nir: Recognize open-coded extract_u16.

No shader-db changes, but does recognize some extract_u16 which enables
the next patch to optimize some code.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index dd26805e1a87aafe6c4a0de6f2a64c760180c553..39be85f639e8372f64c238217dd8f160463661ca 100644 (file)
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -163,6 +163,7 @@ optimizations = [
    (('ushr', 0, a), 0),
    (('ushr', a, 0), a),
    (('iand', 0xff, ('ushr', a, 24)), ('ushr', a, 24)),
+   (('iand', 0xffff, ('ushr', a, 16)), ('ushr', a, 16)),
    # Exponential/logarithmic identities
    (('fexp2', ('flog2', a)), a), # 2^lg2(a) = a
    (('flog2', ('fexp2', a)), a), # lg2(2^a) = a
@@ -220,6 +221,10 @@ optimizations = [
    (('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', a, 16), ('extract_u16', a, 1), '!options->lower_extract_word'),
+   (('iand', 0xffff, a), ('extract_u16', a, 0), '!options->lower_extract_word'),
+
    # Subtracts
    (('fsub', a, ('fsub', 0.0, b)), ('fadd', a, b)),
    (('isub', a, ('isub', 0, b)), ('iadd', a, b)),