[Mesa-dev] [PATCH 2/3] i965/fs: Clear variable from live-set if it's completely overwritten.

[Eric Anholt]

Matt Turner <mattst88 at gmail.com> writes:

> One program affected:
>
> instructions in affected programs:     246 -> 244 (-0.81%)
> ---
>  src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp
> index 6addbb3..1ae7606 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp
> @@ -80,6 +80,13 @@ fs_visitor::dead_code_eliminate()
>              }
>           }
>  
> +         if (inst->dst.file == GRF) {
> +            if (!inst->is_partial_write()) {
> +               int var = live_intervals->var_from_reg(&inst->dst);
> +               BITSET_CLEAR(live, var);
> +            }
> +         }

Any more effect if you:

 +               int var = live_intervals->var_from_vgrf[inst->dst.reg];
 +               for (int i = 0; i < inst->regs_written; i++)
 +                  BITSET_CLEAR(live, var + i);

instead?
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