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/* Save and restore call-clobbered registers which are live across a call.

   Copyright (C) 1989, 1992, 1994, 1995, 1997, 1998,

   1999, 2000, 2001, 2002, 2003, 2004, 2005 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 2, 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 COPYING.  If not, write to the Free

Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301, USA.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "rtl.h"

#include "regs.h"

#include "insn-config.h"

#include "flags.h"

#include "hard-reg-set.h"

#include "recog.h"

#include "basic-block.h"

#include "reload.h"

#include "function.h"

#include "expr.h"

#include "toplev.h"

#include "tm_p.h"

#ifndef MAX_MOVE_MAX

#define MAX_MOVE_MAX MOVE_MAX

#endif

#ifndef MIN_UNITS_PER_WORD

#define MIN_UNITS_PER_WORD UNITS_PER_WORD

#endif

#define MOVE_MAX_WORDS (MOVE_MAX / UNITS_PER_WORD)

/* Modes for each hard register that we can save.  The smallest mode is wide

   enough to save the entire contents of the register.  When saving the

   register because it is live we first try to save in multi-register modes.

   If that is not possible the save is done one register at a time.  */

static enum machine_mode

  regno_save_mode[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];

/* For each hard register, a place on the stack where it can be saved,

   if needed.  */

static rtx

  regno_save_mem[FIRST_PSEUDO_REGISTER][MAX_MOVE_MAX / MIN_UNITS_PER_WORD + 1];

/* We will only make a register eligible for caller-save if it can be

   saved in its widest mode with a simple SET insn as long as the memory

   address is valid.  We record the INSN_CODE is those insns here since

   when we emit them, the addresses might not be valid, so they might not

   be recognized.  */

static int

  reg_save_code[FIRST_PSEUDO_REGISTER][MAX_MACHINE_MODE];

static int

  reg_restore_code[FIRST_PSEUDO_REGISTER][MAX_MACHINE_MODE];

/* Set of hard regs currently residing in save area (during insn scan).  */

static HARD_REG_SET hard_regs_saved;

/* Number of registers currently in hard_regs_saved.  */

static int n_regs_saved;

/* Computed by mark_referenced_regs, all regs referenced in a given

   insn.  */

static HARD_REG_SET referenced_regs;

static void mark_set_regs (rtx, rtx, void *);

static void mark_referenced_regs (rtx);

static int insert_save (struct insn_chain *, int, int, HARD_REG_SET *,

                        enum machine_mode *);

static int insert_restore (struct insn_chain *, int, int, int,

                           enum machine_mode *);

static struct insn_chain *insert_one_insn (struct insn_chain *, int, int,

                                           rtx);

static void add_stored_regs (rtx, rtx, void *);

/* Initialize for caller-save.

   Look at all the hard registers that are used by a call and for which

   regclass.c has not already excluded from being used across a call.

   Ensure that we can find a mode to save the register and that there is a

   simple insn to save and restore the register.  This latter check avoids

   problems that would occur if we tried to save the MQ register of some

   machines directly into memory.  */

void

init_caller_save (void)

{

  rtx addr_reg;

  int offset;

  rtx address;

  int i, j;

  enum machine_mode mode;

  rtx savepat, restpat;

  rtx test_reg, test_mem;

  rtx saveinsn, restinsn;

  /* First find all the registers that we need to deal with and all

     the modes that they can have.  If we can't find a mode to use,

     we can't have the register live over calls.  */

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    {

      if (call_used_regs[i] && ! call_fixed_regs[i])

        {

          for (j = 1; j <= MOVE_MAX_WORDS; j++)

            {

              regno_save_mode[i][j] = HARD_REGNO_CALLER_SAVE_MODE (i, j,

                                                                   VOIDmode);

              if (regno_save_mode[i][j] == VOIDmode && j == 1)

                {

                  call_fixed_regs[i] = 1;

                  SET_HARD_REG_BIT (call_fixed_reg_set, i);

                }

            }

        }

      else

        regno_save_mode[i][1] = VOIDmode;

    }

  /* The following code tries to approximate the conditions under which

     we can easily save and restore a register without scratch registers or

     other complexities.  It will usually work, except under conditions where

     the validity of an insn operand is dependent on the address offset.

     No such cases are currently known.

     We first find a typical offset from some BASE_REG_CLASS register.

