Message-ID: <48812902.5070003@zytor.com>
Date: Fri, 18 Jul 2008 16:36:34 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Mathieu Desnoyers <compudj@krystal.dyndns.org>
CC: Ingo Molnar <mingo@elte.hu>, Ingo Molnar <mingo@redhat.com>,
       Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH ftrace.git] Immedate Values Optimized Jump Fix
References: <20080717031721.GA24504@Krystal> <20080718161523.GY6875@elte.hu> <20080718183124.GA31768@Krystal> <4880F410.3090804@zytor.com> <20080718211205.GA5423@Krystal>
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Mathieu Desnoyers wrote:
> 
> Hrm, I thought that by following the execution flow to both branches and
> by looking at the code pattern found (load immediate, test, branch) and
> by placing a constraint on the eax register to detect the liveliness
> region of that variable we would be guaranteed that the compiler could
> not re-use this variable outside of the pattern scope.
> 

Nope, and you *cannot* allow such registers to be live *anywhere* the C 
compiler is generating code, even between two asm() statements with 
nothing in between.

	-hpa
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