Re: [PATCH] [2.4] [2.5] [i386] Add support for GCC 3.1 -march=pentium{-mmx,3,4}

Dave Jones
2002-05-25T22:54:01Z

On Sun, May 26, 2002 at 01:37:39AM +0200, J.A. Magallon wrote:
> Could you also split
> Pentium-Pro/Celeron/Pentium-II CONFIG_M686
> into
>
> Pentium-Pro CONFIG_M686
> Pentium-II/Celeron CONFIG_MPENTIUMII
>
> Gcc-3.1 has also a -march=pentium2 specific target, that is not a synomym
> for any other.

There are also a few extra Athlon targets iirc. athlon-xp and the like,
which I'm not sure the purpose of. Some gcc know-all want to clue me in
to what these offer over -march=athlon ?

> BTW, I think an option to enable -mmmx would also be useful. Nothing more,
> because afaik sse is only floating point.

Another interesting recently-added option which may be worth
benchmarking on modern CPUs is the prefetch-loops option.
In a lot of cases, the kernel 'knows better' and is adding the
prefetches itself, but it may be interesting to see what difference
gcc can make here. (More interesting would be examining the output to
see *where* gcc is putting the prefetches)

Given the immaturity of all these options, I'd doubt they're that good
an idea for 2.4. Getting them tested during 2.5 may prove to get any
bugs shaken out in time for $compiler_of_the_choice for 2.6 though.

Dave

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