mesa/src/compiler/nir/nir_lower_subgroups.c

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/*
* Copyright © 2017 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "nir.h"
#include "nir_builder.h"
/**
* \file nir_opt_intrinsics.c
*/
static nir_intrinsic_instr *
lower_subgroups_64bit_split_intrinsic(nir_builder *b, nir_intrinsic_instr *intrin,
unsigned int component)
{
nir_ssa_def *comp;
if (component == 0)
comp = nir_unpack_64_2x32_split_x(b, intrin->src[0].ssa);
else
comp = nir_unpack_64_2x32_split_y(b, intrin->src[0].ssa);
nir_intrinsic_instr *intr = nir_intrinsic_instr_create(b->shader, intrin->intrinsic);
nir_ssa_dest_init(&intr->instr, &intr->dest, 1, 32, NULL);
intr->const_index[0] = intrin->const_index[0];
intr->const_index[1] = intrin->const_index[1];
intr->src[0] = nir_src_for_ssa(comp);
if (nir_intrinsic_infos[intrin->intrinsic].num_srcs == 2)
nir_src_copy(&intr->src[1], &intrin->src[1], intr);
intr->num_components = 1;
nir_builder_instr_insert(b, &intr->instr);
return intr;
}
static nir_ssa_def *
lower_subgroup_op_to_32bit(nir_builder *b, nir_intrinsic_instr *intrin)
{
assert(intrin->src[0].ssa->bit_size == 64);
nir_intrinsic_instr *intr_x = lower_subgroups_64bit_split_intrinsic(b, intrin, 0);
nir_intrinsic_instr *intr_y = lower_subgroups_64bit_split_intrinsic(b, intrin, 1);
return nir_pack_64_2x32_split(b, &intr_x->dest.ssa, &intr_y->dest.ssa);
}
static nir_ssa_def *
ballot_type_to_uint(nir_builder *b, nir_ssa_def *value, unsigned bit_size)
{
/* We only use this on uvec4 types */
assert(value->num_components == 4 && value->bit_size == 32);
if (bit_size == 32) {
return nir_channel(b, value, 0);
} else {
assert(bit_size == 64);
return nir_pack_64_2x32_split(b, nir_channel(b, value, 0),
nir_channel(b, value, 1));
}
}
/* Converts a uint32_t or uint64_t value to uint64_t or uvec4 */
static nir_ssa_def *
uint_to_ballot_type(nir_builder *b, nir_ssa_def *value,
unsigned num_components, unsigned bit_size)
{
assert(value->num_components == 1);
assert(value->bit_size == 32 || value->bit_size == 64);
nir_ssa_def *zero = nir_imm_int(b, 0);
if (num_components > 1) {
/* SPIR-V uses a uvec4 for ballot values */
assert(num_components == 4);
assert(bit_size == 32);
if (value->bit_size == 32) {
return nir_vec4(b, value, zero, zero, zero);
} else {
assert(value->bit_size == 64);
return nir_vec4(b, nir_unpack_64_2x32_split_x(b, value),
nir_unpack_64_2x32_split_y(b, value),
zero, zero);
}
} else {
/* GLSL uses a uint64_t for ballot values */
assert(num_components == 1);
assert(bit_size == 64);
if (value->bit_size == 32) {
return nir_pack_64_2x32_split(b, value, zero);
} else {
assert(value->bit_size == 64);
return value;
}
}
}
static nir_ssa_def *
lower_subgroup_op_to_scalar(nir_builder *b, nir_intrinsic_instr *intrin,
bool lower_to_32bit)
{
/* This is safe to call on scalar things but it would be silly */
assert(intrin->dest.ssa.num_components > 1);
nir_ssa_def *value = nir_ssa_for_src(b, intrin->src[0],
intrin->num_components);
nir_ssa_def *reads[NIR_MAX_VEC_COMPONENTS];
for (unsigned i = 0; i < intrin->num_components; i++) {
nir_intrinsic_instr *chan_intrin =
nir_intrinsic_instr_create(b->shader, intrin->intrinsic);
nir_ssa_dest_init(&chan_intrin->instr, &chan_intrin->dest,
1, intrin->dest.ssa.bit_size, NULL);
chan_intrin->num_components = 1;
/* value */
chan_intrin->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
/* invocation */
if (nir_intrinsic_infos[intrin->intrinsic].num_srcs > 1) {
assert(nir_intrinsic_infos[intrin->intrinsic].num_srcs == 2);
nir_src_copy(&chan_intrin->src[1], &intrin->src[1], chan_intrin);
