  sp -= align_up (len, 16);

  if (mips_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_eabi_push_dummy_call: sp=0x%s allocated %ld\n",
                        paddr_nz (sp), (long) align_up (len, 16));

  /* Initialize the integer and float register pointers.  */
  argreg = MIPS_A0_REGNUM;
  float_argreg = mips_fpa0_regnum (current_gdbarch);

  /* The struct_return pointer occupies the first parameter-passing reg.  */
  if (struct_return)
    {
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_eabi_push_dummy_call: struct_return reg=%d 0x%s\n",
                            argreg, paddr_nz (struct_addr));
      write_register (argreg++, struct_addr);
    }

  /* Now load as many as possible of the first arguments into
     registers, and push the rest onto the stack.  Loop thru args
     from first to last.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      char *val;
      char valbuf[MAX_REGISTER_SIZE];
      struct value *arg = args[argnum];
      struct type *arg_type = check_typedef (value_type (arg));
      int len = TYPE_LENGTH (arg_type);
      enum type_code typecode = TYPE_CODE (arg_type);

      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_eabi_push_dummy_call: %d len=%d type=%d",
                            argnum + 1, len, (int) typecode);

      /* The EABI passes structures that do not fit in a register by
         reference.  */
      if (len > mips_abi_regsize (gdbarch)
          && (typecode == TYPE_CODE_STRUCT || typecode == TYPE_CODE_UNION))
        {
          store_unsigned_integer (valbuf, mips_abi_regsize (gdbarch),
                                  VALUE_ADDRESS (arg));
          typecode = TYPE_CODE_PTR;
          len = mips_abi_regsize (gdbarch);
          val = valbuf;
          if (mips_debug)
            fprintf_unfiltered (gdb_stdlog, " push");
        }
      else
        val = (char *) VALUE_CONTENTS (arg);

      /* 32-bit ABIs always start floating point arguments in an
         even-numbered floating point register.  Round the FP register
         up before the check to see if there are any FP registers
         left.  Non MIPS_EABI targets also pass the FP in the integer
         registers so also round up normal registers.  */
      if (mips_abi_regsize (gdbarch) < 8
          && fp_register_arg_p (typecode, arg_type))
        {
          if ((float_argreg & 1))
            float_argreg++;
        }

      /* Floating point arguments passed in registers have to be
         treated specially.  On 32-bit architectures, doubles
         are passed in register pairs; the even register gets
         the low word, and the odd register gets the high word.
         On non-EABI processors, the first two floating point arguments are
         also copied to general registers, because MIPS16 functions
         don't use float registers for arguments.  This duplication of
         arguments in general registers can't hurt non-MIPS16 functions
         because those registers are normally skipped.  */
      /* MIPS_EABI squeezes a struct that contains a single floating
         point value into an FP register instead of pushing it onto the
         stack.  */
      if (fp_register_arg_p (typecode, arg_type)
          && float_argreg <= MIPS_LAST_FP_ARG_REGNUM)
        {
          if (mips_abi_regsize (gdbarch) < 8 && len == 8)
            {
              int low_offset = TARGET_BYTE_ORDER == BFD_ENDIAN_BIG ? 4 : 0;
              unsigned long regval;

              /* Write the low word of the double to the even register(s).  */
              regval = extract_unsigned_integer (val + low_offset, 4);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, 4));
              write_register (float_argreg++, regval);

              /* Write the high word of the double to the odd register(s).  */
              regval = extract_unsigned_integer (val + 4 - low_offset, 4);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, 4));
              write_register (float_argreg++, regval);
            }
          else
            {
              /* This is a floating point value that fits entirely
                 in a single register.  */
              /* On 32 bit ABI's the float_argreg is further adjusted
                 above to ensure that it is even register aligned.  */
              LONGEST regval = extract_unsigned_integer (val, len);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, len));
              write_register (float_argreg++, regval);
            }
        }
      else
        {
          /* Copy the argument to general registers or the stack in
             register-sized pieces.  Large arguments are split between
             registers and stack.  */
          /* Note: structs whose size is not a multiple of
             mips_abi_regsize() are treated specially: Irix cc passes
             them in registers where gcc sometimes puts them on the
             stack.  For maximum compatibility, we will put them in
             both places.  */
          int odd_sized_struct = ((len > mips_abi_regsize (gdbarch))
                                  && (len % mips_abi_regsize (gdbarch) != 0));

          /* Note: Floating-point values that didn't fit into an FP
             register are only written to memory.  */
          while (len > 0)
            {
              /* Remember if the argument was written to the stack.  */
              int stack_used_p = 0;
              int partial_len = (len < mips_abi_regsize (gdbarch)
                                 ? len : mips_abi_regsize (gdbarch));

              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " -- partial=%d",
                                    partial_len);

              /* Write this portion of the argument to the stack.  */
              if (argreg > MIPS_LAST_ARG_REGNUM
                  || odd_sized_struct
                  || fp_register_arg_p (typecode, arg_type))
                {
                  /* Should shorter than int integer values be
                     promoted to int before being stored? */
                  int longword_offset = 0;
                  CORE_ADDR addr;
                  stack_used_p = 1;
                  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
                    {
                      if (mips_stack_argsize (gdbarch) == 8
                          && (typecode == TYPE_CODE_INT
                              || typecode == TYPE_CODE_PTR
                              || typecode == TYPE_CODE_FLT) && len <= 4)
                        longword_offset = mips_stack_argsize (gdbarch) - len;
                      else if ((typecode == TYPE_CODE_STRUCT
                                || typecode == TYPE_CODE_UNION)
                               && (TYPE_LENGTH (arg_type)
                                   < mips_stack_argsize (gdbarch)))
                        longword_offset = mips_stack_argsize (gdbarch) - len;
                    }

                  if (mips_debug)
                    {
                      fprintf_unfiltered (gdb_stdlog, " - stack_offset=0x%s",
                                          paddr_nz (stack_offset));
                      fprintf_unfiltered (gdb_stdlog, " longword_offset=0x%s",
                                          paddr_nz (longword_offset));
                    }

                  addr = sp + stack_offset + longword_offset;

                  if (mips_debug)
                    {
                      int i;
                      fprintf_unfiltered (gdb_stdlog, " @0x%s ",
                                          paddr_nz (addr));
                      for (i = 0; i < partial_len; i++)
                        {
                          fprintf_unfiltered (gdb_stdlog, "%02x",
                                              val[i] & 0xff);
                        }
                    }
                  write_memory (addr, val, partial_len);
                }

              /* Note!!! This is NOT an else clause.  Odd sized
                 structs may go thru BOTH paths.  Floating point
                 arguments will not.  */
              /* Write this portion of the argument to a general
                 purpose register.  */
              if (argreg <= MIPS_LAST_ARG_REGNUM
                  && !fp_register_arg_p (typecode, arg_type))
                {
                  LONGEST regval =
                    extract_unsigned_integer (val, partial_len);

                  if (mips_debug)
                    fprintf_filtered (gdb_stdlog, " - reg=%d val=%s",
                                      argreg,
                                      phex (regval,
                                            mips_abi_regsize (gdbarch)));
                  write_register (argreg, regval);
                  argreg++;
                }

              len -= partial_len;
              val += partial_len;

              /* Compute the the offset into the stack at which we
                 will copy the next parameter.

                 In the new EABI (and the NABI32), the stack_offset
                 only needs to be adjusted when it has been used.  */

              if (stack_used_p)
                stack_offset += align_up (partial_len,
                                          mips_stack_argsize (gdbarch));
            }
        }
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog, "\n");
    }

  regcache_cooked_write_signed (regcache, MIPS_SP_REGNUM, sp);

  /* Return adjusted stack pointer.  */
  return sp;
}

/* Determin the return value convention being used.  */

static enum return_value_convention
mips_eabi_return_value (struct gdbarch *gdbarch,
                        struct type *type, struct regcache *regcache,
                        void *readbuf, const void *writebuf)
{
  if (TYPE_LENGTH (type) > 2 * mips_abi_regsize (gdbarch))
    return RETURN_VALUE_STRUCT_CONVENTION;
  if (readbuf)
    memset (readbuf, 0, TYPE_LENGTH (type));
  return RETURN_VALUE_REGISTER_CONVENTION;
}


/* N32/N64 ABI stuff.  */

static CORE_ADDR
mips_n32n64_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
                             struct regcache *regcache, CORE_ADDR bp_addr,
                             int nargs, struct value **args, CORE_ADDR sp,
                             int struct_return, CORE_ADDR struct_addr)
{
  int argreg;
  int float_argreg;
  int argnum;
  int len = 0;
  int stack_offset = 0;
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  CORE_ADDR func_addr = find_function_addr (function, NULL);

  /* For shared libraries, "t9" needs to point at the function
     address.  */
  regcache_cooked_write_signed (regcache, MIPS_T9_REGNUM, func_addr);

  /* Set the return address register to point to the entry point of
     the program, where a breakpoint lies in wait.  */
  regcache_cooked_write_signed (regcache, MIPS_RA_REGNUM, bp_addr);

  /* First ensure that the stack and structure return address (if any)
     are properly aligned.  The stack has to be at least 64-bit
     aligned even on 32-bit machines, because doubles must be 64-bit
     aligned.  For n32 and n64, stack frames need to be 128-bit
     aligned, so we round to this widest known alignment.  */

  sp = align_down (sp, 16);
  struct_addr = align_down (struct_addr, 16);

  /* Now make space on the stack for the args.  */
  for (argnum = 0; argnum < nargs; argnum++)
    len += align_up (TYPE_LENGTH (value_type (args[argnum])),
                     mips_stack_argsize (gdbarch));
  sp -= align_up (len, 16);

  if (mips_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_n32n64_push_dummy_call: sp=0x%s allocated %ld\n",
                        paddr_nz (sp), (long) align_up (len, 16));

  /* Initialize the integer and float register pointers.  */
  argreg = MIPS_A0_REGNUM;
  float_argreg = mips_fpa0_regnum (current_gdbarch);

  /* The struct_return pointer occupies the first parameter-passing reg.  */
  if (struct_return)
    {
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_n32n64_push_dummy_call: struct_return reg=%d 0x%s\n",
                            argreg, paddr_nz (struct_addr));
      write_register (argreg++, struct_addr);
    }

  /* Now load as many as possible of the first arguments into
     registers, and push the rest onto the stack.  Loop thru args
     from first to last.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      char *val;
      struct value *arg = args[argnum];
      struct type *arg_type = check_typedef (value_type (arg));
      int len = TYPE_LENGTH (arg_type);
      enum type_code typecode = TYPE_CODE (arg_type);

      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_n32n64_push_dummy_call: %d len=%d type=%d",
                            argnum + 1, len, (int) typecode);

      val = (char *) VALUE_CONTENTS (arg);

      if (fp_register_arg_p (typecode, arg_type)
          && float_argreg <= MIPS_LAST_FP_ARG_REGNUM)
        {
          /* This is a floating point value that fits entirely
             in a single register.  */
          /* On 32 bit ABI's the float_argreg is further adjusted
             above to ensure that it is even register aligned.  */
          LONGEST regval = extract_unsigned_integer (val, len);
          if (mips_debug)
            fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                float_argreg, phex (regval, len));
          write_register (float_argreg++, regval);

          if (mips_debug)
            fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                argreg, phex (regval, len));
          write_register (argreg, regval);
          argreg += 1;
        }
      else
        {
          /* Copy the argument to general registers or the stack in
             register-sized pieces.  Large arguments are split between
             registers and stack.  */
          /* Note: structs whose size is not a multiple of
             mips_abi_regsize() are treated specially: Irix cc passes
             them in registers where gcc sometimes puts them on the
             stack.  For maximum compatibility, we will put them in
             both places.  */
          int odd_sized_struct = ((len > mips_abi_regsize (gdbarch))
                                  && (len % mips_abi_regsize (gdbarch) != 0));
          /* Note: Floating-point values that didn't fit into an FP
             register are only written to memory.  */
          while (len > 0)
            {
              /* Rememer if the argument was written to the stack.  */
              int stack_used_p = 0;
              int partial_len = (len < mips_abi_regsize (gdbarch)
                                 ? len : mips_abi_regsize (gdbarch));

              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " -- partial=%d",
                                    partial_len);

              /* Write this portion of the argument to the stack.  */
              if (argreg > MIPS_LAST_ARG_REGNUM
                  || odd_sized_struct
                  || fp_register_arg_p (typecode, arg_type))
                {
                  /* Should shorter than int integer values be
                     promoted to int before being stored? */
                  int longword_offset = 0;
                  CORE_ADDR addr;
                  stack_used_p = 1;
                  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
                    {
                      if (mips_stack_argsize (gdbarch) == 8
                          && (typecode == TYPE_CODE_INT
                              || typecode == TYPE_CODE_PTR
                              || typecode == TYPE_CODE_FLT) && len <= 4)
                        longword_offset = mips_stack_argsize (gdbarch) - len;
                    }

                  if (mips_debug)
                    {
                      fprintf_unfiltered (gdb_stdlog, " - stack_offset=0x%s",
                                          paddr_nz (stack_offset));
                      fprintf_unfiltered (gdb_stdlog, " longword_offset=0x%s",
                                          paddr_nz (longword_offset));
                    }

                  addr = sp + stack_offset + longword_offset;

                  if (mips_debug)
                    {
                      int i;
                      fprintf_unfiltered (gdb_stdlog, " @0x%s ",
                                          paddr_nz (addr));
                      for (i = 0; i < partial_len; i++)
                        {
                          fprintf_unfiltered (gdb_stdlog, "%02x",
                                              val[i] & 0xff);
                        }
                    }
                  write_memory (addr, val, partial_len);
                }

              /* Note!!! This is NOT an else clause.  Odd sized
                 structs may go thru BOTH paths.  Floating point
                 arguments will not.  */
              /* Write this portion of the argument to a general
                 purpose register.  */
              if (argreg <= MIPS_LAST_ARG_REGNUM
                  && !fp_register_arg_p (typecode, arg_type))
                {
                  LONGEST regval =
                    extract_unsigned_integer (val, partial_len);

                  /* A non-floating-point argument being passed in a
                     general register.  If a struct or union, and if
                     the remaining length is smaller than the register
                     size, we have to adjust the register value on
                     big endian targets.

