Re: [Mesa-dev] [PATCH 1/2] nir: optimize min(min(a, b), c) to min3(a, b, c) under an option

[Samuel Pitoiset]

On 05/31/2018 11:25 AM, Bas Nieuwenhuizen wrote:

On Thu, May 31, 2018 at 11:13 AM, Samuel Pitoiset
<samuel.pitoi...@gmail.com> wrote:

On 05/31/2018 01:55 AM, Timothy Arceri wrote:

On 31/05/18 03:06, Samuel Pitoiset wrote:

Similar for max().

Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com>
---
   src/compiler/nir/nir.h                | 3 +++
   src/compiler/nir/nir_opt_algebraic.py | 8 ++++++++
   2 files changed, 11 insertions(+)

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index f6086bd6c0..04991b7d04 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1897,6 +1897,9 @@ typedef struct nir_shader_compiler_options {
      /* lower b2f to iand */
      bool lower_b2f;
+   /* lower min(min(a, b), c) to min3(a, b, c) (same for max()). */
+   bool lower_minmax3;
+
      /* Does the native fdot instruction replicate its result for four
       * components?  If so, then opt_algebraic_late will turn all fdotN
       * instructions into fdot_replicatedN instructions.
diff --git a/src/compiler/nir/nir_opt_algebraic.py
b/src/compiler/nir/nir_opt_algebraic.py
index 909ea3daf4..1d67e2d88c 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -224,6 +224,14 @@ optimizations = [
      (('imax', a, a), a),
      (('umin', a, a), a),
      (('umax', a, a), a),
+
+   (('fmin', ('fmin', a, b), c), ('fmin3', a, b, c),
'options->lower_minmax3'),
+   (('imin', ('imin', a, b), c), ('imin3', a, b, c),
'options->lower_minmax3'),
+   (('umin', ('umin', a, b), c), ('umin3', a, b, c),
'options->lower_minmax3'),
+   (('fmax', ('fmax', a, b), c), ('fmax3', a, b, c),
'options->lower_minmax3'),
+   (('imax', ('imax', a, b), c), ('imax3', a, b, c),
'options->lower_minmax3'),
+   (('umax', ('umax', a, b), c), ('umax3', a, b, c),
'options->lower_minmax3'),

These look like they would be better suited in late_optimizations rather
than optimizations?

Totals from affected shaders:
SGPRS: 104 -> 104 (0.00 %)
VGPRS: 64 -> 64 (0.00 %)
Spilled SGPRs: 0 -> 0 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 0 -> 0 (0.00 %) dwords per thread
Code Size: 4652 -> 4644 (-0.17 %) bytes
LDS: 4 -> 4 (0.00 %) blocks
Max Waves: 24 -> 24 (0.00 %)
Wait states: 0 -> 0 (0.00 %)

When moved to late_optimizations.

Is that compared to no min3/max3 lowering at all or compared to doing
those non-late?

Compared to "default" for both.

+
      (('fmin', a, ('fneg', a)), ('fneg', ('fabs', a))),
      (('imin', a, ('ineg', a)), ('ineg', ('iabs', a))),
      (('fmin', a, ('fneg', ('fabs', a))), ('fneg', ('fabs', a))),

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