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

On Thu, 28 Jul 2005, Linus Torvalds wrote:

> >  Since you're considering GCC-generated code for ffs(), ffz() and friends, 
> > how about trying __builtin_ffs(), __builtin_clz() and __builtin_ctz() as 
> > apropriate?
> 
> Please don't. Try again in three years when everybody has them.

 Well, __builtin_ffs() has been there since at least gcc 2.95.  The two 
others are quite recent, indeed -- apparently only since GCC 3.4.  They 
may still be considered to be used conditionally if there is justified 
benefit.

  Maciej
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• References:
  • [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Daniel Walker <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Steven Rostedt <[email protected]>
  • Re: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
    • From: Nick Piggin <[email protected]>
  • [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
    • From: Steven Rostedt <[email protected]>
  • Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
    • From: Linus Torvalds <[email protected]>
  • Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
    • From: Steven Rostedt <[email protected]>
  • Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
    • From: "Maciej W. Rozycki" <[email protected]>
  • Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
    • From: Linus Torvalds <[email protected]>

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