                     It does not seem to be necessary to do the
                     same for integral types.

                     cagney/2001-07-23: gdb/179: Also, GCC, when
                     outputting LE O32 with sizeof (struct) <
                     mips_abi_regsize(), generates a left shift as
                     part of storing the argument in a register a
                     register (the left shift isn't generated when
                     sizeof (struct) >= mips_abi_regsize()).  Since
                     it is quite possible that this is GCC
                     contradicting the LE/O32 ABI, GDB has not been
                     adjusted to accommodate this.  Either someone
                     needs to demonstrate that the LE/O32 ABI
                     specifies such a left shift OR this new ABI gets
                     identified as such and GDB gets tweaked
                     accordingly.  */

                  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
                      && partial_len < mips_abi_regsize (gdbarch)
                      && (typecode == TYPE_CODE_STRUCT ||
                          typecode == TYPE_CODE_UNION))
                    regval <<= ((mips_abi_regsize (gdbarch) - partial_len) *
                                TARGET_CHAR_BIT);

                  if (mips_debug)
                    fprintf_filtered (gdb_stdlog, " - reg=%d val=%s",
                                      argreg,
                                      phex (regval,
                                            mips_abi_regsize (gdbarch)));
                  write_register (argreg, regval);
                  argreg++;
                }

              len -= partial_len;
              val += partial_len;

              /* Compute the the offset into the stack at which we
                 will copy the next parameter.

                 In N32 (N64?), the stack_offset only needs to be
                 adjusted when it has been used.  */

              if (stack_used_p)
                stack_offset += align_up (partial_len,
                                          mips_stack_argsize (gdbarch));
            }
        }
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog, "\n");
    }

  regcache_cooked_write_signed (regcache, MIPS_SP_REGNUM, sp);

  /* Return adjusted stack pointer.  */
  return sp;
}

static enum return_value_convention
mips_n32n64_return_value (struct gdbarch *gdbarch,
                          struct type *type, struct regcache *regcache,
                          void *readbuf, const void *writebuf)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  if (TYPE_CODE (type) == TYPE_CODE_STRUCT
      || TYPE_CODE (type) == TYPE_CODE_UNION
      || TYPE_CODE (type) == TYPE_CODE_ARRAY
      || TYPE_LENGTH (type) > 2 * mips_abi_regsize (gdbarch))
    return RETURN_VALUE_STRUCT_CONVENTION;
  else if (TYPE_CODE (type) == TYPE_CODE_FLT
           && tdep->mips_fpu_type != MIPS_FPU_NONE)
    {
      /* A floating-point value belongs in the least significant part
         of FP0.  */
      if (mips_debug)
        fprintf_unfiltered (gdb_stderr, "Return float in $fp0\n");
      mips_xfer_register (regcache,
                          NUM_REGS + mips_regnum (current_gdbarch)->fp0,
                          TYPE_LENGTH (type),
                          TARGET_BYTE_ORDER, readbuf, writebuf, 0);
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
  else if (TYPE_CODE (type) == TYPE_CODE_STRUCT
           && TYPE_NFIELDS (type) <= 2
           && TYPE_NFIELDS (type) >= 1
           && ((TYPE_NFIELDS (type) == 1
                && (TYPE_CODE (TYPE_FIELD_TYPE (type, 0))
                    == TYPE_CODE_FLT))
               || (TYPE_NFIELDS (type) == 2
                   && (TYPE_CODE (TYPE_FIELD_TYPE (type, 0))
                       == TYPE_CODE_FLT)
                   && (TYPE_CODE (TYPE_FIELD_TYPE (type, 1))
                       == TYPE_CODE_FLT)))
           && tdep->mips_fpu_type != MIPS_FPU_NONE)
    {
      /* A struct that contains one or two floats.  Each value is part
         in the least significant part of their floating point
         register..  */
      int regnum;
      int field;
      for (field = 0, regnum = mips_regnum (current_gdbarch)->fp0;
           field < TYPE_NFIELDS (type); field++, regnum += 2)
        {
          int offset = (FIELD_BITPOS (TYPE_FIELDS (type)[field])
                        / TARGET_CHAR_BIT);
          if (mips_debug)
            fprintf_unfiltered (gdb_stderr, "Return float struct+%d\n",
                                offset);
          mips_xfer_register (regcache, NUM_REGS + regnum,
                              TYPE_LENGTH (TYPE_FIELD_TYPE (type, field)),
                              TARGET_BYTE_ORDER, readbuf, writebuf, offset);
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
  else if (TYPE_CODE (type) == TYPE_CODE_STRUCT
           || TYPE_CODE (type) == TYPE_CODE_UNION)
    {
      /* A structure or union.  Extract the left justified value,
         regardless of the byte order.  I.e. DO NOT USE
         mips_xfer_lower.  */
      int offset;
      int regnum;
      for (offset = 0, regnum = MIPS_V0_REGNUM;
           offset < TYPE_LENGTH (type);
           offset += register_size (current_gdbarch, regnum), regnum++)
        {
          int xfer = register_size (current_gdbarch, regnum);
          if (offset + xfer > TYPE_LENGTH (type))
            xfer = TYPE_LENGTH (type) - offset;
          if (mips_debug)
            fprintf_unfiltered (gdb_stderr, "Return struct+%d:%d in $%d\n",
                                offset, xfer, regnum);
          mips_xfer_register (regcache, NUM_REGS + regnum, xfer,
                              BFD_ENDIAN_UNKNOWN, readbuf, writebuf, offset);
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
  else
    {
      /* A scalar extract each part but least-significant-byte
         justified.  */
      int offset;
      int regnum;
      for (offset = 0, regnum = MIPS_V0_REGNUM;
           offset < TYPE_LENGTH (type);
           offset += register_size (current_gdbarch, regnum), regnum++)
        {
          int xfer = register_size (current_gdbarch, regnum);
          if (offset + xfer > TYPE_LENGTH (type))
            xfer = TYPE_LENGTH (type) - offset;
          if (mips_debug)
            fprintf_unfiltered (gdb_stderr, "Return scalar+%d:%d in $%d\n",
                                offset, xfer, regnum);
          mips_xfer_register (regcache, NUM_REGS + regnum, xfer,
                              TARGET_BYTE_ORDER, readbuf, writebuf, offset);
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
}

/* O32 ABI stuff.  */

static CORE_ADDR
mips_o32_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
                          struct regcache *regcache, CORE_ADDR bp_addr,
                          int nargs, struct value **args, CORE_ADDR sp,
                          int struct_return, CORE_ADDR struct_addr)
{
  int argreg;
  int float_argreg;
  int argnum;
  int len = 0;
  int stack_offset = 0;
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  CORE_ADDR func_addr = find_function_addr (function, NULL);

  /* For shared libraries, "t9" needs to point at the function
     address.  */
  regcache_cooked_write_signed (regcache, MIPS_T9_REGNUM, func_addr);

  /* Set the return address register to point to the entry point of
     the program, where a breakpoint lies in wait.  */
  regcache_cooked_write_signed (regcache, MIPS_RA_REGNUM, bp_addr);

  /* First ensure that the stack and structure return address (if any)
     are properly aligned.  The stack has to be at least 64-bit
     aligned even on 32-bit machines, because doubles must be 64-bit
     aligned.  For n32 and n64, stack frames need to be 128-bit
     aligned, so we round to this widest known alignment.  */

  sp = align_down (sp, 16);
  struct_addr = align_down (struct_addr, 16);

  /* Now make space on the stack for the args.  */
  for (argnum = 0; argnum < nargs; argnum++)
    len += align_up (TYPE_LENGTH (value_type (args[argnum])),
                     mips_stack_argsize (gdbarch));
  sp -= align_up (len, 16);

  if (mips_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_o32_push_dummy_call: sp=0x%s allocated %ld\n",
                        paddr_nz (sp), (long) align_up (len, 16));

  /* Initialize the integer and float register pointers.  */
  argreg = MIPS_A0_REGNUM;
  float_argreg = mips_fpa0_regnum (current_gdbarch);

  /* The struct_return pointer occupies the first parameter-passing reg.  */
  if (struct_return)
    {
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_o32_push_dummy_call: struct_return reg=%d 0x%s\n",
                            argreg, paddr_nz (struct_addr));
      write_register (argreg++, struct_addr);
      stack_offset += mips_stack_argsize (gdbarch);
    }

  /* Now load as many as possible of the first arguments into
     registers, and push the rest onto the stack.  Loop thru args
     from first to last.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      char *val;
      struct value *arg = args[argnum];
      struct type *arg_type = check_typedef (value_type (arg));
      int len = TYPE_LENGTH (arg_type);
      enum type_code typecode = TYPE_CODE (arg_type);

      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_o32_push_dummy_call: %d len=%d type=%d",
                            argnum + 1, len, (int) typecode);

      val = (char *) VALUE_CONTENTS (arg);

      /* 32-bit ABIs always start floating point arguments in an
         even-numbered floating point register.  Round the FP register
         up before the check to see if there are any FP registers
         left.  O32/O64 targets also pass the FP in the integer
         registers so also round up normal registers.  */
      if (mips_abi_regsize (gdbarch) < 8
          && fp_register_arg_p (typecode, arg_type))
        {
          if ((float_argreg & 1))
            float_argreg++;
        }

      /* Floating point arguments passed in registers have to be
         treated specially.  On 32-bit architectures, doubles
         are passed in register pairs; the even register gets
         the low word, and the odd register gets the high word.
         On O32/O64, the first two floating point arguments are
         also copied to general registers, because MIPS16 functions
         don't use float registers for arguments.  This duplication of
         arguments in general registers can't hurt non-MIPS16 functions
         because those registers are normally skipped.  */

      if (fp_register_arg_p (typecode, arg_type)
          && float_argreg <= MIPS_LAST_FP_ARG_REGNUM)
        {
          if (mips_abi_regsize (gdbarch) < 8 && len == 8)
            {
              int low_offset = TARGET_BYTE_ORDER == BFD_ENDIAN_BIG ? 4 : 0;
              unsigned long regval;

              /* Write the low word of the double to the even register(s).  */
              regval = extract_unsigned_integer (val + low_offset, 4);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, 4));
              write_register (float_argreg++, regval);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                    argreg, phex (regval, 4));
              write_register (argreg++, regval);

              /* Write the high word of the double to the odd register(s).  */
              regval = extract_unsigned_integer (val + 4 - low_offset, 4);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, 4));
              write_register (float_argreg++, regval);

              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                    argreg, phex (regval, 4));
              write_register (argreg++, regval);
            }
          else
            {
              /* This is a floating point value that fits entirely
                 in a single register.  */
              /* On 32 bit ABI's the float_argreg is further adjusted
                 above to ensure that it is even register aligned.  */
              LONGEST regval = extract_unsigned_integer (val, len);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, len));
              write_register (float_argreg++, regval);
              /* CAGNEY: 32 bit MIPS ABI's always reserve two FP
                 registers for each argument.  The below is (my
                 guess) to ensure that the corresponding integer
                 register has reserved the same space.  */
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                    argreg, phex (regval, len));
              write_register (argreg, regval);
              argreg += (mips_abi_regsize (gdbarch) == 8) ? 1 : 2;
            }
          /* Reserve space for the FP register.  */
          stack_offset += align_up (len, mips_stack_argsize (gdbarch));
        }
      else
        {
          /* Copy the argument to general registers or the stack in
             register-sized pieces.  Large arguments are split between
             registers and stack.  */
          /* Note: structs whose size is not a multiple of
             mips_abi_regsize() are treated specially: Irix cc passes
             them in registers where gcc sometimes puts them on the
             stack.  For maximum compatibility, we will put them in
             both places.  */
          int odd_sized_struct = ((len > mips_abi_regsize (gdbarch))
                                  && (len % mips_abi_regsize (gdbarch) != 0));
          /* Structures should be aligned to eight bytes (even arg registers)
             on MIPS_ABI_O32, if their first member has double precision.  */
          if (mips_abi_regsize (gdbarch) < 8
              && mips_type_needs_double_align (arg_type))
            {
              if ((argreg & 1))
                argreg++;
            }
          /* Note: Floating-point values that didn't fit into an FP
             register are only written to memory.  */
          while (len > 0)
            {
              /* Remember if the argument was written to the stack.  */
              int stack_used_p = 0;
              int partial_len = (len < mips_abi_regsize (gdbarch)
                                 ? len : mips_abi_regsize (gdbarch));

              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " -- partial=%d",
                                    partial_len);

              /* Write this portion of the argument to the stack.  */
              if (argreg > MIPS_LAST_ARG_REGNUM
                  || odd_sized_struct
                  || fp_register_arg_p (typecode, arg_type))
                {
                  /* Should shorter than int integer values be
                     promoted to int before being stored? */
                  int longword_offset = 0;
                  CORE_ADDR addr;
                  stack_used_p = 1;
                  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
                    {
                      if (mips_stack_argsize (gdbarch) == 8
                          && (typecode == TYPE_CODE_INT
                              || typecode == TYPE_CODE_PTR
                              || typecode == TYPE_CODE_FLT) && len <= 4)
                        longword_offset = mips_stack_argsize (gdbarch) - len;
                    }

                  if (mips_debug)
                    {
                      fprintf_unfiltered (gdb_stdlog, " - stack_offset=0x%s",
                                          paddr_nz (stack_offset));
                      fprintf_unfiltered (gdb_stdlog, " longword_offset=0x%s",
                                          paddr_nz (longword_offset));
                    }

                  addr = sp + stack_offset + longword_offset;

                  if (mips_debug)
                    {
                      int i;
                      fprintf_unfiltered (gdb_stdlog, " @0x%s ",
                                          paddr_nz (addr));
                      for (i = 0; i < partial_len; i++)
                        {
                          fprintf_unfiltered (gdb_stdlog, "%02x",
                                              val[i] & 0xff);
                        }
                    }
                  write_memory (addr, val, partial_len);
                }

              /* Note!!! This is NOT an else clause.  Odd sized
                 structs may go thru BOTH paths.  Floating point
                 arguments will not.  */
              /* Write this portion of the argument to a general
                 purpose register.  */
              if (argreg <= MIPS_LAST_ARG_REGNUM
                  && !fp_register_arg_p (typecode, arg_type))
                {
                  LONGEST regval = extract_signed_integer (val, partial_len);
                  /* Value may need to be sign extended, because
                     mips_isa_regsize() != mips_abi_regsize().  */

                  /* A non-floating-point argument being passed in a
                     general register.  If a struct or union, and if
                     the remaining length is smaller than the register
                     size, we have to adjust the register value on
                     big endian targets.

