From: Richard Biener <rguenther@suse.de>
Date: Thu, 24 Aug 2023 08:30:12 +0000 (+0200)
Subject: tree-optimization/111125 - properly cost BB reduction remain stmt handling
X-Git-Tag: basepoints/gcc-15~6699
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e80f7c13f64e10c6a3354c5d6b42da60b21ed0b8;p=thirdparty%2Fgcc.git

tree-optimization/111125 - properly cost BB reduction remain stmt handling

We assume that all root stmts which compose the total reduction chain
are vectorized but fail to account for the cost of adding back the
scalar defs we are not vectorizing.  The following rectifies this,
fixing the gcc.dg/tree-ssa/slsr-11.c FAIL on aarch64.

	PR tree-optimization/111125
	* tree-vect-slp.cc (vectorizable_bb_reduc_epilogue): Account
	for the remain_defs processing.
---

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index b5f9333fc22e..0bcc53013178 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -6406,6 +6406,11 @@ vectorizable_bb_reduc_epilogue (slp_instance instance,
 		    vectype, 0, vect_body);
   record_stmt_cost (cost_vec, 1, vec_to_scalar, instance->root_stmts[0],
 		    vectype, 0, vect_body);
+
+  /* Since we replace all stmts of a possibly longer scalar reduction
+     chain account for the extra scalar stmts for that.  */
+  record_stmt_cost (cost_vec, instance->remain_defs.length (), scalar_stmt,
+		    instance->root_stmts[0], 0, vect_body);
   return true;
 }