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Re: [PATCH] lib/int_sqrt.c: Optimize square root function

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH] lib/int_sqrt.c: Optimize square root function
Date 2017-07-20 16:20 +0200
Message-ID <u5kt4-bb-13@gated-at.bofh.it> (permalink)
References (1 earlier) <oPsPg-7ue-17@gated-at.bofh.it> <oPuxJ-1C4-35@gated-at.bofh.it> <oPuHo-1NW-17@gated-at.bofh.it> <u5hOy-6De-7@gated-at.bofh.it> <u5ihA-6PH-5@gated-at.bofh.it>
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On Thu, Jul 20, 2017 at 04:52:49AM -0700, Joe Perches wrote:
> On Thu, 2017-07-20 at 13:24 +0200, Peter Zijlstra wrote:
> []
> > +	m = 1UL << ((fls(x) + 1) & ~1UL);
> 
> maybe 
> 
> #if BITS_PER_LONG == 64
> 	m = 1UL << ((fls64(x) + 1) & ~1UL);
> #else
> 	m = 1UL << ((fls(x) + 1) & ~1UL);
> #endif

We do seem to have __fls() which is defined on long.

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Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-20 13:30 +0200
  Re: [PATCH] lib/int_sqrt.c: Optimize square root function Joe Perches <joe@perches.com> - 2017-07-20 14:00 +0200
    Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-20 16:20 +0200
  Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-20 17:30 +0200
  Re: [PATCH] lib/int_sqrt.c: Optimize square root function Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-20 20:40 +0200
    Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-21 00:40 +0200
      Re: [PATCH] lib/int_sqrt.c: Optimize square root function Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-21 01:30 +0200
        Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-21 13:50 +0200
          Re: [PATCH] lib/int_sqrt.c: Optimize square root function Joe Perches <joe@perches.com> - 2017-07-21 14:20 +0200
            Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-21 15:30 +0200
              Re: [PATCH] lib/int_sqrt.c: Optimize square root function Peter Zijlstra <peterz@infradead.org> - 2017-07-21 15:40 +0200

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