Messages in this thread | | | Date | Thu, 28 Jul 2005 17:34:18 +0100 (BST) | From | "Maciej W. Rozycki" <> | Subject | Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work) |
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On Thu, 28 Jul 2005, Steven Rostedt wrote:
> I've been playing with different approaches, (still all hot cache > though), and inspecting the generated code. It's not that the gcc > generated code is always better for the normal case. But since it sees > more and everything is not hidden in asm, it can optimise what is being > used, and how it's used.
Since you're considering GCC-generated code for ffs(), ffz() and friends, how about trying __builtin_ffs(), __builtin_clz() and __builtin_ctz() as apropriate? Reasonably recent GCC may actually be good enough to use the fastest code depending on the processor submodel selected.
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