Re: gcc-2.95.3 vs gcc-3.0.4

Jakub Jelinek
2002-02-25T07:48:56Z

On Mon, Feb 25, 2002 at 01:07:42AM +0100, Luigi Genoni wrote:
> At this link:
>
> http://www.cs.utk.edu/~rwhaley/ATLAS/gcc30.html
>
> you can find an interesting explanation why code compiled with gcc 3.0 is
> mostly slower than code compiled with gcc 2.95 on x86 CPUs (but it is
> really faster on other platforms like alpha and sparc64).
>
> basically the main reasons semm to be the scheduler algorithm and the fpu
> stack handling, but I suggest to read the full study.
>
>
> I would be interested to know if this apply to gcc 3.1 too.

Well, concerning reg-stack, you can completely get away without it in 3.1
by using -mfpmath=sse if you are targeting Pentium 3,4 or Athlon 4,xp,mp
(for float math, for higher precision only for Pentium 4).

Jakub