}
chan_intrin->const_index[0] = intrin->const_index[0];
chan_intrin->const_index[1] = intrin->const_index[1];
if (lower_to_32bit && chan_intrin->src[0].ssa->bit_size == 64) {
reads[i] = lower_subgroup_op_to_32bit(b, chan_intrin);
} else {
nir_builder_instr_insert(b, &chan_intrin->instr);
reads[i] = &chan_intrin->dest.ssa;
}
}
return nir_vec(b, reads, intrin->num_components);
}
static nir_ssa_def *
lower_vote_eq_to_scalar(nir_builder *b, nir_intrinsic_instr *intrin)
{
assert(intrin->src[0].is_ssa);
nir_ssa_def *value = intrin->src[0].ssa;
nir_ssa_def *result = NULL;
for (unsigned i = 0; i < intrin->num_components; i++) {
nir_intrinsic_instr *chan_intrin =
nir_intrinsic_instr_create(b->shader, intrin->intrinsic);
nir_ssa_dest_init(&chan_intrin->instr, &chan_intrin->dest,
1, intrin->dest.ssa.bit_size, NULL);
chan_intrin->num_components = 1;
chan_intrin->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
nir_builder_instr_insert(b, &chan_intrin->instr);
if (result) {
result = nir_iand(b, result, &chan_intrin->dest.ssa);
} else {
result = &chan_intrin->dest.ssa;
}
}
return result;
}
static nir_ssa_def *
lower_vote_eq_to_ballot(nir_builder *b, nir_intrinsic_instr *intrin,
const nir_lower_subgroups_options *options)
{
assert(intrin->src[0].is_ssa);
nir_ssa_def *value = intrin->src[0].ssa;
/* We have to implicitly lower to scalar */
nir_ssa_def *all_eq = NULL;
for (unsigned i = 0; i < intrin->num_components; i++) {
nir_ssa_def *rfi = nir_read_first_invocation(b, nir_channel(b, value, i));
nir_ssa_def *is_eq;
if (intrin->intrinsic == nir_intrinsic_vote_feq) {
is_eq = nir_feq(b, rfi, nir_channel(b, value, i));
} else {
is_eq = nir_ieq(b, rfi, nir_channel(b, value, i));
}
if (all_eq == NULL) {
all_eq = is_eq;
} else {
all_eq = nir_iand(b, all_eq, is_eq);
}
}
nir_ssa_def *ballot = nir_ballot(b, 1, options->ballot_bit_size, nir_inot(b, all_eq));
return nir_ieq(b, ballot, nir_imm_intN_t(b, 0, options->ballot_bit_size));
}
static nir_ssa_def *
lower_shuffle_to_swizzle(nir_builder *b, nir_intrinsic_instr *intrin,
const nir_lower_subgroups_options *options)
{
unsigned mask = nir_src_as_uint(intrin->src[1]);
if (mask >= 32)
return NULL;
nir_intrinsic_instr *swizzle = nir_intrinsic_instr_create(
b->shader, nir_intrinsic_masked_swizzle_amd);
swizzle->num_components = intrin->num_components;
nir_src_copy(&swizzle->src[0], &intrin->src[0], swizzle);
nir_intrinsic_set_swizzle_mask(swizzle, (mask << 10) | 0x1f);
nir_ssa_dest_init(&swizzle->instr, &swizzle->dest,
intrin->dest.ssa.num_components,
intrin->dest.ssa.bit_size, NULL);
if (options->lower_to_scalar && swizzle->num_components > 1) {
return lower_subgroup_op_to_scalar(b, swizzle, options->lower_shuffle_to_32bit);
} else if (options->lower_shuffle_to_32bit && swizzle->src[0].ssa->bit_size == 64) {
return lower_subgroup_op_to_32bit(b, swizzle);
} else {
nir_builder_instr_insert(b, &swizzle->instr);
return &swizzle->dest.ssa;
}
}
static nir_ssa_def *
lower_shuffle(nir_builder *b, nir_intrinsic_instr *intrin,
const nir_lower_subgroups_options *options)
{
if (intrin->intrinsic == nir_intrinsic_shuffle_xor &&
options->lower_shuffle_to_swizzle_amd &&
nir_src_is_const(intrin->src[1])) {
nir_ssa_def *result =
lower_shuffle_to_swizzle(b, intrin, options);
if (result)
return result;
}
nir_ssa_def *index = nir_load_subgroup_invocation(b);
bool is_shuffle = false;
switch (intrin->intrinsic) {
case nir_intrinsic_shuffle_xor:
assert(intrin->src[1].is_ssa);
index = nir_ixor(b, index, intrin->src[1].ssa);
is_shuffle = true;
break;
case nir_intrinsic_shuffle_up:
assert(intrin->src[1].is_ssa);