                     It does not seem to be necessary to do the
                     same for integral types.

                     Also don't do this adjustment on O64 binaries.

                     cagney/2001-07-23: gdb/179: Also, GCC, when
                     outputting LE O32 with sizeof (struct) <
                     mips_abi_regsize(), generates a left shift as
                     part of storing the argument in a register a
                     register (the left shift isn't generated when
                     sizeof (struct) >= mips_abi_regsize()).  Since
                     it is quite possible that this is GCC
                     contradicting the LE/O32 ABI, GDB has not been
                     adjusted to accommodate this.  Either someone
                     needs to demonstrate that the LE/O32 ABI
                     specifies such a left shift OR this new ABI gets
                     identified as such and GDB gets tweaked
                     accordingly.  */

                  if (mips_abi_regsize (gdbarch) < 8
                      && TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
                      && partial_len < mips_abi_regsize (gdbarch)
                      && (typecode == TYPE_CODE_STRUCT ||
                          typecode == TYPE_CODE_UNION))
                    regval <<= ((mips_abi_regsize (gdbarch) - partial_len) *
                                TARGET_CHAR_BIT);

                  if (mips_debug)
                    fprintf_filtered (gdb_stdlog, " - reg=%d val=%s",
                                      argreg,
                                      phex (regval,
                                            mips_abi_regsize (gdbarch)));
                  write_register (argreg, regval);
                  argreg++;

                  /* Prevent subsequent floating point arguments from
                     being passed in floating point registers.  */
                  float_argreg = MIPS_LAST_FP_ARG_REGNUM + 1;
                }

              len -= partial_len;
              val += partial_len;

              /* Compute the the offset into the stack at which we
                 will copy the next parameter.

                 In older ABIs, the caller reserved space for
                 registers that contained arguments.  This was loosely
                 refered to as their "home".  Consequently, space is
                 always allocated.  */

              stack_offset += align_up (partial_len,
                                        mips_stack_argsize (gdbarch));
            }
        }
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog, "\n");
    }

  regcache_cooked_write_signed (regcache, MIPS_SP_REGNUM, sp);

  /* Return adjusted stack pointer.  */
  return sp;
}

static enum return_value_convention
mips_o32_return_value (struct gdbarch *gdbarch, struct type *type,
                       struct regcache *regcache,
                       void *readbuf, const void *writebuf)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (TYPE_CODE (type) == TYPE_CODE_STRUCT
      || TYPE_CODE (type) == TYPE_CODE_UNION
      || TYPE_CODE (type) == TYPE_CODE_ARRAY)
    return RETURN_VALUE_STRUCT_CONVENTION;
  else if (TYPE_CODE (type) == TYPE_CODE_FLT
           && TYPE_LENGTH (type) == 4 && tdep->mips_fpu_type != MIPS_FPU_NONE)
    {
      /* A single-precision floating-point value.  It fits in the
         least significant part of FP0.  */
      if (mips_debug)
        fprintf_unfiltered (gdb_stderr, "Return float in $fp0\n");
      mips_xfer_register (regcache,
                          NUM_REGS + mips_regnum (current_gdbarch)->fp0,
                          TYPE_LENGTH (type),
                          TARGET_BYTE_ORDER, readbuf, writebuf, 0);
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
  else if (TYPE_CODE (type) == TYPE_CODE_FLT
           && TYPE_LENGTH (type) == 8 && tdep->mips_fpu_type != MIPS_FPU_NONE)
    {
      /* A double-precision floating-point value.  The most
         significant part goes in FP1, and the least significant in
         FP0.  */
      if (mips_debug)
        fprintf_unfiltered (gdb_stderr, "Return float in $fp1/$fp0\n");
      switch (TARGET_BYTE_ORDER)
        {
        case BFD_ENDIAN_LITTLE:
          mips_xfer_register (regcache,
                              NUM_REGS + mips_regnum (current_gdbarch)->fp0 +
                              0, 4, TARGET_BYTE_ORDER, readbuf, writebuf, 0);
          mips_xfer_register (regcache,
                              NUM_REGS + mips_regnum (current_gdbarch)->fp0 +
                              1, 4, TARGET_BYTE_ORDER, readbuf, writebuf, 4);
          break;
        case BFD_ENDIAN_BIG:
          mips_xfer_register (regcache,
                              NUM_REGS + mips_regnum (current_gdbarch)->fp0 +
                              1, 4, TARGET_BYTE_ORDER, readbuf, writebuf, 0);
          mips_xfer_register (regcache,
                              NUM_REGS + mips_regnum (current_gdbarch)->fp0 +
                              0, 4, TARGET_BYTE_ORDER, readbuf, writebuf, 4);
          break;
        default:
          internal_error (__FILE__, __LINE__, "bad switch");
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
#if 0
  else if (TYPE_CODE (type) == TYPE_CODE_STRUCT
           && TYPE_NFIELDS (type) <= 2
           && TYPE_NFIELDS (type) >= 1
           && ((TYPE_NFIELDS (type) == 1
                && (TYPE_CODE (TYPE_FIELD_TYPE (type, 0))
                    == TYPE_CODE_FLT))
               || (TYPE_NFIELDS (type) == 2
                   && (TYPE_CODE (TYPE_FIELD_TYPE (type, 0))
                       == TYPE_CODE_FLT)
                   && (TYPE_CODE (TYPE_FIELD_TYPE (type, 1))
                       == TYPE_CODE_FLT)))
           && tdep->mips_fpu_type != MIPS_FPU_NONE)
    {
      /* A struct that contains one or two floats.  Each value is part
         in the least significant part of their floating point
         register..  */
      bfd_byte reg[MAX_REGISTER_SIZE];
      int regnum;
      int field;
      for (field = 0, regnum = mips_regnum (current_gdbarch)->fp0;
           field < TYPE_NFIELDS (type); field++, regnum += 2)
        {
          int offset = (FIELD_BITPOS (TYPE_FIELDS (type)[field])
                        / TARGET_CHAR_BIT);
          if (mips_debug)
            fprintf_unfiltered (gdb_stderr, "Return float struct+%d\n",
                                offset);
          mips_xfer_register (regcache, NUM_REGS + regnum,
                              TYPE_LENGTH (TYPE_FIELD_TYPE (type, field)),
                              TARGET_BYTE_ORDER, readbuf, writebuf, offset);
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
#endif
#if 0
  else if (TYPE_CODE (type) == TYPE_CODE_STRUCT
           || TYPE_CODE (type) == TYPE_CODE_UNION)
    {
      /* A structure or union.  Extract the left justified value,
         regardless of the byte order.  I.e. DO NOT USE
         mips_xfer_lower.  */
      int offset;
      int regnum;
      for (offset = 0, regnum = MIPS_V0_REGNUM;
           offset < TYPE_LENGTH (type);
           offset += register_size (current_gdbarch, regnum), regnum++)
        {
          int xfer = register_size (current_gdbarch, regnum);
          if (offset + xfer > TYPE_LENGTH (type))
            xfer = TYPE_LENGTH (type) - offset;
          if (mips_debug)
            fprintf_unfiltered (gdb_stderr, "Return struct+%d:%d in $%d\n",
                                offset, xfer, regnum);
          mips_xfer_register (regcache, NUM_REGS + regnum, xfer,
                              BFD_ENDIAN_UNKNOWN, readbuf, writebuf, offset);
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
#endif
  else
    {
      /* A scalar extract each part but least-significant-byte
         justified.  o32 thinks registers are 4 byte, regardless of
         the ISA.  mips_stack_argsize controls this.  */
      int offset;
      int regnum;
      for (offset = 0, regnum = MIPS_V0_REGNUM;
           offset < TYPE_LENGTH (type);
           offset += mips_stack_argsize (gdbarch), regnum++)
        {
          int xfer = mips_stack_argsize (gdbarch);
          if (offset + xfer > TYPE_LENGTH (type))
            xfer = TYPE_LENGTH (type) - offset;
          if (mips_debug)
            fprintf_unfiltered (gdb_stderr, "Return scalar+%d:%d in $%d\n",
                                offset, xfer, regnum);
          mips_xfer_register (regcache, NUM_REGS + regnum, xfer,
                              TARGET_BYTE_ORDER, readbuf, writebuf, offset);
        }
      return RETURN_VALUE_REGISTER_CONVENTION;
    }
}

/* O64 ABI.  This is a hacked up kind of 64-bit version of the o32
   ABI.  */

static CORE_ADDR
mips_o64_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
                          struct regcache *regcache, CORE_ADDR bp_addr,
                          int nargs,
                          struct value **args, CORE_ADDR sp,
                          int struct_return, CORE_ADDR struct_addr)
{
  int argreg;
  int float_argreg;
  int argnum;
  int len = 0;
  int stack_offset = 0;
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  CORE_ADDR func_addr = find_function_addr (function, NULL);

  /* For shared libraries, "t9" needs to point at the function
     address.  */
  regcache_cooked_write_signed (regcache, MIPS_T9_REGNUM, func_addr);

  /* Set the return address register to point to the entry point of
     the program, where a breakpoint lies in wait.  */
  regcache_cooked_write_signed (regcache, MIPS_RA_REGNUM, bp_addr);

  /* First ensure that the stack and structure return address (if any)
     are properly aligned.  The stack has to be at least 64-bit
     aligned even on 32-bit machines, because doubles must be 64-bit
     aligned.  For n32 and n64, stack frames need to be 128-bit
     aligned, so we round to this widest known alignment.  */

  sp = align_down (sp, 16);
  struct_addr = align_down (struct_addr, 16);

  /* Now make space on the stack for the args.  */
  for (argnum = 0; argnum < nargs; argnum++)
    len += align_up (TYPE_LENGTH (value_type (args[argnum])),
                     mips_stack_argsize (gdbarch));
  sp -= align_up (len, 16);

  if (mips_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_o64_push_dummy_call: sp=0x%s allocated %ld\n",
                        paddr_nz (sp), (long) align_up (len, 16));

  /* Initialize the integer and float register pointers.  */
  argreg = MIPS_A0_REGNUM;
  float_argreg = mips_fpa0_regnum (current_gdbarch);

  /* The struct_return pointer occupies the first parameter-passing reg.  */
  if (struct_return)
    {
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_o64_push_dummy_call: struct_return reg=%d 0x%s\n",
                            argreg, paddr_nz (struct_addr));
      write_register (argreg++, struct_addr);
      stack_offset += mips_stack_argsize (gdbarch);
    }

  /* Now load as many as possible of the first arguments into
     registers, and push the rest onto the stack.  Loop thru args
     from first to last.  */
  for (argnum = 0; argnum < nargs; argnum++)
    {
      char *val;
      struct value *arg = args[argnum];
      struct type *arg_type = check_typedef (value_type (arg));
      int len = TYPE_LENGTH (arg_type);
      enum type_code typecode = TYPE_CODE (arg_type);

      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "mips_o64_push_dummy_call: %d len=%d type=%d",
                            argnum + 1, len, (int) typecode);

      val = (char *) VALUE_CONTENTS (arg);

      /* 32-bit ABIs always start floating point arguments in an
         even-numbered floating point register.  Round the FP register
         up before the check to see if there are any FP registers
         left.  O32/O64 targets also pass the FP in the integer
         registers so also round up normal registers.  */
      if (mips_abi_regsize (gdbarch) < 8
          && fp_register_arg_p (typecode, arg_type))
        {
          if ((float_argreg & 1))
            float_argreg++;
        }

      /* Floating point arguments passed in registers have to be
         treated specially.  On 32-bit architectures, doubles
         are passed in register pairs; the even register gets
         the low word, and the odd register gets the high word.
         On O32/O64, the first two floating point arguments are
         also copied to general registers, because MIPS16 functions
         don't use float registers for arguments.  This duplication of
         arguments in general registers can't hurt non-MIPS16 functions
         because those registers are normally skipped.  */

      if (fp_register_arg_p (typecode, arg_type)
          && float_argreg <= MIPS_LAST_FP_ARG_REGNUM)
        {
          if (mips_abi_regsize (gdbarch) < 8 && len == 8)
            {
              int low_offset = TARGET_BYTE_ORDER == BFD_ENDIAN_BIG ? 4 : 0;
              unsigned long regval;

