[PATCH] Fix predcom ICE introduced by var clobber changes (PR tree-optimization/51246)

[Jakub Jelinek]

Hi!

When stmt is mem = {v} {CLOBBER};, then lhs is neither
SSA_NAME, but it doesn't satisfy gimple_assign_copy_p either.
With this patch it will set the new_tree also to the clobber,
making it clear that the next iteration uses unitialized variable.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2011-11-24  Jakub Jelinek  <jakub@redhat.com>

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

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

--- gcc/tree-predcom.c.jj	2011-09-26 14:07:06.000000000 +0200
+++ gcc/tree-predcom.c	2011-11-24 09:17:46.872962765 +0100
@@ -1306,8 +1306,10 @@ replace_ref_with (gimple stmt, tree new_
       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)
+		      && (gimple_assign_copy_p (stmt)
+			  || TREE_CLOBBER_P (val)));
 	}
     }
   else
--- gcc/testsuite/gcc.c-torture/compile/pr51246.c.jj	2011-11-24 09:15:10.322906812 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr51246.c	2011-11-24 09:14:52.000000000 +0100
@@ -0,0 +1,14 @@
+/* PR tree-optimization/51246 */
+
+int a, *b;
+
+void
+test (void)
+{
+  while (1)
+    {
+      int c;
+      a = c;
+      b = &c;
+    }
+}

	Jakub