Subversion Repositories openrisc

/* Move registers around to reduce number of move instructions needed.

   Copyright (C) 1987, 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997,

   1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009

   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/>.  */

/* This module makes some simple RTL code transformations which

   improve the subsequent register allocation.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "rtl.h" /* stdio.h must precede rtl.h for FFS.  */

#include "tm_p.h"

#include "insn-config.h"

#include "recog.h"

#include "output.h"

#include "regs.h"

#include "hard-reg-set.h"

#include "flags.h"

#include "function.h"

#include "expr.h"

#include "basic-block.h"

#include "except.h"

#include "toplev.h"

#include "reload.h"

#include "timevar.h"

#include "tree-pass.h"

#include "df.h"

#include "ira.h"

static int optimize_reg_copy_1 (rtx, rtx, rtx);

static void optimize_reg_copy_2 (rtx, rtx, rtx);

static void optimize_reg_copy_3 (rtx, rtx, rtx);

static void copy_src_to_dest (rtx, rtx, rtx);

enum match_use

{

  READ,

  WRITE,

  READWRITE

};

struct match {

  int with[MAX_RECOG_OPERANDS];

  enum match_use use[MAX_RECOG_OPERANDS];

  int commutative[MAX_RECOG_OPERANDS];

  int early_clobber[MAX_RECOG_OPERANDS];

};

static int find_matches (rtx, struct match *);

static int fixup_match_2 (rtx, rtx, rtx, rtx);

/* Return nonzero if registers with CLASS1 and CLASS2 can be merged without

   causing too much register allocation problems.  */

static int

regclass_compatible_p (enum reg_class class0, enum reg_class class1)

{

  return (class0 == class1

          || (reg_class_subset_p (class0, class1)

              && ! CLASS_LIKELY_SPILLED_P (class0))

          || (reg_class_subset_p (class1, class0)

              && ! CLASS_LIKELY_SPILLED_P (class1)));

}

#ifdef AUTO_INC_DEC

/* Find the place in the rtx X where REG is used as a memory address.

   Return the MEM rtx that so uses it.

   If PLUSCONST is nonzero, search instead for a memory address equivalent to

   (plus REG (const_int PLUSCONST)).

   If such an address does not appear, return 0.

   If REG appears more than once, or is used other than in such an address,

   return (rtx) 1.  */

static rtx

find_use_as_address (rtx x, rtx reg, HOST_WIDE_INT plusconst)

{

  enum rtx_code code = GET_CODE (x);

  const char * const fmt = GET_RTX_FORMAT (code);

  int i;

  rtx value = 0;

  rtx tem;

  if (code == MEM && XEXP (x, 0) == reg && plusconst == 0)

    return x;

  if (code == MEM && GET_CODE (XEXP (x, 0)) == PLUS

      && XEXP (XEXP (x, 0), 0) == reg

      && CONST_INT_P (XEXP (XEXP (x, 0), 1))

      && INTVAL (XEXP (XEXP (x, 0), 1)) == plusconst)

    return x;

  if (code == SIGN_EXTRACT || code == ZERO_EXTRACT)

    {

      /* If REG occurs inside a MEM used in a bit-field reference,

         that is unacceptable.  */

      if (find_use_as_address (XEXP (x, 0), reg, 0) != 0)

        return (rtx) (size_t) 1;

    }

  if (x == reg)

    return (rtx) (size_t) 1;

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

    {

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

        {

          tem = find_use_as_address (XEXP (x, i), reg, plusconst);

          if (value == 0)

            value = tem;

          else if (tem != 0)

            return (rtx) (size_t) 1;

        }

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

        {

          int j;

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

            {

              tem = find_use_as_address (XVECEXP (x, i, j), reg, plusconst);

              if (value == 0)

                value = tem;

              else if (tem != 0)

                return (rtx) (size_t) 1;

            }

        }

    }

  return value;

}

/* INC_INSN is an instruction that adds INCREMENT to REG.

