forked from illumos/gcc
/
regmove.c
2542 lines (2201 loc) · 73.7 KB
/
regmove.c
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/* 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 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. */
/* This module looks for cases where matching constraints would force
an instruction to need a reload, and this reload would be a register
to register move. It then attempts to change the registers used by the
instruction to avoid the move instruction. */
#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"
/* Turn STACK_GROWS_DOWNWARD into a boolean. */
#ifdef STACK_GROWS_DOWNWARD
#undef STACK_GROWS_DOWNWARD
#define STACK_GROWS_DOWNWARD 1
#else
#define STACK_GROWS_DOWNWARD 0
#endif
static int perhaps_ends_bb_p (rtx);
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, int);
static int *regmove_bb_head;
struct match {
int with[MAX_RECOG_OPERANDS];
enum { READ, WRITE, READWRITE } use[MAX_RECOG_OPERANDS];
int commutative[MAX_RECOG_OPERANDS];
int early_clobber[MAX_RECOG_OPERANDS];
};
static rtx discover_flags_reg (void);
static void mark_flags_life_zones (rtx);
static void flags_set_1 (rtx, rtx, void *);
static int try_auto_increment (rtx, rtx, rtx, rtx, HOST_WIDE_INT, int);
static int find_matches (rtx, struct match *);
static void replace_in_call_usage (rtx *, unsigned int, rtx, rtx);
static int fixup_match_1 (rtx, rtx, rtx, rtx, rtx, int, int, int, FILE *);
static int reg_is_remote_constant_p (rtx, rtx, rtx);
static int stable_and_no_regs_but_for_p (rtx, rtx, rtx);
static int regclass_compatible_p (int, int);
static int replacement_quality (rtx);
static int fixup_match_2 (rtx, rtx, rtx, rtx, FILE *);
/* Return nonzero if registers with CLASS1 and CLASS2 can be merged without
causing too much register allocation problems. */
static int
regclass_compatible_p (int class0, int 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)));
}
/* 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, Pmode, 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 a sched1 dieing -- 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_MODE (note, REG_UNUSED);
REG_NOTES (insn)
= gen_rtx_EXPR_LIST (REG_INC,
reg, REG_NOTES (insn));
if (! inc_insn_set)
delete_insn (inc_insn);
return 1;
}
}
}
}
return 0;
}
/* Determine if the pattern generated by add_optab has a clobber,
such as might be issued for a flags hard register. To make the
code elsewhere simpler, we handle cc0 in this same framework.
Return the register if one was discovered. Return NULL_RTX if
if no flags were found. Return pc_rtx if we got confused. */
static rtx
discover_flags_reg (void)
{
rtx tmp;
tmp = gen_rtx_REG (word_mode, 10000);
tmp = gen_add3_insn (tmp, tmp, const2_rtx);
/* If we get something that isn't a simple set, or a
[(set ..) (clobber ..)], this whole function will go wrong. */
if (GET_CODE (tmp) == SET)
return NULL_RTX;
else if (GET_CODE (tmp) == PARALLEL)
{
int found;
if (XVECLEN (tmp, 0) != 2)
return pc_rtx;
tmp = XVECEXP (tmp, 0, 1);
if (GET_CODE (tmp) != CLOBBER)
return pc_rtx;
tmp = XEXP (tmp, 0);
/* Don't do anything foolish if the md wanted to clobber a
scratch or something. We only care about hard regs.
Moreover we don't like the notion of subregs of hard regs. */
if (GET_CODE (tmp) == SUBREG
&& REG_P (SUBREG_REG (tmp))
&& REGNO (SUBREG_REG (tmp)) < FIRST_PSEUDO_REGISTER)
return pc_rtx;
found = (REG_P (tmp) && REGNO (tmp) < FIRST_PSEUDO_REGISTER);
return (found ? tmp : NULL_RTX);
}
return pc_rtx;
}
/* It is a tedious task identifying when the flags register is live and
when it is safe to optimize. Since we process the instruction stream
multiple times, locate and record these live zones by marking the
mode of the instructions --
QImode is used on the instruction at which the flags becomes live.
