Re: [Mesa-dev] [RFC PATCH] nir/algebraic: Simplify max(abs(a), 0.0) -> abs(a)
On Fri, May 24, 2019 at 2:46 PM Alyssa Rosenzweig wrote: > > > I /think/ that should be adequate here too. > > Do inexact values not need to handle NaNs strictly, then? I'm not sure > what this corresponds to in the various GLs/CLs/Vulkan specs, hence > labeling this RFC. I don't know about Vulkan, but GL has a very childish approach to NaN's -- you can pretty much do whatever and be in-spec. Applications fall into two categories -- ones that expect NaN's and carefully deal with them (maybe DX10, definitely DX11+), and ones that are from a time before NaN on GPUs existed (DX9 and earlier). I'm generally a lot less concerned about inexact opts that remove NaN's (e.g. a - a -> 0, but Inf - Inf = NaN, or a * 0 -> 0, but Inf * 0 = NaN) than ones that add NaN's such as this one. I don't have a specific example, but I can well imagine an application that would expect this to have cleared out any NaN's, and you'll suddenly remove their op. But I also see the benefit of doing it since 99.9% of the time it's perfectly safe :) -ilia ___ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
Re: [Mesa-dev] [RFC PATCH] nir/algebraic: Simplify max(abs(a), 0.0) -> abs(a)
> I /think/ that should be adequate here too. Do inexact values not need to handle NaNs strictly, then? I'm not sure what this corresponds to in the various GLs/CLs/Vulkan specs, hence labeling this RFC. ___ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
Re: [Mesa-dev] [RFC PATCH] nir/algebraic: Simplify max(abs(a), 0.0) -> abs(a)
On 5/23/19 7:54 PM, Ilia Mirkin wrote:
> How does max(NaN, 0) work? IIRC there's some provision that this
> becomes 0, while abs(NaN) = NaN.
That is correct. There are a couple other algebraic patterns that have
the same potential problem (e.g., the min(max()) -> sat() patterns), and
we just make those as imprecise with ~. I /think/ that should be
adequate here too.
> On Thu, May 23, 2019 at 10:47 PM Alyssa Rosenzweig
> wrote:
>>
>> I noticed this pattern in glmark's jellyfish scene.
>>
>> Assuming this is correct (it should be...?), could someone do a
>> shader-db run? Thank you!
>>
>> Signed-off-by: Alyssa Rosenzweig
>> Cc: Ian Romanick
>> ---
>> 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 89d07aa1261..abd0b6591ce 100644
>> --- a/src/compiler/nir/nir_opt_algebraic.py
>> +++ b/src/compiler/nir/nir_opt_algebraic.py
>> @@ -377,6 +377,7 @@ optimizations = [
>> (('imax', a, a), a),
>> (('umin', a, a), a),
>> (('umax', a, a), a),
>> + (('fmax', ('fabs', a), 0.0), ('fabs', a)),
>> (('fmax', ('fmax', a, b), b), ('fmax', a, b)),
>> (('umax', ('umax', a, b), b), ('umax', a, b)),
>> (('imax', ('imax', a, b), b), ('imax', a, b)),
>> --
>> 2.20.1
>>
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>
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Re: [Mesa-dev] [RFC PATCH] nir/algebraic: Simplify max(abs(a), 0.0) -> abs(a)
On Thu, May 23, 2019 at 10:54:38PM -0400, Ilia Mirkin wrote:
> How does max(NaN, 0) work? IIRC there's some provision that this
> becomes 0, while abs(NaN) = NaN.
Yes max(NaN, 0) should return 0.
At least it's what we do with i965.
See
https://gitlab.freedesktop.org/mesa/mesa/blob/a42163cbbc1abe02b7db4ade74b569f455942d1a/src/compiler/glsl/float64.glsl#L1739
>
> On Thu, May 23, 2019 at 10:47 PM Alyssa Rosenzweig
> wrote:
> >
> > I noticed this pattern in glmark's jellyfish scene.
> >
> > Assuming this is correct (it should be...?), could someone do a
> > shader-db run? Thank you!
> >
> > Signed-off-by: Alyssa Rosenzweig
> > Cc: Ian Romanick
> > ---
> > 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 89d07aa1261..abd0b6591ce 100644
> > --- a/src/compiler/nir/nir_opt_algebraic.py
> > +++ b/src/compiler/nir/nir_opt_algebraic.py
> > @@ -377,6 +377,7 @@ optimizations = [
> > (('imax', a, a), a),
> > (('umin', a, a), a),
> > (('umax', a, a), a),
> > + (('fmax', ('fabs', a), 0.0), ('fabs', a)),
> > (('fmax', ('fmax', a, b), b), ('fmax', a, b)),
> > (('umax', ('umax', a, b), b), ('umax', a, b)),
> > (('imax', ('imax', a, b), b), ('imax', a, b)),
> > --
> > 2.20.1
> >
> > ___
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Re: [Mesa-dev] [RFC PATCH] nir/algebraic: Simplify max(abs(a), 0.0) -> abs(a)
How does max(NaN, 0) work? IIRC there's some provision that this
becomes 0, while abs(NaN) = NaN.
On Thu, May 23, 2019 at 10:47 PM Alyssa Rosenzweig wrote:
>
> I noticed this pattern in glmark's jellyfish scene.
>
> Assuming this is correct (it should be...?), could someone do a
> shader-db run? Thank you!
>
> Signed-off-by: Alyssa Rosenzweig
> Cc: Ian Romanick
> ---
> 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 89d07aa1261..abd0b6591ce 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -377,6 +377,7 @@ optimizations = [
> (('imax', a, a), a),
> (('umin', a, a), a),
> (('umax', a, a), a),
> + (('fmax', ('fabs', a), 0.0), ('fabs', a)),
> (('fmax', ('fmax', a, b), b), ('fmax', a, b)),
> (('umax', ('umax', a, b), b), ('umax', a, b)),
> (('imax', ('imax', a, b), b), ('imax', a, b)),
> --
> 2.20.1
>
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[Mesa-dev] [RFC PATCH] nir/algebraic: Simplify max(abs(a), 0.0) -> abs(a)
I noticed this pattern in glmark's jellyfish scene.
Assuming this is correct (it should be...?), could someone do a
shader-db run? Thank you!
Signed-off-by: Alyssa Rosenzweig
Cc: Ian Romanick
---
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 89d07aa1261..abd0b6591ce 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -377,6 +377,7 @@ optimizations = [
(('imax', a, a), a),
(('umin', a, a), a),
(('umax', a, a), a),
+ (('fmax', ('fabs', a), 0.0), ('fabs', a)),
(('fmax', ('fmax', a, b), b), ('fmax', a, b)),
(('umax', ('umax', a, b), b), ('umax', a, b)),
(('imax', ('imax', a, b), b), ('imax', a, b)),
--
2.20.1
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