[PATCH] Fix for tree-ssa-pre

[Martin Liška]

Hello,
   I've encountered and issue in a ltrans for libxul.so (with LTO). The patch 
fixes uninitialized value for a given argument, pre-approved by Richard.

Thanks,
Martin

gcc/ChangeLog:

2014-09-03  Martin Liska  <mli...@suse.cz>

        * tree-ssa-sccvn.c (vn_reference_lookup_call): default (NULL) value
        is set to preserve uninitialized value for vnresult.

diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 1bcbde3..44656ea 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -2146,6 +2146,9 @@ void
 vn_reference_lookup_call (gimple call, vn_reference_t *vnresult,
 			  vn_reference_t vr)
 {
+  if (vnresult)
+    *vnresult = NULL;
+
   tree vuse = gimple_vuse (call);
 
   vr->vuse = vuse ? SSA_VAL (vuse) : NULL_TREE;