              /* Write the low word of the double to the even register(s).  */
              regval = extract_unsigned_integer (val + low_offset, 4);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, 4));
              write_register (float_argreg++, regval);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                    argreg, phex (regval, 4));
              write_register (argreg++, regval);

              /* Write the high word of the double to the odd register(s).  */
              regval = extract_unsigned_integer (val + 4 - low_offset, 4);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, 4));
              write_register (float_argreg++, regval);

              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                    argreg, phex (regval, 4));
              write_register (argreg++, regval);
            }
          else
            {
              /* This is a floating point value that fits entirely
                 in a single register.  */
              /* On 32 bit ABI's the float_argreg is further adjusted
                 above to ensure that it is even register aligned.  */
              LONGEST regval = extract_unsigned_integer (val, len);
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - fpreg=%d val=%s",
                                    float_argreg, phex (regval, len));
              write_register (float_argreg++, regval);
              /* CAGNEY: 32 bit MIPS ABI's always reserve two FP
                 registers for each argument.  The below is (my
                 guess) to ensure that the corresponding integer
                 register has reserved the same space.  */
              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " - reg=%d val=%s",
                                    argreg, phex (regval, len));
              write_register (argreg, regval);
              argreg += (mips_abi_regsize (gdbarch) == 8) ? 1 : 2;
            }
          /* Reserve space for the FP register.  */
          stack_offset += align_up (len, mips_stack_argsize (gdbarch));
        }
      else
        {
          /* Copy the argument to general registers or the stack in
             register-sized pieces.  Large arguments are split between
             registers and stack.  */
          /* Note: structs whose size is not a multiple of
             mips_abi_regsize() are treated specially: Irix cc passes
             them in registers where gcc sometimes puts them on the
             stack.  For maximum compatibility, we will put them in
             both places.  */
          int odd_sized_struct = ((len > mips_abi_regsize (gdbarch))
                                  && (len % mips_abi_regsize (gdbarch) != 0));
          /* Structures should be aligned to eight bytes (even arg registers)
             on MIPS_ABI_O32, if their first member has double precision.  */
          if (mips_abi_regsize (gdbarch) < 8
              && mips_type_needs_double_align (arg_type))
            {
              if ((argreg & 1))
                argreg++;
            }
          /* Note: Floating-point values that didn't fit into an FP
             register are only written to memory.  */
          while (len > 0)
            {
              /* Remember if the argument was written to the stack.  */
              int stack_used_p = 0;
              int partial_len = (len < mips_abi_regsize (gdbarch)
                                 ? len : mips_abi_regsize (gdbarch));

              if (mips_debug)
                fprintf_unfiltered (gdb_stdlog, " -- partial=%d",
                                    partial_len);

              /* Write this portion of the argument to the stack.  */
              if (argreg > MIPS_LAST_ARG_REGNUM
                  || odd_sized_struct
                  || fp_register_arg_p (typecode, arg_type))
                {
                  /* Should shorter than int integer values be
                     promoted to int before being stored? */
                  int longword_offset = 0;
                  CORE_ADDR addr;
                  stack_used_p = 1;
                  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
                    {
                      if (mips_stack_argsize (gdbarch) == 8
                          && (typecode == TYPE_CODE_INT
                              || typecode == TYPE_CODE_PTR
                              || typecode == TYPE_CODE_FLT) && len <= 4)
                        longword_offset = mips_stack_argsize (gdbarch) - len;
                    }

                  if (mips_debug)
                    {
                      fprintf_unfiltered (gdb_stdlog, " - stack_offset=0x%s",
                                          paddr_nz (stack_offset));
                      fprintf_unfiltered (gdb_stdlog, " longword_offset=0x%s",
                                          paddr_nz (longword_offset));
                    }

                  addr = sp + stack_offset + longword_offset;

                  if (mips_debug)
                    {
                      int i;
                      fprintf_unfiltered (gdb_stdlog, " @0x%s ",
                                          paddr_nz (addr));
                      for (i = 0; i < partial_len; i++)
                        {
                          fprintf_unfiltered (gdb_stdlog, "%02x",
                                              val[i] & 0xff);
                        }
                    }
                  write_memory (addr, val, partial_len);
                }

              /* Note!!! This is NOT an else clause.  Odd sized
                 structs may go thru BOTH paths.  Floating point
                 arguments will not.  */
              /* Write this portion of the argument to a general
                 purpose register.  */
              if (argreg <= MIPS_LAST_ARG_REGNUM
                  && !fp_register_arg_p (typecode, arg_type))
                {
                  LONGEST regval = extract_signed_integer (val, partial_len);
                  /* Value may need to be sign extended, because
                     mips_isa_regsize() != mips_abi_regsize().  */

                  /* A non-floating-point argument being passed in a
                     general register.  If a struct or union, and if
                     the remaining length is smaller than the register
                     size, we have to adjust the register value on
                     big endian targets.

                     It does not seem to be necessary to do the
                     same for integral types.

                     Also don't do this adjustment on O64 binaries.

                     cagney/2001-07-23: gdb/179: Also, GCC, when
                     outputting LE O32 with sizeof (struct) <
                     mips_abi_regsize(), generates a left shift as
                     part of storing the argument in a register a
                     register (the left shift isn't generated when
                     sizeof (struct) >= mips_abi_regsize()).  Since
                     it is quite possible that this is GCC
                     contradicting the LE/O32 ABI, GDB has not been
                     adjusted to accommodate this.  Either someone
                     needs to demonstrate that the LE/O32 ABI
                     specifies such a left shift OR this new ABI gets
                     identified as such and GDB gets tweaked
                     accordingly.  */

                  if (mips_abi_regsize (gdbarch) < 8
                      && TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
                      && partial_len < mips_abi_regsize (gdbarch)
                      && (typecode == TYPE_CODE_STRUCT ||
                          typecode == TYPE_CODE_UNION))
                    regval <<= ((mips_abi_regsize (gdbarch) - partial_len) *
                                TARGET_CHAR_BIT);

                  if (mips_debug)
                    fprintf_filtered (gdb_stdlog, " - reg=%d val=%s",
                                      argreg,
                                      phex (regval,
                                            mips_abi_regsize (gdbarch)));
                  write_register (argreg, regval);
                  argreg++;

                  /* Prevent subsequent floating point arguments from
                     being passed in floating point registers.  */
                  float_argreg = MIPS_LAST_FP_ARG_REGNUM + 1;
                }

              len -= partial_len;
              val += partial_len;

              /* Compute the the offset into the stack at which we
                 will copy the next parameter.

                 In older ABIs, the caller reserved space for
                 registers that contained arguments.  This was loosely
                 refered to as their "home".  Consequently, space is
                 always allocated.  */

              stack_offset += align_up (partial_len,
                                        mips_stack_argsize (gdbarch));
            }
        }
      if (mips_debug)
        fprintf_unfiltered (gdb_stdlog, "\n");
    }

  regcache_cooked_write_signed (regcache, MIPS_SP_REGNUM, sp);

  /* Return adjusted stack pointer.  */
  return sp;
}

static enum return_value_convention
mips_o64_return_value (struct gdbarch *gdbarch,
                       struct type *type, struct regcache *regcache,
                       void *readbuf, const void *writebuf)
{
  return RETURN_VALUE_STRUCT_CONVENTION;
}

/* Floating point register management.

   Background: MIPS1 & 2 fp registers are 32 bits wide.  To support
   64bit operations, these early MIPS cpus treat fp register pairs
   (f0,f1) as a single register (d0).  Later MIPS cpu's have 64 bit fp
   registers and offer a compatibility mode that emulates the MIPS2 fp
   model.  When operating in MIPS2 fp compat mode, later cpu's split
   double precision floats into two 32-bit chunks and store them in
   consecutive fp regs.  To display 64-bit floats stored in this
   fashion, we have to combine 32 bits from f0 and 32 bits from f1.
   Throw in user-configurable endianness and you have a real mess.

   The way this works is:
     - If we are in 32-bit mode or on a 32-bit processor, then a 64-bit
       double-precision value will be split across two logical registers.
       The lower-numbered logical register will hold the low-order bits,
       regardless of the processor's endianness.
     - If we are on a 64-bit processor, and we are looking for a
       single-precision value, it will be in the low ordered bits
       of a 64-bit GPR (after mfc1, for example) or a 64-bit register
       save slot in memory.
     - If we are in 64-bit mode, everything is straightforward.

   Note that this code only deals with "live" registers at the top of the
   stack.  We will attempt to deal with saved registers later, when
   the raw/cooked register interface is in place. (We need a general
   interface that can deal with dynamic saved register sizes -- fp
   regs could be 32 bits wide in one frame and 64 on the frame above
   and below).  */

static struct type *
mips_float_register_type (void)
{
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    return builtin_type_ieee_single_big;
  else
    return builtin_type_ieee_single_little;
}

static struct type *
mips_double_register_type (void)
{
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    return builtin_type_ieee_double_big;
  else
    return builtin_type_ieee_double_little;
}

/* Copy a 32-bit single-precision value from the current frame
   into rare_buffer.  */

static void
mips_read_fp_register_single (struct frame_info *frame, int regno,
                              char *rare_buffer)
{
  int raw_size = register_size (current_gdbarch, regno);
  char *raw_buffer = alloca (raw_size);

  if (!frame_register_read (frame, regno, raw_buffer))
    error ("can't read register %d (%s)", regno, REGISTER_NAME (regno));
  if (raw_size == 8)
    {
      /* We have a 64-bit value for this register.  Find the low-order
         32 bits.  */
      int offset;

      if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
        offset = 4;
      else
        offset = 0;

      memcpy (rare_buffer, raw_buffer + offset, 4);
    }
  else
    {
      memcpy (rare_buffer, raw_buffer, 4);
    }
}

/* Copy a 64-bit double-precision value from the current frame into
   rare_buffer.  This may include getting half of it from the next
   register.  */

static void
mips_read_fp_register_double (struct frame_info *frame, int regno,
                              char *rare_buffer)
{
  int raw_size = register_size (current_gdbarch, regno);

  if (raw_size == 8 && !mips2_fp_compat ())
    {
      /* We have a 64-bit value for this register, and we should use
         all 64 bits.  */
      if (!frame_register_read (frame, regno, rare_buffer))
        error ("can't read register %d (%s)", regno, REGISTER_NAME (regno));
    }
  else
    {
      if ((regno - mips_regnum (current_gdbarch)->fp0) & 1)
        internal_error (__FILE__, __LINE__,
                        "mips_read_fp_register_double: bad access to "
                        "odd-numbered FP register");

      /* mips_read_fp_register_single will find the correct 32 bits from
         each register.  */
      if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
        {
          mips_read_fp_register_single (frame, regno, rare_buffer + 4);
          mips_read_fp_register_single (frame, regno + 1, rare_buffer);
        }
      else
        {
          mips_read_fp_register_single (frame, regno, rare_buffer);
          mips_read_fp_register_single (frame, regno + 1, rare_buffer + 4);
        }
    }
}

static void
mips_print_fp_register (struct ui_file *file, struct frame_info *frame,
                        int regnum)
{                               /* do values for FP (float) regs */
  char *raw_buffer;
  double doub, flt1;    /* doubles extracted from raw hex data */
  int inv1, inv2;

  raw_buffer =
    (char *) alloca (2 *
                     register_size (current_gdbarch,
                                    mips_regnum (current_gdbarch)->fp0));

  fprintf_filtered (file, "%s:", REGISTER_NAME (regnum));
  fprintf_filtered (file, "%*s", 4 - (int) strlen (REGISTER_NAME (regnum)),
                    "");

  if (register_size (current_gdbarch, regnum) == 4 || mips2_fp_compat ())
    {
      /* 4-byte registers: Print hex and floating.  Also print even
         numbered registers as doubles.  */
      mips_read_fp_register_single (frame, regnum, raw_buffer);
      flt1 = unpack_double (mips_float_register_type (), raw_buffer, &inv1);

      print_scalar_formatted (raw_buffer, builtin_type_uint32, 'x', 'w',
                              file);

      fprintf_filtered (file, " flt: ");
      if (inv1)
        fprintf_filtered (file, " <invalid float> ");
      else
        fprintf_filtered (file, "%-17.9g", flt1);

      if (regnum % 2 == 0)
        {
          mips_read_fp_register_double (frame, regnum, raw_buffer);
          doub = unpack_double (mips_double_register_type (), raw_buffer,
                                &inv2);

          fprintf_filtered (file, " dbl: ");
          if (inv2)
            fprintf_filtered (file, "<invalid double>");
          else
            fprintf_filtered (file, "%-24.17g", doub);
        }
    }
  else
    {
      /* Eight byte registers: print each one as hex, float and double.  */
      mips_read_fp_register_single (frame, regnum, raw_buffer);
      flt1 = unpack_double (mips_float_register_type (), raw_buffer, &inv1);

      mips_read_fp_register_double (frame, regnum, raw_buffer);
      doub = unpack_double (mips_double_register_type (), raw_buffer, &inv2);


      print_scalar_formatted (raw_buffer, builtin_type_uint64, 'x', 'g',
                              file);

      fprintf_filtered (file, " flt: ");
      if (inv1)
        fprintf_filtered (file, "<invalid float>");
      else
        fprintf_filtered (file, "%-17.9g", flt1);

      fprintf_filtered (file, " dbl: ");
      if (inv2)
        fprintf_filtered (file, "<invalid double>");
      else
        fprintf_filtered (file, "%-24.17g", doub);
    }
}

static void
mips_print_register (struct ui_file *file, struct frame_info *frame,
                     int regnum, int all)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  char raw_buffer[MAX_REGISTER_SIZE];
  int offset;

  if (TYPE_CODE (gdbarch_register_type (gdbarch, regnum)) == TYPE_CODE_FLT)
    {
      mips_print_fp_register (file, frame, regnum);
      return;
    }

