static int
nios2_in_epilogue_p (struct gdbarch *gdbarch,
		     CORE_ADDR current_pc,
		     CORE_ADDR start_pc)
{
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  /* There has to be a previous instruction in the function.  */
  if (current_pc > start_pc)
    {

      /* Check whether the previous instruction was a stack
	 adjustment.  */
      unsigned int insn
        = read_memory_unsigned_integer (current_pc - NIOS2_OPCODE_SIZE,
					NIOS2_OPCODE_SIZE, byte_order);

      if ((insn & 0xffc0003c) == 0xdec00004	/* ADDI sp, sp, */
	  || (insn & 0xffc1ffff) == 0xdec1883a	/* ADD  sp, sp, */
	  || (insn & 0xffc0003f) == 0xdec00017)	/* LDW  sp, constant(sp) */
	{
	  /* Then check if it's followed by a return or a tail
	     call.  */
          insn = read_memory_unsigned_integer (current_pc, NIOS2_OPCODE_SIZE,
					       byte_order);

	  if (insn == 0xf800283a			/* RET */
	      || insn == 0xe800083a			/* ERET */
	      || (insn & 0x07ffffff) == 0x0000683a	/* JMP */
	      || (insn & 0xffc0003f) == 6)		/* BR */
	    return 1;
	}
    }
  return 0;
}

static CORE_ADDR
amd64_windows_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
{
  CORE_ADDR destination = 0;
  struct gdbarch *gdbarch = get_frame_arch (frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

  /* Check for jmp *<offset>(%rip) (jump near, absolute indirect (/4)).  */
  if (pc && read_memory_unsigned_integer (pc, 2, byte_order) == 0x25ff)
    {
      /* Get opcode offset and see if we can find a reference in our data.  */
      ULONGEST offset
	= read_memory_unsigned_integer (pc + 2, 4, byte_order);

      /* Get address of function pointer at end of pc.  */
      CORE_ADDR indirect_addr = pc + offset + 6;

      struct minimal_symbol *indsym
	= (indirect_addr
	   ? lookup_minimal_symbol_by_pc (indirect_addr).minsym
	   : NULL);
      const char *symname = indsym ? MSYMBOL_LINKAGE_NAME (indsym) : NULL;

      if (symname)
	{
	  if (strncmp (symname, "__imp_", 6) == 0
	      || strncmp (symname, "_imp_", 5) == 0)
	    destination
	      = read_memory_unsigned_integer (indirect_addr, 8, byte_order);
	}
    }

  return destination;
}

static int
i386_darwin_sstep_at_sigreturn (x86_thread_state_t *regs)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
  static const gdb_byte darwin_syscall[] = { 0xcd, 0x80 }; /* int 0x80 */
  gdb_byte buf[sizeof (darwin_syscall)];

  /* Check if PC is at a sigreturn system call.  */
  if (target_read_memory (regs->uts.ts32.__eip, buf, sizeof (buf)) == 0
      && memcmp (buf, darwin_syscall, sizeof (darwin_syscall)) == 0
      && regs->uts.ts32.__eax == 0xb8 /* SYS_sigreturn */)
    {
      ULONGEST uctx_addr;
      ULONGEST mctx_addr;
      ULONGEST flags_addr;
      unsigned int eflags;

      uctx_addr = read_memory_unsigned_integer
		    (regs->uts.ts32.__esp + 4, 4, byte_order);
      mctx_addr = read_memory_unsigned_integer
		    (uctx_addr + 28, 4, byte_order);

      flags_addr = mctx_addr + 12 + 9 * 4;
      read_memory (flags_addr, (gdb_byte *) &eflags, 4);
      eflags |= X86_EFLAGS_T;
      write_memory (flags_addr, (gdb_byte *) &eflags, 4);

      return 1;
    }
  return 0;
}

static CORE_ADDR
ppc_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
{
  unsigned int insnbuf[POWERPC32_PLT_STUB_LEN];
  struct gdbarch *gdbarch = get_frame_arch (frame);
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  CORE_ADDR target = 0;

  if (ppc_insns_match_pattern (frame, pc, powerpc32_plt_stub, insnbuf))
    {
      /* Insn pattern is
		lis   r11, xxxx
		lwz   r11, xxxx(r11)
	 Branch target is in r11.  */

