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Re: Penitum II & egcs 1.1.1 oddity
- To: barry at nibelung dot demon dot co dot uk
- Subject: Re: Penitum II & egcs 1.1.1 oddity
- From: Jeffrey A Law <law at hurl dot cygnus dot com>
- Date: Fri, 22 Jan 1999 08:20:31 -0700
- cc: egcs at cygnus dot com
- Reply-To: law at cygnus dot com
In message <36A85F12.653EF986@nibelung.demon.co.uk>you write:
> I've compiled egcs 1.1.1 having tried the standard 1.1.1 release and the
> 1.1.1 patched release. I've compiled on RedHat Linux 5.2 / PII 400. I
> compiled using 'configure --enable-shared --enable-haifa'.
>
> Is it normal that the compiler is sending -mcpu=pentiumpro but
> -march=pentium by default? For example, this is the output from 'gcc
> -fverbose-asm -S test.c'
Yes, this is normal.
It means schedule for a ppro, but generate (effectively) common-mode
instructions (ie your code can run on all x86 variants).
> Does it make a lot of difference compiling using -march=pentium as
> opposed to -march=pentiumpro on a Pentium II?
"a lot" is a relative term.
-march=pentiumpro will enable ppro specific instructions, namely conditional
moves, which for some code can be a nice improvement. For other code it won't
help in any noticable way. Just depends on your application.
jeff