Subversion Repositories openrisc_2011-10-31

/* Subroutines for manipulating rtx's in semantically interesting ways.

   Copyright (C) 1987, 1991, 1994, 1995, 1996, 1997, 1998,

   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007

   Free Software Foundation, Inc.

This file is part of GCC.

GCC 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 3, or (at your option) any later

version.

GCC 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 GCC; see the file COPYING3.  If not see

<http://www.gnu.org/licenses/>.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "toplev.h"

#include "rtl.h"

#include "tree.h"

#include "tm_p.h"

#include "flags.h"

#include "function.h"

#include "expr.h"

#include "optabs.h"

#include "hard-reg-set.h"

#include "insn-config.h"

#include "ggc.h"

#include "recog.h"

#include "langhooks.h"

#include "target.h"

#include "output.h"

static rtx break_out_memory_refs (rtx);

static void emit_stack_probe (rtx);

/* Truncate and perhaps sign-extend C as appropriate for MODE.  */

HOST_WIDE_INT

trunc_int_for_mode (HOST_WIDE_INT c, enum machine_mode mode)

{

  int width = GET_MODE_BITSIZE (mode);

  /* You want to truncate to a _what_?  */

  gcc_assert (SCALAR_INT_MODE_P (mode));

  /* Canonicalize BImode to 0 and STORE_FLAG_VALUE.  */

  if (mode == BImode)

    return c & 1 ? STORE_FLAG_VALUE : 0;

  /* Sign-extend for the requested mode.  */

  if (width < HOST_BITS_PER_WIDE_INT)

    {

      HOST_WIDE_INT sign = 1;

      sign <<= width - 1;

      c &= (sign << 1) - 1;

      c ^= sign;

      c -= sign;

    }

  return c;

}

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

rtx

plus_constant (rtx x, HOST_WIDE_INT c)

{

  RTX_CODE code;

  rtx y;

  enum machine_mode mode;

  rtx tem;

  int all_constant = 0;

  if (c == 0)

    return x;

 restart:

  code = GET_CODE (x);

  mode = GET_MODE (x);

  y = x;

  switch (code)

    {

    case CONST_INT:

      return GEN_INT (INTVAL (x) + c);

    case CONST_DOUBLE:

      {

        unsigned HOST_WIDE_INT l1 = CONST_DOUBLE_LOW (x);

        HOST_WIDE_INT h1 = CONST_DOUBLE_HIGH (x);

        unsigned HOST_WIDE_INT l2 = c;

        HOST_WIDE_INT h2 = c < 0 ? ~0 : 0;

        unsigned HOST_WIDE_INT lv;

        HOST_WIDE_INT 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.

         Restart or use a recursive call in case the remaining operand is

         something that we handle specially, such as a SYMBOL_REF.

         We may not immediately return from the recursive call here, lest

         all_constant gets lost.  */

      if (GET_CODE (XEXP (x, 1)) == CONST_INT)

        {

          c += INTVAL (XEXP (x, 1));

          if (GET_MODE (x) != VOIDmode)

            c = trunc_int_for_mode (c, GET_MODE (x));

          x = XEXP (x, 0);

          goto restart;

        }

      else if (CONSTANT_P (XEXP (x, 1)))

        {

          x = gen_rtx_PLUS (mode, XEXP (x, 0), plus_constant (XEXP (x, 1), c));

          c = 0;

        }

      else if (find_constant_term_loc (&y))

        {

          /* We need to be careful since X may be shared and we can't

             modify it in place.  */

          rtx copy = copy_rtx (x);

          rtx *const_loc = find_constant_term_loc (&copy);

          *const_loc = plus_constant (*const_loc, c);

          x = copy;

          c = 0;

        }

      break;

    default:

      break;

    }

  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;

}

/* 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 (rtx x, rtx *constptr)

{

  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;

}

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

rtx

expr_size (tree exp)

