tree-vect-slp.c (vect_analyze_slp): When reduction group SLP discovery fails try…

tree-vect-slp.c (vect_analyze_slp): When reduction group SLP discovery fails try to handle the reduction as part of...

2019-10-24  Richard Biener  <rguenther@suse.de>

	* tree-vect-slp.c (vect_analyze_slp): When reduction group
	SLP discovery fails try to handle the reduction as part
	of SLP reduction discovery.

	* gcc.dg/vect/slp-reduc-9.c: New testcase.

From-SVN: r277366

gcc/ChangeLog

+2019-10-24  Richard Biener  <rguenther@suse.de>
+
+	* tree-vect-slp.c (vect_analyze_slp): When reduction group
+	SLP discovery fails try to handle the reduction as part
+	of SLP reduction discovery.
+
 2019-10-23  Michael Meissner  <meissner@linux.ibm.com>
 
 	* config/rs6000/rs6000-protos.h (rs6000_adjust_insn_length): New

gcc/testsuite/ChangeLog

+2019-10-24  Richard Biener  <rguenther@suse.de>
+
+	* gcc.dg/vect/slp-reduc-9.c: New testcase.
+
 2019-10-23  David Edelsohn  <dje.gcc@gmail.com>
 
 	* gcc.target/powerpc/pr70010.c: Add -Wno-psabi.

gcc/testsuite/gcc.dg/vect/slp-reduc-9.c

+/* { dg-do compile } */
+/* { dg-require-effective-target vect_int_mult } */
+
+int
+bar (int *x, int a, int b, int n)
+{
+  x = __builtin_assume_aligned (x, __BIGGEST_ALIGNMENT__);
+  int sum1 = 0;
+  int sum2 = 0;
+  for (int i = 0; i < n; ++i)
+    {
+      /* Reduction chain vectorization fails here because of the
+         different operations but we can still vectorize both
+	 reductions as SLP reductions, saving IVs.  */
+      sum1 += x[2*i] - a;
+      sum1 += x[2*i+1] * b;
+      sum2 += x[2*i] - b;
+      sum2 += x[2*i+1] * a;
+    }
+  return sum1 + sum2;
+}
+
+/* { dg-final { scan-tree-dump "Loop contains only SLP stmts" "vect" } } */
+/* { dg-final { scan-tree-dump "vectorizing stmts using SLP" "vect" } } */
+/* { dg-final { scan-tree-dump "vectorized 1 loops" "vect" } } */

gcc/tree-vect-slp.c

@@ -2271,14 +2271,18 @@ vect_analyze_slp (vec_info *vinfo, unsigned max_tree_size)
 	      {
 		/* Dissolve reduction chain group.  */
 		stmt_vec_info vinfo = first_element;
+		stmt_vec_info last = NULL;
 		while (vinfo)
 		  {
 		    stmt_vec_info next = REDUC_GROUP_NEXT_ELEMENT (vinfo);
 		    REDUC_GROUP_FIRST_ELEMENT (vinfo) = NULL;
 		    REDUC_GROUP_NEXT_ELEMENT (vinfo) = NULL;
+		    last = vinfo;
 		    vinfo = next;
 		  }
 		STMT_VINFO_DEF_TYPE (first_element) = vect_internal_def;
+		/* It can be still vectorized as part of an SLP reduction.  */
+		loop_vinfo->reductions.safe_push (last);
 	      }
 	}