linux-kernel - Re: [PATCH] Fix immediate asm constraint for gcc 3 x86

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Message-ID: <482DFD65.10300@zytor.com>
Date:	Fri, 16 May 2008 14:32:21 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>, Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix immediate asm constraint for gcc 3 x86_64

Mathieu Desnoyers wrote:

> 
> It seems that include/asm-x86/immediate.h in sched-devel.git causes
> this. gcc-3.4 does not seem to like the "i" (&name##__imv) constraint. I
> have seen no such problem with gcc-4.1. This is weird. It seems that
> relaxing the constraint helps fixing this, but it's not clear whether
> fixing the code or gcc-3.4 is the correct solution... here is the fix :
> 
> Fix immediate asm constraint for gcc 3 x86_64
> 

It might make it compile, but it's completely *wrong* for the purpose 
intended.

It permits gcc to present the address in a register, for example, so 
there is no guarantee that you end up with an immediate.

	-hpa
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