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Speed up permute propagation cleanup (pytorch#22161)
Summary: Speed up permute propagation cleanup. ARM lowering spends significant time in permute propagation. Reduce avoidable repeated work while keeping same optimizations: - Canonicalize view/permute chain collection now uses deque + membership set instead of list pop(0) and remove(), avoiding quadratic bookkeeping. - FuseDuplicateUsersPass deduplicates pending producer revisits while preserving same revisit behavior after fusions. - PropagateViewCopyPermutePass still retraces after each moved transform for metadata safety, but defers horizontal/vertical cleanup until full scan finds no more direct propagation moves. Preserves fixed-point behavior while avoiding expensive cleanup after every single moved transform. Behavior-preserving speedup, all existing pass tests pass. On an ensemble network of ~1M parameters, lowering produced identical output while running 102.5 seconds faster (26.7%). Differential Revision: D114224762 Pull Request resolved: pytorch#22161
1 parent d29750b commit 2bcc50c

4 files changed

Lines changed: 145 additions & 37 deletions

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‎backends/arm/test/passes/test_fuse_duplicate_users_pass.py‎

Lines changed: 43 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -133,11 +133,35 @@ def _graph_with_users_not_in_node_order() -> GraphModule:
133133
return GraphModule(torch.nn.Module(), graph)
134134

135135

136+
def _graph_with_erased_node_still_queued() -> GraphModule:
137+
graph = Graph()
138+
x = _set_val(graph.placeholder("x"), torch.ones(1))
139+
first_neg = _set_val(
140+
graph.call_function(torch.ops.aten.neg.default, (x,)), torch.ones(1)
141+
)
142+
second_neg = _set_val(
143+
graph.call_function(torch.ops.aten.neg.default, (x,)), torch.ones(1)
144+
)
145+
first_relu = _set_val(
146+
graph.call_function(torch.ops.aten.relu.default, (first_neg,)), torch.ones(1)
147+
)
148+
second_relu = _set_val(
149+
graph.call_function(torch.ops.aten.relu.default, (second_neg,)), torch.ones(1)
150+
)
151+
output = graph.output((first_relu, second_relu))
152+
output.meta["val"] = (torch.ones(1), torch.ones(1))
153+
graph.lint()
154+
return GraphModule(torch.nn.Module(), graph)
155+
156+
157+
def _nodes_with_target(graph_module, target):
158+
return [node for node in graph_module.graph.nodes if node.target == target]
159+
160+
136161
def _add_node_names(graph_module):
137162
return [
138163
node.name
139-
for node in graph_module.graph.nodes
140-
if node.target == torch.ops.aten.add.Tensor
164+
for node in _nodes_with_target(graph_module, torch.ops.aten.add.Tensor)
141165
]
142166

143167

@@ -183,6 +207,23 @@ def test_fuse_duplicate_users_honors_do_not_fuse_marker():
183207
assert len(_add_node_names(result.graph_module)) == 2
184208

185209

210+
def test_fuse_duplicate_users_skips_erased_queued_nodes():
211+
result = FuseDuplicateUsersPass()(_graph_with_erased_node_still_queued())
212+
213+
neg_nodes = _nodes_with_target(result.graph_module, torch.ops.aten.neg.default)
214+
relu_nodes = _nodes_with_target(result.graph_module, torch.ops.aten.relu.default)
215+
output = next(
216+
node for node in result.graph_module.graph.nodes if node.op == "output"
217+
)
218+
219+
result.graph_module.graph.lint()
220+
assert result.modified
221+
assert len(neg_nodes) == 1
222+
assert len(relu_nodes) == 1
223+
assert relu_nodes[0].args[0] is neg_nodes[0]
224+
assert output.args[0] == (relu_nodes[0], relu_nodes[0])
225+
226+
186227
def test_fuse_duplicate_users_keeps_identical_rescale_users():
187228
graph_module = _graph_with_duplicate_rescale_users()
188229

‎backends/arm/test/passes/test_propagate_permutes_views_pass.py‎

Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1168,6 +1168,39 @@ def test_up_pass_fuses_equivalent_output_permutations_before_fan_out() -> None:
11681168
assert targets.index(PERMUTE) < targets.index(RELU) < targets.index(ADD)
11691169

