Re: gcc4.0 recent >15% runtime performance regression

[tbp <tbptbp at gmail dot com>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19240


On Mon, 3 Jan 2005 10:29:37 +0100, tbp <tbptbp@gmail.com> wrote:
> On Mon, 03 Jan 2005 10:06:30 +0100, Uros Bizjak <uros@kss-loka.si> wrote:
> > It would be nice to have a small testcase, or perhaps access to source
> > code. I googled for mono-ray, but didn't found anything usable.
> I said mono-ray as opposed to ray packets (4 rays bundled together
> which nicely suit SSE), that is the classical aproach of shooting one
> ray at a time: in that path i don't use intrinsics and totally rely on
> the compiler.
> 
> In that regard gcc4.0 used to produce the best code; as it's a bit
> intricate i posted here first to see if that rang a bell regarding a
> recent change... i mean i'm not sure it's because of increased use of
> the fpu instead of pure SSE. All that i know it's that it's slower.
> 
> > I suggest that you file a bugreport
> > (http://gcc.gnu.org/bugzilla/enter_bug.cgi), where all discussion
> > regarding this bug should take place.
> Well, i wanted to avoid to have to make a testcase for something i'm
> not totally sure but if that's what it takes... Thanks anyway.
>