[PATCH] Fix fold making valid VEC_PERMs invalid

[Richard Biener]

The following patch makes fold_ternary no longer make
VEC_PERMs valid for the target invalid.  As pointed out
in the PR we only need to make sure this doesn't happen
after vector lowering.

I won't have time to improve on the following patch this
week - Marc, can you take over here?

Bootstrapped & tested on x86_64-unknown-linux-gnu.

Thanks,
Richard.

2014-10-30  Richard Biener  <rguenther@suse.de>

	PR middle-end/63666
	* fold-const.c: Include optabs.h.
	(fold_ternary_loc): Only change the VEC_PERM mask if it
	then is a valid constant permutation on the target.

Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c	(revision 216834)
+++ gcc/fold-const.c	(working copy)
@@ -82,6 +82,7 @@ along with GCC; see the file COPYING3.
 #include "ipa-ref.h"
 #include "cgraph.h"
 #include "generic-match.h"
+#include "optabs.h"
 
 /* Nonzero if we are folding constants inside an initializer; zero
    otherwise.  */
@@ -14311,7 +14331,8 @@ fold_ternary_loc (location_t loc, enum t
 	  if (op0 == op1 && !single_arg)
 	    changed = true;
 
-	  if (need_mask_canon && arg2 == op2)
+	  if (need_mask_canon && arg2 == op2
+	      && can_vec_perm_p (TYPE_MODE (type), false, sel))
 	    {
 	      tree *tsel = XALLOCAVEC (tree, nelts);
 	      tree eltype = TREE_TYPE (TREE_TYPE (arg2));