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Re: gcc will become the best optimizing x86 compiler
On Thu, 24 Jul 2008, Basile STARYNKEVITCH wrote:
> At last, at the recent (july 2008) GCC summit, someone (sorry I forgot who,
> probably someone from SuSE) proposed in a BOFS to have architecture and
> machine specific hand-tuned (or even hand-written assembly) low level
> libraries for such basic things as memset etc..
I don't recall seeing any BOF minutes on this list yet this year. Are
people going to be posting them?
I don't know if it was proposed in this context, but the ARM EABI has
various __aeabi_mem* functions for calls known to have particular
alignment and the idea is relevant to other platforms if you provide such
functions with the compiler. The compiler could also generate calls to
different functions depending on the -march options and so save the
runtime CPU check cost (you could have options to call either generic
versions, or versions for a particular CPU, depending on whether you are
building a generic binary for CPU-X-or-newer or a binary just for CPU X).
As usual in this area, careful negotiation with the FSF at an early stage
to be able to reuse glibc versions of the functions where useful would be
a good idea. Reusing the glibc testcases for string functions (that e.g.
they don't access beyond the memory they are allowed to access at the end
of a page) would be a good idea as well, and doesn't have the problems
with changing licenses that reusing the functions themselves does.
--
Joseph S. Myers
joseph@codesourcery.com