      target = (ppc_insn_d_field (insnbuf[0]) << 16)
	| ppc_insn_d_field (insnbuf[1]);
      target = read_memory_unsigned_integer (target, 4, byte_order);
    }

  if (ppc_insns_match_pattern (frame, pc, powerpc32_plt_stub_so, insnbuf))
    {
      /* Insn pattern is
		lwz   r11, xxxx(r30)
	 Branch target is in r11.  */

      target = get_frame_register_unsigned (frame, tdep->ppc_gp0_regnum + 30)
	       + ppc_insn_d_field (insnbuf[0]);
      target = read_memory_unsigned_integer (target, 4, byte_order);
    }

  return target;
}

static struct trad_frame_cache *
aix_sighandle_frame_cache (struct frame_info *this_frame,
			   void **this_cache)
{
  LONGEST backchain;
  CORE_ADDR base, base_orig, func;
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  struct trad_frame_cache *this_trad_cache;

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

  this_trad_cache = trad_frame_cache_zalloc (this_frame);
  (*this_cache) = this_trad_cache;

  base = get_frame_register_unsigned (this_frame,
                                      gdbarch_sp_regnum (gdbarch));
  base_orig = base;

  if (tdep->wordsize == 4)
    {
      func = read_memory_unsigned_integer (base_orig +
					   SIG_FRAME_PC_OFFSET + 8,
					   tdep->wordsize, byte_order);
      safe_read_memory_integer (base_orig + SIG_FRAME_FP_OFFSET + 8,
				tdep->wordsize, byte_order, &backchain);
      base = (CORE_ADDR)backchain;
    }
  else
    {
      func = read_memory_unsigned_integer (base_orig +
					   SIG_FRAME_LR_OFFSET64,
					   tdep->wordsize, byte_order);
      safe_read_memory_integer (base_orig + SIG_FRAME_FP_OFFSET64,
				tdep->wordsize, byte_order, &backchain);
      base = (CORE_ADDR)backchain;
    }

  trad_frame_set_reg_value (this_trad_cache, gdbarch_pc_regnum (gdbarch), func);
  trad_frame_set_reg_value (this_trad_cache, gdbarch_sp_regnum (gdbarch), base);

  if (tdep->wordsize == 4)
    trad_frame_set_reg_addr (this_trad_cache, tdep->ppc_lr_regnum,
                             base_orig + 0x38 + 52 + 8);
  else
    trad_frame_set_reg_addr (this_trad_cache, tdep->ppc_lr_regnum,
                             base_orig + 0x70 + 320);

  trad_frame_set_id (this_trad_cache, frame_id_build (base, func));
  trad_frame_set_this_base (this_trad_cache, base);

  return this_trad_cache;
}

static int
x86_push_ebp_pattern_p (CORE_ADDR memaddr)
{
  gdb_byte op = read_memory_unsigned_integer (memaddr, 1);
  if (op == 0x55)
    return 1;
  if (op == 0x6a)
    if (read_memory_unsigned_integer (memaddr + 1, 1) == 0x00)
      return 1;

  return 0;
}

CORE_ADDR
i386bsd_sigcontext_addr (struct frame_info *frame)
{
  if (frame->next)
    /* If this isn't the top frame, the next frame must be for the
       signal handler itself.  A pointer to the sigcontext structure
       is passed as the third argument to the signal handler.  */
    return read_memory_unsigned_integer (frame->next->frame + 16, 4);

  /* This is the top frame.  We'll have to find the address of the
     sigcontext structure by looking at the stack pointer.  */
  return read_memory_unsigned_integer (read_register (SP_REGNUM) + 8, 4);
}

static CORE_ADDR
moxie_analyze_prologue (CORE_ADDR start_addr, CORE_ADDR end_addr,
		      struct moxie_frame_cache *cache,
		      struct frame_info *this_frame)
{
  CORE_ADDR next_addr;
  ULONGEST inst, inst2;
  LONGEST offset;
  int regnum;

  /* Record where the jsra instruction saves the PC and FP.  */
  cache->saved_regs[MOXIE_PC_REGNUM] = -4;
  cache->saved_regs[MOXIE_FP_REGNUM] = 0;
  cache->framesize = 0;

  if (start_addr >= end_addr)
    return end_addr;

  for (next_addr = start_addr; next_addr < end_addr; )
    {
      inst = read_memory_unsigned_integer (next_addr, 2);