   Try to fold INC_INSN as a post/pre in/decrement into INSN.

   Iff INC_INSN_SET is nonzero, inc_insn has a destination different from src.

   Return nonzero for success.  */

static int

try_auto_increment (rtx insn, rtx inc_insn, rtx inc_insn_set, rtx reg,

                    HOST_WIDE_INT increment, int pre)

{

  enum rtx_code inc_code;

  rtx pset = single_set (insn);

  if (pset)

    {

      /* Can't use the size of SET_SRC, we might have something like

         (sign_extend:SI (mem:QI ...  */

      rtx use = find_use_as_address (pset, reg, 0);

      if (use != 0 && use != (rtx) (size_t) 1)

        {

          int size = GET_MODE_SIZE (GET_MODE (use));

          if (0

              || (HAVE_POST_INCREMENT

                  && pre == 0 && (inc_code = POST_INC, increment == size))

              || (HAVE_PRE_INCREMENT

                  && pre == 1 && (inc_code = PRE_INC, increment == size))

              || (HAVE_POST_DECREMENT

                  && pre == 0 && (inc_code = POST_DEC, increment == -size))

              || (HAVE_PRE_DECREMENT

                  && pre == 1 && (inc_code = PRE_DEC, increment == -size))

          )

            {

              if (inc_insn_set)

                validate_change

                  (inc_insn,

                   &SET_SRC (inc_insn_set),

                   XEXP (SET_SRC (inc_insn_set), 0), 1);

              validate_change (insn, &XEXP (use, 0),

                               gen_rtx_fmt_e (inc_code,

                                              GET_MODE (XEXP (use, 0)), reg),

                               1);

              if (apply_change_group ())

                {

                  /* If there is a REG_DEAD note on this insn, we must

                     change this not to REG_UNUSED meaning that the register

                     is set, but the value is dead.  Failure to do so will

                     result in sched1 dying -- when it recomputes lifetime

                     information, the number of REG_DEAD notes will have

                     changed.  */

                  rtx note = find_reg_note (insn, REG_DEAD, reg);

                  if (note)

                    PUT_REG_NOTE_KIND (note, REG_UNUSED);

                  add_reg_note (insn, REG_INC, reg);

                  if (! inc_insn_set)

                    delete_insn (inc_insn);

                  return 1;

                }

            }

        }

    }

  return 0;

}

#endif

static int *regno_src_regno;

/* INSN is a copy from SRC to DEST, both registers, and SRC does not die

   in INSN.

   Search forward to see if SRC dies before either it or DEST is modified,

   but don't scan past the end of a basic block.  If so, we can replace SRC

   with DEST and let SRC die in INSN.

   This will reduce the number of registers live in that range and may enable

   DEST to be tied to SRC, thus often saving one register in addition to a

   register-register copy.  */

static int

optimize_reg_copy_1 (rtx insn, rtx dest, rtx src)

{

  rtx p, q;

  rtx note;

  rtx dest_death = 0;

  int sregno = REGNO (src);

  int dregno = REGNO (dest);

  basic_block bb = BLOCK_FOR_INSN (insn);

  /* We don't want to mess with hard regs if register classes are small.  */

  if (sregno == dregno

      || (SMALL_REGISTER_CLASSES

          && (sregno < FIRST_PSEUDO_REGISTER

              || dregno < FIRST_PSEUDO_REGISTER))

      /* We don't see all updates to SP if they are in an auto-inc memory

         reference, so we must disallow this optimization on them.  */

      || sregno == STACK_POINTER_REGNUM || dregno == STACK_POINTER_REGNUM)

    return 0;

  for (p = NEXT_INSN (insn); p; p = NEXT_INSN (p))

    {

      if (! INSN_P (p))

        continue;

      if (BLOCK_FOR_INSN (p) != bb)

        break;

      if (reg_set_p (src, p) || reg_set_p (dest, p)

