re PR tree-optimization/81573 (wrong code at -O3 on x86_64-linux-gnu)

2017-07-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/81573
	PR tree-optimization/81494
	* tree-vect-loop.c (vect_create_epilog_for_reduction): Handle
	multi defuse cycle case.

	* gcc.dg/torture/pr81573.c: New testcase.

From-SVN: r250627

gcc/ChangeLog

 2017-07-27  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/81573
+	PR tree-optimization/81494
+	* tree-vect-loop.c (vect_create_epilog_for_reduction): Handle
+	multi defuse cycle case.
+
+2017-07-27  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/81571
 	* tree-vect-slp.c (vect_build_slp_tree): Properly verify reduction
 	PHIs.

gcc/testsuite/ChangeLog

 2017-07-27  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/81573
+	PR tree-optimization/81494
+	* gcc.dg/torture/pr81573.c: New testcase.
+
+2017-07-27  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/81571
 	* gcc.dg/torture/pr81571.c: New testcase.
 

gcc/testsuite/gcc.dg/torture/pr81573.c

+/* { dg-do run } */
+
+int a = 1, *c = &a, d;
+char b;
+
+int main ()
+{
+  for (; b > -27; b--)
+    {
+      *c ^= b;
+      *c ^= 1;
+    }
+  while (a > 1)
+    ;
+  return 0; 
+}

gcc/tree-vect-loop.c

@@ -4787,20 +4787,17 @@ vect_create_epilog_for_reduction (vec<tree> vect_defs, gimple *stmt,
   if (GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)))
     {
       tree first_vect = PHI_RESULT (new_phis[0]);
-      tree tmp;
       gassign *new_vec_stmt = NULL;
-
       vec_dest = vect_create_destination_var (scalar_dest, vectype);
       for (k = 1; k < new_phis.length (); k++)
         {
 	  gimple *next_phi = new_phis[k];
           tree second_vect = PHI_RESULT (next_phi);
-
-          tmp = build2 (code, vectype,  first_vect, second_vect);
-          new_vec_stmt = gimple_build_assign (vec_dest, tmp);
-          first_vect = make_ssa_name (vec_dest, new_vec_stmt);
-          gimple_assign_set_lhs (new_vec_stmt, first_vect);
+          tree tem = make_ssa_name (vec_dest, new_vec_stmt);
+          new_vec_stmt = gimple_build_assign (tem, code,
+					      first_vect, second_vect);
           gsi_insert_before (&exit_gsi, new_vec_stmt, GSI_SAME_STMT);
+	  first_vect = tem;
         }
 
       new_phi_result = first_vect;
@@ -4810,6 +4807,28 @@ vect_create_epilog_for_reduction (vec<tree> vect_defs, gimple *stmt,
           new_phis.safe_push (new_vec_stmt);
         }
     }
+  /* Likewise if we couldn't use a single defuse cycle.  */
+  else if (ncopies > 1)
+    {
+      gcc_assert (new_phis.length () == 1);
+      tree first_vect = PHI_RESULT (new_phis[0]);
+      gassign *new_vec_stmt = NULL;
+      vec_dest = vect_create_destination_var (scalar_dest, vectype);
+      gimple *next_phi = new_phis[0];
+      for (int k = 1; k < ncopies; ++k)
+	{
+	  next_phi = STMT_VINFO_RELATED_STMT (vinfo_for_stmt (next_phi));
+	  tree second_vect = PHI_RESULT (next_phi);
+          tree tem = make_ssa_name (vec_dest, new_vec_stmt);
+          new_vec_stmt = gimple_build_assign (tem, code,
+					      first_vect, second_vect);
+          gsi_insert_before (&exit_gsi, new_vec_stmt, GSI_SAME_STMT);
+	  first_vect = tem;
+	}
+      new_phi_result = first_vect;
+      new_phis.truncate (0);
+      new_phis.safe_push (new_vec_stmt);
+    }
   else
     new_phi_result = PHI_RESULT (new_phis[0]);