From: Richard Biener <rguenther@suse.de>
Date: Wed, 3 Sep 2025 09:04:49 +0000 (+0200)
Subject: tree-optimization/121767 - modvar pattern breaking reductions
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6acd5534ad3ab6208cda68fddb48eb73260d6508;p=thirdparty%2Fgcc.git

tree-optimization/121767 - modvar pattern breaking reductions

The a % b -> a - a / b pattern breaks reduction constraints, disable it
for reduction stmts.

	PR tree-optimization/121767
	* tree-vect-patterns.cc (vect_recog_mod_var_pattern): Disable
	for reductions.

	* gcc.dg/vect/pr121767.c: New testcase.
---

diff --git a/gcc/testsuite/gcc.dg/vect/pr121767.c b/gcc/testsuite/gcc.dg/vect/pr121767.c
new file mode 100644
index 00000000000..3b52692a4b4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr121767.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-mcpu=neoverse-v2" { target aarch64-*-* } } */
+
+int foo (int x, int y, int n)
+{
+  for (int i = 0; i < n; ++i)
+    x = x % y;
+  return x;
+}
diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index 41ca0f085f0..f5c97242acb 100644
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -5363,7 +5363,7 @@ vect_recog_mod_var_pattern (vec_info *vinfo,
   gimple *pattern_stmt, *def_stmt;
   enum tree_code rhs_code;
 
-  if (!is_gimple_assign (last_stmt))
+  if (!is_gimple_assign (last_stmt) || vect_is_reduction (stmt_vinfo))
     return NULL;
 
   rhs_code = gimple_assign_rhs_code (last_stmt);