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Date: Thu, 20 Dec 2007 19:30:36 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: akpm@linux-foundation.org, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, Andi Kleen <ak@muc.de>,
       Chuck Ebbert <cebbert@redhat.com>,
       Christoph Hellwig <hch@infradead.org>,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
       Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [patch 14/24] Immediate Values - x86 Optimization
References: <20071221015438.433195466@polymtl.ca> <20071221015726.909058404@polymtl.ca> <476B2B5E.5060204@zytor.com> <20071221031900.GA2414@Krystal>
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Mathieu Desnoyers wrote:
> 
> Argh.. Rusty asked to have a simplified version first, and then to
> implement the "more complex" one on top of it. However, in order to get
> the reentrancy I need for the markers, I need the complex version of the
> immediate values. Therefore, you find, in this patchset, the simple
> version first, and then, the more complex one implemented on top.
> 
> About this patch header, the initial idea was to use the "Q" and "R"
> constraints, but, as stated just below, the "q" and "r" constraints are
> used instead to make sure the REX prefixed opcodes for 1, 2, and 4 bytes
> immediate values are never used. So the complete header follows the
> source code, it's just that this paragraph could be clearer.
> 

Then you have it backwards.  "Q" and "R" avoid REX prefixes, "q" and "r" 
DO NOT.

	-hpa