{

  tree size;

  if (TREE_CODE (exp) == WITH_SIZE_EXPR)

    size = TREE_OPERAND (exp, 1);

  else

    size = SUBSTITUTE_PLACEHOLDER_IN_EXPR (lang_hooks.expr_size (exp), exp);

  return expand_expr (size, NULL_RTX, TYPE_MODE (sizetype), 0);

}

/* Return a wide integer for the size in bytes of the value of EXP, or -1

   if the size can vary or is larger than an integer.  */

HOST_WIDE_INT

int_expr_size (tree exp)

{

  tree size;

  if (TREE_CODE (exp) == WITH_SIZE_EXPR)

    size = TREE_OPERAND (exp, 1);

  else

    size = lang_hooks.expr_size (exp);

  if (size == 0 || !host_integerp (size, 0))

    return -1;

  return tree_low_cst (size, 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 (rtx x)

{

  if (MEM_P (x)

      || (CONSTANT_P (x) && CONSTANT_ADDRESS_P (x)

          && GET_MODE (x) != VOIDmode))

    x = force_reg (GET_MODE (x), x);

  else if (GET_CODE (x) == PLUS || GET_CODE (x) == MINUS

           || GET_CODE (x) == MULT)

    {

      rtx op0 = break_out_memory_refs (XEXP (x, 0));

      rtx op1 = break_out_memory_refs (XEXP (x, 1));

      if (op0 != XEXP (x, 0) || op1 != XEXP (x, 1))

        x = gen_rtx_fmt_ee (GET_CODE (x), Pmode, op0, op1);

    }

  return x;

}

/* Given X, a memory address in ptr_mode, convert it to an address

   in Pmode, or vice versa (TO_MODE says which way).  We take advantage of

   the fact that pointers are not allowed to overflow by commuting arithmetic

   operations over conversions so that address arithmetic insns can be

   used.  */

rtx

convert_memory_address (enum machine_mode to_mode ATTRIBUTE_UNUSED,

                        rtx x)

{

#ifndef POINTERS_EXTEND_UNSIGNED

  gcc_assert (GET_MODE (x) == to_mode || GET_MODE (x) == VOIDmode);

  return x;

#else /* defined(POINTERS_EXTEND_UNSIGNED) */

  enum machine_mode from_mode;

  rtx temp;

  enum rtx_code code;

  /* If X already has the right mode, just return it.  */

  if (GET_MODE (x) == to_mode)

    return x;

  from_mode = to_mode == ptr_mode ? Pmode : ptr_mode;

  /* Here we handle some special cases.  If none of them apply, fall through

     to the default case.  */

  switch (GET_CODE (x))

    {

    case CONST_INT:

    case CONST_DOUBLE:

      if (GET_MODE_SIZE (to_mode) < GET_MODE_SIZE (from_mode))

        code = TRUNCATE;

      else if (POINTERS_EXTEND_UNSIGNED < 0)

        break;

      else if (POINTERS_EXTEND_UNSIGNED > 0)

        code = ZERO_EXTEND;

      else

        code = SIGN_EXTEND;

      temp = simplify_unary_operation (code, to_mode, x, from_mode);

      if (temp)

        return temp;

      break;

    case SUBREG:

      if ((SUBREG_PROMOTED_VAR_P (x) || REG_POINTER (SUBREG_REG (x)))

          && GET_MODE (SUBREG_REG (x)) == to_mode)

        return SUBREG_REG (x);

      break;

    case LABEL_REF:

      temp = gen_rtx_LABEL_REF (to_mode, XEXP (x, 0));

      LABEL_REF_NONLOCAL_P (temp) = LABEL_REF_NONLOCAL_P (x);

      return temp;

      break;

    case SYMBOL_REF:

      temp = shallow_copy_rtx (x);

      PUT_MODE (temp, to_mode);

      return temp;

      break;

    case CONST:

      return gen_rtx_CONST (to_mode,

                            convert_memory_address (to_mode, XEXP (x, 0)));

      break;

    case PLUS:

    case MULT:

