i386.c

gcc库的原代码,对编程有很大帮助.

	      middlehalf[1] = adj_offsettable_operand (operands[1], size-8);
	      latehalf[1] = adj_offsettable_operand (operands[1], size-4);
	    }
	  else
	    {
	      operands[1] = gen_rtx (MEM, DImode, latehalf[0]);
	      latehalf[1] = adj_offsettable_operand (operands[1], size-4);
	    }
	}
      else if (size == 12
		 && reg_mentioned_p (middlehalf[0], XEXP (operands[1], 0)))
	{
	  /* Check for two regs used by both source and dest. */
	  if (reg_mentioned_p (operands[0], XEXP (operands[1], 0))
		|| reg_mentioned_p (latehalf[0], XEXP (operands[1], 0)))
		goto compadr;

	  /* JRV says this can't happen: */
	  if (addreg0 || addreg1)
	      abort();

	  /* Only the middle reg conflicts; simply put it last. */
	  output_asm_insn (singlemove_string (operands), operands);
	  output_asm_insn (singlemove_string (latehalf), latehalf);
	  output_asm_insn (singlemove_string (middlehalf), middlehalf);
	  return "";
	}
      else if (reg_mentioned_p (operands[0], XEXP (operands[1], 0)))
	/* If the low half of dest is mentioned in the source memory
	   address, the arrange to emit the move late half first.  */
	dest_overlapped_low = 1;
    }

  /* If one or both operands autodecrementing,
     do the two words, high-numbered first.  */

  /* Likewise,  the first move would clobber the source of the second one,
     do them in the other order.  This happens only for registers;
     such overlap can't happen in memory unless the user explicitly
     sets it up, and that is an undefined circumstance.  */

/*
  if (optype0 == PUSHOP || optype1 == PUSHOP
      || (optype0 == REGOP && optype1 == REGOP
	  && REGNO (operands[0]) == REGNO (latehalf[1]))
      || dest_overlapped_low)
*/
  if (optype0 == PUSHOP || optype1 == PUSHOP
      || (optype0 == REGOP && optype1 == REGOP
	  && ((middlehalf[1] && REGNO (operands[0]) == REGNO (middlehalf[1]))
	      || REGNO (operands[0]) == REGNO (latehalf[1])))
      || dest_overlapped_low)
    {
      /* Make any unoffsettable addresses point at high-numbered word.  */
      if (addreg0)
	asm_add (size-4, addreg0);
      if (addreg1)
	asm_add (size-4, addreg1);

      /* Do that word.  */
      output_asm_insn (singlemove_string (latehalf), latehalf);

      /* Undo the adds we just did.  */
      if (addreg0)
         asm_add (-4, addreg0);
      if (addreg1)
	asm_add (-4, addreg1);

      if (size == 12)
        {
        output_asm_insn (singlemove_string (middlehalf), middlehalf);
        if (addreg0)
           asm_add (-4, addreg0);
        if (addreg1)
	   asm_add (-4, addreg1);
	}

      /* Do low-numbered word.  */
      return singlemove_string (operands);
    }

  /* Normal case: do the two words, low-numbered first.  */

  output_asm_insn (singlemove_string (operands), operands);

  /* Do the middle one of the three words for long double */
  if (size == 12)
    {
      if (addreg0)
        asm_add (4, addreg0);
      if (addreg1)
        asm_add (4, addreg1);

      output_asm_insn (singlemove_string (middlehalf), middlehalf);
    }

  /* Make any unoffsettable addresses point at high-numbered word.  */
  if (addreg0)
    asm_add (4, addreg0);
  if (addreg1)
    asm_add (4, addreg1);

  /* Do that word.  */
  output_asm_insn (singlemove_string (latehalf), latehalf);

  /* Undo the adds we just did.  */
  if (addreg0)
    asm_add (4-size, addreg0);
  if (addreg1)
    asm_add (4-size, addreg1);

  return "";
}


#define MAX_TMPS 2		/* max temporary registers used */

/* Output the appropriate code to move push memory on the stack */

char *
output_move_pushmem (operands, insn, length, tmp_start, n_operands)
     rtx operands[];
     rtx insn;
     int length;
     int tmp_start;
     int n_operands;
{

  struct {
    char *load;
    char *push;
    rtx   xops[2];
  } tmp_info[MAX_TMPS];

  rtx src = operands[1];
  int max_tmps = 0;
  int offset = 0;
  int stack_p = reg_overlap_mentioned_p (stack_pointer_rtx, src);
  int stack_offset = 0;
  int i, num_tmps;
  rtx xops[1];

  if (!offsettable_memref_p (src))
    fatal_insn ("Source is not offsettable", insn);

  if ((length & 3) != 0)
    fatal_insn ("Pushing non-word aligned size", insn);

