On 22 Jan 2005, at 22:00, vlobanov wrote:
Hi,
I was just reading over the patch, and had a quick question/comment upon
the SWAP macro defined below. I think it's possible to do a tiny bit
better (better, of course, being subjective), as follows:
#define SWAP(a, b, size) \ do { \ register size_t __size = (size); \ register char * __a = (a), * __b = (b); \ do { \ *__a ^= *__b; \ *__b ^= *__a; \ *__a ^= *__b; \ __a++; \ __b++; \ } while ((--__size) > 0); \ } while (0)
What do you think? :)
AFAIK, XOR is quite expensive on IA32 when compared to simple MOV operatings. Also, since the original patch uses 3 MOVs to perform the swapping, and your version uses 3 XOR operations, I don't see any gains.
Am I missing something?
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