re PR tree-optimization/63800 (ICE on valid code at -O3 on x86_64-linux-gnu)

2014-11-10  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/63800
	* tree-ssa-pre.c (eliminate_push_avail): Push in a way so
	we can restore the previous availability in after_dom_children.
	(eliminate_dom_walker::after_dom_children): Restore
	previous availability.

	* gcc.dg/torture/pr63800.c: New testcase.

From-SVN: r217288

gcc/ChangeLog

 2014-11-10  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/63800
+	* tree-ssa-pre.c (eliminate_push_avail): Push in a way so
+	we can restore the previous availability in after_dom_children.
+	(eliminate_dom_walker::after_dom_children): Restore
+	previous availability.
+
+2014-11-10  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/63798
 	* expr.c (expand_expr_real_2): When expanding FMA_EXPRs
 	properly treat the embedded multiplication as commutative

gcc/testsuite/ChangeLog

+2014-11-10  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/63800
+	* gcc.dg/torture/pr63800.c: New testcase.
+
 2014-11-10  Marek Polacek  <polacek@redhat.com>
 
 	* c-c++-common/ubsan/align-7.c: Skip for -flto -fno-fat-lto-objects.

gcc/testsuite/gcc.dg/torture/pr63800.c

+/* { dg-do compile } */
+
+int a, b, c, d[2];
+
+int
+fn1 ()
+{
+  int f = 0;
+  d[1] = b = 1; 
+  for (; b; b--)
+    {
+      for (c = 0; c < 2; c++)
+	{
+	  d[b] & 1 & b;
+	  if (d[0])
+	    f = d[b] * a;
+	  if (f)
+	    return 0;
+	}
+      d[b] && (d[0] = 0);
+    }
+  return 0;
+}

gcc/tree-ssa-pre.c

@@ -3906,8 +3906,11 @@ eliminate_push_avail (tree op)
     {
       if (el_avail.length () <= SSA_NAME_VERSION (valnum))
 	el_avail.safe_grow_cleared (SSA_NAME_VERSION (valnum) + 1);
+      tree pushop = op;
+      if (el_avail[SSA_NAME_VERSION (valnum)])
+	pushop = el_avail[SSA_NAME_VERSION (valnum)];
+      el_avail_stack.safe_push (pushop);
       el_avail[SSA_NAME_VERSION (valnum)] = op;
-      el_avail_stack.safe_push (op);
     }
 }
 
@@ -4451,7 +4454,14 @@ eliminate_dom_walker::after_dom_children (basic_block)
 {
   tree entry;
   while ((entry = el_avail_stack.pop ()) != NULL_TREE)
-    el_avail[SSA_NAME_VERSION (VN_INFO (entry)->valnum)] = NULL_TREE;
+    {
+      tree valnum = VN_INFO (entry)->valnum;
+      tree old = el_avail[SSA_NAME_VERSION (valnum)];
+      if (old == entry)
+	el_avail[SSA_NAME_VERSION (valnum)] = NULL_TREE;
+      else
+	el_avail[SSA_NAME_VERSION (valnum)] = entry;
+    }
 }
 
 /* Eliminate fully redundant computations.  */