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diff --git a/tensorflow/compiler/xla/service/hlo_subcomputation_unification.cc b/tensorflow/compiler/xla/service/hlo_subcomputation_unification.cc
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+++ b/tensorflow/compiler/xla/service/hlo_subcomputation_unification.cc
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+/* Copyright 2017 The TensorFlow Authors. All Rights Reserved.
+
+Licensed 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.
+==============================================================================*/
+
+#include "tensorflow/compiler/xla/service/hlo_subcomputation_unification.h"
+
+#include <unordered_map>
+
+namespace xla {
+
+StatusOr<bool> HloSubcomputationUnification::Run(HloModule* module) {
+  // For each computation C in the module, find the first computation C0 in the
+  // computations_ list that is identical to C, and adds canon[C] = C0.
+  std::unordered_map<HloComputation*, HloComputation*> canon;
+  const auto& computations = module->computations();
+  for (auto i = computations.begin(); i != computations.end(); ++i) {
+    for (auto j = computations.begin(); j < i; ++j) {
+      // Do not waste time comparing `*i` with `*j` if `*j` is not canonical.
+      if (canon.find(j->get()) == canon.end() && **i == **j) {
+        canon[i->get()] = j->get();
+        break;
+      }
+    }
+  }
+
+  if (canon.empty()) {
+    return false;
+  }
+
+  module->ReplaceComputations(canon);
+  return true;
+}
+
+}  // namespace xla