In addition to the familiar iand/ior/ixor, some architectures feature
destination-inverted versions inand/inor/inxor. Certain
architectures also have source-inverted forms, dubbed iandnot/iornot
here. Midgard has the all of these opcodes natively. Many arches have
comparible features to implement some/all of the above. Paired with De
Morgan's Laws, these opcodes allow anything of the form
"~? (~?a [&|] ~?b)" to complete in one instruction.
This can be used to simplify some backend-specific code on affected
architectures, e.f. 8eb36c91 ("intel/fs: Emit logical-not of operands on
Gen8+").
Signed-off-by: Alyssa Rosenzweig <aly...@rosenzweig.io>
Cc: Ian Romanick <ian.d.roman...@intel.com>
Cc: Kenneth Graunke <kenn...@whitecape.org>
---
src/compiler/nir/nir.h | 4 ++++
src/compiler/nir/nir_opcodes.py | 18 ++++++++++++++++++
src/compiler/nir/nir_opt_algebraic.py | 12 ++++++++++++
3 files changed, 34 insertions(+)
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index e878a63409d..3e01ec2cc06 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2318,6 +2318,10 @@ typedef struct nir_shader_compiler_options {
bool lower_hadd;
bool lower_add_sat;
+ /* Set if inand/inor/inxor and iandnot/iornot supported respectively */
+ bool bitwise_dest_invertable;
+ bool bitwise_src_invertable;
+
/**
* Should nir_lower_io() create load_interpolated_input intrinsics?
*
diff --git a/src/compiler/nir/nir_opcodes.py b/src/compiler/nir/nir_opcodes.py
index d35d820aa5b..f9d92afb53e 100644
--- a/src/compiler/nir/nir_opcodes.py
+++ b/src/compiler/nir/nir_opcodes.py
@@ -690,6 +690,24 @@ binop("iand", tuint, commutative + associative, "src0 &
src1")
binop("ior", tuint, commutative + associative, "src0 | src1")
binop("ixor", tuint, commutative + associative, "src0 ^ src1")
+# inverted bitwise logic operators
+#
+# These variants of the above include bitwise NOTs either on the result of the
+# whole expression or on the latter operand. On some hardware (e.g. Midgard),
+# these are native ops. On other hardware (e.g. Intel Gen8+), these can be
+# implemented as modifiers of the standard three. Along with appropriate
+# algebraic passes, these should permit any permutation of inverses on AND/OR
+# to execute in a single cycle. For example, ~(a & ~b) = ~(~(~a | ~(~b))) = ~a
+# | b = b | ~a = iornot(b, a).
+
+binop("inand", tuint, commutative, "~(src0 & src1)")
+binop("inor", tuint, commutative, "~(src0 | src1)")
+binop("inxor", tuint, commutative, "~(src0 ^ src1)")
+binop("iandnot", tuint, "", "src0 & (~src1)")
+binop("iornot", tuint, "", "src0 & (~src1)")
+
+
+
# floating point logic operators
#
diff --git a/src/compiler/nir/nir_opt_algebraic.py
b/src/compiler/nir/nir_opt_algebraic.py
index dad0545594f..6cb3e8cb950 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -1052,6 +1052,18 @@ late_optimizations = [
(('fmax', ('fadd(is_used_once)', '#c', a), ('fadd(is_used_once)', '#c',
b)), ('fadd', c, ('fmax', a, b))),
(('bcsel', a, 0, ('b2f32', ('inot', 'b@bool'))), ('b2f32', ('inot', ('ior',
a, b)))),
+
+ # We don't want to deal with inverted forms, so run this late. Any
+ # combination of inverts on flags or output should result in a single
+ # instruction if these are supported; cases not explicitly handled would
+ # have been simplified via De Morgan's Law
+ (('inot', ('iand', a, b)), ('inand', a, b),
'options->bitwise_dest_invertable'),
+ (('inot', ('ior', a, b)), ('inor', a, b),
'options->bitwise_dest_invertable'),
+ (('inot', ('ixor', a, b)), ('inxor', a, b),
'options->bitwise_dest_invertable'),
+ (('iand', ('inot', a), b), ('iandnot', b, a),
'options->bitwise_src_invertable'),
+ (('iand', a, ('inot', b)), ('iandnot', a, b),
'options->bitwise_src_invertable'),
+ (('ior', a, ('inot', b)), ('iornot', a, b),
'options->bitwise_src_invertable'),
+ (('ior', ('inot', a), b), ('iornot', b, a),
'options->bitwise_src_invertable'),
]
print(nir_algebraic.AlgebraicPass("nir_opt_algebraic", optimizations).render())
--
2.20.1
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