Messages in this thread | | | Date | Wed, 2 Dec 2020 20:51:27 +0200 | From | Andy Shevchenko <> | Subject | Re: your mail |
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On Thu, Dec 03, 2020 at 03:27:33AM +0900, Yun Levi wrote: > On Thu, Dec 3, 2020 at 2:36 AM Andy Shevchenko > <andriy.shevchenko@linux.intel.com> wrote: > > On Wed, Dec 02, 2020 at 09:26:05AM -0800, Yury Norov wrote:
...
> > Side note: speaking of performance, any plans to fix for_each_*_bit*() for > > cases when the nbits is known to be <= BITS_PER_LONG? > > > > Now it makes an awful code generation (something like few hundred bytes of > > code).
> Frankly Speaking, I don't have an idea in now..... > Could you share your idea or wisdom?
Something like (I may be mistaken by names, etc, I'm not a compiler expert, and this is in pseudo language, I don't remember all API names by hart, just to express the idea) as a rough first step
__builtin_constant(nbits, find_next_set_bit_long, find_next_set_bit)
find_next_set_bit_long() { unsigned long v = BIT_LAST_WORD(i); return ffs_long(v); }
Same for find_first_set_bit() -> map it to ffs_long().
And I believe it can be optimized more.
-- With Best Regards, Andy Shevchenko
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