i386.c

GCC编译器源代码

						    "$_GLOBAL_OFFSET_TABLE_"), 
					   xops[1]));
	}
      else
	{
	  output_asm_insn (AS1 (call,%P1), xops);
	  output_asm_insn ("addl $_GLOBAL_OFFSET_TABLE_,%0", xops);
	  pic_label_rtx = 0;
	}
    }

  else
    {
      xops[0] = pic_offset_table_rtx;
      xops[1] = gen_label_rtx ();
 
      if (do_rtl)
	{
	  /* We can't put a raw CODE_LABEL into the RTL, and we can't emit
	     a new CODE_LABEL after reload, so we need a single pattern to
	     emit the 3 necessary instructions.  */
	  emit_insn (gen_prologue_get_pc_and_set_got (xops[0]));
	}
      else
	{
	  output_asm_insn (AS1 (call,%P1), xops);
	  ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, "L", 
				     CODE_LABEL_NUMBER (xops[1]));
	  output_asm_insn (AS1 (pop%L0,%0), xops);
	  output_asm_insn ("addl $_GLOBAL_OFFSET_TABLE_+[.-%P1],%0", xops);
	}
    } 

  /* When -fpic, we must emit a scheduling barrier, so that the instruction
     that restores %ebx (which is PIC_OFFSET_TABLE_REGNUM), does not get
     moved before any instruction which implicitly uses the got.   */

  if (do_rtl)
    emit_insn (gen_blockage ());
}

static void
ix86_prologue (do_rtl)
     int do_rtl;
{
  register int regno;
  int limit;
  rtx xops[4];
  int pic_reg_used = flag_pic && (current_function_uses_pic_offset_table
				  || current_function_uses_const_pool);
  long tsize = get_frame_size ();
  rtx insn;
  int cfa_offset = INCOMING_FRAME_SP_OFFSET, cfa_store_offset = cfa_offset;
  
  xops[0] = stack_pointer_rtx;
  xops[1] = frame_pointer_rtx;
  xops[2] = GEN_INT (tsize);

  if (frame_pointer_needed)
    {
      if (do_rtl)
	{
	  insn = emit_insn (gen_rtx (SET, VOIDmode,
				     gen_rtx (MEM, SImode,
					      gen_rtx (PRE_DEC, SImode,
						       stack_pointer_rtx)),
				     frame_pointer_rtx));

	  RTX_FRAME_RELATED_P (insn) = 1;
	  insn = emit_move_insn (xops[1], xops[0]);
	  RTX_FRAME_RELATED_P (insn) = 1;
	}

      else
	{
	  output_asm_insn ("push%L1 %1", xops); 
#ifdef INCOMING_RETURN_ADDR_RTX
 	  if (dwarf2out_do_frame ())
 	    {
 	      char *l = dwarf2out_cfi_label ();

 	      cfa_store_offset += 4;
 	      cfa_offset = cfa_store_offset;
 	      dwarf2out_def_cfa (l, STACK_POINTER_REGNUM, cfa_offset);
 	      dwarf2out_reg_save (l, FRAME_POINTER_REGNUM, - cfa_store_offset);
 	    }
#endif

	  output_asm_insn (AS2 (mov%L0,%0,%1), xops); 
#ifdef INCOMING_RETURN_ADDR_RTX
 	  if (dwarf2out_do_frame ())
 	    dwarf2out_def_cfa ("", FRAME_POINTER_REGNUM, cfa_offset);
#endif
	}
    }

  if (tsize == 0)
    ;
  else if (! TARGET_STACK_PROBE || tsize < CHECK_STACK_LIMIT)
    {
      if (do_rtl)
	{
	  insn = emit_insn (gen_prologue_set_stack_ptr (xops[2]));
	  RTX_FRAME_RELATED_P (insn) = 1;
	}
      else 
	{
	  output_asm_insn (AS2 (sub%L0,%2,%0), xops);
#ifdef INCOMING_RETURN_ADDR_RTX
 	  if (dwarf2out_do_frame ())
 	    {
 	      cfa_store_offset += tsize;
 	      if (! frame_pointer_needed)
 		{
 		  cfa_offset = cfa_store_offset;
 		  dwarf2out_def_cfa ("", STACK_POINTER_REGNUM, cfa_offset);
 		}
 	    }
#endif
	}
    }
  else 
    {
      xops[3] = gen_rtx (REG, SImode, 0);
      if (do_rtl)
      emit_move_insn (xops[3], xops[2]);
      else
	output_asm_insn (AS2 (mov%L0,%2,%3), xops);