      /* For addition we can safely permute the conversion and addition

         operation if one operand is a constant and converting the constant

         does not change it.  We can always safely permute them if we are

         making the address narrower.  */

      if (GET_MODE_SIZE (to_mode) < GET_MODE_SIZE (from_mode)

          || (GET_CODE (x) == PLUS

              && GET_CODE (XEXP (x, 1)) == CONST_INT

              && XEXP (x, 1) == convert_memory_address (to_mode, XEXP (x, 1))))

        return gen_rtx_fmt_ee (GET_CODE (x), to_mode,

                               convert_memory_address (to_mode, XEXP (x, 0)),

                               XEXP (x, 1));

      break;

    default:

      break;

    }

  return convert_modes (to_mode, from_mode,

                        x, POINTERS_EXTEND_UNSIGNED);

#endif /* defined(POINTERS_EXTEND_UNSIGNED) */

}

/* 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 (enum machine_mode mode, rtx x)

{

  rtx oldx = x;

  x = convert_memory_address (Pmode, x);

  /* By passing constant addresses through registers

     we get a chance to cse them.  */

  if (! cse_not_expected && CONSTANT_P (x) && CONSTANT_ADDRESS_P (x))

    x = force_reg (Pmode, 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!  */

  else

    {

      if (! cse_not_expected && !REG_P (x))

        x = break_out_memory_refs (x);

      /* At this point, any valid address is accepted.  */

      if (memory_address_p (mode, x))

        goto 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))

            x = force_operand (x, NULL_RTX);

          else

            {

              y = gen_rtx_PLUS (GET_MODE (x), copy_to_reg (y), constant_term);

              if (! memory_address_p (mode, y))

                x = force_operand (x, NULL_RTX);

              else

                x = y;

            }

        }

      else if (GET_CODE (x) == MULT || GET_CODE (x) == MINUS)

        x = 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.  */

      else if (REG_P (x))

        x = copy_to_reg (x);

      /* Last resort: copy the value to a register, since

         the register is a valid address.  */

      else

        x = force_reg (Pmode, x);

      goto done;

    win2:

      x = oldx;

    win:

      if (flag_force_addr && ! cse_not_expected && !REG_P (x))

        {

          x = force_operand (x, NULL_RTX);

          x = force_reg (Pmode, x);

        }

    }

 done:

  /* If we didn't change the address, we are done.  Otherwise, mark

     a reg as a pointer if we have REG or REG + CONST_INT.  */

  if (oldx == x)

    return x;

  else if (REG_P (x))

    mark_reg_pointer (x, BITS_PER_UNIT);

  else if (GET_CODE (x) == PLUS

           && REG_P (XEXP (x, 0))

           && GET_CODE (XEXP (x, 1)) == CONST_INT)

    mark_reg_pointer (XEXP (x, 0), BITS_PER_UNIT);

  /* OLDX may have been the address on a temporary.  Update the address

     to indicate that X is now used.  */

  update_temp_slot_address (oldx, x);

  return x;

}

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

rtx

memory_address_noforce (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 (rtx ref)

{

  if (!MEM_P (ref))

    return ref;

  ref = use_anchored_address (ref);

  if (! (flag_force_addr && CONSTANT_ADDRESS_P (XEXP (ref, 0)))

      && memory_address_p (GET_MODE (ref), XEXP (ref, 0)))

    return ref;

  /* Don't alter REF itself, since that is probably a stack slot.  */

  return replace_equiv_address (ref, XEXP (ref, 0));

}

/* If X is a memory reference to a member of an object block, try rewriting

   it to use an anchor instead.  Return the new memory reference on success

   and the old one on failure.  */

rtx

use_anchored_address (rtx x)

{

  rtx base;

  HOST_WIDE_INT offset;

  if (!flag_section_anchors)

    return x;

  if (!MEM_P (x))

    return x;

  /* Split the address into a base and offset.  */

  base = XEXP (x, 0);

  offset = 0;

  if (GET_CODE (base) == CONST

      && GET_CODE (XEXP (base, 0)) == PLUS

      && GET_CODE (XEXP (XEXP (base, 0), 1)) == CONST_INT)

