From: Jakub Jelinek <jakub@redhat.com>
Date: Sat, 4 Oct 2025 15:06:16 +0000 (+0200)
Subject: widening_mul: Reset flow sensitive info in maybe_optimize_guarding_check [PR122104]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=867f777cee9f44027a3724fbad266c5cfb3a311f;p=thirdparty%2Fgcc.git

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.
---

diff --git a/gcc/testsuite/gcc.target/i386/pr122104.c b/gcc/testsuite/gcc.target/i386/pr122104.c
new file mode 100644
index 00000000000..be88933e3ec
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr122104.c
@@ -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;
+}
diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index a9903b691a4..0db39f330ea 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -3834,6 +3834,7 @@ 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;
 }