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apache--tvm/python/tvm/relax/backend/gpu_generic/cumsum.py
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chore: import upstream snapshot with attribution
2026-07-13 13:36:25 +08:00

196 lines
8.1 KiB
Python

# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
# pylint: disable=invalid-name, too-many-nested-blocks
"""Backend kernels for cumsum operator."""
import math
from tvm.script import tirx as T
from tvm.tirx import PrimFunc
def _is_power_of_two(n: int):
"""Check if n is a power of 2."""
return n > 0 and (n & (n - 1)) == 0
def gpu_2d_continuous_cumsum(
ty_len: int = 4,
tx_len: int = 32,
thread_elem: int = 4,
in_dtype: str = "int32",
out_dtype: str | None = None,
) -> PrimFunc:
"""Generate GPU kernel for 2D continuous cumsum, i.e. The cumsum axis is -1
Parameters
----------
ty_len : int
The length of `threadIdx.y`
tx_len : int
The length of `threadIdx.x`
thread_elem : int
The number of elements processed by single thread
in_dtype : str
The input data type
out_dtype : Optional[str]
The output data type, if None, it will be the same as in_dtype
Returns
-------
cumsum : PrimFunc
The generated cumsum kernel
"""
out_dtype = out_dtype or in_dtype
# Configuration for GPU kernel
TX = T.int64(tx_len) # threadIdx.x
TY = T.int64(ty_len) # threadIdx.y
N = T.int64(thread_elem) # number of elements in single thread
if not _is_power_of_two(TX) or not _is_power_of_two(TY) or not _is_power_of_two(N):
raise ValueError("Configuration of TX, TY, N must be power of 2")
# number of elements to be processed by single warp
warp_elem = T.int64(tx_len * thread_elem)
# number of elements to be processed by single block(SM)
block_elem = T.int64(tx_len * ty_len * thread_elem)
LOG_TX = T.int64(int(math.log2(tx_len)))
LOG_BLOCK_N = T.int64(int(math.log2(tx_len * ty_len * thread_elem)))
@T.macro
def block_inclusive_inside_block(
batch: T.int64,
cur_len: T.int64,
source: T.Buffer,
output: T.Buffer,
tmp_buf: T.Buffer,
src_offset: T.int64,
tmp_offset: T.int64,
):
for by in T.thread_binding(batch, thread="blockIdx.y"):
for bx in T.thread_binding(T.ceildiv(cur_len, block_elem), thread="blockIdx.x"):
with T.sblock():
local_buf = T.sblock_alloc_buffer((thread_elem,), out_dtype, scope="local")
shared_buf = T.sblock_alloc_buffer((block_elem,), out_dtype, scope="shared")
for ty in T.thread_binding(TY, thread="threadIdx.y"):
for tx in T.thread_binding(TX, thread="threadIdx.x"):
tx_idx: T.let[T.int64] = (
bx * block_elem + ty * warp_elem + tx * thread_elem
)
# Load data from global memory
for i in T.vectorized(N):
local_buf[i] = T.if_then_else(
tx_idx + i < cur_len,
T.Cast(out_dtype, source[by, src_offset + tx_idx + i]),
T.Cast(out_dtype, 0),
)
# Inclusive scan inside thread
for i in T.unroll(1, N):
local_buf[i] += local_buf[i - 1]
# Store data to shared memory
for i in T.vectorized(N):
shared_buf[ty * warp_elem + tx * thread_elem + i] = local_buf[i]
# Inclusive scan inside warp
for i in T.unroll(LOG_TX):
for j in T.vectorized(N):
idx: T.let[T.int64] = ty * warp_elem + tx * thread_elem
if tx >= (1 << i):
shared_buf[idx + j] += shared_buf[
idx - (1 << i) * thread_elem + N - 1
]
# Inclusive scan inside block
for i in T.unroll(1, TY):
for j in T.vectorized(N):
if ty == 0:
idx: T.let[T.int64] = i * warp_elem + tx * thread_elem
shared_buf[idx + j] += shared_buf[i * warp_elem - 1]
# Write sum of block to global memory
for i in T.vectorized(N):
idx: T.let[T.int64] = ty * warp_elem + tx * thread_elem + i
if bx * block_elem + idx < cur_len:
output[by, src_offset + bx * block_elem + idx] = shared_buf[idx]
if tx == 0 and ty == 0:
for i in T.vectorized(N):
tmp_buf[by, tmp_offset + bx] = shared_buf[block_elem - 1]
@T.macro
def update_cross_block(
batch: T.int64,
cur_len: T.int64,
source: T.Buffer,
output: T.Buffer,
src_offset: T.int64,
out_offset: T.int64,
):
for by in T.thread_binding(batch, thread="blockIdx.y"):
for bx in T.thread_binding(T.ceildiv(cur_len, block_elem), thread="blockIdx.x"):
for ty in T.thread_binding(TY, thread="threadIdx.y"):
for tx in T.thread_binding(TX, thread="threadIdx.x"):
for i in T.serial(N):
idx: T.let[T.int64] = bx * block_elem + ty * warp_elem + i * TX + tx
if idx < cur_len:
output[by, out_offset + idx] += T.if_then_else(
bx > 0, source[by, src_offset + bx - 1], 0
)
@T.prim_func(private=True, s_tir=True)
def cumsum(var_a: T.handle, var_out: T.handle):
T.func_attr({"tirx.is_scheduled": True}) # prevent further scheduling
m, n = T.int64(), T.int64()
A = T.match_buffer(var_a, [m, n], dtype=in_dtype)
Out = T.match_buffer(var_out, [m, n], dtype=out_dtype)
Tmp = T.alloc_buffer([m, n], dtype=out_dtype)
total_rounds: T.let[T.int64] = (
T.Cast("int64", T.ceil(T.log2(T.Cast("float32", n)))) // LOG_BLOCK_N
)
block_inclusive_inside_block(
m, n, A, Out, Tmp, src_offset=T.int64(0), tmp_offset=T.int64(0)
)
for i in range(total_rounds):
cur_len: T.let[T.int64] = T.ceildiv(n, 1 << (LOG_BLOCK_N * (i + 1)))
block_inclusive_inside_block(
m,
cur_len,
Tmp,
Tmp,
Tmp,
src_offset=i * T.ceildiv(n, block_elem),
tmp_offset=(i + 1) * T.ceildiv(n, block_elem),
)
for i in range(total_rounds - 1):
real_idx: T.let[T.int64] = total_rounds - 1 - i - 1
cur_len: T.let[T.int64] = T.ceildiv(n, 1 << (LOG_BLOCK_N * (real_idx + 1)))
update_cross_block(
m,
cur_len,
Tmp,
Tmp,
src_offset=(real_idx + 1) * T.ceildiv(n, block_elem),
out_offset=real_idx * T.ceildiv(n, block_elem),
)
update_cross_block(m, n, Tmp, Out, src_offset=0, out_offset=0)
return cumsum