Messages in this thread | | | Subject | Re: [PATCH] Improving send_sigio() scalability | Date | Sat, 29 May 1999 12:48:42 -0400 | From | Horst von Brand <> |
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Jamie Lokier <lkd@tantalophile.demon.co.uk> said: > > > > Why don't you use != when that is what you mean?
> Linus Torvalds wrote: > > It used to do noticeably better compiler-wise. I don't know if newer > > versions of gcc have made ^ and != generate the same code.
> Odd. > > I would expect != to generate better code than ^: != uses `cmp' > instruction, ^ uses `xor' unless the compiler gets clever.
Don't "expect", write a proggie and check. E.g. with egcs-19990524, both ifs in this give the same code:
f(int a, int b, int c, int a2, int b2, int c2) { if((a ^ b) && (b ^ c)) do_it1(); if((a2 != b2) && (b2 != c2)) do_it2(); } -- Horst von Brand vonbrand@sleipnir.valparaiso.cl Casilla 9G, Viña del Mar, Chile +56 32 672616
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