Messages in this thread | | | Date | Fri, 15 Jun 2007 11:21:17 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] Optimize is_power_of_2(). |
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Vegard Nossum wrote: > From: Vegard Nossum <vegard@peltkore.net> > Date: Fri, 15 Jun 2007 18:35:49 +0200 > Subject: [PATCH] Optimize is_power_of_2(). > > Rationale: Removes one conditional branch and reduces icache footprint. > Proof: If n is false, the product of n and any value is false. If n is > true, the truth of (n * x) is the truth of x. >
You realize that on a lot of platforms, multiplication is done by an out-of-line subroutine, and that even on those that aren't, it's generally a long-pipeline operation, right?
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