Gabriel Paubert wrote:
> On 3 Sep 2002, H. Peter Anvin wrote:
>
> [Sorry HPA, I forgot to cc to linux-kernel the first time.]
>
>
>>>P.S.
>>> Using "bswap" is little bit tricky.
>>>
>>
>>It needs to be protected by CONFIG_I486 and alternate code implemented
>>for i386 (xchg %al,%ah; rol $16,%eax, xchg %al,%ah for example.)
>
>
> While it would work, this sequence is overkill. Unless I'm mistaken, the
> only property of bswap which is used in this case is that it swaps even
> and odd bytes, which can be done by a simple "roll $8,%eax" (or rorl).
>
> I believe that bswap is one byte shorter than roll. In any case, using a
> rotate might be the right thing to do on other architectures.
>
And again, I think you'll find the rotate faster on at least some x86 cores.
-hpa
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This archive was generated by hypermail 2b29 : Sat Sep 07 2002 - 22:00:23 EST