[PATCH] Fix PR53937

[Richard Guenther]

We fail to handle constant addresses in get_pointer_alignment_1
so we use too pessimistic alignment when accessing a packed
structure via such a pointer.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

2012-07-13  Richard Guenther  <rguent...@suse.de>

        PR middle-end/53937
        * builtins.c (get_pointer_alignment_1): Handle constant
        pointers.

Index: gcc/builtins.c
===================================================================
--- gcc/builtins.c      (revision 189451)
+++ gcc/builtins.c      (working copy)
@@ -536,6 +536,13 @@ get_pointer_alignment_1 (tree exp, unsig
          return false;
        }
     }
+  else if (TREE_CODE (exp) == INTEGER_CST)
+    {
+      *alignp = BIGGEST_ALIGNMENT;
+      *bitposp = ((TREE_INT_CST_LOW (exp) * BITS_PER_UNIT)
+                 & (BIGGEST_ALIGNMENT - 1));
+      return true;
+    }
 
   *bitposp = 0;
   *alignp = BITS_PER_UNIT;