[Bug rtl-optimization/56151] [4.8 Regression] Performance degradation after r194054 on x86 Atom.

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56151

--- Comment #8 from Steven Bosscher <steven at gcc dot gnu.org> 2013-02-04 17:59:22 UTC ---
(In reply to comment #7)
> Created attachment 29350 [details]
> gcc48-pr56151.patch
> 
> Untested patch for the peephole mentioned in previous comment.

I don't think a new set of peepholes is an appropriate solution for
this problem, because the same issue can show up on any CISC-like
target. Before my patch, the code was good after 'expand' by optabs,
perhaps the code your peephole tries to create, can be emitted from
there instead. And perhaps, longer term, combine should be changed
to try the more profitable combination before the one it performs now.