index = nir_isub(b, index, intrin->src[1].ssa);
is_shuffle = true;
break;
case nir_intrinsic_shuffle_down:
assert(intrin->src[1].is_ssa);
index = nir_iadd(b, index, intrin->src[1].ssa);
is_shuffle = true;
break;
case nir_intrinsic_quad_broadcast:
assert(intrin->src[1].is_ssa);
index = nir_ior(b, nir_iand(b, index, nir_imm_int(b, ~0x3)),
intrin->src[1].ssa);
break;
case nir_intrinsic_quad_swap_horizontal:
/* For Quad operations, subgroups are divided into quads where
* (invocation % 4) is the index to a square arranged as follows:
*
* +---+---+
* | 0 | 1 |
* +---+---+
* | 2 | 3 |
* +---+---+
*/
index = nir_ixor(b, index, nir_imm_int(b, 0x1));
break;
case nir_intrinsic_quad_swap_vertical:
index = nir_ixor(b, index, nir_imm_int(b, 0x2));
break;
case nir_intrinsic_quad_swap_diagonal:
index = nir_ixor(b, index, nir_imm_int(b, 0x3));
break;
default:
unreachable("Invalid intrinsic");
}
nir_intrinsic_instr *shuffle =
nir_intrinsic_instr_create(b->shader, nir_intrinsic_shuffle);
shuffle->num_components = intrin->num_components;
nir_src_copy(&shuffle->src[0], &intrin->src[0], shuffle);
shuffle->src[1] = nir_src_for_ssa(index);
nir_ssa_dest_init(&shuffle->instr, &shuffle->dest,
intrin->dest.ssa.num_components,
intrin->dest.ssa.bit_size, NULL);
bool lower_to_32bit = options->lower_shuffle_to_32bit && is_shuffle;
if (options->lower_to_scalar && shuffle->num_components > 1) {
return lower_subgroup_op_to_scalar(b, shuffle, lower_to_32bit);
} else if (lower_to_32bit && shuffle->src[0].ssa->bit_size == 64) {
return lower_subgroup_op_to_32bit(b, shuffle);
} else {
nir_builder_instr_insert(b, &shuffle->instr);
return &shuffle->dest.ssa;
}
}
static bool
lower_subgroups_filter(const nir_instr *instr, const void *_options)
{
return instr->type == nir_instr_type_intrinsic;
}
static nir_ssa_def *
build_subgroup_mask(nir_builder *b, unsigned bit_size,
const nir_lower_subgroups_options *options)
{
return nir_ushr(b, nir_imm_intN_t(b, ~0ull, bit_size),
nir_isub(b, nir_imm_int(b, bit_size),
nir_load_subgroup_size(b)));
}
static nir_ssa_def *
lower_dynamic_quad_broadcast(nir_builder *b, nir_intrinsic_instr *intrin,
const nir_lower_subgroups_options *options)
{
if (!options->lower_quad_broadcast_dynamic_to_const)
return lower_shuffle(b, intrin, options);
nir_ssa_def *dst = NULL;
for (unsigned i = 0; i < 4; ++i) {
nir_intrinsic_instr *qbcst =
nir_intrinsic_instr_create(b->shader, nir_intrinsic_quad_broadcast);
qbcst->num_components = intrin->num_components;
qbcst->src[1] = nir_src_for_ssa(nir_imm_int(b, i));
nir_src_copy(&qbcst->src[0], &intrin->src[0], qbcst);
nir_ssa_dest_init(&qbcst->instr, &qbcst->dest,
intrin->dest.ssa.num_components,
intrin->dest.ssa.bit_size, NULL);
nir_ssa_def *qbcst_dst = NULL;
if (options->lower_to_scalar && qbcst->num_components > 1) {
qbcst_dst = lower_subgroup_op_to_scalar(b, qbcst, false);
} else {
nir_builder_instr_insert(b, &qbcst->instr);
qbcst_dst = &qbcst->dest.ssa;
}
if (i)
dst = nir_bcsel(b, nir_ieq(b, intrin->src[1].ssa,
nir_src_for_ssa(nir_imm_int(b, i)).ssa),
qbcst_dst, dst);
else
dst = qbcst_dst;
}
return dst;
}
static nir_ssa_def *
lower_subgroups_instr(nir_builder *b, nir_instr *instr, void *_options)
{
const nir_lower_subgroups_options *options = _options;
nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
switch (intrin->intrinsic) {
case nir_intrinsic_vote_any:
case nir_intrinsic_vote_all:
if (options->lower_vote_trivial)
return nir_ssa_for_src(b, intrin->src[0], 1);
break;
case nir_intrinsic_vote_feq:
case nir_intrinsic_vote_ieq:
if (options->lower_vote_trivial)
return nir_imm_true(b);
if (options->lower_vote_eq_to_ballot)
