Re: [PR debug/42896] introduce value uids to stabilize value compares

[Richard Guenther <richard dot guenther at gmail dot com>]

On Sat, Jan 30, 2010 at 8:23 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
> There may be multiple values with the same hash number, so we resorted
> to comparing them by pointers, which causes instability that results in
> different debug information when the heap is randomized in the kernel.
>
> This patch introduces uids in values (no size change on 64-bit hosts),
> using them instead of hashes for compares. ?I had this as part of a
> larger patch that introduced bitmaps of decls and values, that's why
> var-tracking keeps them in non-overlapping ranges.
>
> I could readily duplicate the problem without this patch, and I couldn't
> duplicate it any more after the patch. ?Regstrapped on x86_64-linux-gnu.
> Ok to install?

Any reason to make uid signed (I suppose because decl uids are signed)?
I suppose you initialize the cselib
uid with next_decl_uid to avoid clashes between them?  Is that
necessary for this particular patch or only for introducing the bitmaps
with that other patch you were talking about?  If so please remove
that bits from this patch.

Ok with that.

Thanks,
Richard.

>
>
> --
> Alexandre Oliva, freedom fighter ? ?http://FSFLA.org/~lxoliva/
> You must be the change you wish to see in the world. -- Gandhi
> Be Free! -- http://FSFLA.org/ ? FSF Latin America board member
> Free Software Evangelist ? ? ?Red Hat Brazil Compiler Engineer
>
>