      xops[3] = gen_rtx (MEM, FUNCTION_MODE,
			 gen_rtx (SYMBOL_REF, Pmode, "_alloca"));

      if (do_rtl)
	emit_call_insn (gen_rtx (CALL, VOIDmode, xops[3], const0_rtx));
      else
	output_asm_insn (AS1 (call,%P3), xops);
    }

  /* Note If use enter it is NOT reversed args.
     This one is not reversed from intel!!
     I think enter is slower.  Also sdb doesn't like it.
     But if you want it the code is:
     {
     xops[3] = const0_rtx;
     output_asm_insn ("enter %2,%3", xops);
     }
     */

  limit = (frame_pointer_needed ? FRAME_POINTER_REGNUM : STACK_POINTER_REGNUM);
  for (regno = limit - 1; regno >= 0; regno--)
    if ((regs_ever_live[regno] && ! call_used_regs[regno])
	|| (regno == PIC_OFFSET_TABLE_REGNUM && pic_reg_used))
      {
	xops[0] = gen_rtx (REG, SImode, regno);
	if (do_rtl)
	  {
	    insn = emit_insn (gen_rtx (SET, VOIDmode,
				       gen_rtx (MEM, SImode,
						gen_rtx (PRE_DEC, SImode,
							 stack_pointer_rtx)),
				       xops[0]));

	    RTX_FRAME_RELATED_P (insn) = 1;
	  }
	else
	  {
	    output_asm_insn ("push%L0 %0", xops);
#ifdef INCOMING_RETURN_ADDR_RTX
 	    if (dwarf2out_do_frame ())
 	      {
 		char *l = dwarf2out_cfi_label ();

 		cfa_store_offset += 4;
 		if (! frame_pointer_needed)
 		  {
 		    cfa_offset = cfa_store_offset;
 		    dwarf2out_def_cfa (l, STACK_POINTER_REGNUM, cfa_offset);
 		  }

 		dwarf2out_reg_save (l, regno, - cfa_store_offset);
 	      }
#endif
 	  }
      }

  if (pic_reg_used)
    load_pic_register (do_rtl);

  /* If we are profiling, make sure no instructions are scheduled before
     the call to mcount.  However, if -fpic, the above call will have
     done that.  */
  if ((profile_flag || profile_block_flag)
      && ! pic_reg_used && do_rtl)
    emit_insn (gen_blockage ());
}

/* Return 1 if it is appropriate to emit `ret' instructions in the
   body of a function.  Do this only if the epilogue is simple, needing a
   couple of insns.  Prior to reloading, we can't tell how many registers
   must be saved, so return 0 then.  Return 0 if there is no frame 
   marker to de-allocate.

   If NON_SAVING_SETJMP is defined and true, then it is not possible
   for the epilogue to be simple, so return 0.  This is a special case
   since NON_SAVING_SETJMP will not cause regs_ever_live to change
   until final, but jump_optimize may need to know sooner if a
   `return' is OK.  */

int
ix86_can_use_return_insn_p ()
{
  int regno;
  int nregs = 0;
  int reglimit = (frame_pointer_needed
		  ? FRAME_POINTER_REGNUM : STACK_POINTER_REGNUM);
  int pic_reg_used = flag_pic && (current_function_uses_pic_offset_table
				  || current_function_uses_const_pool);

