[Mesa-dev] [PATCH 02/22] nir/algebraic: Add more extract_[iu](8|16) optimizations

[Jason Ekstrand]

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 at 32', 24), 24), ('extract_u8', a, 0), '!options->lower_extract_byte'),
+   (('ushr', ('ishl', 'a at 32', 16), 24), ('extract_u8', a, 1), '!options->lower_extract_byte'),
+   (('ushr', ('ishl', 'a at 32', 8), 24), ('extract_u8', a, 2), '!options->lower_extract_byte'),
    (('ushr', 'a at 32', 24), ('extract_u8', a, 3), '!options->lower_extract_byte'),
+   (('ishr', ('ishl', 'a at 32', 24), 24), ('extract_i8', a, 0), '!options->lower_extract_byte'),
+   (('ishr', ('ishl', 'a at 32', 16), 24), ('extract_i8', a, 1), '!options->lower_extract_byte'),
+   (('ishr', ('ishl', 'a at 32', 8), 24), ('extract_i8', a, 2), '!options->lower_extract_byte'),
+   (('ishr', 'a at 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 at 16', 16), 16), ('extract_u16', a, 0), '!options->lower_extract_word'),
    (('ushr', 'a at 16', 16), ('extract_u16', a, 1), '!options->lower_extract_word'),
+   (('ishr', ('ishl', 'a at 16', 16), 16), ('extract_i16', a, 0), '!options->lower_extract_word'),
+   (('ishr', 'a at 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