  /* Get the data in raw format.  */
  if (!frame_register_read (frame, regnum, raw_buffer))
    {
      fprintf_filtered (file, "%s: [Invalid]", REGISTER_NAME (regnum));
      return;
    }

  fputs_filtered (REGISTER_NAME (regnum), file);

  /* The problem with printing numeric register names (r26, etc.) is that
     the user can't use them on input.  Probably the best solution is to
     fix it so that either the numeric or the funky (a2, etc.) names
     are accepted on input.  */
  if (regnum < MIPS_NUMREGS)
    fprintf_filtered (file, "(r%d): ", regnum);
  else
    fprintf_filtered (file, ": ");

  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    offset =
      register_size (current_gdbarch,
                     regnum) - register_size (current_gdbarch, regnum);
  else
    offset = 0;

  print_scalar_formatted (raw_buffer + offset,
                          gdbarch_register_type (gdbarch, regnum), 'x', 0,
                          file);
}

/* Replacement for generic do_registers_info.
   Print regs in pretty columns.  */

static int
print_fp_register_row (struct ui_file *file, struct frame_info *frame,
                       int regnum)
{
  fprintf_filtered (file, " ");
  mips_print_fp_register (file, frame, regnum);
  fprintf_filtered (file, "\n");
  return regnum + 1;
}


/* Print a row's worth of GP (int) registers, with name labels above */

static int
print_gp_register_row (struct ui_file *file, struct frame_info *frame,
                       int start_regnum)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  /* do values for GP (int) regs */
  char raw_buffer[MAX_REGISTER_SIZE];
  int ncols = (mips_abi_regsize (gdbarch) == 8 ? 4 : 8);        /* display cols per row */
  int col, byte;
  int regnum;

  /* For GP registers, we print a separate row of names above the vals */
  fprintf_filtered (file, "     ");
  for (col = 0, regnum = start_regnum;
       col < ncols && regnum < NUM_REGS + NUM_PSEUDO_REGS; regnum++)
    {
      if (*REGISTER_NAME (regnum) == '\0')
        continue;               /* unused register */
      if (TYPE_CODE (gdbarch_register_type (gdbarch, regnum)) ==
          TYPE_CODE_FLT)
        break;                  /* end the row: reached FP register */
      fprintf_filtered (file,
                        mips_abi_regsize (current_gdbarch) == 8 ? "%17s" : "%9s",
                        REGISTER_NAME (regnum));
      col++;
    }
  /* print the R0 to R31 names */
  if ((start_regnum % NUM_REGS) < MIPS_NUMREGS)
    fprintf_filtered (file, "\n R%-4d", start_regnum % NUM_REGS);
  else
    fprintf_filtered (file, "\n      ");

  /* now print the values in hex, 4 or 8 to the row */
  for (col = 0, regnum = start_regnum;
       col < ncols && regnum < NUM_REGS + NUM_PSEUDO_REGS; regnum++)
    {
      if (*REGISTER_NAME (regnum) == '\0')
        continue;               /* unused register */
      if (TYPE_CODE (gdbarch_register_type (gdbarch, regnum)) ==
          TYPE_CODE_FLT)
        break;                  /* end row: reached FP register */
      /* OK: get the data in raw format.  */
      if (!frame_register_read (frame, regnum, raw_buffer))
        error ("can't read register %d (%s)", regnum, REGISTER_NAME (regnum));
      /* pad small registers */
      for (byte = 0;
           byte < (mips_abi_regsize (current_gdbarch)
                   - register_size (current_gdbarch, regnum)); byte++)
        printf_filtered ("  ");
      /* Now print the register value in hex, endian order. */
      if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
        for (byte =
             register_size (current_gdbarch,
                            regnum) - register_size (current_gdbarch, regnum);
             byte < register_size (current_gdbarch, regnum); byte++)
          fprintf_filtered (file, "%02x", (unsigned char) raw_buffer[byte]);
      else
        for (byte = register_size (current_gdbarch, regnum) - 1;
             byte >= 0; byte--)
          fprintf_filtered (file, "%02x", (unsigned char) raw_buffer[byte]);
      fprintf_filtered (file, " ");
      col++;
    }
  if (col > 0)                  /* ie. if we actually printed anything... */
    fprintf_filtered (file, "\n");

  return regnum;
}

/* MIPS_DO_REGISTERS_INFO(): called by "info register" command */

static void
mips_print_registers_info (struct gdbarch *gdbarch, struct ui_file *file,
                           struct frame_info *frame, int regnum, int all)
{
  if (regnum != -1)             /* do one specified register */
    {
      gdb_assert (regnum >= NUM_REGS);
      if (*(REGISTER_NAME (regnum)) == '\0')
        error ("Not a valid register for the current processor type");

      mips_print_register (file, frame, regnum, 0);
      fprintf_filtered (file, "\n");
    }
  else
    /* do all (or most) registers */
    {
      regnum = NUM_REGS;
      while (regnum < NUM_REGS + NUM_PSEUDO_REGS)
        {
          if (TYPE_CODE (gdbarch_register_type (gdbarch, regnum)) ==
              TYPE_CODE_FLT)
            {
              if (all)          /* true for "INFO ALL-REGISTERS" command */
                regnum = print_fp_register_row (file, frame, regnum);
              else
                regnum += MIPS_NUMREGS; /* skip floating point regs */
            }
          else
            regnum = print_gp_register_row (file, frame, regnum);
        }
    }
}

/* Is this a branch with a delay slot?  */

static int
is_delayed (unsigned long insn)
{
  int i;
  for (i = 0; i < NUMOPCODES; ++i)
    if (mips_opcodes[i].pinfo != INSN_MACRO
        && (insn & mips_opcodes[i].mask) == mips_opcodes[i].match)
      break;
  return (i < NUMOPCODES
          && (mips_opcodes[i].pinfo & (INSN_UNCOND_BRANCH_DELAY
                                       | INSN_COND_BRANCH_DELAY
                                       | INSN_COND_BRANCH_LIKELY)));
}

int
mips_single_step_through_delay (struct gdbarch *gdbarch,
                                struct frame_info *frame)
{
  CORE_ADDR pc = get_frame_pc (frame);
  char buf[MIPS_INSN32_SIZE];

  /* There is no branch delay slot on MIPS16.  */
  if (mips_pc_is_mips16 (pc))
    return 0;

  if (!safe_frame_unwind_memory (frame, pc, buf, sizeof buf))
    /* If error reading memory, guess that it is not a delayed
       branch.  */
    return 0;
  return is_delayed (extract_unsigned_integer (buf, sizeof buf));
}

/* To skip prologues, I use this predicate.  Returns either PC itself
   if the code at PC does not look like a function prologue; otherwise
   returns an address that (if we're lucky) follows the prologue.  If
   LENIENT, then we must skip everything which is involved in setting
   up the frame (it's OK to skip more, just so long as we don't skip
   anything which might clobber the registers which are being saved.
   We must skip more in the case where part of the prologue is in the
   delay slot of a non-prologue instruction).  */

static CORE_ADDR
mips_skip_prologue (CORE_ADDR pc)
{
  CORE_ADDR limit_pc;
  CORE_ADDR func_addr;

  /* See if we can determine the end of the prologue via the symbol table.
     If so, then return either PC, or the PC after the prologue, whichever
     is greater.  */
  if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
    {
      CORE_ADDR post_prologue_pc = skip_prologue_using_sal (func_addr);
      if (post_prologue_pc != 0)
        return max (pc, post_prologue_pc);
    }

  /* Can't determine prologue from the symbol table, need to examine
     instructions.  */

  /* Find an upper limit on the function prologue using the debug
     information.  If the debug information could not be used to provide
     that bound, then use an arbitrary large number as the upper bound.  */
  limit_pc = skip_prologue_using_sal (pc);
  if (limit_pc == 0)
    limit_pc = pc + 100;          /* Magic.  */

  if (mips_pc_is_mips16 (pc))
    return mips16_scan_prologue (pc, limit_pc, NULL, NULL);
  else
    return mips32_scan_prologue (pc, limit_pc, NULL, NULL);
}

/* Root of all "set mips "/"show mips " commands. This will eventually be
   used for all MIPS-specific commands.  */

static void
show_mips_command (char *args, int from_tty)
{
  help_list (showmipscmdlist, "show mips ", all_commands, gdb_stdout);
}

static void
set_mips_command (char *args, int from_tty)
{
  printf_unfiltered
    ("\"set mips\" must be followed by an appropriate subcommand.\n");
  help_list (setmipscmdlist, "set mips ", all_commands, gdb_stdout);
}

/* Commands to show/set the MIPS FPU type.  */

static void
show_mipsfpu_command (char *args, int from_tty)
{
  char *fpu;
  switch (MIPS_FPU_TYPE)
    {
    case MIPS_FPU_SINGLE:
      fpu = "single-precision";
      break;
    case MIPS_FPU_DOUBLE:
      fpu = "double-precision";
      break;
    case MIPS_FPU_NONE:
      fpu = "absent (none)";
      break;
    default:
      internal_error (__FILE__, __LINE__, "bad switch");
    }
  if (mips_fpu_type_auto)
    printf_unfiltered
      ("The MIPS floating-point coprocessor is set automatically (currently %s)\n",
       fpu);
  else
    printf_unfiltered
      ("The MIPS floating-point coprocessor is assumed to be %s\n", fpu);
}


static void
set_mipsfpu_command (char *args, int from_tty)
{
  printf_unfiltered
    ("\"set mipsfpu\" must be followed by \"double\", \"single\",\"none\" or \"auto\".\n");
  show_mipsfpu_command (args, from_tty);
}

static void
set_mipsfpu_single_command (char *args, int from_tty)
{
  struct gdbarch_info info;
  gdbarch_info_init (&info);
  mips_fpu_type = MIPS_FPU_SINGLE;
  mips_fpu_type_auto = 0;
  /* FIXME: cagney/2003-11-15: Should be setting a field in "info"
     instead of relying on globals.  Doing that would let generic code
     handle the search for this specific architecture.  */
  if (!gdbarch_update_p (info))
    internal_error (__FILE__, __LINE__, "set mipsfpu failed");
}

static void
set_mipsfpu_double_command (char *args, int from_tty)
{
  struct gdbarch_info info;
  gdbarch_info_init (&info);
  mips_fpu_type = MIPS_FPU_DOUBLE;
  mips_fpu_type_auto = 0;
  /* FIXME: cagney/2003-11-15: Should be setting a field in "info"
     instead of relying on globals.  Doing that would let generic code
     handle the search for this specific architecture.  */
  if (!gdbarch_update_p (info))
    internal_error (__FILE__, __LINE__, "set mipsfpu failed");
}

static void
set_mipsfpu_none_command (char *args, int from_tty)
{
  struct gdbarch_info info;
  gdbarch_info_init (&info);
  mips_fpu_type = MIPS_FPU_NONE;
  mips_fpu_type_auto = 0;
  /* FIXME: cagney/2003-11-15: Should be setting a field in "info"
     instead of relying on globals.  Doing that would let generic code
     handle the search for this specific architecture.  */
  if (!gdbarch_update_p (info))
    internal_error (__FILE__, __LINE__, "set mipsfpu failed");
}

static void
set_mipsfpu_auto_command (char *args, int from_tty)
{
  mips_fpu_type_auto = 1;
}

/* Attempt to identify the particular processor model by reading the
   processor id.  NOTE: cagney/2003-11-15: Firstly it isn't clear that
   the relevant processor still exists (it dates back to '94) and
   secondly this is not the way to do this.  The processor type should
   be set by forcing an architecture change.  */

void
deprecated_mips_set_processor_regs_hack (void)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  CORE_ADDR prid;

  prid = read_register (MIPS_PRID_REGNUM);

  if ((prid & ~0xf) == 0x700)
    tdep->mips_processor_reg_names = mips_r3041_reg_names;
}

/* Just like reinit_frame_cache, but with the right arguments to be
   callable as an sfunc.  */

static void
reinit_frame_cache_sfunc (char *args, int from_tty,
                          struct cmd_list_element *c)
{
  reinit_frame_cache ();
}

static int
gdb_print_insn_mips (bfd_vma memaddr, struct disassemble_info *info)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  /* FIXME: cagney/2003-06-26: Is this even necessary?  The
     disassembler needs to be able to locally determine the ISA, and
     not rely on GDB.  Otherwize the stand-alone 'objdump -d' will not
     work.  */
  if (mips_pc_is_mips16 (memaddr))
    info->mach = bfd_mach_mips16;

  /* Round down the instruction address to the appropriate boundary.  */
  memaddr &= (info->mach == bfd_mach_mips16 ? ~1 : ~3);

  /* Set the disassembler options.  */
  if (tdep->mips_abi == MIPS_ABI_N32 || tdep->mips_abi == MIPS_ABI_N64)
    {
      /* Set up the disassembler info, so that we get the right
         register names from libopcodes.  */
      if (tdep->mips_abi == MIPS_ABI_N32)
        info->disassembler_options = "gpr-names=n32";
      else
        info->disassembler_options = "gpr-names=64";
      info->flavour = bfd_target_elf_flavour;
    }
  else
    /* This string is not recognized explicitly by the disassembler,
       but it tells the disassembler to not try to guess the ABI from
       the bfd elf headers, such that, if the user overrides the ABI
       of a program linked as NewABI, the disassembly will follow the
       register naming conventions specified by the user.  */
    info->disassembler_options = "gpr-names=32";

  /* Call the appropriate disassembler based on the target endian-ness.  */
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    return print_insn_big_mips (memaddr, info);
  else
    return print_insn_little_mips (memaddr, info);
}

