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Fix suboptimal code generation by register elimination

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From-SVN: r32446
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Bernd Schmidt 2000-03-09 16:01:10 +00:00 committed by Bernd Schmidt
parent fb863f625e
commit aa5524a98e
2 changed files with 53 additions and 32 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2000-03-09 Bernd Schmidt <bernds@cygnus.co.uk>
* reload1.c (eliminate_regs_in_insn): Handle additions of eliminable
register and a constant specially.
2000-03-08 Kaveh R. Ghazi <ghazi@caip.rutgers.edu>
* libgcc2.h: New file.

80
gcc/reload1.c
View File

@ -2903,41 +2903,57 @@ eliminate_regs_in_insn (insn, replace)
val = 1;
goto done;
}
}
/* Check for (set (reg) (plus (reg from) (offset))) where the offset
in the insn is the negative of the offset in FROM. Substitute
(set (reg) (reg to)) for the insn and change its code.
/* We allow one special case which happens to work on all machines we
currently support: a single set with the source being a PLUS of an
eliminable register and a constant. */
if (old_set
&& GET_CODE (SET_SRC (old_set)) == PLUS
&& GET_CODE (XEXP (SET_SRC (old_set), 0)) == REG
&& GET_CODE (XEXP (SET_SRC (old_set), 1)) == CONST_INT
&& REGNO (XEXP (SET_SRC (old_set), 0)) < FIRST_PSEUDO_REGISTER)
{
rtx reg = XEXP (SET_SRC (old_set), 0);
int offset = INTVAL (XEXP (SET_SRC (old_set), 1));
We have to do this here, rather than in eliminate_regs, so that we can
change the insn code. */
for (ep = reg_eliminate; ep < &reg_eliminate[NUM_ELIMINABLE_REGS]; ep++)
if (ep->from_rtx == reg && ep->can_eliminate)
{
offset += ep->offset;
if (GET_CODE (SET_SRC (old_set)) == PLUS
&& GET_CODE (XEXP (SET_SRC (old_set), 0)) == REG
&& GET_CODE (XEXP (SET_SRC (old_set), 1)) == CONST_INT)
for (ep = reg_eliminate; ep < &reg_eliminate[NUM_ELIMINABLE_REGS];
ep++)
if (ep->from_rtx == XEXP (SET_SRC (old_set), 0)
&& ep->can_eliminate)
{
/* We must stop at the first elimination that will be used.
If this one would replace the PLUS with a REG, do it
now. Otherwise, quit the loop and let eliminate_regs
do its normal replacement. */
if (ep->offset == - INTVAL (XEXP (SET_SRC (old_set), 1)))
{
/* We assume here that we don't need a PARALLEL of
any CLOBBERs for this assignment. There's not
much we can do if we do need it. */
PATTERN (insn) = gen_rtx_SET (VOIDmode,
SET_DEST (old_set),
ep->to_rtx);
INSN_CODE (insn) = -1;
val = 1;
goto done;
}
if (offset == 0)
{
/* We assume here that we don't need a PARALLEL of
any CLOBBERs for this assignment. There's not
much we can do if we do need it. */
PATTERN (insn) = gen_rtx_SET (VOIDmode,
SET_DEST (old_set),
ep->to_rtx);
INSN_CODE (insn) = recog (PATTERN (insn), insn, 0);
if (INSN_CODE (insn) < 0)
abort ();
}
else
{
new_body = old_body;
if (! replace)
{
new_body = copy_insn (old_body);
if (REG_NOTES (insn))
REG_NOTES (insn) = copy_insn_1 (REG_NOTES (insn));
}
PATTERN (insn) = new_body;
old_set = single_set (insn);
break;
}
XEXP (SET_SRC (old_set), 0) = ep->to_rtx;
XEXP (SET_SRC (old_set), 1) = GEN_INT (offset);
}
val = 1;
/* This can't have an effect on elimination offsets, so skip right
to the end. */
goto done;
}
}
/* Determine the effects of this insn on elimination offsets. */
@ -2990,7 +3006,7 @@ eliminate_regs_in_insn (insn, replace)
for (i = 0; i < recog_data.n_dups; i++)
*recog_data.dup_loc[i]
= *recog_data.operand_loc[(int)recog_data.dup_num[i]];
= *recog_data.operand_loc[(int)recog_data.dup_num[i]];
/* If any eliminable remain, they aren't eliminable anymore. */
check_eliminable_occurrences (old_body);