#ifdef NON_SAVING_SETJMP
  if (NON_SAVING_SETJMP && current_function_calls_setjmp)
    return 0;
#endif

  if (! reload_completed)
    return 0;

  for (regno = reglimit - 1; regno >= 0; regno--)
    if ((regs_ever_live[regno] && ! call_used_regs[regno])
	|| (regno == PIC_OFFSET_TABLE_REGNUM && pic_reg_used))
      nregs++;

  return nregs == 0 || ! frame_pointer_needed;
}

/* This function generates the assembly code for function exit.
   FILE is an stdio stream to output the code to.
   SIZE is an int: how many units of temporary storage to deallocate. */

void
function_epilogue (file, size)
     FILE *file;
     int size;
{
    return;
}

/* Restore function stack, frame, and registers. */ 

void
ix86_expand_epilogue ()
{
  ix86_epilogue (1);
}

static void
ix86_epilogue (do_rtl)
     int do_rtl;
{
  register int regno;
  register int nregs, limit;
  int offset;
  rtx xops[3];
  int pic_reg_used = flag_pic && (current_function_uses_pic_offset_table
				  || current_function_uses_const_pool);
  long tsize = get_frame_size ();

  /* Compute the number of registers to pop */

  limit = (frame_pointer_needed ? FRAME_POINTER_REGNUM : STACK_POINTER_REGNUM);

  nregs = 0;

  for (regno = limit - 1; regno >= 0; regno--)
    if ((regs_ever_live[regno] && ! call_used_regs[regno])
	|| (regno == PIC_OFFSET_TABLE_REGNUM && pic_reg_used))
      nregs++;

  /* sp is often  unreliable so we must go off the frame pointer.

     In reality, we may not care if sp is unreliable, because we can restore
     the register relative to the frame pointer.  In theory, since each move
     is the same speed as a pop, and we don't need the leal, this is faster.
     For now restore multiple registers the old way. */

  offset = - tsize - (nregs * UNITS_PER_WORD);

  xops[2] = stack_pointer_rtx;

  /* When -fpic, we must emit a scheduling barrier, so that the instruction
     that restores %ebx (which is PIC_OFFSET_TABLE_REGNUM), does not get
     moved before any instruction which implicitly uses the got.  This
     includes any instruction which uses a SYMBOL_REF or a LABEL_REF.

     Alternatively, this could be fixed by making the dependence on the
     PIC_OFFSET_TABLE_REGNUM explicit in the RTL.  */

  if (flag_pic || profile_flag || profile_block_flag)
    emit_insn (gen_blockage ());

  if (nregs > 1 || ! frame_pointer_needed)
    {
      if (frame_pointer_needed)
	{
	  xops[0] = adj_offsettable_operand (AT_BP (QImode), offset);
	  if (do_rtl)
	    emit_insn (gen_movsi_lea (xops[2], XEXP (xops[0], 0)));
	  else
	    output_asm_insn (AS2 (lea%L2,%0,%2), xops);
	}

      for (regno = 0; regno < limit; regno++)
	if ((regs_ever_live[regno] && ! call_used_regs[regno])
	    || (regno == PIC_OFFSET_TABLE_REGNUM && pic_reg_used))
	  {
	    xops[0] = gen_rtx (REG, SImode, regno);

	    if (do_rtl)
	      emit_insn (gen_pop (xops[0]));
	    else
	      output_asm_insn ("pop%L0 %0", xops);
	  }
    }

  else
    for (regno = 0; regno < limit; regno++)
      if ((regs_ever_live[regno] && ! call_used_regs[regno])
	  || (regno == PIC_OFFSET_TABLE_REGNUM && pic_reg_used))
	{
	  xops[0] = gen_rtx (REG, SImode, regno);
	  xops[1] = adj_offsettable_operand (AT_BP (Pmode), offset);

	  if (do_rtl)
	    emit_move_insn (xops[0], xops[1]);
	  else
	    output_asm_insn (AS2 (mov%L0,%1,%0), xops);

	  offset += 4;
	}

  if (frame_pointer_needed)
    {
      /* If not an i386, mov & pop is faster than "leave". */

      if (TARGET_USE_LEAVE)
	{
	  if (do_rtl)
	    emit_insn (gen_leave());
	  else
	    output_asm_insn ("leave", xops);
	}
      else
	{
	  xops[0] = frame_pointer_rtx;
	  xops[1] = stack_pointer_rtx;