     This address is chosen by finding the first register in the class

     and by finding the smallest power of two that is a valid offset from

     that register in every mode we will use to save registers.  */

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    if (TEST_HARD_REG_BIT

        (reg_class_contents

         [(int) MODE_BASE_REG_CLASS (regno_save_mode [i][1])], i))

      break;

  gcc_assert (i < FIRST_PSEUDO_REGISTER);

  addr_reg = gen_rtx_REG (Pmode, i);

  for (offset = 1 << (HOST_BITS_PER_INT / 2); offset; offset >>= 1)

    {

      address = gen_rtx_PLUS (Pmode, addr_reg, GEN_INT (offset));

      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

        if (regno_save_mode[i][1] != VOIDmode

          && ! strict_memory_address_p (regno_save_mode[i][1], address))

          break;

      if (i == FIRST_PSEUDO_REGISTER)

        break;

    }

  /* If we didn't find a valid address, we must use register indirect.  */

  if (offset == 0)

    address = addr_reg;

  /* Next we try to form an insn to save and restore the register.  We

     see if such an insn is recognized and meets its constraints.

     To avoid lots of unnecessary RTL allocation, we construct all the RTL

     once, then modify the memory and register operands in-place.  */

  test_reg = gen_rtx_REG (VOIDmode, 0);

  test_mem = gen_rtx_MEM (VOIDmode, address);

  savepat = gen_rtx_SET (VOIDmode, test_mem, test_reg);

  restpat = gen_rtx_SET (VOIDmode, test_reg, test_mem);

  saveinsn = gen_rtx_INSN (VOIDmode, 0, 0, 0, 0, 0, savepat, -1, 0, 0);

  restinsn = gen_rtx_INSN (VOIDmode, 0, 0, 0, 0, 0, restpat, -1, 0, 0);

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    for (mode = 0 ; mode < MAX_MACHINE_MODE; mode++)

      if (HARD_REGNO_MODE_OK (i, mode))

        {

          int ok;

          /* Update the register number and modes of the register

             and memory operand.  */

          REGNO (test_reg) = i;

          PUT_MODE (test_reg, mode);

          PUT_MODE (test_mem, mode);

          /* Force re-recognition of the modified insns.  */

          INSN_CODE (saveinsn) = -1;

          INSN_CODE (restinsn) = -1;

          reg_save_code[i][mode] = recog_memoized (saveinsn);

          reg_restore_code[i][mode] = recog_memoized (restinsn);

          /* Now extract both insns and see if we can meet their

             constraints.  */

          ok = (reg_save_code[i][mode] != -1

                && reg_restore_code[i][mode] != -1);

          if (ok)

            {

              extract_insn (saveinsn);

              ok = constrain_operands (1);

              extract_insn (restinsn);

              ok &= constrain_operands (1);

            }

          if (! ok)

            {

              reg_save_code[i][mode] = -1;

              reg_restore_code[i][mode] = -1;

            }

        }

      else

        {

          reg_save_code[i][mode] = -1;

          reg_restore_code[i][mode] = -1;

        }

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    for (j = 1; j <= MOVE_MAX_WORDS; j++)

      if (reg_save_code [i][regno_save_mode[i][j]] == -1)

        {

          regno_save_mode[i][j] = VOIDmode;

          if (j == 1)

            {

              call_fixed_regs[i] = 1;

              SET_HARD_REG_BIT (call_fixed_reg_set, i);

            }

        }

}

/* Initialize save areas by showing that we haven't allocated any yet.  */

void

init_save_areas (void)

{

  int i, j;

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    for (j = 1; j <= MOVE_MAX_WORDS; j++)

      regno_save_mem[i][j] = 0;

}

/* Allocate save areas for any hard registers that might need saving.

   We take a conservative approach here and look for call-clobbered hard

   registers that are assigned to pseudos that cross calls.  This may

   overestimate slightly (especially if some of these registers are later

   used as spill registers), but it should not be significant.

   Future work:

     In the fallback case we should iterate backwards across all possible

     modes for the save, choosing the largest available one instead of

     falling back to the smallest mode immediately.  (eg TF -> DF -> SF).

     We do not try to use "move multiple" instructions that exist

     on some machines (such as the 68k moveml).  It could be a win to try

     and use them when possible.  The hard part is doing it in a way that is

     machine independent since they might be saving non-consecutive

     registers. (imagine caller-saving d0,d1,a0,a1 on the 68k) */

void

setup_save_areas (void)

{

  int i, j, k;

  unsigned int r;

  HARD_REG_SET hard_regs_used;

  /* Allocate space in the save area for the largest multi-register

     pseudos first, then work backwards to single register

     pseudos.  */

  /* Find and record all call-used hard-registers in this function.  */

  CLEAR_HARD_REG_SET (hard_regs_used);

  for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)

    if (reg_renumber[i] >= 0 && REG_N_CALLS_CROSSED (i) > 0)

