[Mesa-dev] [PATCH 1/2] nir: Add optimization for (a || True == True)

[Erik Faye-Lund]

On Thu, Jul 7, 2016 at 2:12 AM, Eric Anholt <eric at anholt.net> wrote:
> This was appearing in vc4 VS/CS in mupen64, due to vertex attrib lowering
> producing some constants that were getting compared.
>
> total instructions in shared programs: 112276 -> 112198 (-0.07%)
> instructions in affected programs:     2239 -> 2161 (-3.48%)
> total estimated cycles in shared programs: 283102 -> 283038 (-0.02%)
> estimated cycles in affected programs:     2365 -> 2301 (-2.71%)
> ---
>  src/compiler/nir/nir_opt_algebraic.py | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
> index fd228017c54e..7d04ef941b73 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -197,6 +197,7 @@ optimizations = [
>     (('iand', a, 0), 0),
>     (('ior', a, a), a),
>     (('ior', a, 0), a),
> +   (('ior', a, True), True),

Is it guaranteed that evaluating 'a' doesn't have side-effects at this point?