[trunk, 4.7, PR 38474] Avoid unnecessary vdef walks in compute_known_type_jump_func

[Martin Jambor]

Hi,

PR 38474 testcase revealed what we can do a lot of entirely
unnecessary vdef walking only to throw away the result later because
of a much cheaper check.  This patch fixes that.

The patch applies to both trunk and the 4.7 branch, I have
bootstrapped and tested it on both on an x86_64-linux without any
problems.  Because of Richi's comment #63 in bugzilla, I assume it is
approved for both trunk and the branch too and will commit it on
Monday, unless someone objects.

Thanks,

Martin


2012-06-27  Martin Jambor  <mjam...@suse.cz>

        PR middle-end/38474
        * ipa-prop.c (compute_known_type_jump_func): Put BINFO check before a
        dynamic type change check.

Index: src/gcc/ipa-prop.c
===================================================================
--- src.orig/gcc/ipa-prop.c
+++ src/gcc/ipa-prop.c
@@ -912,8 +912,8 @@ compute_known_type_jump_func (tree op, s
       || is_global_var (base))
     return;
 
-  if (detect_type_change (op, base, call, jfunc, offset)
-      || !TYPE_BINFO (TREE_TYPE (base)))
+  if (!TYPE_BINFO (TREE_TYPE (base))
+      || detect_type_change (op, base, call, jfunc, offset))
     return;
 
   ipa_set_jf_known_type (jfunc, offset, TREE_TYPE (base), TREE_TYPE (op));