[ET-VK] Add pass to remove copy ops

backends/vulkan/_passes/TARGETS

@@ -43,6 +43,19 @@ runtime.python_library(
     ],
 )
 
+runtime.python_library(
+    name = "remove_redundant_ops",
+    srcs = ["remove_redundant_ops.py"],
+    visibility = [
+        "//executorch/backends/...",
+    ],
+    deps = [
+        "//caffe2:torch",
+        "//executorch/exir:pass_base",
+        "//executorch/exir/dialects:lib",
+    ],
+)
+
 runtime.python_library(
     name = "tag_memory_meta_pass",
     srcs = ["tag_memory_meta_pass.py"],
@@ -71,6 +84,7 @@ runtime.python_library(
         ":insert_prepack_nodes",
         ":int4_weight_only_quantizer",
         ":remove_local_scalar_dense",
+        ":remove_redundant_ops",
         ":tag_memory_meta_pass"
     ]
 )

backends/vulkan/_passes/__init__.py

@@ -5,11 +5,15 @@
 from executorch.backends.vulkan._passes.remove_local_scalar_dense_ops import (
     RemoveLocalScalarDenseOpsTransform,
 )
+from executorch.backends.vulkan._passes.remove_redundant_ops import (
+    RemoveRedundantOpsTransform,
+)
 from executorch.backends.vulkan._passes.tag_memory_meta_pass import TagMemoryMetaPass
 
 __all__ = [
     "insert_prepack_nodes",
     "VkInt4WeightOnlyQuantizer",
     "RemoveLocalScalarDenseOpsTransform",
+    "RemoveRedundantOpsTransform",
     "TagMemoryMetaPass",
 ]

backends/vulkan/_passes/remove_redundant_ops.py

@@ -0,0 +1,69 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+# pyre-strict
+
+from typing import Set, Union
+
+import torch
+from executorch.exir.dialects._ops import ops as exir_ops
+from executorch.exir.dialects.edge._ops import EdgeOpOverload
+from executorch.exir.pass_base import ExportPass, PassResult
+from executorch.exir.passes import dead_code_elimination_pass
+
+OpType = Union[str, torch._ops.OpOverload, EdgeOpOverload]
+
+
+class RemoveRedundantOpsTransform(ExportPass):
+    """
+    Trim certain operators to reduce unnecessary overhead.
+    """
+
+    redundant_ops: Set[OpType] = {
+        torch.clone,
+        torch.ops.aten.clone.default,
+        exir_ops.edge.aten.clone.default,
+        torch.ops.aten.alias.default,
+        exir_ops.edge.aten.alias.default,
+        exir_ops.edge.aten.lift_fresh_copy.default,
+        exir_ops.edge.dim_order_ops._to_dim_order_copy.default,
+    }
+
+    def __init__(self) -> None:
+        super(RemoveRedundantOpsTransform, self).__init__()
+
+    def _should_remove(self, node: torch.fx.Node) -> bool:
+        if node.target in self.redundant_ops:
+            return True
+
+        # Only remove to_copy if dtype does not change. Otherwise, memory format changes
+        # will be handled internally by the backend.
+        if (
+            node.target == exir_ops.edge.aten._to_copy.default
+            or node.target == torch.ops.aten._to_copy.default
+        ):
+            src_dtype = node.meta["val"].dtype
+            # pyre-ignore
+            dst_dtype = node.args[0].meta["val"].dtype
+            return src_dtype == dst_dtype
+
+        return False
+
+    def _remove(self, graph_module: torch.fx.GraphModule) -> None:
+        for node in graph_module.graph.nodes:
+            if not self._should_remove(node):
+                continue
+
+            with graph_module.graph.inserting_after(node):
+                node.replace_all_uses_with(node.args[0])
+
+        graph_module.graph.eliminate_dead_code()
+
+    def call(self, graph_module: torch.fx.GraphModule) -> PassResult:
+        self._remove(graph_module)
+        graph_module.recompile()
+        dead_code_elimination_pass(graph_module)
+        return PassResult(graph_module, True)

backends/vulkan/op_registry.py

@@ -228,6 +228,8 @@ def update_features_impl(op: OpKey):
         exir_ops.edge.quantized_decomposed.dequantize_per_tensor.default,
         exir_ops.edge.quantized_decomposed.dequantize_per_tensor.tensor,
         exir_ops.edge.quantized_decomposed.dequantize_per_channel.default,
+        # dim order copy operator will be removed; memory layout is handled internally
+        exir_ops.edge.dim_order_ops._to_dim_order_copy.default,
     ]
 )
 def register_ephemeral_op(features: OpFeatures):

backends/vulkan/vulkan_preprocess.py

@@ -17,11 +17,11 @@
 from executorch.backends.transforms.fuse_conv_with_clamp import FuseClampPass
 from executorch.backends.transforms.fuse_dequant_linear import FuseDequantLinearPass
 from executorch.backends.transforms.fuse_view_copy import FuseViewCopyTransform
-from executorch.backends.transforms.remove_clone_ops import RemoveCloneOpsTransform
 
 from executorch.backends.vulkan._passes import (
     insert_prepack_nodes,
     RemoveLocalScalarDenseOpsTransform,
+    RemoveRedundantOpsTransform,
     TagMemoryMetaPass,
 )
 
@@ -143,7 +143,7 @@ def preprocess(  # noqa: C901
         program = apply_passes(
             program,
             [
-                RemoveCloneOpsTransform(),
+                RemoveRedundantOpsTransform(),
                 AddmmToLinearTransform(),
                 FuseDequantLinearPass(),
                 FuseViewCopyTransform(),