explow.c

早期freebsd实现

/* Subroutines for manipulating rtx's in semantically interesting ways.
   Copyright (C) 1987, 1991 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */


#include "config.h"
#include "rtl.h"
#include "tree.h"
#include "flags.h"
#include "expr.h"
#include "hard-reg-set.h"
#include "insn-config.h"
#include "recog.h"
#include "insn-flags.h"
#include "insn-codes.h"

/* Return an rtx for the sum of X and the integer C.

   This fucntion should be used via the `plus_constant' macro.  */

rtx
plus_constant_wide (x, c)
     register rtx x;
     register HOST_WIDE_INT c;
{
  register RTX_CODE code;
  register enum machine_mode mode;
  register rtx tem;
  int all_constant = 0;

  if (c == 0)
    return x;

 restart:

  code = GET_CODE (x);
  mode = GET_MODE (x);
  switch (code)
    {
    case CONST_INT:
      return GEN_INT (INTVAL (x) + c);

    case CONST_DOUBLE:
      {
	HOST_WIDE_INT l1 = CONST_DOUBLE_LOW (x);
	HOST_WIDE_INT h1 = CONST_DOUBLE_HIGH (x);
	HOST_WIDE_INT l2 = c;
	HOST_WIDE_INT h2 = c < 0 ? ~0 : 0;
	HOST_WIDE_INT lv, hv;

	add_double (l1, h1, l2, h2, &lv, &hv);

	return immed_double_const (lv, hv, VOIDmode);
      }

    case MEM:
      /* If this is a reference to the constant pool, try replacing it with
	 a reference to a new constant.  If the resulting address isn't
	 valid, don't return it because we have no way to validize it.  */
      if (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
	  && CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)))
	{
	  tem
	    = force_const_mem (GET_MODE (x),
			       plus_constant (get_pool_constant (XEXP (x, 0)),
					      c));
	  if (memory_address_p (GET_MODE (tem), XEXP (tem, 0)))
	    return tem;
	}
      break;

    case CONST:
      /* If adding to something entirely constant, set a flag
	 so that we can add a CONST around the result.  */
      x = XEXP (x, 0);
      all_constant = 1;
      goto restart;

    case SYMBOL_REF:
    case LABEL_REF:
      all_constant = 1;
      break;

    case PLUS:
      /* The interesting case is adding the integer to a sum.
	 Look for constant term in the sum and combine
	 with C.  For an integer constant term, we make a combined
	 integer.  For a constant term that is not an explicit integer,
	 we cannot really combine, but group them together anyway.  

	 Use a recursive call in case the remaining operand is something
	 that we handle specially, such as a SYMBOL_REF.  */

      if (GET_CODE (XEXP (x, 1)) == CONST_INT)
	return plus_constant (XEXP (x, 0), c + INTVAL (XEXP (x, 1)));
      else if (CONSTANT_P (XEXP (x, 0)))
	return gen_rtx (PLUS, mode,
			plus_constant (XEXP (x, 0), c),
			XEXP (x, 1));
      else if (CONSTANT_P (XEXP (x, 1)))
	return gen_rtx (PLUS, mode,
			XEXP (x, 0),
			plus_constant (XEXP (x, 1), c));
    }

  if (c != 0)
    x = gen_rtx (PLUS, mode, x, GEN_INT (c));

  if (GET_CODE (x) == SYMBOL_REF || GET_CODE (x) == LABEL_REF)
    return x;
  else if (all_constant)
    return gen_rtx (CONST, mode, x);
  else
    return x;
}

/* This is the same as `plus_constant', except that it handles LO_SUM.

