[PATCH] Fix PR87168

[Richard Biener]

I am testing the following patch to fix a missed optimization and 
wrong-code issue in region VN.

{,O1-}Bootstrap and regtest running on x86_64-unknown-linux-gnu.

2018-08-31  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/87168
        * tree-ssa-sccvn.c (SSA_VAL): Add visited output parameter.
        (rpo_elim::eliminate_avail): When OP was not visited it must
        be available.

        * gcc.dg/torture/pr87168.c: New testcase.

Index: gcc/tree-ssa-sccvn.c
===================================================================
--- gcc/tree-ssa-sccvn.c        (revision 263982)
+++ gcc/tree-ssa-sccvn.c        (working copy)
@@ -456,10 +456,14 @@ VN_INFO (tree name)
 /* Return the SSA value of X.  */
 
 inline tree
-SSA_VAL (tree x)
+SSA_VAL (tree x, bool *visited = NULL)
 {
   vn_ssa_aux_t tem = vn_ssa_aux_hash->find_with_hash (x, SSA_NAME_VERSION (x));
-  return tem && tem->visited ? tem->valnum : x;
+  if (!tem)
+    return x;
+  if (visited)
+    *visited = tem->visited;
+  return tem->visited ? tem->valnum : x;
 }
 
 /* Return whether X was visited.  */
@@ -5681,7 +5685,12 @@ rpo_elim::~rpo_elim ()
 tree
 rpo_elim::eliminate_avail (basic_block bb, tree op)
 {
-  tree valnum = SSA_VAL (op);
+  bool visited;
+  tree valnum = SSA_VAL (op, &visited);
+  /* If we didn't visit OP then it must be defined outside of the
+     region we process and also dominate it.  So it is available.  */
+  if (!visited)
+    return op;
   if (TREE_CODE (valnum) == SSA_NAME)
     {
       if (SSA_NAME_IS_DEFAULT_DEF (valnum))
Index: gcc/testsuite/gcc.dg/torture/pr87168.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr87168.c      (nonexistent)
+++ gcc/testsuite/gcc.dg/torture/pr87168.c      (working copy)
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+
+int a, b, c, d, e, f, *g;
+
+int main ()
+{ 
+  unsigned i;
+  while (b)
+    { 
+      int j, m;
+L1:
+      f = j;
+L2:
+      if (i && e)
+       { 
+         i = f;
+         goto L2;
+       }
+      j = f;
+      if (a)
+       goto L3;
+      for (m = 0; m < 2; m++)
+       if (d)
+         goto L1;
+      goto L2;
+L3:
+      (&j != g) | c;
+    }
+  return 0;
+}