This adds the "(a << N) >> M" family of mask or sign-extensions. Not a
huge win right now but this pattern will soon be generated by NIR format
lowering code.
Shader-db results on Kaby Lake:
total instructions in shared programs: 15166918 -> 15166916 (<.01%)
instructions in affected programs: 36 -> 34 (-5.56%)
helped: 2
HURT: 0
---
src/compiler/nir/nir_opt_algebraic.py | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/src/compiler/nir/nir_opt_algebraic.py
b/src/compiler/nir/nir_opt_algebraic.py
index 28090d069cd..07fbb161a4e 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -543,13 +543,23 @@ optimizations = [
('unpack_64_2x32_split_y', a)), a),
# Byte extraction
+ (('ushr', ('ishl', 'a@32', 24), 24), ('extract_u8', a, 0),
'!options->lower_extract_byte'),
+ (('ushr', ('ishl', 'a@32', 16), 24), ('extract_u8', a, 1),
'!options->lower_extract_byte'),
+ (('ushr', ('ishl', 'a@32', 8), 24), ('extract_u8', a, 2),
'!options->lower_extract_byte'),
(('ushr', 'a@32', 24), ('extract_u8', a, 3),
'!options->lower_extract_byte'),
+ (('ishr', ('ishl', 'a@32', 24), 24), ('extract_i8', a, 0),
'!options->lower_extract_byte'),
+ (('ishr', ('ishl', 'a@32', 16), 24), ('extract_i8', a, 1),
'!options->lower_extract_byte'),
+ (('ishr', ('ishl', 'a@32', 8), 24), ('extract_i8', a, 2),
'!options->lower_extract_byte'),
+ (('ishr', 'a@32', 24), ('extract_i8', a, 3),
'!options->lower_extract_byte'),
(('iand', 0xff, ('ushr', a, 16)), ('extract_u8', a, 2),
'!options->lower_extract_byte'),
(('iand', 0xff, ('ushr', a, 8)), ('extract_u8', a, 1),
'!options->lower_extract_byte'),
(('iand', 0xff, a), ('extract_u8', a, 0), '!options->lower_extract_byte'),
# Word extraction
+ (('ushr', ('ishl', 'a@16', 16), 16), ('extract_u16', a, 0),
'!options->lower_extract_word'),
(('ushr', 'a@16', 16), ('extract_u16', a, 1),
'!options->lower_extract_word'),
+ (('ishr', ('ishl', 'a@16', 16), 16), ('extract_i16', a, 0),
'!options->lower_extract_word'),
+ (('ishr', 'a@16', 16), ('extract_i16', a, 1),
'!options->lower_extract_word'),
(('iand', 0xffff, a), ('extract_u16', a, 0),
'!options->lower_extract_word'),
# Subtracts
--
2.17.1
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