https://gcc.gnu.org/g:23db87301b623ecf162c9df718ce82ed9aa354a8
commit r15-1059-g23db87301b623ecf162c9df718ce82ed9aa354a8
Author: Hongyu Wang <hongyu.w...@intel.com>
Date: Tue Apr 9 16:05:26 2024 +0800
[APX CCMP] Adjust startegy for selecting ccmp candidates
For general ccmp scenario, the tree sequence is like
_1 = (a < b)
_2 = (c < d)
_3 = _1 & _2
current ccmp expanding will try to swap compare order for _1 and _2,
compare the expansion cost/cost2 for expanding _1 or _2 first, then
return the sequence with lower cost.
It is possible that one expansion succeeds and the other fails.
For example, x86 has int ccmp but not fp ccmp, so a combined fp and
int comparison must be ordered such that the fp comparison happens
first. The costs are not meaningful for failed expansions.
Check the expand_ccmp_next result ret and ret2, returns the valid one
before cost comparison.
gcc/ChangeLog:
* ccmp.cc (expand_ccmp_expr_1): Check ret and ret2 of
expand_ccmp_next, returns the valid one first instead of
comparing cost.
Diff:
---
gcc/ccmp.cc | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/gcc/ccmp.cc b/gcc/ccmp.cc
index 7cb525addf4..4d50708d986 100644
--- a/gcc/ccmp.cc
+++ b/gcc/ccmp.cc
@@ -247,7 +247,15 @@ expand_ccmp_expr_1 (gimple *g, rtx_insn **prep_seq,
rtx_insn **gen_seq)
cost2 = seq_cost (prep_seq_2, speed_p);
cost2 += seq_cost (gen_seq_2, speed_p);
}
- if (cost2 < cost1)
+
+ /* It's possible that one expansion succeeds and the other
+ fails.
+ For example, x86 has int ccmp but not fp ccmp, and so a
+ combined fp and int comparison must be ordered such that
+ the fp comparison happens first. The costs are not
+ meaningful for failed expansions. */
+
+ if (ret2 && (!ret || cost2 < cost1))
{
*prep_seq = prep_seq_2;
*gen_seq = gen_seq_2;