11701170

1171+
def test_up_pass_fusion_enables_further_propagation() -> None:
1172+
graph = torch.fx.Graph()
1173+
x = graph.placeholder("x")
1174+
x.meta["val"] = torch.empty((1, 2, 3, 4))
1175+
relu = graph.call_function(RELU, args=(x,))
1176+
relu.meta["val"] = torch.empty((1, 2, 3, 4))
1177+
neg = graph.call_function(NEG, args=(relu,))
1178+
neg.meta["val"] = torch.empty((1, 2, 3, 4))
1179+
first_permute = graph.call_function(PERMUTE, args=(neg, [0, 2, 3, 1]))
1180+
first_permute.meta["val"] = torch.empty((1, 3, 4, 2))
1181+
second_permute = graph.call_function(PERMUTE, args=(relu, [0, 2, 3, 1]))
1182+
second_permute.meta["val"] = torch.empty((1, 3, 4, 2))
1183+
add = graph.call_function(ADD, args=(first_permute, second_permute))
1184+
add.meta["val"] = torch.empty((1, 3, 4, 2))
1185+
graph.output(add)
1186+
1187+
graph_module = _run_pass_on_graph_module(graph, PropagateViewCopyPermuteUpPass)
1188+
call_nodes = [
1189+
node for node in graph_module.graph.nodes if node.op == "call_function"
1190+
]
1191+
permutes = [node for node in call_nodes if node.target == PERMUTE]
1192+
x = next(node for node in graph_module.graph.nodes if node.op == "placeholder")
1193+
relu = next(node for node in call_nodes if node.target == RELU)
1194+
neg = next(node for node in call_nodes if node.target == NEG)
1195+
add = next(node for node in call_nodes if node.target == ADD)
1196+
1197+
assert len(permutes) == 1
1198+
assert permutes[0].args[0] is x
1199+
assert relu.args[0] is permutes[0]
1200+
assert neg.args[0] is relu
1201+
assert set(add.all_input_nodes) == {relu, neg}
1202+
1203+
11711204
def test_propagate_moves_before_dtype_changing_rescale() -> None:
11721205
graph = torch.fx.Graph()
11731206
x = graph.placeholder("x")

‎backends/transforms/canonicalize_view_copy_permute_pass.py‎

Lines changed: 14 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,7 @@
55

66
from __future__ import annotations
77

8+
from collections import deque
89
from typing import Any, cast, Iterable, Sequence, Set, Type
910

1011
import torch
@@ -104,20 +105,29 @@ def _collect_chains(self, graph_module: GraphModule) -> list[list[Node]]:
104105
"""Returns a list of linear chains of view/permutes in the graph."""
105106
chains: list[list[Node]] = []
106107

107-
view_permute_nodes = [
108+
view_permute_nodes = deque(
108109
node for node in graph_module.graph.nodes if node.target in self._targets
109-
]
110+
)
111+
remaining = set(view_permute_nodes)
110112

111113
while view_permute_nodes:
112-
node = view_permute_nodes.pop(0)
114+
node = view_permute_nodes.popleft()
115+
if node not in remaining:
116+
continue
117+
remaining.remove(node)
118+
113119
chain = [node]
114120
current = node
115121

116122
while len(current.users) == 1:
117123
user = next(iter(current.users))
118124
if user.target not in self._targets:
119125
break
120-
view_permute_nodes.remove(user)
126+
if user not in remaining:
127+
raise RuntimeError(
128+
f"View/permute node {user.name} belongs to multiple chains"
129+
)
130+
remaining.remove(user)
121131
chain.append(user)
122132
current = user
123133

‎backends/transforms/fuse_duplicate_users_pass.py‎

Lines changed: 55 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
# LICENSE file in the root directory of this source tree.
55

66
from collections import deque
7-
from typing import Any, Deque, Dict, Hashable, List, Set, Tuple, Type
7+
from typing import Any, Callable, Deque, Dict, Hashable, List, Set, Tuple, Type
88

99
import torch
1010
from executorch.exir.dialects.edge._ops import EdgeOpOverload
@@ -83,6 +83,12 @@ def build_node_signature(
8383
return (node.op, _get_target_key(node.target), normalized_args, normalized_kwargs)
8484

