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nir/opt_algebraic: add fmad and ffma_weak lowering rules

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Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41165>
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Karol Herbst 2026-04-20 04:03:02 +02:00 • committed by Marge Bot
parent 9ffa7c826f
commit bb2b7c58fc
1 changed files with 22 additions and 0 deletions
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22
src/compiler/nir/nir_opt_algebraic.py
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@ -414,6 +414,28 @@ optimizations += [
('fexp2', ('fmulz', a, 'mb'))), {'mb': b}),
]
# float multadd related rules
for sz in (16, 32, 64):
has_ffma = f'(options->float_mul_add{sz} & nir_float_muladd_support_has_ffma)'
has_fmad = f'(options->float_mul_add{sz} & nir_float_muladd_support_has_fmad)'
has_none = f'(!options->float_mul_add{sz})'
prefers_split = f'(options->float_mul_add{sz} & nir_float_muladd_support_prefers_split)'
keep_ffma_weak = f'(options->float_mul_add{sz} & nir_float_muladd_support_keep_weak_ffma)'
optimizations += [
# Split contract ffma_weak for better optimizations. It will be refused later.
((f'ffma_weak@{sz}(contract)', a, b, c), ('fadd', ('fmul', a, b), c), f'!{keep_ffma_weak}'),
# Convert ffma_weak to backend supported ops
((f'ffma_weak@{sz}', a, b, c), ('ffma', a, b, c), f'!{keep_ffma_weak} && !{prefers_split} && {has_ffma}'),
((f'ffma_weak@{sz}', a, b, c), ('fadd', ('fmul', a, b), c), f'!{keep_ffma_weak} && ({prefers_split} || {has_fmad} || {has_none})'),
]
optimizations += [
# Split fmad better for optimizations. It might get merged to fmad later.
(('fmad', a, b, c), ('fadd', ('fmul', a, b), c)),
(('fmadz', a, b, c), ('fadd', ('fmulz', a, b), c)),
]
# Bitwise operations affecting the sign may be replaced by equivalent
# floating point operations, except possibly for denormal
# behaviour hence the is_only_used_as_float.