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widening_mul: Reset flow sensitive info in maybe_optimize_guarding_check [PR122104] 

In PR95852 I've added an optimization where next to just pattern
recognizing r = x * y; r / x != y or r = x * y; r / x == y
as .MUL_OVERFLOW or negation thereof it also recognizes
r = x * y; x && (r / x != y) or r = x * y; !x || (r / x == y)
by optimizing the guarding condition to always true/false.

The problem with that is that some value ranges recorded for
the SSA_NAMEs in the formerly conditional, now unconditional
basic block can be invalid.

This patch fixes it by calling reset_flow_sensitive_info_in_bb
if we optimize the guarding condition.

2025-10-04  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/122104
	* tree-ssa-math-opts.cc (maybe_optimize_guarding_check): Call
	reset_flow_sensitive_info_in_bb on bb when optimizing out the
	guarding condition.

	* gcc.target/i386/pr122104.c: New test.

(cherry picked from commit 867f777cee)
This commit is contained in:
Jakub Jelinek 2025-10-04 17:06:16 +02:00 committed by Jakub Jelinek
parent 28061487f8
commit 5d74b473f8
2 changed files with 13 additions and 0 deletions
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12
gcc/testsuite/gcc.target/i386/pr122104.c Normal file
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@ -0,0 +1,12 @@
/* PR tree-optimization/122104 */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-widening_mul-alias" } */
/* { dg-final { scan-tree-dump "\\.MUL_OVERFLOW" "widening_mul" } } */
/* { dg-final { scan-tree-dump-not "# RANGE \\\[irange\\\] unsigned int \\\[1, " "widening_mul" } } */
int
foo (int x)
{
int r = (unsigned) x * 35;
return x && ((unsigned) r / x) != 35U;
}

1
gcc/tree-ssa-math-opts.cc
View File

@ -3802,6 +3802,7 @@ maybe_optimize_guarding_check (vec<gimple *> &mul_stmts, gimple *cond_stmt,
else
gimple_cond_make_false (zero_cond);
update_stmt (zero_cond);
reset_flow_sensitive_info_in_bb (bb);
*cfg_changed = true;
}