return lower_vote_eq_to_ballot(b, intrin, options);
if (options->lower_to_scalar && intrin->num_components > 1)
return lower_vote_eq_to_scalar(b, intrin);
break;
case nir_intrinsic_load_subgroup_size:
if (options->subgroup_size)
return nir_imm_int(b, options->subgroup_size);
break;
case nir_intrinsic_read_invocation:
case nir_intrinsic_read_first_invocation:
if (options->lower_to_scalar && intrin->num_components > 1)
return lower_subgroup_op_to_scalar(b, intrin, false);
break;
case nir_intrinsic_load_subgroup_eq_mask:
case nir_intrinsic_load_subgroup_ge_mask:
case nir_intrinsic_load_subgroup_gt_mask:
case nir_intrinsic_load_subgroup_le_mask:
case nir_intrinsic_load_subgroup_lt_mask: {
if (!options->lower_subgroup_masks)
return NULL;
/* If either the result or the requested bit size is 64-bits then we
* know that we have 64-bit types and using them will probably be more
* efficient than messing around with 32-bit shifts and packing.
*/
const unsigned bit_size = MAX2(options->ballot_bit_size,
intrin->dest.ssa.bit_size);
nir_ssa_def *count = nir_load_subgroup_invocation(b);
nir_ssa_def *val;
switch (intrin->intrinsic) {
case nir_intrinsic_load_subgroup_eq_mask:
val = nir_ishl(b, nir_imm_intN_t(b, 1ull, bit_size), count);
break;
case nir_intrinsic_load_subgroup_ge_mask:
val = nir_iand(b, nir_ishl(b, nir_imm_intN_t(b, ~0ull, bit_size), count),
build_subgroup_mask(b, bit_size, options));
break;
case nir_intrinsic_load_subgroup_gt_mask:
val = nir_iand(b, nir_ishl(b, nir_imm_intN_t(b, ~1ull, bit_size), count),
build_subgroup_mask(b, bit_size, options));
break;
case nir_intrinsic_load_subgroup_le_mask:
val = nir_inot(b, nir_ishl(b, nir_imm_intN_t(b, ~1ull, bit_size), count));
break;
case nir_intrinsic_load_subgroup_lt_mask:
val = nir_inot(b, nir_ishl(b, nir_imm_intN_t(b, ~0ull, bit_size), count));
break;
default:
unreachable("you seriously can't tell this is unreachable?");
}
return uint_to_ballot_type(b, val,
intrin->dest.ssa.num_components,
intrin->dest.ssa.bit_size);
}
case nir_intrinsic_ballot: {
if (intrin->dest.ssa.num_components == 1 &&
intrin->dest.ssa.bit_size == options->ballot_bit_size)
return NULL;
nir_ssa_def *ballot = nir_ballot(b, 1, options->ballot_bit_size, intrin->src[0].ssa);
return uint_to_ballot_type(b, ballot,
intrin->dest.ssa.num_components,
intrin->dest.ssa.bit_size);
}
case nir_intrinsic_ballot_bitfield_extract:
case nir_intrinsic_ballot_bit_count_reduce:
case nir_intrinsic_ballot_find_lsb:
case nir_intrinsic_ballot_find_msb: {
assert(intrin->src[0].is_ssa);
nir_ssa_def *int_val = ballot_type_to_uint(b, intrin->src[0].ssa,
options->ballot_bit_size);
if (intrin->intrinsic != nir_intrinsic_ballot_bitfield_extract &&
intrin->intrinsic != nir_intrinsic_ballot_find_lsb) {
/* For OpGroupNonUniformBallotFindMSB, the SPIR-V Spec says:
*
* "Find the most significant bit set to 1 in Value, considering
* only the bits in Value required to represent all bits of the
* groups invocations. If none of the considered bits is set to
* 1, the result is undefined."
*
* It has similar text for the other three. This means that, in case
* the subgroup size is less than 32, we have to mask off the unused
* bits. If the subgroup size is fixed and greater than or equal to
* 32, the mask will be 0xffffffff and nir_opt_algebraic will delete
* the iand.
*
* We only have to worry about this for BitCount and FindMSB because
* FindLSB counts from the bottom and BitfieldExtract selects
* individual bits. In either case, if run outside the range of
* valid bits, we hit the undefined results case and we can return
* anything we want.
