From: "H. Peter Anvin" <hpa@zytor.com>
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
Date: Fri, 18 Jul 2008 16:36:34 -0700 [thread overview]
Message-ID: <48812902.5070003@zytor.com> (raw)
In-Reply-To: <20080718211205.GA5423@Krystal>
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
next prev parent reply other threads:[~2008-07-18 23:37 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-17 3:17 [PATCH ftrace.git] Immedate Values Optimized Jump Fix Mathieu Desnoyers
2008-07-18 16:15 ` Ingo Molnar
2008-07-18 18:31 ` Mathieu Desnoyers
2008-07-18 19:50 ` H. Peter Anvin
2008-07-18 21:12 ` Mathieu Desnoyers
2008-07-18 23:36 ` H. Peter Anvin [this message]
2008-07-18 23:38 ` H. Peter Anvin
2008-07-18 21:51 ` [git pull tip/tracing/immediates] Immediate values fixes/redux Mathieu Desnoyers
2008-07-19 5:59 ` Mathieu Desnoyers
2008-07-18 22:32 ` [PATCH ftrace.git] Immedate Values Optimized Jump Fix Ingo Molnar
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