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Re: [PATCH] Fix loop-header copying do-while loop detection (PR85116)
- From: Richard Biener <rguenther at suse dot de>
- To: David Edelsohn <dje dot gcc at gmail dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Sat, 28 Apr 2018 08:46:06 +0200 (CEST)
- Subject: Re: [PATCH] Fix loop-header copying do-while loop detection (PR85116)
- References: <CAGWvny=TmGYAY1JtZYimxVdm+EHPiEnAhET1s-191RDyLxyq7g@mail.gmail.com> <alpine.LSU.2.20.1804271026040.24704@zhemvz.fhfr.qr>
On Fri, 27 Apr 2018, Richard Biener wrote:
> On Fri, 27 Apr 2018, David Edelsohn wrote:
>
> > Hi, Richi
> >
> > This patches causes a boostrap failure on AIX. Everything miscompares.
> > The code itself is the same, but the DWARF debug information contains many
> > differences.
>
> Does AIX use bootstrap-debug by default? I don't see how the patch
> can cause this kind of issue directly but of course it will change
> CH decisions which may expose latent bugs somewhere.
>
> Can you provide more details please, like actual differences?
> I would have expected the dwarf2out.c change to be a more likely
> candidate for such symtoms but I trust that you did properly
> bisect to my patch?
OK, so the x86-64 -O3 bootstrap failure is not caused by this patch,
reverting it doesn't fix the issue.
The difference w/ the patch reverted is in debug info, all (indirect)
strings reside at different offsets. If I strip the objects they
compare identical.
I'm trying reversal of that dwarf2out patch now.
Richard.