	  if (do_rtl)
	    {
	      emit_insn (gen_epilogue_set_stack_ptr());
	      emit_insn (gen_pop (xops[0]));
	    }
	  else
	    {
	      output_asm_insn (AS2 (mov%L2,%0,%2), xops);
	      output_asm_insn ("pop%L0 %0", xops);
	    }
	}
    }

  else if (tsize)
    {
      /* If there is no frame pointer, we must still release the frame. */
      xops[0] = GEN_INT (tsize);

      if (do_rtl)
	emit_insn (gen_rtx (SET, VOIDmode, xops[2],
			    gen_rtx (PLUS, SImode, xops[2], xops[0])));
      else
	output_asm_insn (AS2 (add%L2,%0,%2), xops);
    }

#ifdef FUNCTION_BLOCK_PROFILER_EXIT
  if (profile_block_flag == 2)
    {
      FUNCTION_BLOCK_PROFILER_EXIT(file);
    }
#endif

  if (current_function_pops_args && current_function_args_size)
    {
      xops[1] = GEN_INT (current_function_pops_args);

      /* i386 can only pop 32K bytes (maybe 64K?  Is it signed?).  If
	 asked to pop more, pop return address, do explicit add, and jump
	 indirectly to the caller. */

      if (current_function_pops_args >= 32768)
	{
	  /* ??? Which register to use here? */
	  xops[0] = gen_rtx (REG, SImode, 2);

	  if (do_rtl)
	    {
	      emit_insn (gen_pop (xops[0]));
	      emit_insn (gen_rtx (SET, VOIDmode, xops[2],
				  gen_rtx (PLUS, SImode, xops[1], xops[2])));
	      emit_jump_insn (xops[0]);
	    }
	  else
	    {
	      output_asm_insn ("pop%L0 %0", xops);
	      output_asm_insn (AS2 (add%L2,%1,%2), xops);
	      output_asm_insn ("jmp %*%0", xops);
	    }
	}
      else 
	{
	  if (do_rtl)
	    emit_jump_insn (gen_return_pop_internal (xops[1]));
	  else
	    output_asm_insn ("ret %1", xops);
	}
    }
  else
    {
      if (do_rtl)
	emit_jump_insn (gen_return_internal ());
      else
	output_asm_insn ("ret", xops);
    }
}

/* GO_IF_LEGITIMATE_ADDRESS recognizes an RTL expression
   that is a valid memory address for an instruction.
   The MODE argument is the machine mode for the MEM expression
   that wants to use this address.

   On x86, legitimate addresses are:
	base				movl (base),reg
	displacement			movl disp,reg
	base + displacement		movl disp(base),reg
	index + base			movl (base,index),reg
	(index + base) + displacement	movl disp(base,index),reg
	index*scale			movl (,index,scale),reg
	index*scale + disp		movl disp(,index,scale),reg
	index*scale + base 		movl (base,index,scale),reg
	(index*scale + base) + disp	movl disp(base,index,scale),reg

	In each case, scale can be 1, 2, 4, 8.  */

/* This is exactly the same as print_operand_addr, except that
   it recognizes addresses instead of printing them.

   It only recognizes address in canonical form.  LEGITIMIZE_ADDRESS should
   convert common non-canonical forms to canonical form so that they will
   be recognized.  */

#define ADDR_INVALID(msg,insn)						\
do {									\
  if (TARGET_DEBUG_ADDR)						\
    {									\
      fprintf (stderr, msg);						\
      debug_rtx (insn);							\
    }									\
} while (0)

int
legitimate_address_p (mode, addr, strict)
     enum machine_mode mode;
     register rtx addr;
     int strict;
{
  rtx base  = NULL_RTX;
  rtx indx  = NULL_RTX;
  rtx scale = NULL_RTX;
  rtx disp  = NULL_RTX;

  if (TARGET_DEBUG_ADDR)
    {
      fprintf (stderr,
	       "\n======\nGO_IF_LEGITIMATE_ADDRESS, mode = %s, strict = %d\n",
	       GET_MODE_NAME (mode), strict);

      debug_rtx (addr);
    }