[Mesa-dev] [PATCH 19/20] nir: Optimize find_lsb/imsb/umsb error checks

[Connor Abbott]

Reviewed-by: Connor Abbott <cwabbott0 at gmail.com>

On Thu, Jul 6, 2017 at 4:48 PM, Matt Turner <mattst88 at gmail.com> wrote:
> Two of the ARB_shader_ballot piglit tests hit the find_lsb case,
> removing some of the noise allowed me to better debug the test when it
> was failing.
> ---
>  src/compiler/nir/nir_opt_algebraic.py | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
> index fe6e33d313..df5854270c 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -357,6 +357,17 @@ optimizations = [
>     (('~fadd', '#a', ('fadd', b, '#c')), ('fadd', ('fadd', a, c), b)),
>     (('iadd', '#a', ('iadd', b, '#c')), ('iadd', ('iadd', a, c), b)),
>
> +   # By definition...
> +   (('bcsel', ('ige', ('find_lsb', a), 0), ('find_lsb', a), -1), ('find_lsb', a)),
> +   (('bcsel', ('ige', ('ifind_msb', a), 0), ('ifind_msb', a), -1), ('ifind_msb', a)),
> +   (('bcsel', ('ige', ('ufind_msb', a), 0), ('ufind_msb', a), -1), ('ufind_msb', a)),
> +
> +   (('bcsel', ('ine', a, 0), ('find_lsb', a), -1), ('find_lsb', a)),
> +   (('bcsel', ('ine', a, 0), ('ifind_msb', a), -1), ('ifind_msb', a)),
> +   (('bcsel', ('ine', a, 0), ('ufind_msb', a), -1), ('ufind_msb', a)),
> +
> +   (('bcsel', ('ine', a, -1), ('ifind_msb', a), -1), ('ifind_msb', a)),
> +
>     # Misc. lowering
>     (('fmod at 32', a, b), ('fsub', a, ('fmul', b, ('ffloor', ('fdiv', a, b)))), 'options->lower_fmod32'),
>     (('fmod at 64', a, b), ('fsub', a, ('fmul', b, ('ffloor', ('fdiv', a, b)))), 'options->lower_fmod64'),
> --
> 2.13.0
>
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