[nativert] Move SerialGraphExecutor to PyTorch core (#156459)

Summary: `SerialGraphExecutor` inherits from `GraphExecutorBase` and executes all nodes in the graph in a serial manner

Test Plan:
CI

Rollback Plan:

Differential Revision: D76917966

Pull Request resolved: https://github.com/pytorch/pytorch/pull/156459
Approved by: https://github.com/zhxchen17, https://github.com/jingsh

build_variables.bzl

@@ -603,6 +603,7 @@ libtorch_nativert_sources = [
     "torch/nativert/executor/GraphExecutorBase.cpp",
     "torch/nativert/executor/OpKernel.cpp",
     "torch/nativert/executor/PlacementUtils.cpp",
+    "torch/nativert/executor/SerialGraphExecutor.cpp",
     "torch/nativert/executor/Weights.cpp",
     "torch/nativert/executor/memory/FunctionSchema.cpp",
     "torch/nativert/common/FileUtil.cpp",

torch/nativert/executor/SerialGraphExecutor.cpp

@@ -0,0 +1,33 @@
+#include <torch/nativert/executor/ExecutionPlanner.h>
+#include <torch/nativert/executor/ExecutorConfig.h>
+#include <torch/nativert/executor/SerialGraphExecutor.h>
+
+namespace torch::nativert {
+
+std::vector<c10::IValue> SerialGraphExecutor::execute(
+    ExecutionFrame& executionFrame,
+    std::vector<c10::IValue> inputs) {
+  fillUserInputs(executionFrame, std::move(inputs));
+
+  return executeWithPrefilledFrame(executionFrame);
+}
+
+std::vector<c10::IValue> SerialGraphExecutor::executeWithPrefilledFrame(
+    ExecutionFrame& executionFrame) {
+  // Execute kernels for all nodes except prim.Input and prim.Output
+  for (NodeIndex nodeIdx = 1; nodeIdx < nodeKernels_.size() - 1; ++nodeIdx) {
+    nodeKernels_[nodeIdx]->compute(executionFrame);
+
+    // don't free intermediate values when static memory planning is enabled
+    if (!executorConfig_.enableStaticMemoryPlanning) {
+      // Free the intermediate values that are no used anymore
+      for (const auto& valueKey : execPlan_->valuesToFree[nodeIdx]) {
+        executionFrame.releaseValue(valueKey);
+      }
+    }
+  }
+
+  return executionFrame.tryMoveUserOutputs();
+}
+
+} // namespace torch::nativert

torch/nativert/executor/SerialGraphExecutor.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <torch/nativert/executor/GraphExecutorBase.h>
+
+namespace torch::nativert {
+
+class SerialGraphExecutor : public GraphExecutorBase {
+ public:
+  SerialGraphExecutor(
+      const Graph& graph,
+      std::vector<std::unique_ptr<OpKernel>> nodeKernels,
+      const ExecutorConfig& executorConfig)
+      : GraphExecutorBase(graph, std::move(nodeKernels), executorConfig) {}
+
+  std::vector<c10::IValue> execute(
+      ExecutionFrame& frame,
+      std::vector<c10::IValue> inputs) override;
+
+  std::vector<c10::IValue> executeWithPrefilledFrame(
+      ExecutionFrame& frame) override;
+};
+
+} // namespace torch::nativert