HImode is used within the range (exclusive) that the flags are
live. Thus the user of the flags is not marked.
All other instructions are cleared to VOIDmode. */
/* Used to communicate with flags_set_1. */
static rtx flags_set_1_rtx;
static int flags_set_1_set;
static void
mark_flags_life_zones (rtx flags)
{
int flags_regno;
int flags_nregs;
basic_block block;
#ifdef HAVE_cc0
/* If we found a flags register on a cc0 host, bail. */
if (flags == NULL_RTX)
flags = cc0_rtx;
else if (flags != cc0_rtx)
flags = pc_rtx;
#endif
/* Simple cases first: if no flags, clear all modes. If confusing,
mark the entire function as being in a flags shadow. */
if (flags == NULL_RTX || flags == pc_rtx)
{
enum machine_mode mode = (flags ? HImode : VOIDmode);
rtx insn;
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
PUT_MODE (insn, mode);
return;
}
#ifdef HAVE_cc0
flags_regno = -1;
flags_nregs = 1;
#else
flags_regno = REGNO (flags);
flags_nregs = hard_regno_nregs[flags_regno][GET_MODE (flags)];
#endif
flags_set_1_rtx = flags;
/* Process each basic block. */
FOR_EACH_BB_REVERSE (block)
{
rtx insn, end;
int live;
insn = BB_HEAD (block);
end = BB_END (block);
/* Look out for the (unlikely) case of flags being live across
basic block boundaries. */
live = 0;
#ifndef HAVE_cc0
{
int i;
for (i = 0; i < flags_nregs; ++i)
live |= REGNO_REG_SET_P (block->il.rtl->global_live_at_start,
flags_regno + i);
}
#endif
while (1)
{
/* Process liveness in reverse order of importance --
alive, death, birth. This lets more important info
overwrite the mode of lesser info. */
if (INSN_P (insn))
{
#ifdef HAVE_cc0
/* In the cc0 case, death is not marked in reg notes,
but is instead the mere use of cc0 when it is alive. */
if (live && reg_mentioned_p (cc0_rtx, PATTERN (insn)))
live = 0;
#else
/* In the hard reg case, we watch death notes. */
if (live && find_regno_note (insn, REG_DEAD, flags_regno))
live = 0;
#endif
PUT_MODE (insn, (live ? HImode : VOIDmode));
/* In either case, birth is denoted simply by its presence
as the destination of a set. */
flags_set_1_set = 0;
note_stores (PATTERN (insn), flags_set_1, NULL);
if (flags_set_1_set)
{
live = 1;
PUT_MODE (insn, QImode);
}
}
else
PUT_MODE (insn, (live ? HImode : VOIDmode));
if (insn == end)
break;
insn = NEXT_INSN (insn);
}
}
}
/* A subroutine of mark_flags_life_zones, called through note_stores. */
static void
flags_set_1 (rtx x, rtx pat, void *data ATTRIBUTE_UNUSED)
{
if (GET_CODE (pat) == SET
&& reg_overlap_mentioned_p (x, flags_set_1_rtx))
flags_set_1_set = 1;
}
static int *regno_src_regno;
/* Indicate how good a choice REG (which appears as a source) is to replace
a destination register with. The higher the returned value, the better
the choice. The main objective is to avoid using a register that is
a candidate for tying to a hard register, since the output might in
turn be a candidate to be tied to a different hard register. */
static int
replacement_quality (rtx reg)
{
int src_regno;
/* Bad if this isn't a register at all. */
if (!REG_P (reg))
return 0;
/* If this register is not meant to get a hard register,
it is a poor choice. */
if (REG_LIVE_LENGTH (REGNO (reg)) < 0)
return 0;
src_regno = regno_src_regno[REGNO (reg)];
/* If it was not copied from another register, it is fine. */
if (src_regno < 0)
return 3;
/* Copied from a hard register? */
if (src_regno < FIRST_PSEUDO_REGISTER)
return 1;
/* Copied from a pseudo register - not as bad as from a hard register,
yet still cumbersome, since the register live length will be lengthened
when the registers get tied. */
return 2;
}
/* Return 1 if INSN might end a basic block. */
static int perhaps_ends_bb_p (rtx insn)
{
switch (GET_CODE (insn))
{
case CODE_LABEL:
case JUMP_INSN:
/* These always end a basic block. */
return 1;
case CALL_INSN:
/* A CALL_INSN might be the last insn of a basic block, if it is inside
an EH region or if there are nonlocal gotos. Note that this test is
very conservative. */
if (nonlocal_goto_handler_labels)
return 1;
/* Fall through. */
default:
return can_throw_internal (insn);
}
}