          /* If SRC is an asm-declared register, it must not be replaced

             in any asm.  Unfortunately, the REG_EXPR tree for the asm

             variable may be absent in the SRC rtx, so we can't check the

             actual register declaration easily (the asm operand will have

             it, though).  To avoid complicating the test for a rare case,

             we just don't perform register replacement for a hard reg

             mentioned in an asm.  */

          || (sregno < FIRST_PSEUDO_REGISTER

              && asm_noperands (PATTERN (p)) >= 0

              && reg_overlap_mentioned_p (src, PATTERN (p)))

          /* Don't change hard registers used by a call.  */

          || (CALL_P (p) && sregno < FIRST_PSEUDO_REGISTER

              && find_reg_fusage (p, USE, src))

          /* Don't change a USE of a register.  */

          || (GET_CODE (PATTERN (p)) == USE

              && reg_overlap_mentioned_p (src, XEXP (PATTERN (p), 0))))

        break;

      /* See if all of SRC dies in P.  This test is slightly more

         conservative than it needs to be.  */

      if ((note = find_regno_note (p, REG_DEAD, sregno)) != 0

          && GET_MODE (XEXP (note, 0)) == GET_MODE (src))

        {

          int failed = 0;

          int d_length = 0;

          int s_length = 0;

          int d_n_calls = 0;

          int s_n_calls = 0;

          int s_freq_calls = 0;

          int d_freq_calls = 0;

          /* We can do the optimization.  Scan forward from INSN again,

             replacing regs as we go.  Set FAILED if a replacement can't

             be done.  In that case, we can't move the death note for SRC.

             This should be rare.  */

          /* Set to stop at next insn.  */

          for (q = next_real_insn (insn);

               q != next_real_insn (p);

               q = next_real_insn (q))

            {

              if (reg_overlap_mentioned_p (src, PATTERN (q)))

                {

                  /* If SRC is a hard register, we might miss some

                     overlapping registers with validate_replace_rtx,

                     so we would have to undo it.  We can't if DEST is

                     present in the insn, so fail in that combination

                     of cases.  */

                  if (sregno < FIRST_PSEUDO_REGISTER

                      && reg_mentioned_p (dest, PATTERN (q)))

                    failed = 1;

                  /* Attempt to replace all uses.  */

                  else if (!validate_replace_rtx (src, dest, q))

                    failed = 1;

                  /* If this succeeded, but some part of the register

                     is still present, undo the replacement.  */

                  else if (sregno < FIRST_PSEUDO_REGISTER

                           && reg_overlap_mentioned_p (src, PATTERN (q)))

                    {

                      validate_replace_rtx (dest, src, q);

                      failed = 1;

                    }

                }

              /* For SREGNO, count the total number of insns scanned.

                 For DREGNO, count the total number of insns scanned after

                 passing the death note for DREGNO.  */

              if (!DEBUG_INSN_P (p))

                {

                  s_length++;

                  if (dest_death)

                    d_length++;

                }

              /* If the insn in which SRC dies is a CALL_INSN, don't count it

                 as a call that has been crossed.  Otherwise, count it.  */

              if (q != p && CALL_P (q))

                {

                  /* Similarly, total calls for SREGNO, total calls beyond

                     the death note for DREGNO.  */

                  s_n_calls++;

                  s_freq_calls += REG_FREQ_FROM_BB  (BLOCK_FOR_INSN (q));

                  if (dest_death)

                    {

                      d_n_calls++;

                      d_freq_calls += REG_FREQ_FROM_BB  (BLOCK_FOR_INSN (q));

                    }

                }

              /* If DEST dies here, remove the death note and save it for

                 later.  Make sure ALL of DEST dies here; again, this is

                 overly conservative.  */

              if (dest_death == 0

                  && (dest_death = find_regno_note (q, REG_DEAD, dregno)) != 0)

                {

                  if (GET_MODE (XEXP (dest_death, 0)) != GET_MODE (dest))

                    failed = 1, dest_death = 0;

                  else

                    remove_note (q, dest_death);

                }

            }

          if (! failed)

