Gentoo Archives: gentoo-performance

From: Andrea Pretto <prettz_it@×××××.it>
To: gentoo-performance@l.g.o
Subject: Re: [gentoo-performance] gcc optimizations
Date: Thu, 01 Jul 2004 09:17:54
Message-Id: 20040701091749.83445.qmail@web25102.mail.ukl.yahoo.com
In Reply to: Re: [gentoo-performance] gcc optimizations by Paul Ingelbrant
Gcc cannot to preview the contents of  "if{ ... }".
In this case there is a single instruction, but in
others cases the if  statement can contain a lot of
instructions.
The I think gcc deals the "if" mechanically, and it
don't look for particular "if" with one istruction as
in your example.

After that, there is not a flag or a special
opitmization that favourite use of cmov in asm code,
cmov it's only a instruction.Than you can use it
"manually" in inline assembler.

--- Paul Ingelbrant <pi@×××××.se> ha scritto: >
Quoting Andrea Pretto <prettz_it@×××××.it>:
> > > The flag -mmmx ( like -msse -m3dnow etc...) > activate > > some extensions for C language. > > > > See this: > > >
http://gcc.gnu.org/onlinedocs/gcc-3.3.3/gcc/X86-Built-in-Functions.html#X86%20Built-in%20Functions
> > > > So, those flag activate these built-in functions. > > I see. > > But what's the matter with the cmov instruction? > Should be reasonably "simple" > for gcc to use it automatically... > > -- > gentoo-performance@g.o mailing list >
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