[Mesa-dev] [PATCH 2/5] nir: Recognize sum of open-coded pow()s.

[Jason Ekstrand]

On Thu, Feb 4, 2016 at 5:47 PM, Matt Turner <mattst88 at gmail.com> wrote:

> Prevents regressions in the next commit.
> ---
>  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 60df69f..0a248a2 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -167,6 +167,7 @@ optimizations = [
>     (('flog2', ('fexp2', a)), a), # lg2(2^a) = a
>     (('fpow', a, b), ('fexp2', ('fmul', ('flog2', a), b)),
> 'options->lower_fpow'), # a^b = 2^(lg2(a)*b)
>     (('fexp2', ('fmul', ('flog2', a), b)), ('fpow', a, b),
> '!options->lower_fpow'), # 2^(lg2(a)*b) = a^b
> +   (('fexp2', ('fadd', ('fmul', ('flog2', a), b), ('fmul', ('flog2', c),
> d))), ('fadd', ('fpow', a, b), ('fpow', c, d))),
>

I think you mean ('fmul', ('fpow', a, b), ('fpow', c, d)).  You can't pull
an add out of an exp and get another add.


>     (('fpow', a, 1.0), a),
>     (('fpow', a, 2.0), ('fmul', a, a)),
>     (('fpow', a, 4.0), ('fmul', ('fmul', a, a), ('fmul', a, a))),
> --
> 2.4.10
>
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