re PR tree-optimization/60382 (ICE on valid code at -O3 on x86_64-linux-gnu (in…

re PR tree-optimization/60382 (ICE on valid code at -O3 on x86_64-linux-gnu (in vect_create_epilog_for_reduction, at tree-vect-loop.c:4352))

2014-03-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/60382
	* tree-vect-loop.c (vect_is_simple_reduction_1): Do not consider
	dead PHIs a reduction.

	* gcc.dg/vect/pr60382.c: New testcase.

From-SVN: r208305

gcc/ChangeLog

+2014-03-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/60382
+	* tree-vect-loop.c (vect_is_simple_reduction_1): Do not consider
+	dead PHIs a reduction.
+
 2014-03-03  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/xmmintrin.h (enum _mm_hint) <_MM_HINT_ET0>: Correct

gcc/testsuite/ChangeLog

+2014-03-04  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/60382
+	* gcc.dg/vect/pr60382.c: New testcase.
+
 2014-03-03  Jerry DeLisle  <jvdelisle@gcc.gnu>
 
 	PR libfortran/60148

gcc/testsuite/gcc.dg/vect/pr60382.c

+#include "tree-vect.h"
+
+int a, b, c, e, f;
+
+void
+foo ()
+{
+  for (b = 0; b < 3; b++)
+    if (e)
+      {
+	for (c = 0; c < 4; c++)
+	  {
+	    if (b)
+	      continue;
+	    f = 1;
+	    for (a = 0; a < 2; a++)
+	      f |= 1;
+	  }
+	for (;;)
+	  ;
+      }
+}
+
+int
+main ()
+{
+  check_vect ();
+  foo ();
+  return 0;
+}
+
+/* { dg-final { cleanup-tree-dump "vect" } } */

gcc/tree-vect-loop.c

@@ -2193,6 +2193,12 @@ vect_is_simple_reduction_1 (loop_vec_info loop_info, gimple phi,
               || (!check_reduction && flow_loop_nested_p (vect_loop, loop)));
 
   name = PHI_RESULT (phi);
+  /* ???  If there are no uses of the PHI result the inner loop reduction
+     won't be detected as possibly double-reduction by vectorizable_reduction
+     because that tries to walk the PHI arg from the preheader edge which
+     can be constant.  See PR60382.  */
+  if (has_zero_uses (name))
+    return NULL;
   nloop_uses = 0;
   FOR_EACH_IMM_USE_FAST (use_p, imm_iter, name)
     {