From: Richard Biener <rguenther@suse.de>
Date: Fri, 9 Apr 2021 07:35:51 +0000 (+0200)
Subject: tree-optimization/99971 - improve BB vect dependence analysis
X-Git-Tag: basepoints/gcc-13~8234
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=700e542971251b11623cce877075567815f72965;p=thirdparty%2Fgcc.git

tree-optimization/99971 - improve BB vect dependence analysis

We can use TBAA even when we have a DR, do so.  For the testcase
that means fully vectorizing it instead of only vectorizing
the first store group resulting in suboptimal code.

2021-04-09  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/99971
	* tree-vect-data-refs.c (vect_slp_analyze_node_dependences):
	Always use TBAA for loads.

	* g++.dg/vect/slp-pr99971.cc: New testcase.
---

diff --git a/gcc/testsuite/g++.dg/vect/slp-pr99971.cc b/gcc/testsuite/g++.dg/vect/slp-pr99971.cc
new file mode 100644
index 000000000000..bec6418d4e80
--- /dev/null
+++ b/gcc/testsuite/g++.dg/vect/slp-pr99971.cc
@@ -0,0 +1,36 @@
+// { dg-do compile }
+// { dg-require-effective-target vect_int }
+
+struct A
+{
+  unsigned int a, b, c, d;
+
+  A& operator+= (A const& that)
+    {
+      a += that.a;
+      b += that.b;
+      c += that.c;
+      d += that.d;
+      return *this;
+    }
+
+  A& operator-= (A const& that)
+    {
+      a -= that.a;
+      b -= that.b;
+      c -= that.c;
+      d -= that.d;
+      return *this;
+    }
+};
+
+void test(A& x, A const& y1, A const& y2)
+{
+  x += y1;
+  x -= y2;
+}
+
+// We want to SLP vectorize a single connected SLP subgraph with two instances
+// { dg-final { scan-tree-dump-not "removing SLP instance" "slp2" } }
+// { dg-final { scan-tree-dump-times "SLPing BB part" 1 "slp2" } }
+// { dg-final { scan-tree-dump-times "Vectorizing SLP" 2 "slp2" } }
diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index 97c8577ebe72..b317df532a9a 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -780,16 +780,20 @@ vect_slp_analyze_node_dependences (vec_info *vinfo, slp_tree node,
 		 stmt we have to resort to the alias oracle.  */
 	      stmt_vec_info stmt_info = vinfo->lookup_stmt (stmt);
 	      data_reference *dr_b = STMT_VINFO_DATA_REF (stmt_info);
-	      if (!dr_b)
+
+	      /* We are hoisting a load - this means we can use
+		 TBAA for disambiguation.  */
+	      if (!ref_initialized_p)
+		ao_ref_init (&ref, DR_REF (dr_a));
+	      if (stmt_may_clobber_ref_p_1 (stmt, &ref, true))
 		{
-		  /* We are hoisting a load - this means we can use
-		     TBAA for disambiguation.  */
-		  if (!ref_initialized_p)
-		    ao_ref_init (&ref, DR_REF (dr_a));
-		  if (stmt_may_clobber_ref_p_1 (stmt, &ref, true))
+		  if (!dr_b)
 		    return false;
-		  continue;
+		  /* Resort to dependence checking below.  */
 		}
+	      else
+		/* No dependence.  */
+		continue;
 
 	      bool dependent = false;
 	      /* If we run into a store of this same instance (we've just