https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111467
Bug ID: 111467
Summary: REE failing to eliminate redundant extension due to
multiple reaching def(s)
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: vineetg at gcc dot gnu.org
Reporter: vineetg at gcc dot gnu.org
CC: jeffreyalaw at gmail dot com, jivanhakobyan9 at gmail dot
com,
kito at gcc dot gnu.org, palmer at gcc dot gnu.org
Target Milestone: ---
For the trivial test case below (credit goes to Palmer for mentioning this
almost 2 years ago).
int
foo6(int a, int b)
{
return a > b ? a : b;
}
-O2 -march=rv64gc
foo6:
mv a5,a1
bge a1,a0,.L5
mv a5,a0
.L5:
sext.w a0,a5
ret
REE fails to eliminate the sign extension due to multiple reaching definitions
constraint.
I don't know how involved or runtime cost relaxing the constraint is, so
opening this PR to investigate.
FWIW a zba build generates a max insn, eliminating the sext.w, but the vanilla
case shows where things can possibly be improved.
