re PR tree-optimization/51246 (ICE in replace_ref_with, at tree-predcom.c:1309)

	PR tree-optimization/51246
	* tree-predcom.c (replace_ref_with): Handle also clobber on the
	rhs.

	* gcc.c-torture/compile/pr51246.c: New test.

From-SVN: r181884

gcc/ChangeLog

 2011-12-01  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/51246
+	* tree-predcom.c (replace_ref_with): Handle also clobber on the
+	rhs.
+
 	PR rtl-optimization/51014
 	* loop-unroll.c (apply_opt_in_copies): Ignore label DEBUG_INSNs
 	both from bb and orig_bb.

gcc/testsuite/ChangeLog

 2011-12-01  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/51246
+	* gcc.c-torture/compile/pr51246.c: New test.
+
 	PR rtl-optimization/51014
 	* g++.dg/opt/pr51014.C: New test.
 

gcc/testsuite/gcc.c-torture/compile/pr51246.c

+/* PR tree-optimization/51246 */
+
+int a, *b;
+
+void
+test (void)
+{
+  while (1)
+    {
+      int c;
+      a = c;
+      b = &c;
+    }
+}

gcc/tree-predcom.c

@@ -1306,8 +1306,20 @@ replace_ref_with (gimple stmt, tree new_tree, bool set, bool in_lhs)
       val = gimple_assign_lhs (stmt);
       if (TREE_CODE (val) != SSA_NAME)
 	{
-	  gcc_assert (gimple_assign_copy_p (stmt));
 	  val = gimple_assign_rhs1 (stmt);
+	  gcc_assert (gimple_assign_single_p (stmt));
+	  if (TREE_CLOBBER_P (val))
+	    {
+	      val = gimple_default_def (cfun, SSA_NAME_VAR (new_tree));
+	      if (val == NULL_TREE)
+		{
+		  val = make_ssa_name (SSA_NAME_VAR (new_tree),
+				       gimple_build_nop ());
+		  set_default_def (SSA_NAME_VAR (new_tree), val);
+		}
+	    }
+	  else
+	    gcc_assert (gimple_assign_copy_p (stmt));
 	}
     }
   else