8585

86+
def _is_erased(node: Node) -> bool:
87+
# FX currently retains graph after erase_node(), but also handle versions
88+
# that detach erased nodes from their graph.
89+
return node.graph is None or getattr(node, "_erased", False)
90+
91+
8692
class FuseDuplicateUsersPass(ExportPass):
8793
"""Fuse identical users of a producer node into a single operation.
8894
@@ -112,12 +118,20 @@ def call(self, graph_module: GraphModule) -> PassResult:
112118

113119
node_order = {node: index for index, node in enumerate(graph.nodes)}
114120
producers: Deque[Node] = deque(node for node in graph.nodes)
121+
queued_producers: Set[Node] = set(producers)
122+
123+
def enqueue_producer(node: Node) -> None:
124+
if _is_erased(node) or node in queued_producers:
125+
return
126+
producers.append(node)
127+
queued_producers.add(node)
115128

116129
while producers:
117130
producer = producers.popleft()
131+
queued_producers.discard(producer)
118132

119-
if producer.graph is None:
120-
# Node was deleted by a previous rewrite while still queued.
133+
if _is_erased(producer):
134+
# Graph.erase_node marks nodes retained by iterators as erased.
121135
continue
122136

123137
# Only meaningful if a value is consumed by multiple users.
@@ -126,33 +140,9 @@ def call(self, graph_module: GraphModule) -> PassResult:
126140
continue
127141

128142
candidate_groups = self._get_candidate_groups(node_order, user_nodes)
129-
130-
signature_to_user: Dict[Tuple[Hashable, ...], Node] = {}
131-
for group in candidate_groups:
132-
for user in group:
133-
signature = self._build_user_signature(user)
134-
if signature is None:
135-
continue
136-
137-
representative = signature_to_user.get(signature)
138-
if representative is None:
139-
# Check if we already encountered identical node that we can fuse with.
140-
signature_to_user[signature] = user
141-
continue
142-
143-
if user is representative:
144-
# The queue can enqueue the surviving node again after rewrites.
145-
continue
146-
147-
user.replace_all_uses_with(representative)
148-
graph.erase_node(user)
149-
modified = True
150-
151-
# Revisit the current producer and the surviving user so that
152-
# newly formed duplicate chains can be fused in later
153-
# iterations.
154-
producers.append(producer)
155-
producers.append(representative)
143+
modified |= self._fuse_candidate_groups(
144+
graph, producer, candidate_groups, enqueue_producer
145+
)
156146

157147
if modified:
158148
if self._recompile_before_retrace:
@@ -162,10 +152,44 @@ def call(self, graph_module: GraphModule) -> PassResult:
162152

163153
return PassResult(graph_module, modified)
164154

155+
def _fuse_candidate_groups(
156+
self,
157+
graph: torch.fx.Graph,
158+
producer: Node,
159+
candidate_groups: List[List[Node]],
160+
enqueue_producer: Callable[[Node], None],
161+
) -> bool:
162+
modified = False
163+
signature_to_user: Dict[Tuple[Hashable, ...], Node] = {}
164+
for group in candidate_groups:
165+
for user in group:
166+
signature = self._build_user_signature(user)
167+
if signature is None:
168+
continue
169+
170+
representative = signature_to_user.get(signature)
171+
if representative is None:
172+
signature_to_user[signature] = user
173+
continue
174+
175+
if user is representative:
176+
continue
177+
178+
user.replace_all_uses_with(representative)
179+
graph.erase_node(user)
180+
modified = True
181+
182+
# Revisit the producer and survivor because this fusion can expose
183+
# another duplicate pair later in the chain.
184+
enqueue_producer(producer)
185+
enqueue_producer(representative)
186+
187+
return modified
188+
165189
def _get_candidate_groups(self, node_order, user_nodes):
166190
users_by_target: Dict[Tuple[str, Hashable], List[Node]] = {}
167191
for user in user_nodes:
168-
if user.graph is None:
192+
if _is_erased(user):
169193
# User might already have been removed by a prior rewrite.
170194
continue
171195

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