Module: Mesa
Branch: master
Commit: d4c7c3c225b7c34669498c15c2d3186cf6a4647e
URL:
http://cgit.freedesktop.org/mesa/mesa/commit/?id=d4c7c3c225b7c34669498c15c2d3186cf6a4647e
Author: Eric Anholt <e...@anholt.net>
Date: Fri May 4 13:33:47 2018 -0700
nir: Add lowering for ifind_msb to ufind_msb.
ufind_msb is easily expressed in terms of clz, and we can reduce ifind_msb
to that.
Reviewed-by: Matt Turner <matts...@gmail.com>
Reviewed-by: Ian Romanick <ian.d.roman...@intel.com>
---
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 519c019887..9fca61f007 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1913,6 +1913,8 @@ 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 eaa8b14164..f6685977f3 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -555,6 +555,10 @@ 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'),
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