[match-and-simplify] set simplify::capture_max to 0 if pattern contains no captures

[Prathamesh Kulkarni]

Caused segfault for pattern containing no captures at:
info.safe_grow_cleared(capture_max + 1); in capture_info::capture_info

artificial test-case:
(define_predicates integer_zerop)
(simplify
  (bit_not integer_zerop)
  { build_zero_cst (type); })

* genmatch.c
  (simplify::simplify): Set simplify::capture_max to 0 if pattern
contains no captures.

Thanks,
Prathamesh

Index: gcc/genmatch.c
===================================================================
--- gcc/genmatch.c	(revision 218664)
+++ gcc/genmatch.c	(working copy)
@@ -576,7 +576,7 @@
       : match (match_), match_location (match_location_),
       result (result_), result_location (result_location_),
       ifexpr_vec (ifexpr_vec_), for_vec (for_vec_),
-      capture_ids (capture_ids_), capture_max (capture_ids_->elements () - 1) {}
+      capture_ids (capture_ids_), capture_max (capture_ids_->elements () ? capture_ids_->elements () - 1 : 0) {}
 
   /* The expression that is matched against the GENERIC or GIMPLE IL.  */
   operand *match;