Re: [PATCH 2/2] util: add util function buffer_zero_avx512()

[Robert Hoo]

On Mon, 2020-02-24 at 08:13 -0800, Richard Henderson wrote:
> On 2/23/20 11:07 PM, Robert Hoo wrote:
> > Inspired by your suggestion, I'm thinking go further: use immediate
> > rather than a global variable, so that saves 1 memory(/cache)
> > access. 
> > 
> > #ifdef CONFIG_AVX512F_OPT   
> > #define OPTIMIZE_LEN    256
> > #else
> > #define OPTIMIZE_LEN    64
> > #endif
> 
> With that, the testing in tests/test-bufferiszero.c, looping through
> the
> implementations, is invalidated.  Because once you start compiling
> for avx512,
> you're no longer testing sse2 et al with the same inputs.
> 
Right. Thanks pointing out. I didn't noticed that.
More precisely, it would cause no longer testing sse2 et al with < 256
length.

> IF we want to change the length to suit avx512, we would want to
> change it
> unconditionally.  And then you could also tidy up avx2 to avoid the
> extra
> comparisons there.
Considering the length's dependency on sse2/sse4/avx2/avx512 and the
algorithms, as well as future's possible changes, additions, I'd rather
roll back to your original suggestion, use a companion variable with
each accel_fn(). How do you like it?

> 
> 
> r~