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Re: [PATCH] x86-64: Add sinf with FMA
On Tue, Dec 5, 2017 at 5:47 AM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> And with a simple modification to avoid int to fp conversion:
>
> ---
> diff --git a/sysdeps/ieee754/flt-32/s_sinf.c b/sysdeps/ieee754/flt-32/s_sinf.c
> index 40d3d19..a2fd3cf 100644
> --- a/sysdeps/ieee754/flt-32/s_sinf.c
> +++ b/sysdeps/ieee754/flt-32/s_sinf.c
> @@ -75,7 +75,7 @@ static const double invpio4_table[] = {
> 0x1.0e4107cp-169
> };
>
> -static const int ones[] = { +1, -1 };
> +static const double ones[] = { 1.0, -1.0 };
>
> /* Compute the sine value using Chebyshev polynomials where
> THETA is the range reduced absolute value of the input
> @@ -92,7 +92,7 @@ reduced (const double theta, const unsigned long int n,
> const double theta2 = theta * theta;
> /* We are operating on |x|, so we need to add back the original
> signbit for sinf. */
> - int sign;
> + double sign;
> /* Determine positive or negative primary interval. */
> sign = ones[((n >> 2) & 1) ^ signbit];
> /* Are we in the primary interval of sin or cos? */
> ---
>
> I get:
>
> "sinf": {
> "": {
> "duration": 4.0015e+10,
> "iterations": 1.4535e+09,
> "max": 640.456,
> "min": 11.437,
> "mean": 27.5301
> }
>
> Which is roughly 3% on mean and 11.5% on min. I think we can improve it
> even more by avoiding the int to fp conversion to get the sign right
> and try operate with sign as double argument.
I tried it on Skylake with the current master. Before:
"sinf": {
"": {
"duration": 3.4044e+10,
"iterations": 1.9942e+09,
"max": 141.106,
"min": 7.704,
"mean": 17.0715
}
}
After:
"sinf": {
"": {
"duration": 3.40665e+10,
"iterations": 2.03199e+09,
"max": 95.994,
"min": 7.704,
"mean": 16.765
}
}
Generic is faster than asm now:
"sinf": {
"": {
"duration": 3.40417e+10,
"iterations": 1.87792e+09,
"max": 138.868,
"min": 8.546,
"mean": 18.1273
}
}
Can you submit your patch?
Thanks.
--
H.J.