Nios II R2 support for GDB.

Nios II R2 support for GDB.

2015-08-03  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/
	* nios2-tdep.h: Include opcode/nios2.h here.
	(NIOS2_CDX_OPCODE_SIZE): New.
	(struct gdbarch_tdep): Add OP parameter to syscall_next_pc.
	* nios2-tdep.c: Don't include opcode/nios2.h here.
	(nios2_fetch_insn): For R2, try reading 2-byte instruction if
	4-byte read fails.
	(nios2_match_add, nios2_match_sub): Add cases for R2 encodings.
	(nios2_match_addi, nios2_match_orhi): Likewise.
	(nios2_match_stw, nios2_match_ldw): Likewise.
	(nios2_match_rdctl): Likewise.
	(nios2_match_stwm, nios2_match_ldwm): New.
	(nios2_match_branch): Add cases for R2 encodings.
	(nios2_match_jmpi, nios2_match_calli): Likewise.
	(nios2_match_jmpr, nios2_match_callr): Likewise.
	(nios2_match_break, nios2_match_trap): Likewise.
	(nios2_in_epilogue_p): Add R2 support.
	(nios2_analyze_prologue): Update comments.  Recognize R2 CDX
	prologues.
	(nios2_breakpoint_from_pc): Handle R2 instructions.
	(nios2_get_next_pc): Likewise.  Adjust call to
	tdep->syscall_next_pc.
	* nios2-linux-tdep.c (nios2_r1_linux_rt_sigreturn_tramp_frame):
	Renamed from nios2_linux_rt_sigreturn_tramp_frame.  Use
	instruction field macros instead of literal hex values.
	(nios2_r2_linux_rt_sigreturn_tramp_frame): New.
	(nios2_linux_syscall_next_pc): Adjust signature to pass OP.
	Use size field from OP instead of assuming all instructions
	are the same size.
	(nios2_linux_init_abi): Register appropriate unwinder for mach.

	gdb/gdbserver/
	* linux-nios2-low.c (NIOS2_BREAKPOINT): Conditionalize for
	arch variant.
	(CDX_BREAKPOINT): Define for R2.
	(nios2_breakpoint_at): Check for CDX_BREAKPOINT when R2.
	(the_low_target): Add comments.