      {

        unsigned int regno = reg_renumber[i];

        unsigned int endregno

          = regno + hard_regno_nregs[regno][GET_MODE (regno_reg_rtx[i])];

        for (r = regno; r < endregno; r++)

          if (call_used_regs[r])

            SET_HARD_REG_BIT (hard_regs_used, r);

      }

  /* Now run through all the call-used hard-registers and allocate

     space for them in the caller-save area.  Try to allocate space

     in a manner which allows multi-register saves/restores to be done.  */

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    for (j = MOVE_MAX_WORDS; j > 0; j--)

      {

        int do_save = 1;

        /* If no mode exists for this size, try another.  Also break out

           if we have already saved this hard register.  */

        if (regno_save_mode[i][j] == VOIDmode || regno_save_mem[i][1] != 0)

          continue;

        /* See if any register in this group has been saved.  */

        for (k = 0; k < j; k++)

          if (regno_save_mem[i + k][1])

            {

              do_save = 0;

              break;

            }

        if (! do_save)

          continue;

        for (k = 0; k < j; k++)

          if (! TEST_HARD_REG_BIT (hard_regs_used, i + k))

            {

              do_save = 0;

              break;

            }

        if (! do_save)

          continue;

        /* We have found an acceptable mode to store in.  */

        regno_save_mem[i][j]

          = assign_stack_local (regno_save_mode[i][j],

                                GET_MODE_SIZE (regno_save_mode[i][j]), 0);

        /* Setup single word save area just in case...  */

        for (k = 0; k < j; k++)

          /* This should not depend on WORDS_BIG_ENDIAN.

             The order of words in regs is the same as in memory.  */

          regno_save_mem[i + k][1]

            = adjust_address_nv (regno_save_mem[i][j],

                                 regno_save_mode[i + k][1],

                                 k * UNITS_PER_WORD);

      }

  /* Now loop again and set the alias set of any save areas we made to

     the alias set used to represent frame objects.  */

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)

    for (j = MOVE_MAX_WORDS; j > 0; j--)

      if (regno_save_mem[i][j] != 0)

        set_mem_alias_set (regno_save_mem[i][j], get_frame_alias_set ());

}

/* Find the places where hard regs are live across calls and save them.  */

void

save_call_clobbered_regs (void)

{

  struct insn_chain *chain, *next;

  enum machine_mode save_mode [FIRST_PSEUDO_REGISTER];

  /* Computed in mark_set_regs, holds all registers set by the current

     instruction.  */

  HARD_REG_SET this_insn_sets;

  CLEAR_HARD_REG_SET (hard_regs_saved);

  n_regs_saved = 0;

  for (chain = reload_insn_chain; chain != 0; chain = next)

    {

      rtx insn = chain->insn;

      enum rtx_code code = GET_CODE (insn);

      next = chain->next;

      gcc_assert (!chain->is_caller_save_insn);

      if (INSN_P (insn))

        {

          /* If some registers have been saved, see if INSN references

             any of them.  We must restore them before the insn if so.  */

          if (n_regs_saved)

            {

              int regno;

              if (code == JUMP_INSN)

                /* Restore all registers if this is a JUMP_INSN.  */

                COPY_HARD_REG_SET (referenced_regs, hard_regs_saved);

              else

                {

                  CLEAR_HARD_REG_SET (referenced_regs);

                  mark_referenced_regs (PATTERN (insn));

                  AND_HARD_REG_SET (referenced_regs, hard_regs_saved);

                }

              for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)

                if (TEST_HARD_REG_BIT (referenced_regs, regno))

                  regno += insert_restore (chain, 1, regno, MOVE_MAX_WORDS, save_mode);

            }

          if (code == CALL_INSN && ! find_reg_note (insn, REG_NORETURN, NULL))

            {

              unsigned regno;

              HARD_REG_SET hard_regs_to_save;

              reg_set_iterator rsi;

              /* Use the register life information in CHAIN to compute which

                 regs are live during the call.  */

              REG_SET_TO_HARD_REG_SET (hard_regs_to_save,

                                       &chain->live_throughout);

              /* Save hard registers always in the widest mode available.  */

              for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)

                if (TEST_HARD_REG_BIT (hard_regs_to_save, regno))

                  save_mode [regno] = regno_save_mode [regno][1];

                else

                  save_mode [regno] = VOIDmode;

              /* Look through all live pseudos, mark their hard registers

                 and choose proper mode for saving.  */

              EXECUTE_IF_SET_IN_REG_SET

                (&chain->live_throughout, FIRST_PSEUDO_REGISTER, regno, rsi)

