[PATCH] Fix PR55882

[Richard Biener]

This fixes PR55882 - set_mem_attributes_minus_bitpos misses to
account for the to-be applied bitpos when computing MEM_ALIGN.
It extracts alignment from 't' instead of &t - bitpos.

Bootstrapped and tested on x86_64-unknown-linux-gnu, bootstrap
and regtest running on mips.

Does this look sensible?

Thanks,
Richard.

2013-01-09  Richard Biener  <rguent...@suse.de>

        PR middle-end/55882
        * emit-rtl.c (set_mem_attributes_minus_bitpos): Correctly
        account for the to-be applied bitpos when computing alignment.

Index: gcc/emit-rtl.c
===================================================================
--- gcc/emit-rtl.c      (revision 195014)
+++ gcc/emit-rtl.c      (working copy)
@@ -1839,7 +1839,12 @@ set_mem_attributes_minus_bitpos (rtx ref
 
       if (!align_computed)
        {
-         unsigned int obj_align = get_object_alignment (t);
+         unsigned int obj_align;
+         unsigned HOST_WIDE_INT obj_bitpos;
+         get_object_alignment_1 (t, &obj_align, &obj_bitpos);
+         obj_bitpos = (obj_bitpos - apply_bitpos) & (obj_align - 1);
+         if (obj_bitpos != 0)
+           obj_align = (obj_bitpos & -obj_bitpos);
          attrs.align = MAX (attrs.align, obj_align);
        }
     }