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spirv: Add bfloat16 support to SpecConstantOp

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Handle bfloat16 by converting sources to float, performing the
operation, and converting result back to bfloat16 if needed.  This is
done because not all ALU ops have a `bf` version in NIR.

Reviewed-by: Rohan Garg <rohan.garg@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Georg Lehmann <dadschoorse@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34105>
This commit is contained in:
Caio Oliveira 2025-03-19 09:12:38 -07:00 • committed by Marge Bot
parent dc8074683d
commit 90e1b12890
1 changed files with 27 additions and 3 deletions
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30
src/compiler/spirv/spirv_to_nir.c
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@ -40,6 +40,7 @@
#include "util/u_debug.h"
#include "util/u_printf.h"
#include "util/mesa-blake3.h"
#include "util/bfloat.h"
#include <stdio.h>
@ -2697,6 +2698,12 @@ vtn_handle_constant(struct vtn_builder *b, SpvOp opcode,
const glsl_type *dst_type = val->type->type;
const glsl_type *src_type = dst_type;
const bool bfloat_dst = glsl_type_is_bfloat_16(dst_type);
bool bfloat_src = bfloat_dst;
if (bfloat_dst)
dst_type = glsl_float_type();
unsigned num_components = glsl_get_vector_elements(val->type->type);
vtn_assert(count <= 7);
@ -2704,10 +2711,14 @@ vtn_handle_constant(struct vtn_builder *b, SpvOp opcode,
switch (opcode) {
case SpvOpSConvert:
case SpvOpFConvert:
case SpvOpUConvert:
case SpvOpUConvert: {
/* We have a different source type in a conversion. */
src_type = vtn_get_value_type(b, w[4])->type;
bfloat_src = glsl_type_is_bfloat_16(src_type);
if (bfloat_src)
src_type = glsl_float_type();
break;
}
default:
break;
};
@ -2721,7 +2732,7 @@ vtn_handle_constant(struct vtn_builder *b, SpvOp opcode,
*/
assert(!exact);
unsigned bit_size = glsl_get_bit_size(val->type->type);
unsigned bit_size = glsl_get_bit_size(src_type);
nir_const_value src[3][NIR_MAX_VEC_COMPONENTS];
for (unsigned i = 0; i < count - 4; i++) {
@ -2739,8 +2750,11 @@ vtn_handle_constant(struct vtn_builder *b, SpvOp opcode,
num_components;
unsigned j = swap ? 1 - i : i;
for (unsigned c = 0; c < src_comps; c++)
for (unsigned c = 0; c < src_comps; c++) {
src[j][c] = src_val->constant->values[c];
if (bfloat_src)
src[j][c].f32 = _mesa_bfloat16_bits_to_float(src[j][c].u16);
}
}
/* fix up fixed size sources */
@ -2769,6 +2783,16 @@ vtn_handle_constant(struct vtn_builder *b, SpvOp opcode,
nir_eval_const_opcode(op, val->constant->values,
num_components, bit_size, srcs,
b->shader->info.float_controls_execution_mode);
if (bfloat_dst) {
for (int i = 0; i < num_components; i++) {
/* Ensure the pad bits are zeroed by fully assigning the value. */
const uint16_t b =
_mesa_float_to_bfloat16_bits_rte(val->constant->values[i].f32);
val->constant->values[i] = (nir_const_value){ .u16 = b };
}
}
break;
} /* default */
}