Messages in this thread | | | Date | Mon, 17 Dec 2007 13:37:35 +0000 | From | "Jan Beulich" <> | Subject | Re: [PATCH] x86-64: make pda's cpunumber and nodenumber unsigned |
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>>> 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
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