* Small tweak to combine_validate_cost
@ 2011-04-08 22:32 Eric Botcazou
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From: Eric Botcazou @ 2011-04-08 22:32 UTC (permalink / raw)
To: gcc-patches
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At the end of combine_validate_cost, when the combination is validated, the
registered cost of I1 is zero-ed. This should be done for I0 as well.
Bootstrapped/regtested on x86_64-suse-linux, applied on the mainline.
2011-04-08 Eric Botcazou <ebotcazou@adacore.com>
* combine.c (combine_validate_cost): Adjust comments. Set registered
cost of I0 to zero at the end, if any.
--
Eric Botcazou
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Index: combine.c
===================================================================
--- combine.c (revision 172166)
+++ combine.c (working copy)
@@ -789,14 +789,13 @@ do_SUBST_MODE (rtx *into, enum machine_m
#define SUBST_MODE(INTO, NEWVAL) do_SUBST_MODE(&(INTO), (NEWVAL))
\f
-/* Subroutine of try_combine. Determine whether the combine replacement
- patterns NEWPAT, NEWI2PAT and NEWOTHERPAT are cheaper according to
- insn_rtx_cost that the original instruction sequence I0, I1, I2, I3 and
- undobuf.other_insn. Note that I1 and/or NEWI2PAT may be NULL_RTX.
- NEWOTHERPAT and undobuf.other_insn may also both be NULL_RTX. This
- function returns false, if the costs of all instructions can be
- estimated, and the replacements are more expensive than the original
- sequence. */
+/* Subroutine of try_combine. Determine whether the replacement patterns
+ NEWPAT, NEWI2PAT and NEWOTHERPAT are cheaper according to insn_rtx_cost
+ than the original sequence I0, I1, I2, I3 and undobuf.other_insn. Note
+ that I0, I1 and/or NEWI2PAT may be NULL_RTX. Similarly, NEWOTHERPAT and
+ undobuf.other_insn may also both be NULL_RTX. Return false if the cost
+ of all the instructions can be estimated and the replacements are more
+ expensive than the original sequence. */
static bool
combine_validate_cost (rtx i0, rtx i1, rtx i2, rtx i3, rtx newpat,
@@ -861,10 +860,9 @@ combine_validate_cost (rtx i0, rtx i1, r
old_cost = 0;
}
- /* Disallow this recombination if both new_cost and old_cost are
- greater than zero, and new_cost is greater than old cost. */
- if (old_cost > 0
- && new_cost > old_cost)
+ /* Disallow this combination if both new_cost and old_cost are greater than
+ zero, and new_cost is greater than old cost. */
+ if (old_cost > 0 && new_cost > old_cost)
{
if (dump_file)
{
@@ -910,7 +908,11 @@ combine_validate_cost (rtx i0, rtx i1, r
INSN_COST (i2) = new_i2_cost;
INSN_COST (i3) = new_i3_cost;
if (i1)
- INSN_COST (i1) = 0;
+ {
+ INSN_COST (i1) = 0;
+ if (i0)
+ INSN_COST (i0) = 0;
+ }
return true;
}
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