MIPS: Make the extracted stack offset signed in the prologue scanner

Make the extracted stack offset signed in the standard MIPS prologue
scanner, to simplify handling and make sure register offsets are correct
in all cases, especially where $fp equals the virtual frame pointer (old
GCC frames) and therefore offsets to save slots are negative.

	* mips-tdep.c (mips32_scan_prologue): Make the extracted stack
	offset signed.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 8b016dc..1d1e32c 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2015-01-02  Maciej W. Rozycki  <macro@codesourcery.com>
+
+       * mips-tdep.c (mips32_scan_prologue): Keep the extracted stack
+       offset signed.
+
 2015-01-02  Doug Evans  <dje@google.com>
 
        * dwarf2read.c (setup_type_unit_groups): Remove outdated comment.

diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index 5cd66a1..bd8faef 100644 (file)
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -3438,7 +3438,8 @@ 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;
+      unsigned long inst, high_word;
+      long offset;
       int reg;
 
       this_non_prologue_insn = 0;
@@ -3450,15 +3451,15 @@ restart:
 
       /* Save some code by pre-extracting some useful fields.  */
       high_word = (inst >> 16) & 0xffff;
-      low_word = inst & 0xffff;
+      offset = ((inst & 0xffff) ^ 0x8000) - 0x8000;
       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;
+         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
@@ -3469,19 +3470,19 @@ restart:
       else if (((high_word & 0xFFE0) == 0xafa0) /* sw reg,offset($sp) */
                && !regsize_is_64_bits)
        {
-         set_reg_offset (gdbarch, this_cache, reg, sp + low_word);
+         set_reg_offset (gdbarch, this_cache, reg, sp + offset);
        }
       else if (((high_word & 0xFFE0) == 0xffa0)        /* sd reg,offset($sp) */
                && regsize_is_64_bits)
        {
          /* Irix 6.2 N32 ABI uses sd instructions for saving $gp and $ra.  */
-         set_reg_offset (gdbarch, this_cache, reg, sp + low_word);
+         set_reg_offset (gdbarch, this_cache, reg, sp + offset);
        }
       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;
+         if (offset != frame_offset)
+           frame_addr = sp + offset;
          else if (this_frame && frame_reg == MIPS_SP_REGNUM)
            {
              unsigned alloca_adjust;
@@ -3491,7 +3492,7 @@ restart:
                (this_frame, gdbarch_num_regs (gdbarch) + 30);
              frame_offset = 0;
 
-             alloca_adjust = (unsigned) (frame_addr - (sp + low_word));
+             alloca_adjust = (unsigned) (frame_addr - (sp + offset));
              if (alloca_adjust > 0)
                {
                   /* FP > SP + frame_size.  This may be because of
@@ -3540,7 +3541,7 @@ restart:
       else if ((high_word & 0xFFE0) == 0xafc0  /* sw reg,offset($30) */
                && !regsize_is_64_bits)
        {
-         set_reg_offset (gdbarch, this_cache, reg, frame_addr + low_word);
+         set_reg_offset (gdbarch, this_cache, reg, frame_addr + offset);
        }
       else if ((high_word & 0xFFE0) == 0xE7A0 /* swc1 freg,n($sp) */
                || (high_word & 0xF3E0) == 0xA3C0 /* sx reg,n($s8) */