ufind_msb is easily expressed in terms of clz, and we can reduce ifind_msb
to that.
---
src/compiler/nir/nir.h | 2 ++
src/compiler/nir/nir_opt_algebraic.py | 4 ++++
2 files changed, 6 insertions(+)
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index ee1d59ffe7cd..ee45b0709636 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1889,6 +1889,8 @@ typedef struct nir_shader_compiler_options {
bool lower_bitfield_insert_to_shifts;
/** Lowers bfm to shifts and subtracts. */
bool lower_bfm;
+ /** Lowers ifind_msb to compare and ufind_msb */
+ bool lower_ifind_msb;
bool lower_uadd_carry;
bool lower_usub_borrow;
/** lowers fneg and ineg to fsub and isub. */
diff --git a/src/compiler/nir/nir_opt_algebraic.py
b/src/compiler/nir/nir_opt_algebraic.py
index cb0ea5549169..616f734ac9b2 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -532,6 +532,10 @@ optimizations = [
('bfm', 'bits', 0))),
'options->lower_bitfield_extract_to_shifts'),
+ (('ifind_msb', 'value'),
+ ('ufind_msb', ('bcsel', ('ilt', 'value', 0), ('inot', 'value'), 'value')),
+ 'options->lower_ifind_msb'),
+
(('extract_i8', a, 'b@32'),
('ishr', ('ishl', a, ('imul', ('isub', 3, b), 8)), 24),
'options->lower_extract_byte'),
--
2.17.0
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