[PATCH] Fix PR91896

[Richard Biener]

Removing operand swapping for reduction vectorization has enabled
more pattern recognition which in turn triggers a latent bug
in reduction vectorization.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2019-09-25  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/91896
        * tree-vect-loop.c (vectorizable_reduction): The single
        def-use cycle optimization cannot apply when there's more
        than one pattern stmt involved.

        * gcc.dg/torture/pr91896.c: New testcase.

Index: gcc/testsuite/gcc.dg/torture/pr91896.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr91896.c      (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr91896.c      (working copy)
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ftree-vectorize" } */
+
+unsigned int
+zj (unsigned int et)
+{
+  signed char jr = 0;
+
+  do {
+    et *= 3;
+    jr += 2;
+  } while (jr >= 0);
+
+  if (et == (unsigned int) jr)
+    et = 0;
+
+  return et;
+}
Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c        (revision 276120)
+++ gcc/tree-vect-loop.c        (working copy)
@@ -6101,6 +6101,8 @@ vectorizable_reduction (stmt_vec_info st
       if (ncopies > 1
          && STMT_VINFO_RELEVANT (reduc_stmt_info) <= vect_used_only_live
          && (use_stmt_info = loop_vinfo->lookup_single_use (phi_result))
+         && (!STMT_VINFO_IN_PATTERN_P (use_stmt_info)
+             || !STMT_VINFO_PATTERN_DEF_SEQ (use_stmt_info))
          && vect_stmt_to_vectorize (use_stmt_info) == reduc_stmt_info)
        single_defuse_cycle = true;
 
@@ -6868,6 +6870,8 @@ vectorizable_reduction (stmt_vec_info st
   if (ncopies > 1
       && (STMT_VINFO_RELEVANT (stmt_info) <= vect_used_only_live)
       && (use_stmt_info = loop_vinfo->lookup_single_use (reduc_phi_result))
+      && (!STMT_VINFO_IN_PATTERN_P (use_stmt_info)
+         || !STMT_VINFO_PATTERN_DEF_SEQ (use_stmt_info))
       && vect_stmt_to_vectorize (use_stmt_info) == stmt_info)
     {
       single_defuse_cycle = true;