  /* Figure out which temporary registers we have available */
  for (i = tmp_start; i < n_operands; i++)
    {
      if (GET_CODE (operands[i]) == REG)
	{
	  if (reg_overlap_mentioned_p (operands[i], src))
	    continue;

	  tmp_info[ max_tmps++ ].xops[1] = operands[i];
	  if (max_tmps == MAX_TMPS)
	    break;
	}
    }

  if (max_tmps == 0)
    for (offset = length - 4; offset >= 0; offset -= 4)
      {
	xops[0] = adj_offsettable_operand (src, offset + stack_offset);
	output_asm_insn (AS1(push%L0,%0), xops);
	if (stack_p)
	  stack_offset += 4;
      }

  else
    for (offset = length - 4; offset >= 0; )
      {
	for (num_tmps = 0; num_tmps < max_tmps && offset >= 0; num_tmps++)
	  {
	    tmp_info[num_tmps].load    = AS2(mov%L0,%0,%1);
	    tmp_info[num_tmps].push    = AS1(push%L0,%1);
	    tmp_info[num_tmps].xops[0] = adj_offsettable_operand (src, offset + stack_offset);
	    offset -= 4;
	  }

	for (i = 0; i < num_tmps; i++)
	  output_asm_insn (tmp_info[i].load, tmp_info[i].xops);

	for (i = 0; i < num_tmps; i++)
	  output_asm_insn (tmp_info[i].push, tmp_info[i].xops);

	if (stack_p)
	  stack_offset += 4*num_tmps;
      }

  return "";
}



/* Output the appropriate code to move data between two memory locations */

char *
output_move_memory (operands, insn, length, tmp_start, n_operands)
     rtx operands[];
     rtx insn;
     int length;
     int tmp_start;
     int n_operands;
{
  struct {
    char *load;
    char *store;
    rtx   xops[3];
  } tmp_info[MAX_TMPS];

  rtx dest = operands[0];
  rtx src  = operands[1];
  rtx qi_tmp = NULL_RTX;
  int max_tmps = 0;
  int offset = 0;
  int i, num_tmps;
  rtx xops[3];

  if (GET_CODE (dest) == MEM
      && GET_CODE (XEXP (dest, 0)) == PRE_INC
      && XEXP (XEXP (dest, 0), 0) == stack_pointer_rtx)
    return output_move_pushmem (operands, insn, length, tmp_start, n_operands);

  if (!offsettable_memref_p (src))
    fatal_insn ("Source is not offsettable", insn);

  if (!offsettable_memref_p (dest))
    fatal_insn ("Destination is not offsettable", insn);

  /* Figure out which temporary registers we have available */
  for (i = tmp_start; i < n_operands; i++)
    {
      if (GET_CODE (operands[i]) == REG)
	{
	  if ((length & 1) != 0 && !qi_tmp && QI_REG_P (operands[i]))
	    qi_tmp = operands[i];

	  if (reg_overlap_mentioned_p (operands[i], dest))
	    fatal_insn ("Temporary register overlaps the destination", insn);

	  if (reg_overlap_mentioned_p (operands[i], src))
	    fatal_insn ("Temporary register overlaps the source", insn);

	  tmp_info[ max_tmps++ ].xops[2] = operands[i];
	  if (max_tmps == MAX_TMPS)
	    break;
	}
    }

  if (max_tmps == 0)
    fatal_insn ("No scratch registers were found to do memory->memory moves", insn);

  if ((length & 1) != 0)
    {
      if (!qi_tmp)
	fatal_insn ("No byte register found when moving odd # of bytes.", insn);
    }

  while (length > 1)
    {
      for (num_tmps = 0; num_tmps < max_tmps; num_tmps++)
	{
	  if (length >= 4)
	    {
	      tmp_info[num_tmps].load    = AS2(mov%L0,%1,%2);
	      tmp_info[num_tmps].store   = AS2(mov%L0,%2,%0);
	      tmp_info[num_tmps].xops[0] = adj_offsettable_operand (dest, offset);
	      tmp_info[num_tmps].xops[1] = adj_offsettable_operand (src, offset);
	      offset += 4;
	      length -= 4;
	    }
	  else if (length >= 2)
	    {
	      tmp_info[num_tmps].load    = AS2(mov%W0,%1,%2);
	      tmp_info[num_tmps].store   = AS2(mov%W0,%2,%0);
	      tmp_info[num_tmps].xops[0] = adj_offsettable_operand (dest, offset);
	      tmp_info[num_tmps].xops[1] = adj_offsettable_operand (src, offset);
	      offset += 2;
	      length -= 2;
	    }
	  else
	    break;
	}

      for (i = 0; i < num_tmps; i++)
	output_asm_insn (tmp_info[i].load, tmp_info[i].xops);

      for (i = 0; i < num_tmps; i++)
	output_asm_insn (tmp_info[i].store, tmp_info[i].xops);
    }

  if (length == 1)
    {
      xops[0] = adj_offsettable_operand (dest, offset);
      xops[1] = adj_offsettable_operand (src, offset);
      xops[2] = qi_tmp;
      output_asm_insn (AS2(mov%B0,%1,%2), xops);
      output_asm_insn (AS2(mov%B0,%2,%0), xops);
    }

  return "";
}


int
standard_80387_constant_p (x)
     rtx x;
{
#if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
  REAL_VALUE_TYPE d;
  jmp_buf handler;
  int is0, is1;

  if (setjmp (handler))
    return 0;

  set_float_handler (handler);
  REAL_VALUE_FROM_CONST_DOUBLE (d, x);
  is0 = REAL_VALUES_EQUAL (d, dconst0);
  is1 = REAL_VALUES_EQUAL (d, dconst1);
  set_float_handler (NULL_PTR);

  if (is0)
    return 1;

  if (is1)
    return 2;

