This fixes PR60382 where the vectorizer identified a double-reduction
it cannot later re-identify properly. The only reasonable fix at this
point is to not identify that as a double-reduction.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk,
will apply to branch after testing there.
Richard.
2014-03-04 Richard Biener <rguent...@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.
Index: gcc/tree-vect-loop.c
===================================================================
--- gcc/tree-vect-loop.c (revision 208269)
+++ gcc/tree-vect-loop.c (working copy)
@@ -2193,6 +2193,12 @@ vect_is_simple_reduction_1 (loop_vec_inf
|| (!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)
{
Index: gcc/testsuite/gcc.dg/vect/pr60382.c
===================================================================
--- gcc/testsuite/gcc.dg/vect/pr60382.c (revision 0)
+++ gcc/testsuite/gcc.dg/vect/pr60382.c (working copy)
@@ -0,0 +1,32 @@
+#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" } } */
