From: "Jan Beulich" <jbeulich@novell.com>
To: "Ingo Molnar" <mingo@elte.hu>
Cc: <tglx@linutronix.de>, "Andrew Morton" <akpm@linux-foundation.org>,
<mingo@redhat.com>, <linux-kernel@vger.kernel.org>,
<hpa@zytor.com>
Subject: Re: [PATCH] x86-64: make pda's cpunumber and nodenumber unsigned
Date: Mon, 17 Dec 2007 13:37:35 +0000 [thread overview]
Message-ID: <476689AF.76E4.0078.0@novell.com> (raw)
In-Reply-To: <20071217132619.GB1870@elte.hu>
>>> Ingo Molnar <mingo@elte.hu> 17.12.07 14:26 >>>
>
>* Jan Beulich <jbeulich@novell.com> wrote:
>
>> This generally allows better code to be generated, since the zero-
>> extension during 32-bit operations comes for free (needed when the
>> result is used as array index or similar), whereas sign extension must
>> be done explicitly and frequently requires a one byte larger
>> instruction due to the necessary rex64 prefix.
>
>good catch! Applied your patch to x86.git - queued it up for v2.6.25. I
>bet there are tons of other instances where we use signed instead of
>unsigned and get worse code generation.
Yes, definitely. This patch was kind of a testing one whether this is a
welcome change. As it appears to be, I'll probably produce more as I
run into respective cases.
Jan
next prev parent reply other threads:[~2007-12-17 13:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-13 9:10 [PATCH] x86-64: make pda's cpunumber and nodenumber unsigned Jan Beulich
2007-12-17 13:26 ` Ingo Molnar
2007-12-17 13:37 ` Jan Beulich [this message]
2007-12-17 14:53 ` Ingo Molnar
2007-12-17 15:34 ` Cyrill Gorcunov
2007-12-17 16:00 ` Ingo Molnar
2007-12-17 16:01 ` Ingo Molnar
2007-12-17 16:10 ` Cyrill Gorcunov
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