                {

                  int r = reg_renumber[regno];

                  int nregs;

                  enum machine_mode mode;

                  gcc_assert (r >= 0);

                  nregs = hard_regno_nregs[r][PSEUDO_REGNO_MODE (regno)];

                  mode = HARD_REGNO_CALLER_SAVE_MODE

                    (r, nregs, PSEUDO_REGNO_MODE (regno));

                  if (GET_MODE_BITSIZE (mode)

                      > GET_MODE_BITSIZE (save_mode[r]))

                    save_mode[r] = mode;

                  while (nregs-- > 0)

                    SET_HARD_REG_BIT (hard_regs_to_save, r + nregs);

                }

              /* Record all registers set in this call insn.  These don't need

                 to be saved.  N.B. the call insn might set a subreg of a

                 multi-hard-reg pseudo; then the pseudo is considered live

                 during the call, but the subreg that is set isn't.  */

              CLEAR_HARD_REG_SET (this_insn_sets);

              note_stores (PATTERN (insn), mark_set_regs, &this_insn_sets);

              /* Sibcalls are considered to set the return value,

                 compare flow.c:propagate_one_insn.  */

              if (SIBLING_CALL_P (insn) && current_function_return_rtx)

                mark_set_regs (current_function_return_rtx, NULL_RTX,

                               &this_insn_sets);

              /* Compute which hard regs must be saved before this call.  */

              AND_COMPL_HARD_REG_SET (hard_regs_to_save, call_fixed_reg_set);

              AND_COMPL_HARD_REG_SET (hard_regs_to_save, this_insn_sets);

              AND_COMPL_HARD_REG_SET (hard_regs_to_save, hard_regs_saved);

              AND_HARD_REG_SET (hard_regs_to_save, call_used_reg_set);

              for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)

                if (TEST_HARD_REG_BIT (hard_regs_to_save, regno))

                  regno += insert_save (chain, 1, regno, &hard_regs_to_save, save_mode);

              /* Must recompute n_regs_saved.  */

              n_regs_saved = 0;

              for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)

                if (TEST_HARD_REG_BIT (hard_regs_saved, regno))

                  n_regs_saved++;

            }

        }

      if (chain->next == 0 || chain->next->block > chain->block)

        {

          int regno;

          /* At the end of the basic block, we must restore any registers that

             remain saved.  If the last insn in the block is a JUMP_INSN, put

             the restore before the insn, otherwise, put it after the insn.  */

          if (n_regs_saved)

            for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)

              if (TEST_HARD_REG_BIT (hard_regs_saved, regno))

                regno += insert_restore (chain, JUMP_P (insn),

                                         regno, MOVE_MAX_WORDS, save_mode);

        }

    }

}

/* Here from note_stores, or directly from save_call_clobbered_regs, when

   an insn stores a value in a register.

   Set the proper bit or bits in this_insn_sets.  All pseudos that have

   been assigned hard regs have had their register number changed already,

   so we can ignore pseudos.  */

static void

mark_set_regs (rtx reg, rtx setter ATTRIBUTE_UNUSED, void *data)

{

  int regno, endregno, i;

  enum machine_mode mode = GET_MODE (reg);

  HARD_REG_SET *this_insn_sets = data;

  if (GET_CODE (reg) == SUBREG)

    {

      rtx inner = SUBREG_REG (reg);

      if (!REG_P (inner) || REGNO (inner) >= FIRST_PSEUDO_REGISTER)

        return;

      regno = subreg_regno (reg);

    }

  else if (REG_P (reg)

           && REGNO (reg) < FIRST_PSEUDO_REGISTER)

    regno = REGNO (reg);

  else

    return;

  endregno = regno + hard_regno_nregs[regno][mode];

  for (i = regno; i < endregno; i++)

    SET_HARD_REG_BIT (*this_insn_sets, i);

}

/* Here from note_stores when an insn stores a value in a register.