            {

              /* These counters need to be updated if and only if we are

                 going to move the REG_DEAD note.  */

              if (sregno >= FIRST_PSEUDO_REGISTER)

                {

                  if (REG_LIVE_LENGTH (sregno) >= 0)

                    {

                      REG_LIVE_LENGTH (sregno) -= s_length;

                      /* REG_LIVE_LENGTH is only an approximation after

                         combine if sched is not run, so make sure that we

                         still have a reasonable value.  */

                      if (REG_LIVE_LENGTH (sregno) < 2)

                        REG_LIVE_LENGTH (sregno) = 2;

                    }

                  REG_N_CALLS_CROSSED (sregno) -= s_n_calls;

                  REG_FREQ_CALLS_CROSSED (sregno) -= s_freq_calls;

                }

              /* Move death note of SRC from P to INSN.  */

              remove_note (p, note);

              XEXP (note, 1) = REG_NOTES (insn);

              REG_NOTES (insn) = note;

            }

          /* DEST is also dead if INSN has a REG_UNUSED note for DEST.  */

          if (! dest_death

              && (dest_death = find_regno_note (insn, REG_UNUSED, dregno)))

            {

              PUT_REG_NOTE_KIND (dest_death, REG_DEAD);

              remove_note (insn, dest_death);

            }

          /* Put death note of DEST on P if we saw it die.  */

          if (dest_death)

            {

              XEXP (dest_death, 1) = REG_NOTES (p);

              REG_NOTES (p) = dest_death;

              if (dregno >= FIRST_PSEUDO_REGISTER)

                {

                  /* If and only if we are moving the death note for DREGNO,

                     then we need to update its counters.  */

                  if (REG_LIVE_LENGTH (dregno) >= 0)

                    REG_LIVE_LENGTH (dregno) += d_length;

                  REG_N_CALLS_CROSSED (dregno) += d_n_calls;

                  REG_FREQ_CALLS_CROSSED (dregno) += d_freq_calls;

                }

            }

          return ! failed;

        }

      /* If SRC is a hard register which is set or killed in some other

         way, we can't do this optimization.  */

      else if (sregno < FIRST_PSEUDO_REGISTER

               && dead_or_set_p (p, src))

        break;

    }

  return 0;

}

/* INSN is a copy of SRC to DEST, in which SRC dies.  See if we now have

   a sequence of insns that modify DEST followed by an insn that sets

   SRC to DEST in which DEST dies, with no prior modification of DEST.

   (There is no need to check if the insns in between actually modify

   DEST.  We should not have cases where DEST is not modified, but

   the optimization is safe if no such modification is detected.)

   In that case, we can replace all uses of DEST, starting with INSN and

   ending with the set of SRC to DEST, with SRC.  We do not do this

   optimization if a CALL_INSN is crossed unless SRC already crosses a

   call or if DEST dies before the copy back to SRC.

   It is assumed that DEST and SRC are pseudos; it is too complicated to do

   this for hard registers since the substitutions we may make might fail.  */

static void

optimize_reg_copy_2 (rtx insn, rtx dest, rtx src)

{

  rtx p, q;

  rtx set;

  int sregno = REGNO (src);

  int dregno = REGNO (dest);

  basic_block bb = BLOCK_FOR_INSN (insn);

  for (p = NEXT_INSN (insn); p; p = NEXT_INSN (p))

    {

      if (! INSN_P (p))

        continue;

      if (BLOCK_FOR_INSN (p) != bb)

        break;

      set = single_set (p);

      if (set && SET_SRC (set) == dest && SET_DEST (set) == src

          && find_reg_note (p, REG_DEAD, dest))

        {

          /* We can do the optimization.  Scan forward from INSN again,

             replacing regs as we go.  */

          /* Set to stop at next insn.  */

          for (q = insn; q != NEXT_INSN (p); q = NEXT_INSN (q))

            if (INSN_P (q))

              {

                if (reg_mentioned_p (dest, PATTERN (q)))

                  {

                    rtx note;

