may_be_unaligned_p bug?

[DJ Delorie]

I can confirm this fixes my test case.  Had I known about
highest_pow2_factor() I might have come up with this myself ;-)

> Index: tree-ssa-loop-ivopts.c
> ===================================================================
> --- tree-ssa-loop-ivopts.c	(revision 158148)
> +++ tree-ssa-loop-ivopts.c	(working copy)
> @@ -1537,16 +1537,18 @@ may_be_unaligned_p (tree ref, tree step)
>  
>    if (mode != BLKmode)
>      {
> -      double_int mul;
> -      tree al = build_int_cst (TREE_TYPE (step),
> -			       GET_MODE_ALIGNMENT (mode) / BITS_PER_UNIT);
> +      unsigned mode_align = GET_MODE_ALIGNMENT (mode);
>  
> -      if (base_align < GET_MODE_ALIGNMENT (mode)
> -	  || bitpos % GET_MODE_ALIGNMENT (mode) != 0
> -	  || bitpos % BITS_PER_UNIT != 0)
> +      if (base_align < mode_align
> +	  || (bitpos % mode_align) != 0
> +	  || (bitpos % BITS_PER_UNIT) != 0)
>  	return true;
>  
> -      if (!constant_multiple_of (step, al, &mul))
> +      if (toffset
> +	  && (highest_pow2_factor (toffset) * BITS_PER_UNIT) < mode_align)
> +	return true;
> +
> +      if ((highest_pow2_factor (step) * BITS_PER_UNIT) < mode_align)
>  	return true;
>      }
>