[m-rev.] diff: improve simplify_info

[Peter Wang]

On Wed, 08 Mar 2017 12:25:13 +1100 (AEDT), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> 
> I was under the impression that there was much more rounding up
> of allocation sizes, though that came from what Fergus told me about
> much older versions of Boehm. Any idea *when* that changed? I just looked
> on Hans Boehm's gc page, and in "git blame" for the seemingly-relevant
> gc header files in the boehm directory, and did not find that information.

I'm not sure that it ever rounded up to powers of two.

You can look at older tarball imports in the bdwgc repository.
The oldest tag is 'gc1_9'.  size_map exists in misc.c
https://github.com/Mercury-Language/bdwgc/blob/gc1_9/misc.c#L37

Peter