/* 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);
/* 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))
{
/* ??? We can't scan past the end of a basic block without updating
the register lifetime info (REG_DEAD/basic_block_live_at_start). */
if (perhaps_ends_bb_p (p))
break;
else if (! INSN_P (p))
continue;
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;
/* 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;
/* Replace all uses and make sure that the register
isn't still present. */
else if (validate_replace_rtx (src, dest, q)
&& (sregno >= FIRST_PSEUDO_REGISTER
|| ! reg_overlap_mentioned_p (src,
PATTERN (q))))
;
else
{
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. */
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++;
if (dest_death)
d_n_calls++;
}
/* 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;
}
/* 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;
}
}
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);
for (p = NEXT_INSN (insn); p; p = NEXT_INSN (p))
{
/* ??? We can't scan past the end of a basic block without updating
the register lifetime info (REG_DEAD/basic_block_live_at_start). */
if (perhaps_ends_bb_p (p))
break;
else if (! INSN_P (p))
continue;
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)))
PATTERN (q) = replace_rtx (PATTERN (q), dest, src);
if (CALL_P (q))
{
REG_N_CALLS_CROSSED (dregno)--;
REG_N_CALLS_CROSSED (sregno)++;
}
}
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;
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))
/* ??? We can't scan past the end of a basic block without updating
the register lifetime info (REG_DEAD/basic_block_live_at_start). */
if (perhaps_ends_bb_p (p))
break;
if (! p)
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, int old_max_uid)
{
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;
int bb;
int insn_uid;
int move_uid;
/* 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 = ®_NOTES (move_insn);
p_insn_notes = ®_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;
/* Is the insn the head of a basic block? If so extend it. */
insn_uid = INSN_UID (insn);
move_uid = INSN_UID (move_insn);
if (insn_uid < old_max_uid)
{
bb = regmove_bb_head[insn_uid];
if (bb >= 0)
{
BB_HEAD (BASIC_BLOCK (bb)) = move_insn;
regmove_bb_head[insn_uid] = -1;
}
}
/* Update the various register tables. */
dest_regno = REGNO (dest);
REG_N_SETS (dest_regno) ++;
REG_LIVE_LENGTH (dest_regno)++;
if (REGNO_FIRST_UID (dest_regno) == insn_uid)
REGNO_FIRST_UID (dest_regno) = move_uid;
src_regno = REGNO (src);
if (! find_reg_note (move_insn, REG_DEAD, src))
REG_LIVE_LENGTH (src_regno)++;
if (REGNO_FIRST_UID (src_regno) == insn_uid)
REGNO_FIRST_UID (src_regno) = move_uid;
if (REGNO_LAST_UID (src_regno) == insn_uid)
REGNO_LAST_UID (src_regno) = move_uid;
}
}
/* 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,
because we'll probably need a register anyhow (??? but what if REG
is used in a different basic block as well as this one?). FIRST is
the first insn in the function. */
static int
reg_is_remote_constant_p (rtx reg, rtx insn, rtx first)
{
rtx p;
if (REG_N_SETS (REGNO (reg)) != 1)
return 0;
/* Look for the set. */
for (p = BB_HEAD (BLOCK_FOR_INSN (insn)); p != insn; p = NEXT_INSN (p))
{
rtx s;
if (!INSN_P (p))
continue;
s = single_set (p);
if (s != 0
&& REG_P (SET_DEST (s))
&& REGNO (SET_DEST (s)) == REGNO (reg))
{
/* The register is set in the same basic block. */
return 0;
}
}
for (p = first; p && p != insn; p = NEXT_INSN (p))
{
rtx s;
if (! INSN_P (p))
continue;
s = single_set (p);
if (s != 0
&& REG_P (SET_DEST (s))
&& REGNO (SET_DEST (s)) == REGNO (reg))
{
/* This is the instruction which sets REG. If there is a
REG_EQUAL note, then REG is equivalent to a constant. */
if (find_reg_note (p, REG_EQUAL, NULL_RTX))
return 1;
return 0;
}
}
return 0;
}
/* INSN is adding a CONST_INT to a REG. We search backwards looking for
another add immediate instruction with the same source and dest registers,
and if we find one, we change INSN to an increment, and return 1. If
no changes are made, we return 0.