   This function should be used via the `plus_constant_for_output' macro.  */

rtx
plus_constant_for_output_wide (x, c)
     register rtx x;
     register HOST_WIDE_INT c;
{
  register RTX_CODE code = GET_CODE (x);
  register enum machine_mode mode = GET_MODE (x);
  int all_constant = 0;

  if (GET_CODE (x) == LO_SUM)
    return gen_rtx (LO_SUM, mode, XEXP (x, 0),
		    plus_constant_for_output (XEXP (x, 1), c));

  else
    return plus_constant (x, c);
}

/* If X is a sum, return a new sum like X but lacking any constant terms.
   Add all the removed constant terms into *CONSTPTR.
   X itself is not altered.  The result != X if and only if
   it is not isomorphic to X.  */

rtx
eliminate_constant_term (x, constptr)
     rtx x;
     rtx *constptr;
{
  register rtx x0, x1;
  rtx tem;

  if (GET_CODE (x) != PLUS)
    return x;

  /* First handle constants appearing at this level explicitly.  */
  if (GET_CODE (XEXP (x, 1)) == CONST_INT
      && 0 != (tem = simplify_binary_operation (PLUS, GET_MODE (x), *constptr,
						XEXP (x, 1)))
      && GET_CODE (tem) == CONST_INT)
    {
      *constptr = tem;
      return eliminate_constant_term (XEXP (x, 0), constptr);
    }

  tem = const0_rtx;
  x0 = eliminate_constant_term (XEXP (x, 0), &tem);
  x1 = eliminate_constant_term (XEXP (x, 1), &tem);
  if ((x1 != XEXP (x, 1) || x0 != XEXP (x, 0))
      && 0 != (tem = simplify_binary_operation (PLUS, GET_MODE (x),
						*constptr, tem))
      && GET_CODE (tem) == CONST_INT)
    {
      *constptr = tem;
      return gen_rtx (PLUS, GET_MODE (x), x0, x1);
    }

  return x;
}

/* Returns the insn that next references REG after INSN, or 0
   if REG is clobbered before next referenced or we cannot find
   an insn that references REG in a straight-line piece of code.  */

rtx
find_next_ref (reg, insn)
     rtx reg;
     rtx insn;
{
  rtx next;

  for (insn = NEXT_INSN (insn); insn; insn = next)
    {
      next = NEXT_INSN (insn);
      if (GET_CODE (insn) == NOTE)
	continue;
      if (GET_CODE (insn) == CODE_LABEL
	  || GET_CODE (insn) == BARRIER)
	return 0;
      if (GET_CODE (insn) == INSN
	  || GET_CODE (insn) == JUMP_INSN
	  || GET_CODE (insn) == CALL_INSN)
	{
	  if (reg_set_p (reg, insn))
	    return 0;
	  if (reg_mentioned_p (reg, PATTERN (insn)))
	    return insn;
	  if (GET_CODE (insn) == JUMP_INSN)
	    {
	      if (simplejump_p (insn))
		next = JUMP_LABEL (insn);
	      else
		return 0;
	    }
	  if (GET_CODE (insn) == CALL_INSN
	      && REGNO (reg) < FIRST_PSEUDO_REGISTER
	      && call_used_regs[REGNO (reg)])
	    return 0;
	}
      else
	abort ();
    }
  return 0;
}

/* Return an rtx for the size in bytes of the value of EXP.  */

rtx
expr_size (exp)
     tree exp;
{
  return expand_expr (size_in_bytes (TREE_TYPE (exp)),
		      NULL_RTX, TYPE_MODE (sizetype), 0);
}

/* Return a copy of X in which all memory references
   and all constants that involve symbol refs
   have been replaced with new temporary registers.
   Also emit code to load the memory locations and constants
   into those registers.

   If X contains no such constants or memory references,
   X itself (not a copy) is returned.

   If a constant is found in the address that is not a legitimate constant
   in an insn, it is left alone in the hope that it might be valid in the
   address.

