linux-kernel - Re: PROBLEM: compilation issue, inline assembly arch/x86/kvm/emulate.c fails at -O0

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Message-ID: <50A433D3.6090301@zytor.com>
Date:	Wed, 14 Nov 2012 16:14:11 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Blower, Melanie" <melanie.blower@...el.com>
CC:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"avi@...hat.com" <avi@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: PROBLEM: compilation issue, inline assembly arch/x86/kvm/emulate.c
 fails at -O0

On 11/14/2012 11:45 AM, Blower, Melanie wrote:
> [1.] gcc -O0 assembly arch/x86/kvm/emulate.c gets compilation failure -- incorrect register restrictions
> [2.] Full description of the problem/report:
> I'm trying to compile this file at -O0, but gcc chokes in register allocation at the inline assembly.
>
> In the ordinary Linux build, this file compiles with gcc at -O2, without compilation errors.

Compiling with -O0 is not really expected to work (although -O1 *is*), 
although what you are reporting is an actual bug ("+a" : "a" should
either be "+a" or "=a" : "a").

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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