[committed] Fix -D_FORTIFY_SOURCE infinite recursion (PR middle-end/51077)

[Jakub Jelinek]

Hi!

The PR50700 change caused infinite recursion - we shouldn't
call compute_builtin_object_size on SSA_NAMEs more than two times,
otherwise we risk calling it endlessly.  But TREE_CODE (pt_var)
in this code is known to be MEM_REF, so always != SSA_NAME.

Fixed thusly, committed as obvious to trunk/4.6 after bootstrap/regtest
on x86_64-linux and i686-linux.

2011-11-10  Jakub Jelinek  <ja...@redhat.com>

        PR middle-end/51077
        * tree-object-size.c (addr_object_size): Check TREE_CODE of
        MEM_REF's operand rather than code of the MEM_REF itself.

        * gcc.c-torture/compile/pr51077.c: New test.

--- gcc/tree-object-size.c.jj   2011-10-12 20:28:20.000000000 +0200
+++ gcc/tree-object-size.c      2011-11-10 11:53:37.106777916 +0100
@@ -175,7 +175,7 @@ addr_object_size (struct object_size_inf
       unsigned HOST_WIDE_INT sz;
 
       if (!osi || (object_size_type & 1) != 0
-         || TREE_CODE (pt_var) != SSA_NAME)
+         || TREE_CODE (TREE_OPERAND (pt_var, 0)) != SSA_NAME)
        {
          sz = compute_builtin_object_size (TREE_OPERAND (pt_var, 0),
                                            object_size_type & ~1);
--- gcc/testsuite/gcc.c-torture/compile/pr51077.c.jj    2011-11-10 
12:05:24.797638658 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr51077.c       2011-11-10 
12:04:59.000000000 +0100
@@ -0,0 +1,15 @@
+/* PR middle-end/51077 */
+
+struct S { unsigned char s, t[256]; };
+
+void
+foo (const struct S *x, struct S *y, int z)
+{
+  int i;
+  for (i = 0; i < 8; i++)
+    {
+      const struct S *a = &x[i];
+      __builtin___memcpy_chk (y->t, a->t, z, __builtin_object_size (y->t, 0));
+      y = (struct S *) &y->t[z];
+    }
+}

        Jakub