i386.c

gcc库的原代码,对编程有很大帮助.

	}
      current_function_uses_pic_offset_table = 1;
      return reg;
    }
  else if (GET_CODE (addr) == CONST || GET_CODE (addr) == PLUS)
    {
      rtx base;

      if (GET_CODE (addr) == CONST)
	{
	  addr = XEXP (addr, 0);
	  if (GET_CODE (addr) != PLUS)
	    abort ();
	}

      if (XEXP (addr, 0) == pic_offset_table_rtx)
	return orig;

      if (reg == 0)
	reg = gen_reg_rtx (Pmode);

      base = legitimize_pic_address (XEXP (addr, 0), reg);
      addr = legitimize_pic_address (XEXP (addr, 1),
				     base == reg ? NULL_RTX : reg);

      if (GET_CODE (addr) == CONST_INT)
	return plus_constant (base, INTVAL (addr));

      if (GET_CODE (addr) == PLUS && CONSTANT_P (XEXP (addr, 1)))
	{
	  base = gen_rtx (PLUS, Pmode, base, XEXP (addr, 0));
	  addr = XEXP (addr, 1);
	}
	return gen_rtx (PLUS, Pmode, base, addr);
    }
  return new;
}


/* Emit insns to move operands[1] into operands[0].  */

void
emit_pic_move (operands, mode)
     rtx *operands;
     enum machine_mode mode;
{
  rtx temp = reload_in_progress ? operands[0] : gen_reg_rtx (Pmode);

  if (GET_CODE (operands[0]) == MEM && SYMBOLIC_CONST (operands[1]))
    operands[1] = (rtx) force_reg (SImode, operands[1]);
  else
    operands[1] = legitimize_pic_address (operands[1], temp);
}


/* Try machine-dependent ways of modifying an illegitimate address
   to be legitimate.  If we find one, return the new, valid address.
   This macro is used in only one place: `memory_address' in explow.c.

   OLDX is the address as it was before break_out_memory_refs was called.
   In some cases it is useful to look at this to decide what needs to be done.

   MODE and WIN are passed so that this macro can use
   GO_IF_LEGITIMATE_ADDRESS.

   It is always safe for this macro to do nothing.  It exists to recognize
   opportunities to optimize the output.

   For the 80386, we handle X+REG by loading X into a register R and
   using R+REG.  R will go in a general reg and indexing will be used.
   However, if REG is a broken-out memory address or multiplication,
   nothing needs to be done because REG can certainly go in a general reg.

   When -fpic is used, special handling is needed for symbolic references.
   See comments by legitimize_pic_address in i386.c for details.  */

rtx
legitimize_address (x, oldx, mode)
     register rtx x;
     register rtx oldx;
     enum machine_mode mode;
{
  int changed = 0;
  unsigned log;

  if (TARGET_DEBUG_ADDR)
    {
      fprintf (stderr, "\n==========\nLEGITIMIZE_ADDRESS, mode = %s\n", GET_MODE_NAME (mode));
      debug_rtx (x);
    }

  if (flag_pic && SYMBOLIC_CONST (x))
    return legitimize_pic_address (x, 0);

  /* Canonicalize shifts by 0, 1, 2, 3 into multiply */
  if (GET_CODE (x) == ASHIFT
      && GET_CODE (XEXP (x, 1)) == CONST_INT
      && (log = (unsigned)exact_log2 (INTVAL (XEXP (x, 1)))) < 4)
    {
      changed = 1;
      x = gen_rtx (MULT, Pmode,
		   force_reg (Pmode, XEXP (x, 0)),
		   GEN_INT (1 << log));
    }

  if (GET_CODE (x) == PLUS)
    {
      /* Canonicalize shifts by 0, 1, 2, 3 into multiply */
      if (GET_CODE (XEXP (x, 0)) == ASHIFT
	  && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT
	  && (log = (unsigned)exact_log2 (INTVAL (XEXP (XEXP (x, 0), 1)))) < 4)
	{
	  changed = 1;
	  XEXP (x, 0) = gen_rtx (MULT, Pmode,
				 force_reg (Pmode, XEXP (XEXP (x, 0), 0)),
				 GEN_INT (1 << log));
	}

