Re: [Qemu-devel] [PATCH 1/2] target/mips: Improve performance for MSA binary operations

["Alex Bennée" <alex.bennee@linaro.org>]

Mateja Marjanovic <mateja.marjanovic@rt-rk.com> writes:

> From: Mateja Marjanovic <Mateja.Marjanovic@rt-rk.com>
>
> Eliminate loops for better performance.

Have you done any measurements of the bellow loop unrolling? Because
this is something that maybe we can achieve and let the compiler make
the choice.

>
> Signed-off-by: Mateja Marjanovic <mateja.marjanovic@rt-rk.com>
> ---
>  target/mips/msa_helper.c | 43 ++++++++++++++++++++++++++++++-------------
>  1 file changed, 30 insertions(+), 13 deletions(-)
>
> diff --git a/target/mips/msa_helper.c b/target/mips/msa_helper.c
> index 4c7ec05..1152fda 100644
> --- a/target/mips/msa_helper.c
> +++ b/target/mips/msa_helper.c
> @@ -804,28 +804,45 @@ void helper_msa_ ## func ## _df(CPUMIPSState *env, uint32_t df,         \
>      wr_t *pwd = &(env->active_fpu.fpr[wd].wr);                          \
>      wr_t *pws = &(env->active_fpu.fpr[ws].wr);                          \
>      wr_t *pwt = &(env->active_fpu.fpr[wt].wr);
> \

If we can ensure alignment for the various vector registers then the
compiler always has the option of using host vectors (certainly for int
and logic operations).

> -    uint32_t i;                                                         \
>                                                                          \

>      switch (df) {                                                       \
>      case DF_BYTE:                                                       \
> -        for (i = 0; i < DF_ELEMENTS(DF_BYTE); i++) {                    \
> -            pwd->b[i] = msa_ ## func ## _df(df, pws->b[i], pwt->b[i]);  \
> -        }                                                               \
> +        pwd->b[0]  = msa_ ## func ## _df(df, pws->b[0], pwt->b[0]);     \
> +        pwd->b[1]  = msa_ ## func ## _df(df, pws->b[1], pwt->b[1]);     \
> +        pwd->b[2]  = msa_ ## func ## _df(df, pws->b[2], pwt->b[2]);     \
> +        pwd->b[3]  = msa_ ## func ## _df(df, pws->b[3], pwt->b[3]);     \
> +        pwd->b[4]  = msa_ ## func ## _df(df, pws->b[4], pwt->b[4]);     \
> +        pwd->b[5]  = msa_ ## func ## _df(df, pws->b[5], pwt->b[5]);     \
> +        pwd->b[6]  = msa_ ## func ## _df(df, pws->b[6], pwt->b[6]);     \
> +        pwd->b[7]  = msa_ ## func ## _df(df, pws->b[7], pwt->b[7]);     \
> +        pwd->b[8]  = msa_ ## func ## _df(df, pws->b[8], pwt->b[8]);     \
> +        pwd->b[9]  = msa_ ## func ## _df(df, pws->b[9], pwt->b[9]);     \
> +        pwd->b[10] = msa_ ## func ## _df(df, pws->b[10], pwt->b[10]);   \
> +        pwd->b[11] = msa_ ## func ## _df(df, pws->b[11], pwt->b[11]);   \
> +        pwd->b[12] = msa_ ## func ## _df(df, pws->b[12], pwt->b[12]);   \
> +        pwd->b[13] = msa_ ## func ## _df(df, pws->b[13], pwt->b[13]);   \
> +        pwd->b[14] = msa_ ## func ## _df(df, pws->b[14], pwt->b[14]);   \
> +        pwd->b[15] = msa_ ## func ## _df(df, pws->b[15], pwt->b[15]);   \
>          break;                                                          \
>      case DF_HALF:                                                       \
> -        for (i = 0; i < DF_ELEMENTS(DF_HALF); i++) {                    \
> -            pwd->h[i] = msa_ ## func ## _df(df, pws->h[i], pwt->h[i]);  \
> -        }                                                               \
> +        pwd->h[0] = msa_ ## func ## _df(df, pws->h[0], pwt->h[0]);      \
> +        pwd->h[1] = msa_ ## func ## _df(df, pws->h[1], pwt->h[1]);      \
> +        pwd->h[2] = msa_ ## func ## _df(df, pws->h[2], pwt->h[2]);      \
> +        pwd->h[3] = msa_ ## func ## _df(df, pws->h[3], pwt->h[3]);      \
> +        pwd->h[4] = msa_ ## func ## _df(df, pws->h[4], pwt->h[4]);      \
> +        pwd->h[5] = msa_ ## func ## _df(df, pws->h[5], pwt->h[5]);      \
> +        pwd->h[6] = msa_ ## func ## _df(df, pws->h[6], pwt->h[6]);      \
> +        pwd->h[7] = msa_ ## func ## _df(df, pws->h[7], pwt->h[7]);      \
>          break;                                                          \
>      case DF_WORD:                                                       \
> -        for (i = 0; i < DF_ELEMENTS(DF_WORD); i++) {                    \
> -            pwd->w[i] = msa_ ## func ## _df(df, pws->w[i], pwt->w[i]);  \
> -        }                                                               \
> +        pwd->w[0] = msa_ ## func ## _df(df, pws->w[0], pwt->w[0]);      \
> +        pwd->w[1] = msa_ ## func ## _df(df, pws->w[1], pwt->w[1]);      \
> +        pwd->w[2] = msa_ ## func ## _df(df, pws->w[2], pwt->w[2]);      \
> +        pwd->w[3] = msa_ ## func ## _df(df, pws->w[3], pwt->w[3]);      \
>          break;                                                          \
>      case DF_DOUBLE:                                                     \
> -        for (i = 0; i < DF_ELEMENTS(DF_DOUBLE); i++) {                  \
> -            pwd->d[i] = msa_ ## func ## _df(df, pws->d[i], pwt->d[i]);  \
> -        }                                                               \
> +        pwd->d[0] = msa_ ## func ## _df(df, pws->d[0], pwt->d[0]);      \
> +        pwd->d[1] = msa_ ## func ## _df(df, pws->d[1], pwt->d[1]);      \
>          break;                                                          \
>      default:                                                            \
>          assert(0);                                                      \


--
Alex Bennée