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cutlass/python/cutlass_cppgen/backend/evt/passes/pass_preprocess_red.py
2025-09-18 14:26:57 -04:00

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Python

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"""
Preprocess the reduction nodes.
The parser treats reduction as Compute(op=(reg_reduce_fn, gmem_reduce_fn)) - Store()
This pass fuses these into a single store node, and then replaces all uses of the
current node with the new store node.
"""
from cutlass_cppgen.backend.evt.ir import ComputeNode, StoreNode
from cutlass_cppgen.backend.evt.passes.pass_manager import EVTPassBase
class PassPreprocessRed(EVTPassBase):
"""
Preprocess red nodes
"""
def call(self):
# Step 1: find the compute nodes with op=red
red_compute_nodes = []
for node_meta in self.dag_ir.nodes_meta:
if isinstance(node_meta, ComputeNode):
if type(node_meta.fn) == tuple:
# To keep the frontend simple, the reduction nodes
# are parsed into compute nodes by default
# The simple heuristic to distinguish between compute
# and reduction node is that compute node is a single function,
# while the reduction node is a tuple of functions for
# in-register reduction and atomic global memory reduction
red_compute_nodes.append(node_meta.name)
# Step 2: for each compute, merge it with the succeeding store
for node in red_compute_nodes:
# Verify
users = self.dag_ir.get_users(node)
inputs = self.dag_ir.get_all_inputs(node)
# Has a single user
assert len(users) == 1
assert len(inputs) == 1
user = users[0]
input = inputs[0]
user_meta = self.dag_ir.get_node_meta(user)
# Must be a store node
assert isinstance(user_meta, StoreNode)
# With output degree == 0
assert self.dag_ir.out_degree(user) == 0
# Register the reduce op
node_meta = self.dag_ir.get_node_meta(node)
user_meta.reg_reduce_fn, user_meta.gmem_reduce_fn = node_meta.fn
user_meta.element_compute = node_meta.element_compute
user_meta.round_style = node_meta.round_style
# Replace all uses
self.dag_ir.remove_edge(input, node)
input_users = self.dag_ir.get_users(input)
for iu in input_users:
weight = self.dag_ir.get_edge_weight(input, iu)
self.dag_ir.add_edge(user, iu, weight)
self.dag_ir.remove_edge(input, iu)
self.dag_ir.add_edge(input, user)
self.dag_ir.remove_node(node)
# Register the reduction name
self.dag_ir.reduction_names.append(user)