Re: [PATCH] speed up on find_first_bit for i386 (let compiler dothe work)

[Maciej W. Rozycki]

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.

  Maciej
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/