    {

      offset += INTVAL (XEXP (XEXP (base, 0), 1));

      base = XEXP (XEXP (base, 0), 0);

    }

  /* Check whether BASE is suitable for anchors.  */

  if (GET_CODE (base) != SYMBOL_REF

      || !SYMBOL_REF_HAS_BLOCK_INFO_P (base)

      || SYMBOL_REF_ANCHOR_P (base)

      || SYMBOL_REF_BLOCK (base) == NULL

      || !targetm.use_anchors_for_symbol_p (base))

    return x;

  /* Decide where BASE is going to be.  */

  place_block_symbol (base);

  /* Get the anchor we need to use.  */

  offset += SYMBOL_REF_BLOCK_OFFSET (base);

  base = get_section_anchor (SYMBOL_REF_BLOCK (base), offset,

                             SYMBOL_REF_TLS_MODEL (base));

  /* Work out the offset from the anchor.  */

  offset -= SYMBOL_REF_BLOCK_OFFSET (base);

  /* If we're going to run a CSE pass, force the anchor into a register.

     We will then be able to reuse registers for several accesses, if the

     target costs say that that's worthwhile.  */

  if (!cse_not_expected)

    base = force_reg (GET_MODE (base), base);

  return replace_equiv_address (x, plus_constant (base, offset));

}

/* Copy the value or contents of X to a new temp reg and return that reg.  */

rtx

copy_to_reg (rtx x)

{

  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 (rtx x)

{

  return copy_to_mode_reg (Pmode, x);

}

/* Like copy_to_reg but always give the new register mode MODE

   in case X is a constant.  */

rtx

copy_to_mode_reg (enum machine_mode mode, rtx x)

{

  rtx temp = gen_reg_rtx (mode);

  /* 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);

  gcc_assert (GET_MODE (x) == mode || GET_MODE (x) == VOIDmode);

  if (x != temp)

    emit_move_insn (temp, x);

  return temp;

}

/* Load X into a register if it is not already one.

   Use mode MODE for the register.

   X should be valid for mode MODE, but it may be a constant which

   is valid for all integer modes; that's why caller must specify MODE.

   The caller must not alter the value in the register we return,

   since we mark it as a "constant" register.  */

rtx

force_reg (enum machine_mode mode, rtx x)

{

  rtx temp, insn, set;

  if (REG_P (x))

    return x;

  if (general_operand (x, mode))

    {

      temp = gen_reg_rtx (mode);

      insn = emit_move_insn (temp, x);

    }

  else

    {

      temp = force_operand (x, NULL_RTX);

      if (REG_P (temp))

        insn = get_last_insn ();

      else

        {

          rtx temp2 = gen_reg_rtx (mode);

          insn = emit_move_insn (temp2, temp);

          temp = temp2;

        }

    }

  /* Let optimizers know that TEMP's value never changes

     and that X can be substituted for it.  Don't get confused

     if INSN set something else (such as a SUBREG of TEMP).  */

  if (CONSTANT_P (x)

      && (set = single_set (insn)) != 0

      && SET_DEST (set) == temp

      && ! rtx_equal_p (x, SET_SRC (set)))

    set_unique_reg_note (insn, REG_EQUAL, x);

  /* Let optimizers know that TEMP is a pointer, and if so, the

     known alignment of that pointer.  */

  {

    unsigned align = 0;

    if (GET_CODE (x) == SYMBOL_REF)

      {

        align = BITS_PER_UNIT;

        if (SYMBOL_REF_DECL (x) && DECL_P (SYMBOL_REF_DECL (x)))

          align = DECL_ALIGN (SYMBOL_REF_DECL (x));

      }

    else if (GET_CODE (x) == LABEL_REF)

      align = BITS_PER_UNIT;

    else if (GET_CODE (x) == CONST

             && GET_CODE (XEXP (x, 0)) == PLUS

             && GET_CODE (XEXP (XEXP (x, 0), 0)) == SYMBOL_REF

             && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT)