nir/algebraic: optimize (a < 0.0) ? -a : a -> fabs(a)

Totals from affected shaders: (VEGA)
SGPRS: 13920 -> 13920 (0.00 %)
VGPRS: 10252 -> 10252 (0.00 %)
Spilled SGPRs: 62 -> 62 (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: 587648 -> 587224 (-0.07 %) bytes
LDS: 5 -> 5 (0.00 %) blocks
Max Waves: 1489 -> 1489 (0.00 %)

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4830>

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index bd84966821acb8dfd8ec1d9e6447ed1be50f0746..bd0da989c9ea9be87104b9f10b3b8941366dbb0b 100644 (file)
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -1136,6 +1136,7 @@ optimizations.extend([
 
    (('~fmul', ('bcsel(is_used_once)', c, -1.0, 1.0), b), ('bcsel', c, ('fneg', b), b)),
    (('~fmul', ('bcsel(is_used_once)', c, 1.0, -1.0), b), ('bcsel', c, b, ('fneg', b))),
+   (('~bcsel', ('flt', a, 0.0), ('fneg', a), a), ('fabs', a)),
 
    (('fmin3@64', a, b, c), ('fmin@64', a, ('fmin@64', b, c))),
    (('fmax3@64', a, b, c), ('fmax@64', a, ('fmax@64', b, c))),