From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC][PATCH 2/3] math128: Introduce {mult,add,cmp}_u128
Date: Tue, 24 Apr 2012 17:09:41 -0700
Message-ID: <4F9740C5.6050306@zytor.com>
References: <20120424161039.293018424@chello.nl>  <20120424162224.526249106@chello.nl>  <CA+55aFyvBTDh_DkXs6Z6zFmjyYxvWaAEm9-rJDXhvPx8CpDiKA@mail.gmail.com> <1335304497.28150.243.camel@twins>
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To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, Juri Lelli <juri.lelli@gmail.com>, Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>

On 04/24/2012 02:54 PM, Peter Zijlstra wrote:
> -       andl    $4294967295, %edx
>         shrq    $32, %rcx
> -       andl    $4294967295, %esi
> +       mov     %esi, %esi

If you can *ever* get gcc to generate those andl instructions on x86,
then please file a gcc bug report: the constant is 0xffffffff and those
are plain zero-extension instructions which is much better done with mov.

	-hpa