From: Ingo Molnar <mingo@elte.hu>
To: Jan Beulich <jbeulich@novell.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] x86-64: make pda's cpunumber and nodenumber unsigned
Date: Mon, 17 Dec 2007 14:26:19 +0100 [thread overview]
Message-ID: <20071217132619.GB1870@elte.hu> (raw)
In-Reply-To: <47610530.76E4.0078.0@novell.com>
* 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.
Ingo
next prev parent reply other threads:[~2007-12-17 13:26 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 [this message]
2007-12-17 13:37 ` Jan Beulich
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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