      /* Match "push $rN" where N is between 2 and 13 inclusive.  */
      if (inst >= 0x0614 && inst <= 0x061f)
	{
	  regnum = inst & 0x000f;
	  cache->framesize += 4;
	  cache->saved_regs[regnum] = cache->framesize;
	  next_addr += 2;
	}

      /* Optional stack allocation for args and local vars <= 4
	 byte.  */
      else if (inst == 0x01f0)           /* ldi.l $r12, X */
	{
	  offset = read_memory_integer (next_addr + 2, 4);
	  inst2 = read_memory_unsigned_integer (next_addr + 6, 2);

	  if (inst2 == 0x051f)           /* add.l $sp, $r12 */
	    {
	      cache->framesize += offset;
	    }

	  return (next_addr + 8);
	}
      else  /* This is not a prologue instruction.  */
	break;
    }

  return next_addr;
}

static int
x86_mov_reg_to_local_stack_frame_p (CORE_ADDR memaddr, int *regnum, int *offset)
{
  gdb_byte op;
  int source_reg_mod = 0;
  int target_reg_mod = 0;
  op = read_memory_unsigned_integer (memaddr, 1);

  if (REX_W_PREFIX_P (op))
    {
      source_reg_mod = REX_W_R (op) << 3;
      target_reg_mod = REX_W_B (op) << 3;
      /* The target register should be ebp/rbp which doesn't require an
         extra bit to specify.  */
      if (target_reg_mod == 1)
        return 0;
      op = read_memory_unsigned_integer (++memaddr, 1);
    }

  /* Detect a 'mov %ebx,-0xc(%ebp)' type instruction.
     aka 'MOV r/m32,r32' in Intel syntax terms.  */
  if (op == 0x89)
    {
      op = read_memory_unsigned_integer (memaddr + 1, 1);
      /* Mask off the 3-5 bits which indicate the destination register
         if this is a ModR/M byte.  */
      int op_sans_dest_reg = op & (~0x38);

      /* Look for a ModR/M byte with Mod bits 01 and R/M bits 101 
         ([EBP] disp8), i.e. 01xxx101
         I want to see a destination of ebp-disp8 or ebp-disp32.   */
      if (op_sans_dest_reg != 0x45 && op_sans_dest_reg != 0x85)
        return 0;

      int saved_reg = ((op >> 3) & 0x7) | source_reg_mod;
      int off = 0;
      if (op_sans_dest_reg == 0x45)
        off = (int8_t) read_memory_unsigned_integer (memaddr + 2, 1);
      if (op_sans_dest_reg == 0x85)
        off = (uint32_t) read_memory_unsigned_integer (memaddr + 2, 4);

      if (off > 0)
        return 0;

      if (regnum != NULL)
        *regnum = saved_reg;
      if (offset != NULL)
        *offset = abs (off);
      return 1;
    }

static CORE_ADDR
vax_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  gdb_byte op = read_memory_unsigned_integer (pc, 1, byte_order);

  if (op == 0x11)
    pc += 2;			/* skip brb */
  if (op == 0x31)
    pc += 3;			/* skip brw */
  if (op == 0xC2
      && read_memory_unsigned_integer (pc + 2, 1, byte_order) == 0x5E)
    pc += 3;			/* skip subl2 */
  if (op == 0x9E
      && read_memory_unsigned_integer (pc + 1, 1, byte_order) == 0xAE
      && read_memory_unsigned_integer (pc + 3, 1, byte_order) == 0x5E)
    pc += 4;			/* skip movab */
  if (op == 0x9E
      && read_memory_unsigned_integer (pc + 1, 1, byte_order) == 0xCE
      && read_memory_unsigned_integer (pc + 4, 1, byte_order) == 0x5E)
    pc += 5;			/* skip movab */
  if (op == 0x9E
      && read_memory_unsigned_integer (pc + 1, 1, byte_order) == 0xEE
      && read_memory_unsigned_integer (pc + 6, 1, byte_order) == 0x5E)
    pc += 7;			/* skip movab */

  return pc;
}

static int
x86_pop_p (CORE_ADDR memaddr)
{
  gdb_byte op = read_memory_unsigned_integer (memaddr, 1);

  /* A REX.W prefix opcode indicating that the register being popped is
     in the second half of the reg set.  */
  if (op == 0x41)
    op = read_memory_unsigned_integer (memaddr + 1, 1);
    
