Re: [PATCH v2] combine: Fix ICE in try_combine on pr112494.c [PR112560]

[Richard Biener <rguenther@suse.de>]

On Thu, 7 Mar 2024, Jakub Jelinek wrote:

> On Thu, Mar 07, 2024 at 11:11:35AM +0100, Uros Bizjak wrote:
> > > Since you CCed me - looking at the code I wonder why we fatally fail.
> > > The following might also fix the issue and preserve more of the
> > > rest of the flow of the function.
> > >
> > > If that works I'd prefer it.  But I'll defer approval to the combine
> > > maintainer which is Segher.
> > 
> > Your patch is basically what v1 did [1], but it was suggested (in a
> > reply by you ;) ) that we should stop the attempt to combine if we
> > can't handle the use. So, the v2 patch undoes the combine and records
> > a nice message in this case.
> 
> My understanding of Richi's patch is that it it treats the non-COMPARISON_P
> the same as if find_single_use fails, which is a common case that certainly
> has to be handled right and it doesn't seem that we are giving up completely
> for that case.  So, I think it is reasonable to treat the non-COMPARISON_P
> *cc_use_loc as NULL cc_use_loc.

The question is, whether a NULL cc_use_loc (find_single_use returning 
NULL) means "there is no use" or it can mean "huh, don't know, maybe
more than one, maybe I was too stupid to indentify the single use".
The implementation suggests it's all broken ;)

Richard.