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Subject: Re: [PATCH 1/4] Remove architecture specific sched_cpucount
 optimizations
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>,
 Florian Weimer <fweimer@redhat.com>,
 Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>
Cc: crrodriguez@opensuse.org
References: <20210329182520.323665-1-adhemerval.zanella@linaro.org>
 <87a6p9dr9n.fsf@oldenburg.str.redhat.com>
 <61040ff8-caac-a3d9-91cc-9b445c4e98fd@cs.ucla.edu>
 <abe2474a-165b-4216-7d61-b27b76dc17b5@linaro.org>
From: Paul Eggert <eggert@cs.ucla.edu>
Organization: UCLA Computer Science Department
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Date: Thu, 6 May 2021 10:12:54 -0700
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On 5/6/21 6:33 AM, Adhemerval Zanella wrote:
> +/* Counting bits set, Brian Kernighan's way  */
> +static inline unsigned int
> +countbits (__cpu_mask v)
> +{
> +  unsigned int s = 0;
> +  for (; v != 0; s++)
> +    v &= v - 1;
> +  return s;
> +}

Looks OK, except please use 'int' rather than 'unsigned int' (twice) as 
we should prefer signed to unsigned where either will do and the caller 
wants plain int anyway.

More important, please add a comment saying why we're not using the GCC 
builtin (summarizing Florian's and your followup remarks) since it is a 
little odd to see code that simply replicates a compiler builtin (what's 
next, we'll forgo multiplication in favor of repeated addition? :-).