/* This function implements the BREAKPOINT_FROM_PC macro.  It uses the program
   counter value to determine whether a 16- or 32-bit breakpoint should be
   used.  It returns a pointer to a string of bytes that encode a breakpoint
   instruction, stores the length of the string to *lenptr, and adjusts pc
   (if necessary) to point to the actual memory location where the
   breakpoint should be inserted.  */

static const unsigned char *
mips_breakpoint_from_pc (CORE_ADDR *pcptr, int *lenptr)
{
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      if (mips_pc_is_mips16 (*pcptr))
        {
          static unsigned char mips16_big_breakpoint[] = { 0xe8, 0xa5 };
          *pcptr = unmake_mips16_addr (*pcptr);
          *lenptr = sizeof (mips16_big_breakpoint);
          return mips16_big_breakpoint;
        }
      else
        {
          /* The IDT board uses an unusual breakpoint value, and
             sometimes gets confused when it sees the usual MIPS
             breakpoint instruction.  */
          static unsigned char big_breakpoint[] = { 0, 0x5, 0, 0xd };
          static unsigned char pmon_big_breakpoint[] = { 0, 0, 0, 0xd };
          static unsigned char idt_big_breakpoint[] = { 0, 0, 0x0a, 0xd };

          *lenptr = sizeof (big_breakpoint);

          if (strcmp (target_shortname, "mips") == 0)
            return idt_big_breakpoint;
          else if (strcmp (target_shortname, "ddb") == 0
                   || strcmp (target_shortname, "pmon") == 0
                   || strcmp (target_shortname, "lsi") == 0)
            return pmon_big_breakpoint;
          else
            return big_breakpoint;
        }
    }
  else
    {
      if (mips_pc_is_mips16 (*pcptr))
        {
          static unsigned char mips16_little_breakpoint[] = { 0xa5, 0xe8 };
          *pcptr = unmake_mips16_addr (*pcptr);
          *lenptr = sizeof (mips16_little_breakpoint);
          return mips16_little_breakpoint;
        }
      else
        {
          static unsigned char little_breakpoint[] = { 0xd, 0, 0x5, 0 };
          static unsigned char pmon_little_breakpoint[] = { 0xd, 0, 0, 0 };
          static unsigned char idt_little_breakpoint[] = { 0xd, 0x0a, 0, 0 };

          *lenptr = sizeof (little_breakpoint);

          if (strcmp (target_shortname, "mips") == 0)
            return idt_little_breakpoint;
          else if (strcmp (target_shortname, "ddb") == 0
                   || strcmp (target_shortname, "pmon") == 0
                   || strcmp (target_shortname, "lsi") == 0)
            return pmon_little_breakpoint;
          else
            return little_breakpoint;
        }
    }
}

/* If PC is in a mips16 call or return stub, return the address of the target
   PC, which is either the callee or the caller.  There are several
   cases which must be handled:

   * If the PC is in __mips16_ret_{d,s}f, this is a return stub and the
   target PC is in $31 ($ra).
   * If the PC is in __mips16_call_stub_{1..10}, this is a call stub
   and the target PC is in $2.
   * If the PC at the start of __mips16_call_stub_{s,d}f_{0..10}, i.e.
   before the jal instruction, this is effectively a call stub
   and the the target PC is in $2.  Otherwise this is effectively
   a return stub and the target PC is in $18.

   See the source code for the stubs in gcc/config/mips/mips16.S for
   gory details.  */

static CORE_ADDR
mips_skip_trampoline_code (CORE_ADDR pc)
{
  char *name;
  CORE_ADDR start_addr;

  /* Find the starting address and name of the function containing the PC.  */
  if (find_pc_partial_function (pc, &name, &start_addr, NULL) == 0)
    return 0;

  /* If the PC is in __mips16_ret_{d,s}f, this is a return stub and the
     target PC is in $31 ($ra).  */
  if (strcmp (name, "__mips16_ret_sf") == 0
      || strcmp (name, "__mips16_ret_df") == 0)
    return read_signed_register (MIPS_RA_REGNUM);

  if (strncmp (name, "__mips16_call_stub_", 19) == 0)
    {
      /* If the PC is in __mips16_call_stub_{1..10}, this is a call stub
         and the target PC is in $2.  */
      if (name[19] >= '0' && name[19] <= '9')
        return read_signed_register (2);

      /* If the PC at the start of __mips16_call_stub_{s,d}f_{0..10}, i.e.
         before the jal instruction, this is effectively a call stub
         and the the target PC is in $2.  Otherwise this is effectively
         a return stub and the target PC is in $18.  */
      else if (name[19] == 's' || name[19] == 'd')
        {
          if (pc == start_addr)
            {
              /* Check if the target of the stub is a compiler-generated
                 stub.  Such a stub for a function bar might have a name
                 like __fn_stub_bar, and might look like this:
                 mfc1    $4,$f13
                 mfc1    $5,$f12
                 mfc1    $6,$f15
                 mfc1    $7,$f14
                 la      $1,bar   (becomes a lui/addiu pair)
                 jr      $1
                 So scan down to the lui/addi and extract the target
                 address from those two instructions.  */

              CORE_ADDR target_pc = read_signed_register (2);
              ULONGEST inst;
              int i;

              /* See if the name of the target function is  __fn_stub_*.  */
              if (find_pc_partial_function (target_pc, &name, NULL, NULL) ==
                  0)
                return target_pc;
              if (strncmp (name, "__fn_stub_", 10) != 0
                  && strcmp (name, "etext") != 0
                  && strcmp (name, "_etext") != 0)
                return target_pc;

              /* Scan through this _fn_stub_ code for the lui/addiu pair.
                 The limit on the search is arbitrarily set to 20
                 instructions.  FIXME.  */
              for (i = 0, pc = 0; i < 20; i++, target_pc += MIPS_INSN32_SIZE)
                {
                  inst = mips_fetch_instruction (target_pc);
                  if ((inst & 0xffff0000) == 0x3c010000)        /* lui $at */
                    pc = (inst << 16) & 0xffff0000;     /* high word */
                  else if ((inst & 0xffff0000) == 0x24210000)   /* addiu $at */
                    return pc | (inst & 0xffff);        /* low word */
                }

              /* Couldn't find the lui/addui pair, so return stub address.  */
              return target_pc;
            }
          else
            /* This is the 'return' part of a call stub.  The return
               address is in $r18.  */
            return read_signed_register (18);
        }
    }
  return 0;                     /* not a stub */
}

/* Convert a dbx stab register number (from `r' declaration) to a GDB
   [1 * NUM_REGS .. 2 * NUM_REGS) REGNUM.  */

static int
mips_stab_reg_to_regnum (int num)
{
  int regnum;
  if (num >= 0 && num < 32)
    regnum = num;
  else if (num >= 38 && num < 70)
    regnum = num + mips_regnum (current_gdbarch)->fp0 - 38;
  else if (num == 70)
    regnum = mips_regnum (current_gdbarch)->hi;
  else if (num == 71)
    regnum = mips_regnum (current_gdbarch)->lo;
  else
    /* This will hopefully (eventually) provoke a warning.  Should
       we be calling complaint() here?  */
    return NUM_REGS + NUM_PSEUDO_REGS;
  return NUM_REGS + regnum;
}


/* Convert a dwarf, dwarf2, or ecoff register number to a GDB [1 *
   NUM_REGS .. 2 * NUM_REGS) REGNUM.  */

static int
mips_dwarf_dwarf2_ecoff_reg_to_regnum (int num)
{
  int regnum;
  if (num >= 0 && num < 32)
    regnum = num;
  else if (num >= 32 && num < 64)
    regnum = num + mips_regnum (current_gdbarch)->fp0 - 32;
  else if (num == 64)
    regnum = mips_regnum (current_gdbarch)->hi;
  else if (num == 65)
    regnum = mips_regnum (current_gdbarch)->lo;
  else
    /* This will hopefully (eventually) provoke a warning.  Should we
       be calling complaint() here?  */
    return NUM_REGS + NUM_PSEUDO_REGS;
  return NUM_REGS + regnum;
}

static int
mips_register_sim_regno (int regnum)
{
  /* Only makes sense to supply raw registers.  */
  gdb_assert (regnum >= 0 && regnum < NUM_REGS);
  /* FIXME: cagney/2002-05-13: Need to look at the pseudo register to
     decide if it is valid.  Should instead define a standard sim/gdb
     register numbering scheme.  */
  if (REGISTER_NAME (NUM_REGS + regnum) != NULL
      && REGISTER_NAME (NUM_REGS + regnum)[0] != '\0')
    return regnum;
  else
    return LEGACY_SIM_REGNO_IGNORE;
}


/* Convert an integer into an address.  By first converting the value
   into a pointer and then extracting it signed, the address is
   guarenteed to be correctly sign extended.  */

static CORE_ADDR
mips_integer_to_address (struct type *type, void *buf)
{
  char *tmp = alloca (TYPE_LENGTH (builtin_type_void_data_ptr));
  LONGEST val = unpack_long (type, buf);
  store_signed_integer (tmp, TYPE_LENGTH (builtin_type_void_data_ptr), val);
  return extract_signed_integer (tmp,
                                 TYPE_LENGTH (builtin_type_void_data_ptr));
}

static void
mips_find_abi_section (bfd *abfd, asection *sect, void *obj)
{
  enum mips_abi *abip = (enum mips_abi *) obj;
  const char *name = bfd_get_section_name (abfd, sect);

  if (*abip != MIPS_ABI_UNKNOWN)
    return;

  if (strncmp (name, ".mdebug.", 8) != 0)
    return;

  if (strcmp (name, ".mdebug.abi32") == 0)
    *abip = MIPS_ABI_O32;
  else if (strcmp (name, ".mdebug.abiN32") == 0)
    *abip = MIPS_ABI_N32;
  else if (strcmp (name, ".mdebug.abi64") == 0)
    *abip = MIPS_ABI_N64;
  else if (strcmp (name, ".mdebug.abiO64") == 0)
    *abip = MIPS_ABI_O64;
  else if (strcmp (name, ".mdebug.eabi32") == 0)
    *abip = MIPS_ABI_EABI32;
  else if (strcmp (name, ".mdebug.eabi64") == 0)
    *abip = MIPS_ABI_EABI64;
  else
    warning ("unsupported ABI %s.", name + 8);
}

static enum mips_abi
global_mips_abi (void)
{
  int i;

  for (i = 0; mips_abi_strings[i] != NULL; i++)
    if (mips_abi_strings[i] == mips_abi_string)
      return (enum mips_abi) i;

  internal_error (__FILE__, __LINE__, "unknown ABI string");
}

static struct gdbarch *
mips_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
{
  struct gdbarch *gdbarch;
  struct gdbarch_tdep *tdep;
  int elf_flags;
  enum mips_abi mips_abi, found_abi, wanted_abi;
  int num_regs;
  enum mips_fpu_type fpu_type;

  /* First of all, extract the elf_flags, if available.  */
  if (info.abfd && bfd_get_flavour (info.abfd) == bfd_target_elf_flavour)
    elf_flags = elf_elfheader (info.abfd)->e_flags;
  else if (arches != NULL)
    elf_flags = gdbarch_tdep (arches->gdbarch)->elf_flags;
  else
    elf_flags = 0;
  if (gdbarch_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_gdbarch_init: elf_flags = 0x%08x\n", elf_flags);

  /* Check ELF_FLAGS to see if it specifies the ABI being used.  */
  switch ((elf_flags & EF_MIPS_ABI))
    {
    case E_MIPS_ABI_O32:
      found_abi = MIPS_ABI_O32;
      break;
    case E_MIPS_ABI_O64:
      found_abi = MIPS_ABI_O64;
      break;
    case E_MIPS_ABI_EABI32:
      found_abi = MIPS_ABI_EABI32;
      break;
    case E_MIPS_ABI_EABI64:
      found_abi = MIPS_ABI_EABI64;
      break;
    default:
      if ((elf_flags & EF_MIPS_ABI2))
        found_abi = MIPS_ABI_N32;
      else
        found_abi = MIPS_ABI_UNKNOWN;
      break;
    }

  /* GCC creates a pseudo-section whose name describes the ABI.  */
  if (found_abi == MIPS_ABI_UNKNOWN && info.abfd != NULL)
    bfd_map_over_sections (info.abfd, mips_find_abi_section, &found_abi);

  /* If we have no useful BFD information, use the ABI from the last
     MIPS architecture (if there is one).  */
  if (found_abi == MIPS_ABI_UNKNOWN && info.abfd == NULL && arches != NULL)
    found_abi = gdbarch_tdep (arches->gdbarch)->found_abi;

  /* Try the architecture for any hint of the correct ABI.  */
  if (found_abi == MIPS_ABI_UNKNOWN
      && info.bfd_arch_info != NULL
      && info.bfd_arch_info->arch == bfd_arch_mips)
    {
      switch (info.bfd_arch_info->mach)
        {
        case bfd_mach_mips3900:
          found_abi = MIPS_ABI_EABI32;
          break;
        case bfd_mach_mips4100:
        case bfd_mach_mips5000:
          found_abi = MIPS_ABI_EABI64;
          break;
        case bfd_mach_mips8000:
        case bfd_mach_mips10000:
          /* On Irix, ELF64 executables use the N64 ABI.  The
             pseudo-sections which describe the ABI aren't present
             on IRIX.  (Even for executables created by gcc.)  */
          if (bfd_get_flavour (info.abfd) == bfd_target_elf_flavour
              && elf_elfheader (info.abfd)->e_ident[EI_CLASS] == ELFCLASS64)
            found_abi = MIPS_ABI_N64;
          else
            found_abi = MIPS_ABI_N32;
          break;
        }
    }

  if (gdbarch_debug)
    fprintf_unfiltered (gdb_stdlog, "mips_gdbarch_init: found_abi = %d\n",
                        found_abi);

