From: Richard Biener <rguenther@suse.de>
Date: Thu, 17 Jul 2025 06:51:11 +0000 (+0200)
Subject: tree-optimization/121048 - move check for only having vector(1)
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=175b49933ffeea6d4a690e40bba006854977f43f;p=thirdparty%2Fgcc.git

tree-optimization/121048 - move check for only having vector(1)

The following moves rejecting loop vectorization with vector(1)
typed vectors from the initial vector type determining to after
SLP discovery when we can check whether there's any instance
with other than vector(1) vectors.  For RVV at least vector(1)
instances serve as a limited way to support partial loop vectorization.
The following restores this.

	PR tree-optimization/121048
	* tree-vect-loop.cc (vect_determine_vectype_for_stmt_1):
	Remove rejecting vector(1) vector types.
	(vect_set_stmts_vectype): Likewise.
	* tree-vect-slp.cc (vect_make_slp_decision): Only
	count instances with non-vector(1) root towards whether
	we have any interesting instances to vectorize.
---

diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index edad40cef30..01df51c9a99 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -191,12 +191,6 @@ vect_determine_vectype_for_stmt_1 (vec_info *vinfo, stmt_vec_info stmt_info,
 
   if (stmt_vectype)
     {
-      if (known_le (TYPE_VECTOR_SUBPARTS (stmt_vectype), 1U))
-	return opt_result::failure_at (STMT_VINFO_STMT (stmt_info),
-				       "not vectorized: unsupported "
-				       "data-type in %G",
-				       STMT_VINFO_STMT (stmt_info));
-
       if (STMT_VINFO_VECTYPE (stmt_info))
 	/* The only case when a vectype had been already set is for stmts
 	   that contain a data ref, or for "pattern-stmts" (stmts generated
@@ -303,8 +297,7 @@ vect_set_stmts_vectype (loop_vec_info loop_vinfo)
 				 scalar_type);
 
 	      vectype = get_vectype_for_scalar_type (loop_vinfo, scalar_type);
-	      if (!vectype
-		  || known_le (TYPE_VECTOR_SUBPARTS (vectype), 1U))
+	      if (!vectype)
 		return opt_result::failure_at (phi,
 					       "not vectorized: unsupported "
 					       "data-type %T\n",
diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index fe67d4dbc46..7c23496b5e0 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -7586,20 +7586,25 @@ vect_make_slp_decision (loop_vec_info loop_vinfo)
   hash_set<slp_tree> visited;
   FOR_EACH_VEC_ELT (slp_instances, i, instance)
     {
-      /* FORNOW: SLP if you can.  */
+      slp_tree root = SLP_INSTANCE_TREE (instance);
+
       /* All unroll factors have the form:
 
 	   GET_MODE_SIZE (vinfo->vector_mode) * X
 
 	 for some rational X, so they must have a common multiple.  */
-      vect_update_slp_vf_for_node (SLP_INSTANCE_TREE (instance),
-				   unrolling_factor, visited);
+      vect_update_slp_vf_for_node (root, unrolling_factor, visited);
 
       /* Mark all the stmts that belong to INSTANCE as PURE_SLP stmts.  Later we
 	 call vect_detect_hybrid_slp () to find stmts that need hybrid SLP and
 	 loop-based vectorization.  Such stmts will be marked as HYBRID.  */
-      vect_mark_slp_stmts (loop_vinfo, SLP_INSTANCE_TREE (instance));
-      decided_to_slp++;
+      vect_mark_slp_stmts (loop_vinfo, root);
+
+      /* If all instances ended up with vector(1) T roots make sure to
+	 not vectorize.  RVV for example relies on loop vectorization
+	 when some instances are essentially kept scalar.  See PR121048.  */
+      if (known_gt (TYPE_VECTOR_SUBPARTS (SLP_TREE_VECTYPE (root)), 1U))
+	decided_to_slp++;
     }
 
   LOOP_VINFO_SLP_UNROLLING_FACTOR (loop_vinfo) = unrolling_factor;