   X may contain no arithmetic except addition, subtraction and multiplication.
   Values returned by expand_expr with 1 for sum_ok fit this constraint.  */

static rtx
break_out_memory_refs (x)
     register rtx x;
{
  if (GET_CODE (x) == MEM
      || (CONSTANT_P (x) && LEGITIMATE_CONSTANT_P (x)
	  && GET_MODE (x) != VOIDmode))
    {
      register rtx temp = force_reg (GET_MODE (x), x);
      mark_reg_pointer (temp);
      x = temp;
    }
  else if (GET_CODE (x) == PLUS || GET_CODE (x) == MINUS
	   || GET_CODE (x) == MULT)
    {
      register rtx op0 = break_out_memory_refs (XEXP (x, 0));
      register rtx op1 = break_out_memory_refs (XEXP (x, 1));
      if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
	x = gen_rtx (GET_CODE (x), Pmode, op0, op1);
    }
  return x;
}

/* Given a memory address or facsimile X, construct a new address,
   currently equivalent, that is stable: future stores won't change it.

   X must be composed of constants, register and memory references
   combined with addition, subtraction and multiplication:
   in other words, just what you can get from expand_expr if sum_ok is 1.

   Works by making copies of all regs and memory locations used
   by X and combining them the same way X does.
   You could also stabilize the reference to this address
   by copying the address to a register with copy_to_reg;
   but then you wouldn't get indexed addressing in the reference.  */

rtx
copy_all_regs (x)
     register rtx x;
{
  if (GET_CODE (x) == REG)
    {
      if (REGNO (x) != FRAME_POINTER_REGNUM)
	x = copy_to_reg (x);
    }
  else if (GET_CODE (x) == MEM)
    x = copy_to_reg (x);
  else if (GET_CODE (x) == PLUS || GET_CODE (x) == MINUS
	   || GET_CODE (x) == MULT)
    {
      register rtx op0 = copy_all_regs (XEXP (x, 0));
      register rtx op1 = copy_all_regs (XEXP (x, 1));
      if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))
	x = gen_rtx (GET_CODE (x), Pmode, op0, op1);
    }
  return x;
}

/* Return something equivalent to X but valid as a memory address
   for something of mode MODE.  When X is not itself valid, this
   works by copying X or subexpressions of it into registers.  */

rtx
memory_address (mode, x)
     enum machine_mode mode;
     register rtx x;
{
  register rtx oldx;

  /* By passing constant addresses thru registers
     we get a chance to cse them.  */
  if (! cse_not_expected && CONSTANT_P (x) && LEGITIMATE_CONSTANT_P (x))
    return force_reg (Pmode, x);

  /* Accept a QUEUED that refers to a REG
     even though that isn't a valid address.
     On attempting to put this in an insn we will call protect_from_queue
     which will turn it into a REG, which is valid.  */
  if (GET_CODE (x) == QUEUED
      && GET_CODE (QUEUED_VAR (x)) == REG)
    return x;

  /* We get better cse by rejecting indirect addressing at this stage.
     Let the combiner create indirect addresses where appropriate.
     For now, generate the code so that the subexpressions useful to share
     are visible.  But not if cse won't be done!  */
  oldx = x;
  if (! cse_not_expected && GET_CODE (x) != REG)
    x = break_out_memory_refs (x);

  /* At this point, any valid address is accepted.  */
  GO_IF_LEGITIMATE_ADDRESS (mode, x, win);

  /* If it was valid before but breaking out memory refs invalidated it,
     use it the old way.  */
  if (memory_address_p (mode, oldx))
    goto win2;

  /* Perform machine-dependent transformations on X
     in certain cases.  This is not necessary since the code
     below can handle all possible cases, but machine-dependent
     transformations can make better code.  */
  LEGITIMIZE_ADDRESS (x, oldx, mode, win);

  /* PLUS and MULT can appear in special ways
     as the result of attempts to make an address usable for indexing.
     Usually they are dealt with by calling force_operand, below.
     But a sum containing constant terms is special
     if removing them makes the sum a valid address:
     then we generate that address in a register
     and index off of it.  We do this because it often makes
     shorter code, and because the addresses thus generated
     in registers often become common subexpressions.  */
  if (GET_CODE (x) == PLUS)
    {
      rtx constant_term = const0_rtx;
      rtx y = eliminate_constant_term (x, &constant_term);
      if (constant_term == const0_rtx
	  || ! memory_address_p (mode, y))
	return force_operand (x, NULL_RTX);

      y = gen_rtx (PLUS, GET_MODE (x), copy_to_reg (y), constant_term);
      if (! memory_address_p (mode, y))
	return force_operand (x, NULL_RTX);
      return y;
    }
  if (GET_CODE (x) == MULT || GET_CODE (x) == MINUS)
    return force_operand (x, NULL_RTX);