  /* What has the user specified from the command line?  */
  wanted_abi = global_mips_abi ();
  if (gdbarch_debug)
    fprintf_unfiltered (gdb_stdlog, "mips_gdbarch_init: wanted_abi = %d\n",
                        wanted_abi);

  /* Now that we have found what the ABI for this binary would be,
     check whether the user is overriding it.  */
  if (wanted_abi != MIPS_ABI_UNKNOWN)
    mips_abi = wanted_abi;
  else if (found_abi != MIPS_ABI_UNKNOWN)
    mips_abi = found_abi;
  else
    mips_abi = MIPS_ABI_O32;
  if (gdbarch_debug)
    fprintf_unfiltered (gdb_stdlog, "mips_gdbarch_init: mips_abi = %d\n",
                        mips_abi);

  /* Also used when doing an architecture lookup.  */
  if (gdbarch_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_gdbarch_init: mips64_transfers_32bit_regs_p = %d\n",
                        mips64_transfers_32bit_regs_p);

  /* Determine the MIPS FPU type.  */
  if (!mips_fpu_type_auto)
    fpu_type = mips_fpu_type;
  else if (info.bfd_arch_info != NULL
           && info.bfd_arch_info->arch == bfd_arch_mips)
    switch (info.bfd_arch_info->mach)
      {
      case bfd_mach_mips3900:
      case bfd_mach_mips4100:
      case bfd_mach_mips4111:
      case bfd_mach_mips4120:
        fpu_type = MIPS_FPU_NONE;
        break;
      case bfd_mach_mips4650:
        fpu_type = MIPS_FPU_SINGLE;
        break;
      default:
        fpu_type = MIPS_FPU_DOUBLE;
        break;
      }
  else if (arches != NULL)
    fpu_type = gdbarch_tdep (arches->gdbarch)->mips_fpu_type;
  else
    fpu_type = MIPS_FPU_DOUBLE;
  if (gdbarch_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "mips_gdbarch_init: fpu_type = %d\n", fpu_type);

  /* try to find a pre-existing architecture */
  for (arches = gdbarch_list_lookup_by_info (arches, &info);
       arches != NULL;
       arches = gdbarch_list_lookup_by_info (arches->next, &info))
    {
      /* MIPS needs to be pedantic about which ABI the object is
         using.  */
      if (gdbarch_tdep (arches->gdbarch)->elf_flags != elf_flags)
        continue;
      if (gdbarch_tdep (arches->gdbarch)->mips_abi != mips_abi)
        continue;
      /* Need to be pedantic about which register virtual size is
         used.  */
      if (gdbarch_tdep (arches->gdbarch)->mips64_transfers_32bit_regs_p
          != mips64_transfers_32bit_regs_p)
        continue;
      /* Be pedantic about which FPU is selected.  */
      if (gdbarch_tdep (arches->gdbarch)->mips_fpu_type != fpu_type)
        continue;
      return arches->gdbarch;
    }

  /* Need a new architecture.  Fill in a target specific vector.  */
  tdep = (struct gdbarch_tdep *) xmalloc (sizeof (struct gdbarch_tdep));
  gdbarch = gdbarch_alloc (&info, tdep);
  tdep->elf_flags = elf_flags;
  tdep->mips64_transfers_32bit_regs_p = mips64_transfers_32bit_regs_p;
  tdep->found_abi = found_abi;
  tdep->mips_abi = mips_abi;
  tdep->mips_fpu_type = fpu_type;

  /* Initially set everything according to the default ABI/ISA.  */
  set_gdbarch_short_bit (gdbarch, 16);
  set_gdbarch_int_bit (gdbarch, 32);
  set_gdbarch_float_bit (gdbarch, 32);
  set_gdbarch_double_bit (gdbarch, 64);
  set_gdbarch_long_double_bit (gdbarch, 64);
  set_gdbarch_register_reggroup_p (gdbarch, mips_register_reggroup_p);
  set_gdbarch_pseudo_register_read (gdbarch, mips_pseudo_register_read);
  set_gdbarch_pseudo_register_write (gdbarch, mips_pseudo_register_write);

  set_gdbarch_elf_make_msymbol_special (gdbarch,
                                        mips_elf_make_msymbol_special);

  /* Fill in the OS dependant register numbers and names.  */
  {
    const char **reg_names;
    struct mips_regnum *regnum = GDBARCH_OBSTACK_ZALLOC (gdbarch,
                                                         struct mips_regnum);
    if (info.osabi == GDB_OSABI_IRIX)
      {
        regnum->fp0 = 32;
        regnum->pc = 64;
        regnum->cause = 65;
        regnum->badvaddr = 66;
        regnum->hi = 67;
        regnum->lo = 68;
        regnum->fp_control_status = 69;
        regnum->fp_implementation_revision = 70;
        num_regs = 71;
        reg_names = mips_irix_reg_names;
      }
    else
      {
        regnum->lo = MIPS_EMBED_LO_REGNUM;
        regnum->hi = MIPS_EMBED_HI_REGNUM;
        regnum->badvaddr = MIPS_EMBED_BADVADDR_REGNUM;
        regnum->cause = MIPS_EMBED_CAUSE_REGNUM;
        regnum->pc = MIPS_EMBED_PC_REGNUM;
        regnum->fp0 = MIPS_EMBED_FP0_REGNUM;
        regnum->fp_control_status = 70;
        regnum->fp_implementation_revision = 71;
        num_regs = 90;
        if (info.bfd_arch_info != NULL
            && info.bfd_arch_info->mach == bfd_mach_mips3900)
          reg_names = mips_tx39_reg_names;
        else
          reg_names = mips_generic_reg_names;
      }
    /* FIXME: cagney/2003-11-15: For MIPS, hasn't PC_REGNUM been
       replaced by read_pc?  */
    set_gdbarch_pc_regnum (gdbarch, regnum->pc + num_regs);
    set_gdbarch_sp_regnum (gdbarch, MIPS_SP_REGNUM + num_regs);
    set_gdbarch_fp0_regnum (gdbarch, regnum->fp0);
    set_gdbarch_num_regs (gdbarch, num_regs);
    set_gdbarch_num_pseudo_regs (gdbarch, num_regs);
    set_gdbarch_register_name (gdbarch, mips_register_name);
    tdep->mips_processor_reg_names = reg_names;
    tdep->regnum = regnum;
  }

  switch (mips_abi)
    {
    case MIPS_ABI_O32:
      set_gdbarch_push_dummy_call (gdbarch, mips_o32_push_dummy_call);
      set_gdbarch_return_value (gdbarch, mips_o32_return_value);
      tdep->mips_last_arg_regnum = MIPS_A0_REGNUM + 4 - 1;
      tdep->mips_last_fp_arg_regnum = tdep->regnum->fp0 + 12 + 4 - 1;
      tdep->default_mask_address_p = 0;
      set_gdbarch_long_bit (gdbarch, 32);
      set_gdbarch_ptr_bit (gdbarch, 32);
      set_gdbarch_long_long_bit (gdbarch, 64);
      break;
    case MIPS_ABI_O64:
      set_gdbarch_push_dummy_call (gdbarch, mips_o64_push_dummy_call);
      set_gdbarch_return_value (gdbarch, mips_o64_return_value);
      tdep->mips_last_arg_regnum = MIPS_A0_REGNUM + 4 - 1;
      tdep->mips_last_fp_arg_regnum = tdep->regnum->fp0 + 12 + 4 - 1;
      tdep->default_mask_address_p = 0;
      set_gdbarch_long_bit (gdbarch, 32);
      set_gdbarch_ptr_bit (gdbarch, 32);
      set_gdbarch_long_long_bit (gdbarch, 64);
      break;
    case MIPS_ABI_EABI32:
      set_gdbarch_push_dummy_call (gdbarch, mips_eabi_push_dummy_call);
      set_gdbarch_return_value (gdbarch, mips_eabi_return_value);
      tdep->mips_last_arg_regnum = MIPS_A0_REGNUM + 8 - 1;
      tdep->mips_last_fp_arg_regnum = tdep->regnum->fp0 + 12 + 8 - 1;
      tdep->default_mask_address_p = 0;
      set_gdbarch_long_bit (gdbarch, 32);
      set_gdbarch_ptr_bit (gdbarch, 32);
      set_gdbarch_long_long_bit (gdbarch, 64);
      break;
    case MIPS_ABI_EABI64:
      set_gdbarch_push_dummy_call (gdbarch, mips_eabi_push_dummy_call);
      set_gdbarch_return_value (gdbarch, mips_eabi_return_value);
      tdep->mips_last_arg_regnum = MIPS_A0_REGNUM + 8 - 1;
      tdep->mips_last_fp_arg_regnum = tdep->regnum->fp0 + 12 + 8 - 1;
      tdep->default_mask_address_p = 0;
      set_gdbarch_long_bit (gdbarch, 64);
      set_gdbarch_ptr_bit (gdbarch, 64);
      set_gdbarch_long_long_bit (gdbarch, 64);
      break;
    case MIPS_ABI_N32:
      set_gdbarch_push_dummy_call (gdbarch, mips_n32n64_push_dummy_call);
      set_gdbarch_return_value (gdbarch, mips_n32n64_return_value);
      tdep->mips_last_arg_regnum = MIPS_A0_REGNUM + 8 - 1;
      tdep->mips_last_fp_arg_regnum = tdep->regnum->fp0 + 12 + 8 - 1;
      tdep->default_mask_address_p = 0;
      set_gdbarch_long_bit (gdbarch, 32);
      set_gdbarch_ptr_bit (gdbarch, 32);
      set_gdbarch_long_long_bit (gdbarch, 64);
      set_gdbarch_long_double_bit (gdbarch, 128);
      set_gdbarch_long_double_format (gdbarch,
                                      &floatformat_n32n64_long_double_big);
      break;
    case MIPS_ABI_N64:
      set_gdbarch_push_dummy_call (gdbarch, mips_n32n64_push_dummy_call);
      set_gdbarch_return_value (gdbarch, mips_n32n64_return_value);
      tdep->mips_last_arg_regnum = MIPS_A0_REGNUM + 8 - 1;
      tdep->mips_last_fp_arg_regnum = tdep->regnum->fp0 + 12 + 8 - 1;
      tdep->default_mask_address_p = 0;
      set_gdbarch_long_bit (gdbarch, 64);
      set_gdbarch_ptr_bit (gdbarch, 64);
      set_gdbarch_long_long_bit (gdbarch, 64);
      set_gdbarch_long_double_bit (gdbarch, 128);
      set_gdbarch_long_double_format (gdbarch,
                                      &floatformat_n32n64_long_double_big);
      break;
    default:
      internal_error (__FILE__, __LINE__, "unknown ABI in switch");
    }

  /* FIXME: jlarmour/2000-04-07: There *is* a flag EF_MIPS_32BIT_MODE
     that could indicate -gp32 BUT gas/config/tc-mips.c contains the
     comment:

     ``We deliberately don't allow "-gp32" to set the MIPS_32BITMODE
     flag in object files because to do so would make it impossible to
     link with libraries compiled without "-gp32".  This is
     unnecessarily restrictive.

     We could solve this problem by adding "-gp32" multilibs to gcc,
     but to set this flag before gcc is built with such multilibs will
     break too many systems.''

     But even more unhelpfully, the default linker output target for
     mips64-elf is elf32-bigmips, and has EF_MIPS_32BIT_MODE set, even
     for 64-bit programs - you need to change the ABI to change this,
     and not all gcc targets support that currently.  Therefore using
     this flag to detect 32-bit mode would do the wrong thing given
     the current gcc - it would make GDB treat these 64-bit programs
     as 32-bit programs by default.  */

  set_gdbarch_read_pc (gdbarch, mips_read_pc);
  set_gdbarch_write_pc (gdbarch, mips_write_pc);
  set_gdbarch_read_sp (gdbarch, mips_read_sp);

  /* Add/remove bits from an address.  The MIPS needs be careful to
     ensure that all 32 bit addresses are sign extended to 64 bits.  */
  set_gdbarch_addr_bits_remove (gdbarch, mips_addr_bits_remove);

  /* Unwind the frame.  */
  set_gdbarch_unwind_pc (gdbarch, mips_unwind_pc);
  set_gdbarch_unwind_dummy_id (gdbarch, mips_unwind_dummy_id);

  /* Map debug register numbers onto internal register numbers.  */
  set_gdbarch_stab_reg_to_regnum (gdbarch, mips_stab_reg_to_regnum);
  set_gdbarch_ecoff_reg_to_regnum (gdbarch,
                                   mips_dwarf_dwarf2_ecoff_reg_to_regnum);
  set_gdbarch_dwarf_reg_to_regnum (gdbarch,
                                   mips_dwarf_dwarf2_ecoff_reg_to_regnum);
  set_gdbarch_dwarf2_reg_to_regnum (gdbarch,
                                    mips_dwarf_dwarf2_ecoff_reg_to_regnum);
  set_gdbarch_register_sim_regno (gdbarch, mips_register_sim_regno);

  /* MIPS version of CALL_DUMMY */

  /* NOTE: cagney/2003-08-05: Eventually call dummy location will be
     replaced by a command, and all targets will default to on stack
     (regardless of the stack's execute status).  */
  set_gdbarch_call_dummy_location (gdbarch, AT_SYMBOL);
  set_gdbarch_frame_align (gdbarch, mips_frame_align);

  set_gdbarch_convert_register_p (gdbarch, mips_convert_register_p);
  set_gdbarch_register_to_value (gdbarch, mips_register_to_value);
  set_gdbarch_value_to_register (gdbarch, mips_value_to_register);