      if (GET_CODE (XEXP (x, 1)) == ASHIFT
	  && GET_CODE (XEXP (XEXP (x, 1), 1)) == CONST_INT
	  && (log = (unsigned)exact_log2 (INTVAL (XEXP (XEXP (x, 1), 1)))) < 4)
	{
	  changed = 1;
	  XEXP (x, 1) = gen_rtx (MULT, Pmode,
				 force_reg (Pmode, XEXP (XEXP (x, 1), 0)),
				 GEN_INT (1 << log));
	}

      /* Put multiply first if it isn't already */
      if (GET_CODE (XEXP (x, 1)) == MULT)
	{
	  rtx tmp = XEXP (x, 0);
	  XEXP (x, 0) = XEXP (x, 1);
	  XEXP (x, 1) = tmp;
	  changed = 1;
	}

      /* Canonicalize (plus (mult (reg) (const)) (plus (reg) (const)))
	 into (plus (plus (mult (reg) (const)) (reg)) (const)).  This can be
	 created by virtual register instantiation, register elimination, and
	 similar optimizations.  */
      if (GET_CODE (XEXP (x, 0)) == MULT && GET_CODE (XEXP (x, 1)) == PLUS)
	{
	  changed = 1;
	  x = gen_rtx (PLUS, Pmode,
		       gen_rtx (PLUS, Pmode, XEXP (x, 0), XEXP (XEXP (x, 1), 0)),
		       XEXP (XEXP (x, 1), 1));
	}

      /* Canonicalize (plus (plus (mult (reg) (const)) (plus (reg) (const))) const)
	 into (plus (plus (mult (reg) (const)) (reg)) (const)).  */
      else if (GET_CODE (x) == PLUS && GET_CODE (XEXP (x, 0)) == PLUS
	       && GET_CODE (XEXP (XEXP (x, 0), 0)) == MULT
	       && GET_CODE (XEXP (XEXP (x, 0), 1)) == PLUS
	       && CONSTANT_P (XEXP (x, 1)))
	{
	  rtx constant, other;

	  if (GET_CODE (XEXP (x, 1)) == CONST_INT)
	    {
	      constant = XEXP (x, 1);
	      other = XEXP (XEXP (XEXP (x, 0), 1), 1);
	    }
	  else if (GET_CODE (XEXP (XEXP (XEXP (x, 0), 1), 1)) == CONST_INT)
	    {
	      constant = XEXP (XEXP (XEXP (x, 0), 1), 1);
	      other = XEXP (x, 1);
	    }
	  else
	    constant = 0;

	  if (constant)
	    {
	      changed = 1;
	      x = gen_rtx (PLUS, Pmode,
			   gen_rtx (PLUS, Pmode, XEXP (XEXP (x, 0), 0),
				    XEXP (XEXP (XEXP (x, 0), 1), 0)),
			   plus_constant (other, INTVAL (constant)));
	    }
	}

      if (changed && legitimate_address_p (mode, x, FALSE))
	return x;

      if (GET_CODE (XEXP (x, 0)) == MULT)
	{
	  changed = 1;
	  XEXP (x, 0) = force_operand (XEXP (x, 0), 0);
	}

      if (GET_CODE (XEXP (x, 1)) == MULT)
	{
	  changed = 1;
	  XEXP (x, 1) = force_operand (XEXP (x, 1), 0);
	}

      if (changed
	  && GET_CODE (XEXP (x, 1)) == REG
	  && GET_CODE (XEXP (x, 0)) == REG)
	return x;

      if (flag_pic && SYMBOLIC_CONST (XEXP (x, 1)))
	{
	  changed = 1;
	  x = legitimize_pic_address (x, 0);
	}

      if (changed && legitimate_address_p (mode, x, FALSE))
	return x;

      if (GET_CODE (XEXP (x, 0)) == REG)
	{
	  register rtx temp = gen_reg_rtx (Pmode);
	  register rtx val  = force_operand (XEXP (x, 1), temp);
	  if (val != temp)
	    emit_move_insn (temp, val);