  /* Note that on the 80387, other constants, such as pi,
     are much slower to load as standard constants
     than to load from doubles in memory!  */
#endif

  return 0;
}

char *
output_move_const_single (operands)
     rtx *operands;
{
  if (FP_REG_P (operands[0]))
    {
      int conval = standard_80387_constant_p (operands[1]);

      if (conval == 1)
	return "fldz";

      if (conval == 2)
	return "fld1";
    }
  if (GET_CODE (operands[1]) == CONST_DOUBLE)
    {
      REAL_VALUE_TYPE r; long l;

      if (GET_MODE (operands[1]) == XFmode)
	abort ();

      REAL_VALUE_FROM_CONST_DOUBLE (r, operands[1]);
      REAL_VALUE_TO_TARGET_SINGLE (r, l);
      operands[1] = GEN_INT (l);
    }
  return singlemove_string (operands);
}

/* Returns 1 if OP is either a symbol reference or a sum of a symbol
   reference and a constant.  */

int
symbolic_operand (op, mode)
     register rtx op;
     enum machine_mode mode;
{
  switch (GET_CODE (op))
    {
    case SYMBOL_REF:
    case LABEL_REF:
      return 1;
    case CONST:
      op = XEXP (op, 0);
      return ((GET_CODE (XEXP (op, 0)) == SYMBOL_REF
	       || GET_CODE (XEXP (op, 0)) == LABEL_REF)
	      && GET_CODE (XEXP (op, 1)) == CONST_INT);
    default:
      return 0;
    }
}

/* Test for a valid operand for a call instruction.
   Don't allow the arg pointer register or virtual regs
   since they may change into reg + const, which the patterns
   can't handle yet.  */

int
call_insn_operand (op, mode)
     rtx op;
     enum machine_mode mode;
{
  if (GET_CODE (op) == MEM
      && ((CONSTANT_ADDRESS_P (XEXP (op, 0))
	   /* This makes a difference for PIC.  */
	   && general_operand (XEXP (op, 0), Pmode))
	  || (GET_CODE (XEXP (op, 0)) == REG
	      && XEXP (op, 0) != arg_pointer_rtx
	      && !(REGNO (XEXP (op, 0)) >= FIRST_PSEUDO_REGISTER
		   && REGNO (XEXP (op, 0)) <= LAST_VIRTUAL_REGISTER))))
    return 1;
  return 0;
}

/* Like call_insn_operand but allow (mem (symbol_ref ...))
   even if pic.  */

int
expander_call_insn_operand (op, mode)
     rtx op;
     enum machine_mode mode;
{
  if (GET_CODE (op) == MEM
      && (CONSTANT_ADDRESS_P (XEXP (op, 0))
	  || (GET_CODE (XEXP (op, 0)) == REG
	      && XEXP (op, 0) != arg_pointer_rtx
	      && !(REGNO (XEXP (op, 0)) >= FIRST_PSEUDO_REGISTER
		   && REGNO (XEXP (op, 0)) <= LAST_VIRTUAL_REGISTER))))
    return 1;
  return 0;
}

/* Return 1 if OP is a comparison operator that can use the condition code
   generated by an arithmetic operation. */

int
arithmetic_comparison_operator (op, mode)
     register rtx op;
     enum machine_mode mode;
{
  enum rtx_code code;

  if (mode != VOIDmode && mode != GET_MODE (op))
    return 0;
  code = GET_CODE (op);
  if (GET_RTX_CLASS (code) != '<')
    return 0;

  return (code != GT && code != LE);
}

/* Returns 1 if OP contains a symbol reference */

int
symbolic_reference_mentioned_p (op)
     rtx op;
{
  register char *fmt;
  register int i;

  if (GET_CODE (op) == SYMBOL_REF || GET_CODE (op) == LABEL_REF)
    return 1;

  fmt = GET_RTX_FORMAT (GET_CODE (op));
  for (i = GET_RTX_LENGTH (GET_CODE (op)) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'E')
	{
	  register int j;

	  for (j = XVECLEN (op, i) - 1; j >= 0; j--)
	    if (symbolic_reference_mentioned_p (XVECEXP (op, i, j)))
	      return 1;
	}
      else if (fmt[i] == 'e' && symbolic_reference_mentioned_p (XEXP (op, i)))
	return 1;
    }

  return 0;
}

/* This function generates the assembly code for function entry.
   FILE is an stdio stream to output the code to.
   SIZE is an int: how many units of temporary storage to allocate. */

void
function_prologue (file, size)