  /* 58+ rd      POP r32 */
  if ((op & 0xf8) == 0x58)
    return 1;
  return 0;
}

static CORE_ADDR
ppc64_plt_entry_point (struct gdbarch *gdbarch, CORE_ADDR plt)
{
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  /* The first word of the PLT entry is the function entry point.  */
  return (CORE_ADDR) read_memory_unsigned_integer (plt, 8, byte_order);
}

static void
ppc_linux_sigtramp_cache (struct frame_info *next_frame,
			  struct trad_frame_cache *this_cache,
			  CORE_ADDR func, LONGEST offset,
			  int bias)
{
  CORE_ADDR base;
  CORE_ADDR regs;
  CORE_ADDR gpregs;
  CORE_ADDR fpregs;
  int i;
  struct gdbarch *gdbarch = get_frame_arch (next_frame);
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  base = frame_unwind_register_unsigned (next_frame,
					 gdbarch_sp_regnum (current_gdbarch));
  if (bias > 0 && frame_pc_unwind (next_frame) != func)
    /* See below, some signal trampolines increment the stack as their
       first instruction, need to compensate for that.  */
    base -= bias;

  /* Find the address of the register buffer pointer.  */
  regs = base + offset;
  /* Use that to find the address of the corresponding register
     buffers.  */
  gpregs = read_memory_unsigned_integer (regs, tdep->wordsize);
  fpregs = gpregs + 48 * tdep->wordsize;

  /* General purpose.  */
  for (i = 0; i < 32; i++)
    {
      int regnum = i + tdep->ppc_gp0_regnum;
      trad_frame_set_reg_addr (this_cache, regnum, gpregs + i * tdep->wordsize);
    }
  trad_frame_set_reg_addr (this_cache,
			   gdbarch_pc_regnum (current_gdbarch),
			   gpregs + 32 * tdep->wordsize);
  trad_frame_set_reg_addr (this_cache, tdep->ppc_ctr_regnum,
			   gpregs + 35 * tdep->wordsize);
  trad_frame_set_reg_addr (this_cache, tdep->ppc_lr_regnum,
			   gpregs + 36 * tdep->wordsize);
  trad_frame_set_reg_addr (this_cache, tdep->ppc_xer_regnum,
			   gpregs + 37 * tdep->wordsize);
  trad_frame_set_reg_addr (this_cache, tdep->ppc_cr_regnum,
			   gpregs + 38 * tdep->wordsize);

  if (ppc_floating_point_unit_p (gdbarch))
    {
      /* Floating point registers.  */
      for (i = 0; i < 32; i++)
	{
	  int regnum = i + gdbarch_fp0_regnum (current_gdbarch);
	  trad_frame_set_reg_addr (this_cache, regnum,
				   fpregs + i * tdep->wordsize);
	}
      trad_frame_set_reg_addr (this_cache, tdep->ppc_fpscr_regnum,
                         fpregs + 32 * tdep->wordsize);
    }
  trad_frame_set_id (this_cache, frame_id_build (base, func));
}

static CORE_ADDR
rs6000_convert_from_func_ptr_addr (struct gdbarch *gdbarch,
				   CORE_ADDR addr,
				   struct target_ops *targ)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  struct obj_section *s;

  s = find_pc_section (addr);

  /* Normally, functions live inside a section that is executable.
     So, if ADDR points to a non-executable section, then treat it
     as a function descriptor and return the target address iff
     the target address itself points to a section that is executable.  */
  if (s && (s->the_bfd_section->flags & SEC_CODE) == 0)
    {
      CORE_ADDR pc = 0;
      struct obj_section *pc_section;
      volatile struct gdb_exception e;

      TRY_CATCH (e, RETURN_MASK_ERROR)
        {
          pc = read_memory_unsigned_integer (addr, tdep->wordsize, byte_order);
        }

static enum return_value_convention
sparc32_return_value (struct gdbarch *gdbarch, struct type *type,
		      struct regcache *regcache, gdb_byte *readbuf,
		      const gdb_byte *writebuf)
{
  /* The psABI says that "...every stack frame reserves the word at
     %fp+64.  If a function returns a structure, union, or
     quad-precision value, this word should hold the address of the
     object into which the return value should be copied."  This
     guarantees that we can always find the return value, not just
     before the function returns.  */