	  XEXP (x, 1) = temp;
	  return x;
	}

      else if (GET_CODE (XEXP (x, 1)) == REG)
	{
	  register rtx temp = gen_reg_rtx (Pmode);
	  register rtx val  = force_operand (XEXP (x, 0), temp);
	  if (val != temp)
	    emit_move_insn (temp, val);

	  XEXP (x, 0) = temp;
	  return x;
	}
    }

  return x;
}


/* Print an integer constant expression in assembler syntax.  Addition
   and subtraction are the only arithmetic that may appear in these
   expressions.  FILE is the stdio stream to write to, X is the rtx, and
   CODE is the operand print code from the output string.  */

static void
output_pic_addr_const (file, x, code)
     FILE *file;
     rtx x;
     int code;
{
  char buf[256];

  switch (GET_CODE (x))
    {
    case PC:
      if (flag_pic)
	putc ('.', file);
      else
	abort ();
      break;

    case SYMBOL_REF:
    case LABEL_REF:
      if (GET_CODE (x) == SYMBOL_REF)
	assemble_name (file, XSTR (x, 0));
      else
	{
	  ASM_GENERATE_INTERNAL_LABEL (buf, "L",
				       CODE_LABEL_NUMBER (XEXP (x, 0)));
	  assemble_name (asm_out_file, buf);
	}

      if (GET_CODE (x) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (x))
	fprintf (file, "@GOTOFF(%%ebx)");
      else if (code == 'P')
	fprintf (file, "@PLT");
      else if (GET_CODE (x) == LABEL_REF)
	fprintf (file, "@GOTOFF");
      else if (! SYMBOL_REF_FLAG (x))
	fprintf (file, "@GOT");
      else
	fprintf (file, "@GOTOFF");

      break;

    case CODE_LABEL:
      ASM_GENERATE_INTERNAL_LABEL (buf, "L", CODE_LABEL_NUMBER (x));
      assemble_name (asm_out_file, buf);
      break;

    case CONST_INT:
      fprintf (file, "%d", INTVAL (x));
      break;

    case CONST:
      /* This used to output parentheses around the expression,
	 but that does not work on the 386 (either ATT or BSD assembler).  */
      output_pic_addr_const (file, XEXP (x, 0), code);
      break;

    case CONST_DOUBLE:
      if (GET_MODE (x) == VOIDmode)
	{
	  /* We can use %d if the number is <32 bits and positive.  */
	  if (CONST_DOUBLE_HIGH (x) || CONST_DOUBLE_LOW (x) < 0)
	    fprintf (file, "0x%x%08x",
		     CONST_DOUBLE_HIGH (x), CONST_DOUBLE_LOW (x));
	  else
	    fprintf (file, "%d", CONST_DOUBLE_LOW (x));
	}
      else
	/* We can't handle floating point constants;
	   PRINT_OPERAND must handle them.  */
	output_operand_lossage ("floating constant misused");
      break;

    case PLUS:
      /* Some assemblers need integer constants to appear last (eg masm).  */
      if (GET_CODE (XEXP (x, 0)) == CONST_INT)
	{
	  output_pic_addr_const (file, XEXP (x, 1), code);
	  if (INTVAL (XEXP (x, 0)) >= 0)
	    fprintf (file, "+");
	  output_pic_addr_const (file, XEXP (x, 0), code);
	}
      else
	{
	  output_pic_addr_const (file, XEXP (x, 0), code);
	  if (INTVAL (XEXP (x, 1)) >= 0)
	    fprintf (file, "+");
	  output_pic_addr_const (file, XEXP (x, 1), code);
	}
      break;

