[Mesa-dev] [PATCH 5/8] nir: Add addition/multiplication identities of exp/log.

[Eric Anholt]

Matt Turner <mattst88 at gmail.com> writes:

> instructions in affected programs:     2858 -> 2808 (-1.75%)
> helped:                                12
> ---
>  src/glsl/nir/nir_opt_algebraic.py | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/src/glsl/nir/nir_opt_algebraic.py b/src/glsl/nir/nir_opt_algebraic.py
> index 6730408..34a401a 100644
> --- a/src/glsl/nir/nir_opt_algebraic.py
> +++ b/src/glsl/nir/nir_opt_algebraic.py
> @@ -149,6 +149,14 @@ optimizations = [
>     (('flog', ('frsq', a)), ('fmul', -0.5, ('flog', a))),
>     (('flog2', ('fpow', a, b)), ('fmul', b, ('flog2', a))),
>     (('flog', ('fpow', a, b)), ('fmul', b, ('flog', a))),
> +   (('fadd', ('flog2', a), ('flog2', b)), ('flog2', ('fmul', a, b))),
> +   (('fadd', ('flog', a), ('flog', b)), ('flog', ('fmul', a, b))),
> +   (('fadd', ('flog2', a), ('fneg', ('flog2', b))), ('flog2', ('fdiv', a, b))),
> +   (('fadd', ('flog', a), ('fneg', ('flog', b))), ('flog', ('fdiv', a, b))),

> +   (('fmul', ('fexp2', a), ('fexp2', a)), ('fmul', 2.0, ('fexp2', a))),
> +   (('fmul', ('fexp', a), ('fexp', a)), ('fmul', 2.0, ('fexp', a))),


e^a * e^a -> 2 * e^a?  This doesn't seem right.  And something specific
to this doesn't seem particularly better than the general case below.

> +   (('fmul', ('fexp2', a), ('fexp2', b)), ('fexp2', ('fadd', a, b))),
> +   (('fmul', ('fexp', a), ('fexp', b)), ('fexp', ('fadd', a, b))),
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 818 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20150327/9a4f7d22/attachment.sig>