*/
int_val = nir_iand(b, int_val,
build_subgroup_mask(b, options->ballot_bit_size, options));
}
switch (intrin->intrinsic) {
case nir_intrinsic_ballot_bitfield_extract:
assert(intrin->src[1].is_ssa);
return nir_i2b(b, nir_iand(b, nir_ushr(b, int_val,
intrin->src[1].ssa),
nir_imm_intN_t(b, 1, options->ballot_bit_size)));
case nir_intrinsic_ballot_bit_count_reduce:
return nir_bit_count(b, int_val);
case nir_intrinsic_ballot_find_lsb:
return nir_find_lsb(b, int_val);
case nir_intrinsic_ballot_find_msb:
return nir_ufind_msb(b, int_val);
default:
unreachable("you seriously can't tell this is unreachable?");
}
}
case nir_intrinsic_ballot_bit_count_exclusive:
case nir_intrinsic_ballot_bit_count_inclusive: {
nir_ssa_def *count = nir_load_subgroup_invocation(b);
nir_ssa_def *mask = nir_imm_intN_t(b, ~0ull, options->ballot_bit_size);
if (intrin->intrinsic == nir_intrinsic_ballot_bit_count_inclusive) {
const unsigned bits = options->ballot_bit_size;
mask = nir_ushr(b, mask, nir_isub(b, nir_imm_int(b, bits - 1), count));
} else {
mask = nir_inot(b, nir_ishl(b, mask, count));
}
assert(intrin->src[0].is_ssa);
nir_ssa_def *int_val = ballot_type_to_uint(b, intrin->src[0].ssa,
options->ballot_bit_size);
return nir_bit_count(b, nir_iand(b, int_val, mask));
}
case nir_intrinsic_elect: {
if (!options->lower_elect)
return NULL;
return nir_ieq(b, nir_load_subgroup_invocation(b), nir_first_invocation(b));
}
case nir_intrinsic_shuffle:
if (options->lower_to_scalar && intrin->num_components > 1)
return lower_subgroup_op_to_scalar(b, intrin, options->lower_shuffle_to_32bit);
else if (options->lower_shuffle_to_32bit && intrin->src[0].ssa->bit_size == 64)
return lower_subgroup_op_to_32bit(b, intrin);
break;
case nir_intrinsic_shuffle_xor:
case nir_intrinsic_shuffle_up:
case nir_intrinsic_shuffle_down:
if (options->lower_shuffle)
return lower_shuffle(b, intrin, options);
else if (options->lower_to_scalar && intrin->num_components > 1)
return lower_subgroup_op_to_scalar(b, intrin, options->lower_shuffle_to_32bit);
else if (options->lower_shuffle_to_32bit && intrin->src[0].ssa->bit_size == 64)
return lower_subgroup_op_to_32bit(b, intrin);
break;
case nir_intrinsic_quad_broadcast:
case nir_intrinsic_quad_swap_horizontal:
case nir_intrinsic_quad_swap_vertical:
case nir_intrinsic_quad_swap_diagonal:
if (options->lower_quad ||
(options->lower_quad_broadcast_dynamic &&
intrin->intrinsic == nir_intrinsic_quad_broadcast &&
!nir_src_is_const(intrin->src[1])))
return lower_dynamic_quad_broadcast(b, intrin, options);
else if (options->lower_to_scalar && intrin->num_components > 1)
return lower_subgroup_op_to_scalar(b, intrin, false);
break;
case nir_intrinsic_reduce: {
nir_ssa_def *ret = NULL;
/* A cluster size greater than the subgroup size is implemention defined */
if (options->subgroup_size &&
nir_intrinsic_cluster_size(intrin) >= options->subgroup_size) {
nir_intrinsic_set_cluster_size(intrin, 0);
ret = NIR_LOWER_INSTR_PROGRESS;
}
if (options->lower_to_scalar && intrin->num_components > 1)
ret = lower_subgroup_op_to_scalar(b, intrin, false);
return ret;
}
case nir_intrinsic_inclusive_scan:
case nir_intrinsic_exclusive_scan:
if (options->lower_to_scalar && intrin->num_components > 1)
return lower_subgroup_op_to_scalar(b, intrin, false);
break;
default:
break;
}
return NULL;
}
bool
nir_lower_subgroups(nir_shader *shader,
const nir_lower_subgroups_options *options)
{
return nir_shader_lower_instructions(shader,
lower_subgroups_filter,
lower_subgroups_instr,
(void *)options);
}