On Nov 16, 2011 2:26 PM, "Michael Mol" <mikemol@gmail.com> wrote:
>
> On Wed, Nov 16, 2011 at 2:11 AM, Stéphane Guedon <stephane@22decembre.eu> wrote:
> > On Wednesday 16 November 2011 02:07:12 Pandu Poluan wrote:
> >> And if you're adventurous, add USE "graphite", reemerge gcc, and reemerge
> >> world :)
> >
> > what does "graphite" add ?
>
> Thanks for reminding me; I meant to look it up when I got home.
>
> shortcircuit:1@serenity~
> Wed Nov 16 02:16 AM
> !501 #1 j0 ?0 $ euse -i graphite
> global use flags (searching: graphite)
> ************************************************************
> no matching entries found
>
> local use flags (searching: graphite)
> ************************************************************
>
> [snip]
>
> [- ] graphite
> sys-devel/gcc: Add support for the framework for loop optimizations
> based on a polyhedral intermediate representation
>
> So, a new, experimental optimization model and framework inside your
> compiler. If it's specifically for optimizing on loops, I'll venture a
> guess it's going to be mostly effective for graphics libraries and
> apps. I've got some slightly riskier educated guesses on how it works
> and what some numeric side effects and consequences might be, but they
> scare me, so I think I'll leave it to someone who actually knows more
> about it...
>

I've been using USE "graphite" since gcc-4.5.3-r1 appeared. Upstream says that graphite is stable, feature-complete, and production-ready since 4.5.3.

To fully taste the effect of graphite, I even went the torturous route of emerging gcc + libtool + binutils (in that order) twice, followed by a wholesale-rebuild of everything (emerge --emptytree), then tarballed the result to my own "stage3.1" tarball to spare me the *huge* amount of time required.

I've deployed 3 systems with USE "graphite", and they *felt* snappier. emerge's *felt* slower, though. (no objective tests, I know).

I use Gentoo as a gatewall, and there I did a wholesale-rebuild one more time, this time specifying CFLAGS "-march=native"... and I just couldn't be happier with the resulting performance :-)

Rgds,