                    PATTERN (q) = replace_rtx (PATTERN (q), dest, src);

                    note = FIND_REG_INC_NOTE (q, dest);

                    if (note)

                      {

                        remove_note (q, note);

                        add_reg_note (q, REG_INC, src);

                      }

                    df_insn_rescan (q);

                  }

                if (CALL_P (q))

                  {

                    int freq = REG_FREQ_FROM_BB  (BLOCK_FOR_INSN (q));

                    REG_N_CALLS_CROSSED (dregno)--;

                    REG_N_CALLS_CROSSED (sregno)++;

                    REG_FREQ_CALLS_CROSSED (dregno) -= freq;

                    REG_FREQ_CALLS_CROSSED (sregno) += freq;

                  }

              }

          remove_note (p, find_reg_note (p, REG_DEAD, dest));

          REG_N_DEATHS (dregno)--;

          remove_note (insn, find_reg_note (insn, REG_DEAD, src));

          REG_N_DEATHS (sregno)--;

          return;

        }

      if (reg_set_p (src, p)

          || find_reg_note (p, REG_DEAD, dest)

          || (CALL_P (p) && REG_N_CALLS_CROSSED (sregno) == 0))

        break;

    }

}

/* INSN is a ZERO_EXTEND or SIGN_EXTEND of SRC to DEST.

   Look if SRC dies there, and if it is only set once, by loading

   it from memory.  If so, try to incorporate the zero/sign extension

   into the memory read, change SRC to the mode of DEST, and alter

   the remaining accesses to use the appropriate SUBREG.  This allows

   SRC and DEST to be tied later.  */

static void

optimize_reg_copy_3 (rtx insn, rtx dest, rtx src)

{

  rtx src_reg = XEXP (src, 0);

  int src_no = REGNO (src_reg);

  int dst_no = REGNO (dest);

  rtx p, set;

  enum machine_mode old_mode;

  basic_block bb = BLOCK_FOR_INSN (insn);

  if (src_no < FIRST_PSEUDO_REGISTER

      || dst_no < FIRST_PSEUDO_REGISTER

      || ! find_reg_note (insn, REG_DEAD, src_reg)

      || REG_N_DEATHS (src_no) != 1

      || REG_N_SETS (src_no) != 1)

    return;

  for (p = PREV_INSN (insn); p && ! reg_set_p (src_reg, p); p = PREV_INSN (p))

    if (INSN_P (p) && BLOCK_FOR_INSN (p) != bb)

      break;

  if (! p || BLOCK_FOR_INSN (p) != bb)

    return;

  if (! (set = single_set (p))

      || !MEM_P (SET_SRC (set))

      /* If there's a REG_EQUIV note, this must be an insn that loads an

         argument.  Prefer keeping the note over doing this optimization.  */

      || find_reg_note (p, REG_EQUIV, NULL_RTX)

      || SET_DEST (set) != src_reg)

    return;

  /* Be conservative: although this optimization is also valid for

     volatile memory references, that could cause trouble in later passes.  */

  if (MEM_VOLATILE_P (SET_SRC (set)))

    return;

  /* Do not use a SUBREG to truncate from one mode to another if truncation

     is not a nop.  */

  if (GET_MODE_BITSIZE (GET_MODE (src_reg)) <= GET_MODE_BITSIZE (GET_MODE (src))

      && !TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (GET_MODE (src)),

                                 GET_MODE_BITSIZE (GET_MODE (src_reg))))

    return;

  old_mode = GET_MODE (src_reg);

  PUT_MODE (src_reg, GET_MODE (src));

  XEXP (src, 0) = SET_SRC (set);

  /* Include this change in the group so that it's easily undone if

     one of the changes in the group is invalid.  */

  validate_change (p, &SET_SRC (set), src, 1);

  /* Now walk forward making additional replacements.  We want to be able

     to undo all the changes if a later substitution fails.  */

  while (p = NEXT_INSN (p), p != insn)