  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
  set_gdbarch_breakpoint_from_pc (gdbarch, mips_breakpoint_from_pc);

  set_gdbarch_skip_prologue (gdbarch, mips_skip_prologue);

  set_gdbarch_pointer_to_address (gdbarch, signed_pointer_to_address);
  set_gdbarch_address_to_pointer (gdbarch, address_to_signed_pointer);
  set_gdbarch_integer_to_address (gdbarch, mips_integer_to_address);

  set_gdbarch_register_type (gdbarch, mips_register_type);

  set_gdbarch_print_registers_info (gdbarch, mips_print_registers_info);

  set_gdbarch_print_insn (gdbarch, gdb_print_insn_mips);

  /* FIXME: cagney/2003-08-29: The macros HAVE_STEPPABLE_WATCHPOINT,
     HAVE_NONSTEPPABLE_WATCHPOINT, and HAVE_CONTINUABLE_WATCHPOINT
     need to all be folded into the target vector.  Since they are
     being used as guards for STOPPED_BY_WATCHPOINT, why not have
     STOPPED_BY_WATCHPOINT return the type of watchpoint that the code
     is sitting on?  */
  set_gdbarch_have_nonsteppable_watchpoint (gdbarch, 1);

  set_gdbarch_skip_trampoline_code (gdbarch, mips_skip_trampoline_code);

  set_gdbarch_single_step_through_delay (gdbarch, mips_single_step_through_delay);

  /* Hook in OS ABI-specific overrides, if they have been registered.  */
  gdbarch_init_osabi (info, gdbarch);

  /* Unwind the frame.  */
  frame_unwind_append_sniffer (gdbarch, mips_stub_frame_sniffer);
  frame_unwind_append_sniffer (gdbarch, mips_insn16_frame_sniffer);
  frame_unwind_append_sniffer (gdbarch, mips_insn32_frame_sniffer);
  frame_base_append_sniffer (gdbarch, mips_stub_frame_base_sniffer);
  frame_base_append_sniffer (gdbarch, mips_insn16_frame_base_sniffer);
  frame_base_append_sniffer (gdbarch, mips_insn32_frame_base_sniffer);

  return gdbarch;
}

static void
mips_abi_update (char *ignore_args, int from_tty, struct cmd_list_element *c)
{
  struct gdbarch_info info;

  /* Force the architecture to update, and (if it's a MIPS architecture)
     mips_gdbarch_init will take care of the rest.  */
  gdbarch_info_init (&info);
  gdbarch_update_p (info);
}

/* Print out which MIPS ABI is in use.  */

static void
show_mips_abi (char *ignore_args, int from_tty)
{
  if (gdbarch_bfd_arch_info (current_gdbarch)->arch != bfd_arch_mips)
    printf_filtered
      ("The MIPS ABI is unknown because the current architecture is not MIPS.\n");
  else
    {
      enum mips_abi global_abi = global_mips_abi ();
      enum mips_abi actual_abi = mips_abi (current_gdbarch);
      const char *actual_abi_str = mips_abi_strings[actual_abi];

      if (global_abi == MIPS_ABI_UNKNOWN)
        printf_filtered
          ("The MIPS ABI is set automatically (currently \"%s\").\n",
           actual_abi_str);
      else if (global_abi == actual_abi)
        printf_filtered
          ("The MIPS ABI is assumed to be \"%s\" (due to user setting).\n",
           actual_abi_str);
      else
        {
          /* Probably shouldn't happen...  */
          printf_filtered
            ("The (auto detected) MIPS ABI \"%s\" is in use even though the user setting was \"%s\".\n",
             actual_abi_str, mips_abi_strings[global_abi]);
        }
    }
}

static void
mips_dump_tdep (struct gdbarch *current_gdbarch, struct ui_file *file)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  if (tdep != NULL)
    {
      int ef_mips_arch;
      int ef_mips_32bitmode;
      /* determine the ISA */
      switch (tdep->elf_flags & EF_MIPS_ARCH)
        {
        case E_MIPS_ARCH_1:
          ef_mips_arch = 1;
          break;
        case E_MIPS_ARCH_2:
          ef_mips_arch = 2;
          break;
        case E_MIPS_ARCH_3:
          ef_mips_arch = 3;
          break;
        case E_MIPS_ARCH_4:
          ef_mips_arch = 4;
          break;
        default:
          ef_mips_arch = 0;
          break;
        }
      /* determine the size of a pointer */
      ef_mips_32bitmode = (tdep->elf_flags & EF_MIPS_32BITMODE);
      fprintf_unfiltered (file,
                          "mips_dump_tdep: tdep->elf_flags = 0x%x\n",
                          tdep->elf_flags);
      fprintf_unfiltered (file,
                          "mips_dump_tdep: ef_mips_32bitmode = %d\n",
                          ef_mips_32bitmode);
      fprintf_unfiltered (file,
                          "mips_dump_tdep: ef_mips_arch = %d\n",
                          ef_mips_arch);
      fprintf_unfiltered (file,
                          "mips_dump_tdep: tdep->mips_abi = %d (%s)\n",
                          tdep->mips_abi, mips_abi_strings[tdep->mips_abi]);
      fprintf_unfiltered (file,
                          "mips_dump_tdep: mips_mask_address_p() %d (default %d)\n",
                          mips_mask_address_p (tdep),
                          tdep->default_mask_address_p);
    }
  fprintf_unfiltered (file,
                      "mips_dump_tdep: MIPS_DEFAULT_FPU_TYPE = %d (%s)\n",
                      MIPS_DEFAULT_FPU_TYPE,
                      (MIPS_DEFAULT_FPU_TYPE == MIPS_FPU_NONE ? "none"
                       : MIPS_DEFAULT_FPU_TYPE == MIPS_FPU_SINGLE ? "single"
                       : MIPS_DEFAULT_FPU_TYPE == MIPS_FPU_DOUBLE ? "double"
                       : "???"));
  fprintf_unfiltered (file, "mips_dump_tdep: MIPS_EABI = %d\n", MIPS_EABI);
  fprintf_unfiltered (file,
                      "mips_dump_tdep: MIPS_FPU_TYPE = %d (%s)\n",
                      MIPS_FPU_TYPE,
                      (MIPS_FPU_TYPE == MIPS_FPU_NONE ? "none"
                       : MIPS_FPU_TYPE == MIPS_FPU_SINGLE ? "single"
                       : MIPS_FPU_TYPE == MIPS_FPU_DOUBLE ? "double"
                       : "???"));
  fprintf_unfiltered (file,
                      "mips_dump_tdep: mips_stack_argsize() = %d\n",
                      mips_stack_argsize (current_gdbarch));
}

extern initialize_file_ftype _initialize_mips_tdep;     /* -Wmissing-prototypes */

void
_initialize_mips_tdep (void)
{
  static struct cmd_list_element *mipsfpulist = NULL;
  struct cmd_list_element *c;

  mips_abi_string = mips_abi_strings[MIPS_ABI_UNKNOWN];
  if (MIPS_ABI_LAST + 1
      != sizeof (mips_abi_strings) / sizeof (mips_abi_strings[0]))
    internal_error (__FILE__, __LINE__, "mips_abi_strings out of sync");

  gdbarch_register (bfd_arch_mips, mips_gdbarch_init, mips_dump_tdep);

  mips_pdr_data = register_objfile_data ();

  /* Add root prefix command for all "set mips"/"show mips" commands */
  add_prefix_cmd ("mips", no_class, set_mips_command,
                  "Various MIPS specific commands.",
                  &setmipscmdlist, "set mips ", 0, &setlist);

  add_prefix_cmd ("mips", no_class, show_mips_command,
                  "Various MIPS specific commands.",
                  &showmipscmdlist, "show mips ", 0, &showlist);

  /* Allow the user to override the saved register size. */
  add_setshow_enum_cmd ("saved-gpreg-size", class_obscure,
                        size_enums, &mips_abi_regsize_string, "\
Set size of general purpose registers saved on the stack.\n", "\
Show size of general purpose registers saved on the stack.\n", "\
This option can be set to one of:\n\
  32    - Force GDB to treat saved GP registers as 32-bit\n\
  64    - Force GDB to treat saved GP registers as 64-bit\n\
  auto  - Allow GDB to use the target's default setting or autodetect the\n\
          saved GP register size from information contained in the executable.\n\
          (default: auto)", "\
Size of general purpose registers saved on the stack is %s.\n",
                        NULL, NULL, &setmipscmdlist, &showmipscmdlist);

  /* Allow the user to override the argument stack size. */
  add_setshow_enum_cmd ("stack-arg-size", class_obscure,
                       size_enums, &mips_stack_argsize_string, "\
Set the amount of stack space reserved for each argument.\n", "\
Show the amount of stack space reserved for each argument.\n", "\
This option can be set to one of:\n\
  32    - Force GDB to allocate 32-bit chunks per argument\n\
  64    - Force GDB to allocate 64-bit chunks per argument\n\
  auto  - Allow GDB to determine the correct setting from the current\n\
          target and executable (default)", "\
The amount of stack space reserved for each argument is %s.\n",
                        NULL, NULL, &setmipscmdlist, &showmipscmdlist);

  /* Allow the user to override the ABI. */
  c = add_set_enum_cmd
    ("abi", class_obscure, mips_abi_strings, &mips_abi_string,
     "Set the ABI used by this program.\n"
     "This option can be set to one of:\n"
     "  auto  - the default ABI associated with the current binary\n"
     "  o32\n"
     "  o64\n" "  n32\n" "  n64\n" "  eabi32\n" "  eabi64", &setmipscmdlist);
  set_cmd_sfunc (c, mips_abi_update);
  add_cmd ("abi", class_obscure, show_mips_abi,
           "Show ABI in use by MIPS target", &showmipscmdlist);

  /* Let the user turn off floating point and set the fence post for
     heuristic_proc_start.  */

  add_prefix_cmd ("mipsfpu", class_support, set_mipsfpu_command,
                  "Set use of MIPS floating-point coprocessor.",
                  &mipsfpulist, "set mipsfpu ", 0, &setlist);
  add_cmd ("single", class_support, set_mipsfpu_single_command,
           "Select single-precision MIPS floating-point coprocessor.",
           &mipsfpulist);
  add_cmd ("double", class_support, set_mipsfpu_double_command,
           "Select double-precision MIPS floating-point coprocessor.",
           &mipsfpulist);
  add_alias_cmd ("on", "double", class_support, 1, &mipsfpulist);
  add_alias_cmd ("yes", "double", class_support, 1, &mipsfpulist);
  add_alias_cmd ("1", "double", class_support, 1, &mipsfpulist);
  add_cmd ("none", class_support, set_mipsfpu_none_command,
           "Select no MIPS floating-point coprocessor.", &mipsfpulist);
  add_alias_cmd ("off", "none", class_support, 1, &mipsfpulist);
  add_alias_cmd ("no", "none", class_support, 1, &mipsfpulist);
  add_alias_cmd ("0", "none", class_support, 1, &mipsfpulist);
  add_cmd ("auto", class_support, set_mipsfpu_auto_command,
           "Select MIPS floating-point coprocessor automatically.",
           &mipsfpulist);
  add_cmd ("mipsfpu", class_support, show_mipsfpu_command,
           "Show current use of MIPS floating-point coprocessor target.",
           &showlist);

  /* We really would like to have both "0" and "unlimited" work, but
     command.c doesn't deal with that.  So make it a var_zinteger
     because the user can always use "999999" or some such for unlimited.  */
  add_setshow_zinteger_cmd ("heuristic-fence-post", class_support,
                            &heuristic_fence_post, "\
Set the distance searched for the start of a function.\n", "\
Show the distance searched for the start of a function.\n", "\
If you are debugging a stripped executable, GDB needs to search through the\n\
program for the start of a function.  This command sets the distance of the\n\
search.  The only need to set it is when debugging a stripped executable.", "\
The distance searched for the start of a function is %s.\n",
                            reinit_frame_cache_sfunc, NULL,
                            &setlist, &showlist);

  /* Allow the user to control whether the upper bits of 64-bit
     addresses should be zeroed.  */
  add_setshow_auto_boolean_cmd ("mask-address", no_class, &mask_address_var, "\
Set zeroing of upper 32 bits of 64-bit addresses.", "\
Show zeroing of upper 32 bits of 64-bit addresses.", "\
Use \"on\" to enable the masking, \"off\" to disable it and \"auto\" to \n\
allow GDB to determine the correct value.\n", "\
Zerroing of upper 32 bits of 64-bit address is %s.",
                                NULL, show_mask_address, &setmipscmdlist, &showmipscmdlist);

  /* Allow the user to control the size of 32 bit registers within the
     raw remote packet.  */
  add_setshow_boolean_cmd ("remote-mips64-transfers-32bit-regs", class_obscure,
                           &mips64_transfers_32bit_regs_p, "\
Set compatibility with 64-bit MIPS target that transfers 32-bit quantities.", "\
Show compatibility with 64-bit MIPS target that transfers 32-bit quantities.", "\
Use \"on\" to enable backward compatibility with older MIPS 64 GDB+target\n\
that would transfer 32 bits for some registers (e.g. SR, FSR) and\n\
64 bits for others.  Use \"off\" to disable compatibility mode", "\
Compatibility with 64-bit MIPS target that transfers 32-bit quantities is %s.",
 set_mips64_transfers_32bit_regs, NULL, &setlist, &showlist);

  /* Debug this files internals. */
  add_setshow_zinteger_cmd ("mips", class_maintenance,
                            &mips_debug, "\
Set mips debugging.\n", "\
Show mips debugging.\n", "\
When non-zero, mips specific debugging is enabled.\n", "\
Mips debugging is currently %s.\n",
                            NULL, NULL,
                            &setdebuglist, &showdebuglist);
}