    case MINUS:
      output_pic_addr_const (file, XEXP (x, 0), code);
      fprintf (file, "-");
      output_pic_addr_const (file, XEXP (x, 1), code);
      break;

    default:
      output_operand_lossage ("invalid expression as operand");
    }
}

/* Meaning of CODE:
   f -- float insn (print a CONST_DOUBLE as a float rather than in hex).
   D,L,W,B,Q,S -- print the opcode suffix for specified size of operand.
   R -- print the prefix for register names.
   z -- print the opcode suffix for the size of the current operand.
   * -- print a star (in certain assembler syntax)
   w -- print the operand as if it's a "word" (HImode) even if it isn't.
   c -- don't print special prefixes before constant operands.
   J -- print the appropriate jump operand.
*/

void
print_operand (file, x, code)
     FILE *file;
     rtx x;
     int code;
{
  if (code)
    {
      switch (code)
	{
	case '*':
	  if (USE_STAR)
	    putc ('*', file);
	  return;

	case 'L':
	  PUT_OP_SIZE (code, 'l', file);
	  return;

	case 'W':
	  PUT_OP_SIZE (code, 'w', file);
	  return;

	case 'B':
	  PUT_OP_SIZE (code, 'b', file);
	  return;

	case 'Q':
	  PUT_OP_SIZE (code, 'l', file);
	  return;

	case 'S':
	  PUT_OP_SIZE (code, 's', file);
	  return;

	case 'T':
	  PUT_OP_SIZE (code, 't', file);
	  return;

	case 'z':
	  /* 387 opcodes don't get size suffixes if the operands are
	     registers. */

	  if (STACK_REG_P (x))
	    return;

	  /* this is the size of op from size of operand */
	  switch (GET_MODE_SIZE (GET_MODE (x)))
	    {
	    case 1:
	      PUT_OP_SIZE ('B', 'b', file);
	      return;

	    case 2:
	      PUT_OP_SIZE ('W', 'w', file);
	      return;

	    case 4:
	      if (GET_MODE (x) == SFmode)
		{
		  PUT_OP_SIZE ('S', 's', file);
		  return;
		}
	      else
		PUT_OP_SIZE ('L', 'l', file);
	      return;

	    case 12:
		  PUT_OP_SIZE ('T', 't', file);
		  return;

	    case 8:
	      if (GET_MODE_CLASS (GET_MODE (x)) == MODE_INT)
		{
#ifdef GAS_MNEMONICS
		  PUT_OP_SIZE ('Q', 'q', file);
		  return;
#else
		  PUT_OP_SIZE ('Q', 'l', file);	/* Fall through */
#endif
		}

	      PUT_OP_SIZE ('Q', 'l', file);
	      return;
	    }

	case 'b':
	case 'w':
	case 'k':
	case 'h':
	case 'y':
	case 'P':
	  break;

	case 'J':
	  switch (GET_CODE (x))
	    {
	      /* These conditions are appropriate for testing the result
		 of an arithmetic operation, not for a compare operation.
	         Cases GE, LT assume CC_NO_OVERFLOW true. All cases assume
		 CC_Z_IN_NOT_C false and not floating point.  */
	    case NE:  fputs ("jne", file); return;
	    case EQ:  fputs ("je",  file); return;
	    case GE:  fputs ("jns", file); return;
	    case LT:  fputs ("js",  file); return;
	    case GEU: fputs ("jmp", file); return;
	    case GTU: fputs ("jne",  file); return;
	    case LEU: fputs ("je", file); return;
	    case LTU: fputs ("#branch never",  file); return;

	    /* no matching branches for GT nor LE */
	    }
	  abort ();

	default:
	  {
	    char str[50];

	    sprintf (str, "invalid operand code `%c'", code);
	    output_operand_lossage (str);
	  }
	}
    }
  if (GET_CODE (x) == REG)
    {
      PRINT_REG (x, code, file);
    }
  else if (GET_CODE (x) == MEM)
    {
      PRINT_PTR (x, file);
      if (CONSTANT_ADDRESS_P