https://gcc.gnu.org/g:a30d2e6bd0b965e7687f58530a767a3c3b079158
commit r15-76-ga30d2e6bd0b965e7687f58530a767a3c3b079158
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Sun Apr 28 20:21:02 2024 -0700
PHIOPT: Value-replacement check undef
While moving value replacement part of PHIOPT over
to use match-and-simplify, I ran into the case where
we would have an undef use that was conditional become
unconditional. This prevents that. I can't remember at this
point what the testcase was though.
Bootstrapped and tested on x86_64-linux-gnu with no regressions.
gcc/ChangeLog:
* tree-ssa-phiopt.cc (value_replacement): Reject undef variables
so they don't become unconditional used.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
Diff:
---
gcc/tree-ssa-phiopt.cc | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index a2bdcb5eae8..f166c3132cb 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -1146,6 +1146,13 @@ value_replacement (basic_block cond_bb, basic_block
middle_bb,
if (code != NE_EXPR && code != EQ_EXPR)
return 0;
+ /* Do not make conditional undefs unconditional. */
+ if ((TREE_CODE (arg0) == SSA_NAME
+ && ssa_name_maybe_undef_p (arg0))
+ || (TREE_CODE (arg1) == SSA_NAME
+ && ssa_name_maybe_undef_p (arg1)))
+ return false;
+
/* If the type says honor signed zeros we cannot do this
optimization. */
if (HONOR_SIGNED_ZEROS (arg1))
