From: Richard Biener <rguenther@suse.de>
Date: Wed, 27 Aug 2025 12:39:00 +0000 (+0200)
Subject: The divmod pattern will break reduction constraints
X-Git-Tag: basepoints/gcc-17~5377
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=674b1d73e437cbdbe86da45dbb67364297bb2216;p=thirdparty%2Fgcc.git

The divmod pattern will break reduction constraints

When we apply a divmod pattern this will break reductions by introducing
multiple uses of the reduction var, so avoid this pattern in reductions.

	* tree-vect-patterns.cc (vect_recog_divmod_pattern): Avoid
	for stmts participating in a reduction.
---

diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index ffb320fbf23..3fffcac4b3a 100644
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -4818,7 +4818,9 @@ vect_recog_divmod_pattern (vec_info *vinfo,
   tree q, cst;
   int prec;
 
-  if (!is_gimple_assign (last_stmt))
+  if (!is_gimple_assign (last_stmt)
+      /* The pattern will disrupt the reduction chain with multiple uses.  */
+      || vect_is_reduction (stmt_vinfo))
     return NULL;
 
   rhs_code = gimple_assign_rhs_code (last_stmt);