   Set the proper bit or bits in the passed regset.  All pseudos that have

   been assigned hard regs have had their register number changed already,

   so we can ignore pseudos.  */

static void

add_stored_regs (rtx reg, rtx setter, void *data)

{

  int regno, endregno, i;

  enum machine_mode mode = GET_MODE (reg);

  int offset = 0;

  if (GET_CODE (setter) == CLOBBER)

    return;

  if (GET_CODE (reg) == SUBREG && REG_P (SUBREG_REG (reg)))

    {

      offset = subreg_regno_offset (REGNO (SUBREG_REG (reg)),

                                    GET_MODE (SUBREG_REG (reg)),

                                    SUBREG_BYTE (reg),

                                    GET_MODE (reg));

      reg = SUBREG_REG (reg);

    }

  if (!REG_P (reg) || REGNO (reg) >= FIRST_PSEUDO_REGISTER)

    return;

  regno = REGNO (reg) + offset;

  endregno = regno + hard_regno_nregs[regno][mode];

  for (i = regno; i < endregno; i++)

    SET_REGNO_REG_SET ((regset) data, i);

}

/* Walk X and record all referenced registers in REFERENCED_REGS.  */

static void

mark_referenced_regs (rtx x)

{

  enum rtx_code code = GET_CODE (x);

  const char *fmt;

  int i, j;

  if (code == SET)

    mark_referenced_regs (SET_SRC (x));

  if (code == SET || code == CLOBBER)

    {

      x = SET_DEST (x);

      code = GET_CODE (x);

      if ((code == REG && REGNO (x) < FIRST_PSEUDO_REGISTER)

          || code == PC || code == CC0

          || (code == SUBREG && REG_P (SUBREG_REG (x))

              && REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER

              /* If we're setting only part of a multi-word register,

                 we shall mark it as referenced, because the words

                 that are not being set should be restored.  */

              && ((GET_MODE_SIZE (GET_MODE (x))

                   >= GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))

                  || (GET_MODE_SIZE (GET_MODE (SUBREG_REG (x)))

                      <= UNITS_PER_WORD))))

        return;

    }

  if (code == MEM || code == SUBREG)

    {

      x = XEXP (x, 0);

      code = GET_CODE (x);

    }

  if (code == REG)

    {

      int regno = REGNO (x);

      int hardregno = (regno < FIRST_PSEUDO_REGISTER ? regno

                       : reg_renumber[regno]);

      if (hardregno >= 0)

        {

          int nregs = hard_regno_nregs[hardregno][GET_MODE (x)];

          while (nregs-- > 0)

            SET_HARD_REG_BIT (referenced_regs, hardregno + nregs);

        }

      /* If this is a pseudo that did not get a hard register, scan its

         memory location, since it might involve the use of another

         register, which might be saved.  */

      else if (reg_equiv_mem[regno] != 0)

        mark_referenced_regs (XEXP (reg_equiv_mem[regno], 0));

      else if (reg_equiv_address[regno] != 0)

        mark_referenced_regs (reg_equiv_address[regno]);

      return;

    }

  fmt = GET_RTX_FORMAT (code);

  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)

    {

      if (fmt[i] == 'e')

        mark_referenced_regs (XEXP (x, i));

      else if (fmt[i] == 'E')

        for (j = XVECLEN (x, i) - 1; j >= 0; j--)

          mark_referenced_regs (XVECEXP (x, i, j));

    }

}

/* Insert a sequence of insns to restore.  Place these insns in front of

   CHAIN if BEFORE_P is nonzero, behind the insn otherwise.  MAXRESTORE is

   the maximum number of registers which should be restored during this call.

   It should never be less than 1 since we only work with entire registers.

   Note that we have verified in init_caller_save that we can do this

   with a simple SET, so use it.  Set INSN_CODE to what we save there

   since the address might not be valid so the insn might not be recognized.

   These insns will be reloaded and have register elimination done by

   find_reload, so we need not worry about that here.

   Return the extra number of registers saved.  */

static int

insert_restore (struct insn_chain *chain, int before_p, int regno,

                int maxrestore, enum machine_mode *save_mode)

{

  int i, k;

  rtx pat = NULL_RTX;

  int code;

  unsigned int numregs = 0;

  struct insn_chain *new;

  rtx mem;

  /* A common failure mode if register status is not correct in the

     RTL is for this routine to be called with a REGNO we didn't

     expect to save.  That will cause us to write an insn with a (nil)

     SET_DEST or SET_SRC.  Instead of doing so and causing a crash

     later, check for this common case here instead.  This will remove

     one step in debugging such problems.  */

  gcc_assert (regno_save_mem[regno][1]);

  /* Get the pattern to emit and update our status.

     See if we can restore `maxrestore' registers at once.  Work

     backwards to the single register case.  */

  for (i = maxrestore; i > 0; i--)

    {

      int j;

      int ok = 1;

      if (regno_save_mem[regno][i] == 0)

        continue;

      for (j = 0; j < i; j++)

        if (! TEST_HARD_REG_BIT (hard_regs_saved, regno + j))

          {

            ok = 0;

            break;

          }

      /* Must do this one restore at a time.  */

      if (! ok)

        continue;