  if (sparc_structure_or_union_p (type)
      || (sparc_floating_p (type) && TYPE_LENGTH (type) == 16))
    {
      if (readbuf)
	{
	  ULONGEST sp;
	  CORE_ADDR addr;

	  regcache_cooked_read_unsigned (regcache, SPARC_SP_REGNUM, &sp);
	  addr = read_memory_unsigned_integer (sp + 64, 4);
	  read_memory (addr, readbuf, TYPE_LENGTH (type));
	}

      return RETURN_VALUE_ABI_PRESERVES_ADDRESS;
    }

  if (readbuf)
    sparc32_extract_return_value (type, regcache, readbuf);
  if (writebuf)
    sparc32_store_return_value (type, regcache, writebuf);

  return RETURN_VALUE_REGISTER_CONVENTION;
}

static CORE_ADDR
ppc64_desc_entry_point (struct gdbarch *gdbarch, CORE_ADDR desc)
{
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  /* The first word of the descriptor is the entry point.  */
  return (CORE_ADDR) read_memory_unsigned_integer (desc, 8, byte_order);
}

static int
amd64_darwin_sstep_at_sigreturn (x86_thread_state_t *regs)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
  static const gdb_byte darwin_syscall[] = { 0x0f, 0x05 }; /* syscall */
  gdb_byte buf[sizeof (darwin_syscall)];

  /* Check if PC is at a sigreturn system call.  */
  if (target_read_memory (regs->uts.ts64.__rip, buf, sizeof (buf)) == 0
      && memcmp (buf, darwin_syscall, sizeof (darwin_syscall)) == 0
      && (regs->uts.ts64.__rax & 0xffffffff) == 0x20000b8 /* SYS_sigreturn */)
    {
      ULONGEST mctx_addr;
      ULONGEST flags_addr;
      unsigned int rflags;

      mctx_addr = read_memory_unsigned_integer
		    (regs->uts.ts64.__rdi + 48, 8, byte_order);
      flags_addr = mctx_addr + 16 + 17 * 8;

      /* AMD64 is little endian.  */
      read_memory (flags_addr, (gdb_byte *) &rflags, 4);
      rflags |= X86_EFLAGS_T;
      write_memory (flags_addr, (gdb_byte *) &rflags, 4);

      return 1;
    }
  return 0;
}

static CORE_ADDR
sparc64_linux_step_trap (struct frame_info *frame, unsigned long insn)
{
  if (insn == 0x91d0206d)
    {
      struct gdbarch *gdbarch = get_frame_arch (frame);
      enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);

      ULONGEST sp = get_frame_register_unsigned (frame, SPARC_SP_REGNUM);
      if (sp & 1)
	sp += BIAS;

      /* The kernel puts the sigreturn registers on the stack,
	 and this is where the signal unwinding state is take from
	 when returning from a signal.

	 A siginfo_t sits 192 bytes from the base of the stack.  This
	 siginfo_t is 128 bytes, and is followed by the sigreturn
	 register save area.  The saved PC sits at a 136 byte offset
	 into there.  */

      return read_memory_unsigned_integer (sp + 192 + 128 + 136,
					   8, byte_order);
    }

  return 0;
}

CORE_ADDR
arm_wince_skip_main_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  ULONGEST this_instr;

  this_instr = read_memory_unsigned_integer (pc, 4, byte_order);

  /* bl offset <__gccmain> */
  if ((this_instr & 0xfff00000) == 0xeb000000)
    {
#define sign_extend(V, N) \
  (((long) (V) ^ (1L << ((N) - 1))) - (1L << ((N) - 1)))

      long offset = sign_extend (this_instr & 0x000fffff, 23) << 2;
      CORE_ADDR call_dest = (pc + 8 + offset) & 0xffffffffU;
      struct minimal_symbol *s = lookup_minimal_symbol_by_pc (call_dest);

      if (s != NULL
	  && SYMBOL_LINKAGE_NAME (s) != NULL
	  && strcmp (SYMBOL_LINKAGE_NAME (s), "__gccmain") == 0)
	pc += 4;
    }

  return pc;
}

static CORE_ADDR
sparc32_extract_struct_value_address (struct regcache *regcache)
{
  ULONGEST sp;

  regcache_cooked_read_unsigned (regcache, SPARC_SP_REGNUM, &sp);
  return read_memory_unsigned_integer (sp + 64, 4);
}