[Mesa-dev] [PATCH] st/mesa: use u_bit_scan64() on 64-bit CPUs

[Marek Olšák]

NAK.

This won't make it faster.

Marek

On Fri, Oct 21, 2016 at 11:58 AM, Jan Ziak <0xe2.0x9a.0x9b at gmail.com> wrote:
> st_validate_state() shows up in benchmarks. This patch makes it a little bit
> faster in 64-bit mode.
>
> Signed-off-by: Jan Ziak (http://atom-symbol.net) <0xe2.0x9a.0x9b at gmail.com>
> ---
>  src/mesa/state_tracker/st_atom.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/src/mesa/state_tracker/st_atom.c b/src/mesa/state_tracker/st_atom.c
> index 94e012a..210f6f3 100644
> --- a/src/mesa/state_tracker/st_atom.c
> +++ b/src/mesa/state_tracker/st_atom.c
> @@ -155,7 +155,6 @@ void st_validate_state( struct st_context *st, enum st_pipeline pipeline )
>  {
>     struct gl_context *ctx = st->ctx;
>     uint64_t dirty, pipeline_mask;
> -   uint32_t dirty_lo, dirty_hi;
>
>     /* Get Mesa driver state.
>      *
> @@ -200,17 +199,19 @@ void st_validate_state( struct st_context *st, enum st_pipeline pipeline )
>     if (!dirty)
>        return;
>
> -   dirty_lo = dirty;
> -   dirty_hi = dirty >> 32;
> -
> -   /* Update states.
> -    *
> -    * Don't use u_bit_scan64, it may be slower on 32-bit.
> -    */
> -   while (dirty_lo)
> -      atoms[u_bit_scan(&dirty_lo)]->update(st);
> -   while (dirty_hi)
> -      atoms[32 + u_bit_scan(&dirty_hi)]->update(st);
> +   /* Update states. */
> +   if (sizeof(void*) > 4) {
> +      while (dirty)
> +         atoms[u_bit_scan64(&dirty)]->update(st);
> +   } else {
> +      /* Don't use u_bit_scan64, it may be slower on 32-bit. */
> +      uint32_t dirty_lo = dirty;
> +      uint32_t dirty_hi = dirty >> 32;
> +      while (dirty_lo)
> +         atoms[u_bit_scan(&dirty_lo)]->update(st);
> +      while (dirty_hi)
> +         atoms[32 + u_bit_scan(&dirty_hi)]->update(st);
> +   }
>
>     /* Clear the render or compute state bits. */
>     st->dirty &= ~pipeline_mask;
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