  /* If we have a register that's an invalid address,
     it must be a hard reg of the wrong class.  Copy it to a pseudo.  */
  if (GET_CODE (x) == REG)
    return copy_to_reg (x);

  /* Last resort: copy the value to a register, since
     the register is a valid address.  */
  return force_reg (Pmode, x);

 win2:
  x = oldx;
 win:
  if (flag_force_addr && ! cse_not_expected && GET_CODE (x) != REG
      /* Don't copy an addr via a reg if it is one of our stack slots.  */
      && ! (GET_CODE (x) == PLUS
	    && (XEXP (x, 0) == virtual_stack_vars_rtx
		|| XEXP (x, 0) == virtual_incoming_args_rtx)))
    {
      if (general_operand (x, Pmode))
	return force_reg (Pmode, x);
      else
	return force_operand (x, NULL_RTX);
    }
  return x;
}

/* Like `memory_address' but pretend `flag_force_addr' is 0.  */

rtx
memory_address_noforce (mode, x)
     enum machine_mode mode;
     rtx x;
{
  int ambient_force_addr = flag_force_addr;
  rtx val;

  flag_force_addr = 0;
  val = memory_address (mode, x);
  flag_force_addr = ambient_force_addr;
  return val;
}

/* Convert a mem ref into one with a valid memory address.
   Pass through anything else unchanged.  */

rtx
validize_mem (ref)
     rtx ref;
{
  if (GET_CODE (ref) != MEM)
    return ref;
  if (memory_address_p (GET_MODE (ref), XEXP (ref, 0)))
    return ref;
  /* Don't alter REF itself, since that is probably a stack slot.  */
  return change_address (ref, GET_MODE (ref), XEXP (ref, 0));
}

/* Return a modified copy of X with its memory address copied
   into a temporary register to protect it from side effects.
   If X is not a MEM, it is returned unchanged (and not copied).
   Perhaps even if it is a MEM, if there is no need to change it.  */

rtx
stabilize (x)
     rtx x;
{
  register rtx addr;
  if (GET_CODE (x) != MEM)
    return x;
  addr = XEXP (x, 0);
  if (rtx_unstable_p (addr))
    {
      rtx temp = copy_all_regs (addr);
      rtx mem;
      if (GET_CODE (temp) != REG)
	temp = copy_to_reg (temp);
      mem = gen_rtx (MEM, GET_MODE (x), temp);

      /* Mark returned memref with in_struct if it's in an array or
	 structure.  Copy const and volatile from original memref.  */

      MEM_IN_STRUCT_P (mem) = MEM_IN_STRUCT_P (x) || GET_CODE (addr) == PLUS;
      RTX_UNCHANGING_P (mem) = RTX_UNCHANGING_P (x);
      MEM_VOLATILE_P (mem) = MEM_VOLATILE_P (x);
      return mem;
    }
  return x;
}

/* Copy the value or contents of X to a new temp reg and return that reg.  */

rtx
copy_to_reg (x)
     rtx x;
{
  register rtx temp = gen_reg_rtx (GET_MODE (x));
 
  /* If not an operand, must be an address with PLUS and MULT so
     do the computation.  */ 
  if (! general_operand (x, VOIDmode))
    x = force_operand (x, temp);
  
  if (x != temp)
    emit_move_insn (temp, x);

  return temp;
}

/* Like copy_to_reg but always give the new register mode Pmode
   in case X is a constant.  */

rtx
copy_addr_to_reg (x)
     rtx x;