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

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
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Follow-Ups:
- 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: Linus Torvalds <[email protected]>
- Re: [PATCH] speed up on find_first_bit for i386 (let compiler do the work)
  - From: Steven Rostedt <[email protected]>

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]>

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