> 2011-10-17 Richard Guenther <rguent...@suse.de>
>
> PR middle-end/50716
> * expr.c (get_object_or_type_alignment): New function.
> (expand_assignment): Use it.
> (expand_expr_real_1): Likewise.
Maybe move it to builtins.c alongside the other get_*_alignment functions.
> Index: gcc/expr.c
> ===================================================================
> *** gcc/expr.c (revision 180077)
> --- gcc/expr.c (working copy)
> *************** get_bit_range (unsigned HOST_WIDE_INT *b
> *** 4544,4549 ****
> --- 4544,4568 ----
> }
> }
>
> + /* Return the alignment of the object EXP, also considering its type
> + when we do not know of explicit misalignment.
> + ??? Note that generally the type of an expression is not kept
> + consistent with misalignment information by the frontend, for
> + example when taking the address of a member of a packed structure.
> + So taking into account type information for alignment is generally
> + wrong, but is done here as a compromise. */
This sounds backwards, as taking into account type information is generally
correct, i.e. the packed case is the exception. Maybe use "in the general
case" instead:
??? Note that, in the general case, the type of an expression is not kept
consistent with the misalignment by the front-end, for example when taking
the address of a member of a packed structure. However, in most of the
cases, expressions have the alignment of their type, so we fall back to
the alignment of the type when we cannot compute a misalignment.
+ static unsigned int
+ get_object_or_type_alignment (tree exp)
+ {
+ unsigned HOST_WIDE_INT misalign;
+ unsigned int align = get_object_alignment_1 (exp, &misalign);
+ align = MAX (TYPE_ALIGN (TREE_TYPE (exp)), align);
+ if (misalign != 0)
+ align = (misalign & -misalign);
You don't need to go through the MAX if misalign is non-zero.
--
Eric Botcazou
