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i686 architecture behaviour in gcc
- From: David Fernandez <dfernandez at cct dot co dot uk>
- To: gcc at gcc dot gnu dot org
- Date: Thu, 02 Mar 2006 13:45:24 +0000
- Subject: i686 architecture behaviour in gcc
Nobody seems to know about this in gcc-help, so, there I go:
-------- Forwarded Message --------
From: David Fernandez <firstname.lastname@example.org>
Subject: i686 architecture behaviour in gcc
Date: Tue, 21 Feb 2006 17:08:32 +0000
Can anyone explain why has been chosen that -march=i686 makes the
compiler change the normal behaviour, and zero-expand unsigned short
parameters into 32-bit registers by all means?
void __attribute(( regparm(2) )) myoutl( d, p )
asm(" outl %0,(%w1) \n"
: "a" (d), "d" (p) );
gcc -Os -fomit-frame-pointer -march=i586 ...
but changing "-march=i686" gives us
Is it a bug, or had any developer a good reason to do so?