    {

      if (! INSN_P (p))

        continue;

      /* Make a tentative change.  */

      validate_replace_rtx_group (src_reg,

                                  gen_lowpart_SUBREG (old_mode, src_reg),

                                  p);

    }

  validate_replace_rtx_group (src, src_reg, insn);

  /* Now see if all the changes are valid.  */

  if (! apply_change_group ())

    {

      /* One or more changes were no good.  Back out everything.  */

      PUT_MODE (src_reg, old_mode);

      XEXP (src, 0) = src_reg;

    }

  else

    {

      rtx note = find_reg_note (p, REG_EQUAL, NULL_RTX);

      if (note)

        remove_note (p, note);

    }

}

/* If we were not able to update the users of src to use dest directly, try

   instead moving the value to dest directly before the operation.  */

static void

copy_src_to_dest (rtx insn, rtx src, rtx dest)

{

  rtx seq;

  rtx link;

  rtx next;

  rtx set;

  rtx move_insn;

  rtx *p_insn_notes;

  rtx *p_move_notes;

  int src_regno;

  int dest_regno;

  /* A REG_LIVE_LENGTH of -1 indicates the register is equivalent to a constant

     or memory location and is used infrequently; a REG_LIVE_LENGTH of -2 is

     parameter when there is no frame pointer that is not allocated a register.

     For now, we just reject them, rather than incrementing the live length.  */

  if (REG_P (src)

      && REG_LIVE_LENGTH (REGNO (src)) > 0

      && REG_P (dest)

      && REG_LIVE_LENGTH (REGNO (dest)) > 0

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

      && !reg_mentioned_p (dest, SET_SRC (set))

      && GET_MODE (src) == GET_MODE (dest))

    {

      int old_num_regs = reg_rtx_no;

      /* Generate the src->dest move.  */

      start_sequence ();

      emit_move_insn (dest, src);

      seq = get_insns ();

      end_sequence ();

      /* If this sequence uses new registers, we may not use it.  */

      if (old_num_regs != reg_rtx_no

          || ! validate_replace_rtx (src, dest, insn))

        {

          /* We have to restore reg_rtx_no to its old value, lest

             recompute_reg_usage will try to compute the usage of the

             new regs, yet reg_n_info is not valid for them.  */

          reg_rtx_no = old_num_regs;

          return;

        }

      emit_insn_before (seq, insn);

      move_insn = PREV_INSN (insn);

      p_move_notes = &REG_NOTES (move_insn);

      p_insn_notes = &REG_NOTES (insn);

      /* Move any notes mentioning src to the move instruction.  */

      for (link = REG_NOTES (insn); link != NULL_RTX; link = next)

        {

          next = XEXP (link, 1);

          if (XEXP (link, 0) == src)

            {

              *p_move_notes = link;

              p_move_notes = &XEXP (link, 1);

            }

          else

            {

              *p_insn_notes = link;

              p_insn_notes = &XEXP (link, 1);

            }

        }

      *p_move_notes = NULL_RTX;

      *p_insn_notes = NULL_RTX;

      /* Update the various register tables.  */

      dest_regno = REGNO (dest);

      INC_REG_N_SETS (dest_regno, 1);

      REG_LIVE_LENGTH (dest_regno)++;

      src_regno = REGNO (src);

      if (! find_reg_note (move_insn, REG_DEAD, src))

        REG_LIVE_LENGTH (src_regno)++;

    }

}

/* reg_set_in_bb[REGNO] points to basic block iff the register is set

   only once in the given block and has REG_EQUAL note.  */

static basic_block *reg_set_in_bb;

/* Size of reg_set_in_bb array.  */

static unsigned int max_reg_computed;

/* Return whether REG is set in only one location, and is set to a

   constant, but is set in a different basic block from INSN (an

   instructions which uses REG).  In this case REG is equivalent to a

   constant, and we don't want to break that equivalence, because that

   may increase register pressure and make reload harder.  If REG is

   set in the same basic block as INSN, we don't worry about it,