Mesa (master): nir: do not use De Morgan's Law rules for flt and fge

[GitLab Mirror]

Module: Mesa
Branch: master
Commit: 8e7728077435c5c5ad8c328761277f8ff3b32112
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=8e7728077435c5c5ad8c328761277f8ff3b32112

Author: Samuel Pitoiset <samuel.pitoiset at gmail.com>
Date:   Tue Feb  4 17:25:35 2020 +0100

nir: do not use De Morgan's Law rules for flt and fge

In presence of NaNs, "!(flt(a, b) && flt(c, d))" is NOT EQUAL
to "fge(a, b) || fge(c, d)". These optimizations are unsafe for
apps that rely on NaN behaviour.

pipeline-db (GFX9/LLVM):
Totals from affected shaders:
SGPRS: 3176 -> 3136 (-1.26 %)
VGPRS: 2188 -> 2144 (-2.01 %)
Spilled SGPRs: 227 -> 169 (-25.55 %)
Code Size: 150572 -> 151800 (0.82 %) bytes
Max Waves: 307 -> 310 (0.98 %)

pipeline-db (GFX9/ACO):
Totals from affected shaders:
SGPRS: 18744 -> 18744 (0.00 %)
VGPRS: 15576 -> 15580 (0.03 %)
Spilled SGPRs: 164 -> 164 (0.00 %)
Code Size: 1573012 -> 1576492 (0.22 %) bytes
Max Waves: 1534 -> 1532 (-0.13 %)

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2127
Fixes: d1ed4ffe0b7 ("nir: Use De Morgan's Law on logic compounded comparisons")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3696>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3696>

---

 src/compiler/nir/nir_opt_algebraic.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index f9fc119505f..904b02e0309 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -1279,7 +1279,7 @@ for bit_size in [8, 16, 32, 64]:
                                 ('bcsel', ('ilt', a, ('isub', a, b)), intmin, ('isub', a, b))), 'options->lower_add_sat'),
    ]
 
-invert = OrderedDict([('feq', 'fne'), ('fne', 'feq'), ('fge', 'flt'), ('flt', 'fge')])
+invert = OrderedDict([('feq', 'fne'), ('fne', 'feq')])
 
 for left, right in itertools.combinations_with_replacement(invert.keys(), 2):
    optimizations.append((('inot', ('ior(is_used_once)', (left, a, b), (right, c, d))),