Re: [PATCH v2 10/30] Add x86-specific parity functions

[Borislav Petkov]

On Thu, Apr 07, 2016 at 08:31:09AM +0200, Dmitry Vyukov wrote:
> Hweight custom calling convention caused crashes with KCOV coverage.
> We had to disable instrumentation of the file.

I guess we can do something like this:

       if (likely(static_cpu_has(X86_FEATURE_POPCNT)))
               asm volatile(POPCNT32
                            : "="REG_OUT (res)
                            : REG_IN (w));
       else
               res = __sw_hweight32(w);

and get rid of the custom calling convention.

Along with some numbers showing that the change doesn't cause any
noticeable slowdown...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
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