This changes
(set (reg100) (plus reg1 offset1))
...
(set (reg100) (plus reg1 offset2))
to
(set (reg100) (plus reg1 offset1))
...
(set (reg100) (plus reg100 offset2-offset1)) */
/* ??? What does this comment mean? */
/* cse disrupts preincrement / postdecrement sequences when it finds a
hard register as ultimate source, like the frame pointer. */
static int
fixup_match_2 (rtx insn, rtx dst, rtx src, rtx offset, FILE *regmove_dump_file)
{
rtx p, dst_death = 0;
int length, num_calls = 0;
/* If SRC dies in INSN, we'd have to move the death note. This is
considered to be very unlikely, so we just skip the optimization
in this case. */
if (find_regno_note (insn, REG_DEAD, REGNO (src)))
return 0;
/* Scan backward to find the first instruction that sets DST. */
for (length = 0, p = PREV_INSN (insn); p; p = PREV_INSN (p))
{
rtx pset;
/* ??? We can't scan past the end of a basic block without updating
the register lifetime info (REG_DEAD/basic_block_live_at_start). */
if (perhaps_ends_bb_p (p))
break;
else if (! INSN_P (p))
continue;
if (find_regno_note (p, REG_DEAD, REGNO (dst)))
dst_death = p;
if (! dst_death)
length++;
pset = single_set (p);
if (pset && SET_DEST (pset) == dst
&& GET_CODE (SET_SRC (pset)) == PLUS
&& XEXP (SET_SRC (pset), 0) == src
&& GET_CODE (XEXP (SET_SRC (pset), 1)) == CONST_INT)
{
HOST_WIDE_INT newconst
= INTVAL (offset) - INTVAL (XEXP (SET_SRC (pset), 1));
rtx add = gen_add3_insn (dst, dst, GEN_INT (newconst));
if (add && validate_change (insn, &PATTERN (insn), add, 0))
{
/* Remove the death note for DST from DST_DEATH. */
if (dst_death)
{
remove_death (REGNO (dst), dst_death);
REG_LIVE_LENGTH (REGNO (dst)) += length;
REG_N_CALLS_CROSSED (REGNO (dst)) += num_calls;
}
if (regmove_dump_file)
fprintf (regmove_dump_file,
"Fixed operand of insn %d.\n",
INSN_UID (insn));
#ifdef AUTO_INC_DEC
for (p = PREV_INSN (insn); p; p = PREV_INSN (p))
{
if (LABEL_P (p)
|| JUMP_P (p))
break;
if (! INSN_P (p))
continue;
if (reg_overlap_mentioned_p (dst, PATTERN (p)))
{
if (try_auto_increment (p, insn, 0, dst, newconst, 0))
return 1;
break;
}
}
for (p = NEXT_INSN (insn); p; p = NEXT_INSN (p))
{
if (LABEL_P (p)
|| JUMP_P (p))
break;
if (! INSN_P (p))
continue;
if (reg_overlap_mentioned_p (dst, PATTERN (p)))
{
try_auto_increment (p, insn, 0, dst, newconst, 1);
break;
}
}