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Re: question about gcc assembly
- From: "Coline Lelong-Pantel" <coline dot lelong-pantel at laposte dot net>
- To: "tprince" <tprince at myrealbox dot com>
- Cc: "gcc-help" <gcc-help at gcc dot gnu dot org>
- Date: Tue, 27 Jun 2006 16:21:09 +0200
- Subject: Re: question about gcc assembly
> Both gcc versions you quote are fairly old; if efficiency
interests you,
> you might try a current version. Were you able to show a
significant
> difference in performance on a CPU which is important to you?
I have not checked that, my goal is to produce, if it is
possible, the same assembly code.
I would
> guess the most important reason for avoiding use of eax here
would be to
> keep that register available for other use. The
optimization could be
> affected by compiler switches (-Os, -O2) or by selection of
-march
> option, and many other possibilities.
If I try using optimisation flags or -march, i get a
completely different code.
> Newer CPUs have hardware merging of operations, as well as
stalls on
> certain immediate data operations, so it is impossible to
know the
> performance implications from what you have presented.
What do you mean by "hardware merging of operations" ?
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