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nir/opt_algebraic: optimize fadd/fmul with 16-bit source and constant

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Signed-off-by: Lorenzo Rossi <lorenzo.rossi@collabora.com>
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41096>
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Lorenzo Rossi 2026-04-21 19:11:49 +02:00 • committed by Marge Bot
parent 89436db611
commit 2a7d817591
2 changed files with 25 additions and 0 deletions
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5
src/compiler/nir/nir_opt_algebraic.py
View file

@ -1941,6 +1941,11 @@ optimizations.extend([
(('f2u32', ('f2fmp', 'a@32')), ('f2u32', a), 'true', TestStatus.UNSUPPORTED),
(('i2f32', ('i2imp', 'a@32')), ('i2f32', a), 'true', TestStatus.UNSUPPORTED),
# f16 -> f2f32 -> fmul32 -> f2fmp when the second operand is a constant
# The optimization only works when the constant can be safely represented with 16 bits
(('f2fmp', ('fmul(is_used_once,contract)', ('f2f32', 'a@16'), '#b(is_representable_as_f16)')), ('fmul', a, ('f2fmp', b)), 'true', TestStatus.UNSUPPORTED),
(('f2fmp', ('fadd(is_used_once,contract)', ('f2f32', 'a@16'), '#b(is_representable_as_f16)')), ('fadd', a, ('f2fmp', b)), 'true', TestStatus.UNSUPPORTED),
(('ffloor', 'a(is_integral)'), a),
(('fceil', 'a(is_integral)'), a),
(('ftrunc', 'a(is_integral)'), a),

20
src/compiler/nir/nir_search_helpers.h
View file

@ -30,6 +30,7 @@
#include <math.h>
#include "util/bitscan.h"
#include "util/u_math.h"
#include "util/half_float.h"
#include "nir.h"
#include "nir_range_analysis.h"
#include "nir_search.h"
@ -355,6 +356,25 @@ is_neg2x_16_bits(UNUSED const nir_search_state *state, const nir_alu_instr *inst
return is_16_bits_with_scale(instr, src, num_components, swizzle, -2);
}
/** Is this a float constant that could fit in a half? */
static inline bool
is_representable_as_f16(UNUSED const nir_search_state *state,
const nir_alu_instr *instr,
unsigned src, unsigned num_components,
const uint8_t *swizzle)
{
/* only constant srcs: */
if (!nir_src_is_const(instr->src[src].src))
return false;
for (unsigned i = 0; i < num_components; i++) {
double value = nir_src_comp_as_float(instr->src[src].src, swizzle[i]);
if (!_mesa_float_is_half(value))
return false;
}
return true;
}
static inline bool
is_not_const(UNUSED const nir_search_state *state, const nir_alu_instr *instr,
unsigned src, UNUSED unsigned num_components,