[PR64817-related 3/3] simplify xor of (and or ior) of xor

[Jakub Jelinek]

On Wed, Feb 04, 2015 at 09:54:53AM +0100, Richard Biener wrote:
> On February 4, 2015 9:35:13 AM CET, Jakub Jelinek <jakub@redhat.com> wrote:
> >On Wed, Feb 04, 2015 at 04:21:43AM -0200, Alexandre Oliva wrote:
> >> I'm a bit surprised the gimple layer does not even attempt to
> >simplify
> >> them, but I didn't try to tackle that, since I was not even sure this
> >> was a useful optimization.  After all, how often do we see xor of and
> >of
> >> xor of and of xor of... in the wild, rather than in pathological
> >> testcases? :-)  But hey, at least the rtl simplification is cheap, so
> >> why not?
> >
> >I think we should teach at least VRP to simplify debug stmts similarly
> >how
> >it simplifies normal comparisons etc. using value ranges, but that
> >would be
> >stage1 material.
> 
> So I suppose this is only about debug exprs and we optimize regular gimple
> well?  Otherwise adding some patterns to match.PD could help.

Sure.  For e.g. VRP I meant that simplify_stmt_using_ranges could also
attempt to simplify (some) debug_bind stmts, similarly how it optimizes
normal stmts.

	Jakub