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diff --git a/source/opt/block_merge_pass.h b/source/opt/block_merge_pass.h
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+// Copyright (c) 2017 The Khronos Group Inc.
+// Copyright (c) 2017 Valve Corporation
+// Copyright (c) 2017 LunarG Inc.
+//
+// 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.
+
+#ifndef LIBSPIRV_OPT_BLOCK_MERGE_PASS_H_
+#define LIBSPIRV_OPT_BLOCK_MERGE_PASS_H_
+
+#include <algorithm>
+#include <map>
+#include <queue>
+#include <unordered_map>
+#include <unordered_set>
+#include <utility>
+
+#include "basic_block.h"
+#include "def_use_manager.h"
+#include "module.h"
+#include "pass.h"
+
+namespace spvtools {
+namespace opt {
+
+// See optimizer.hpp for documentation.
+class BlockMergePass : public Pass {
+ public:
+  BlockMergePass();
+  const char* name() const override { return "sroa"; }
+  Status Process(ir::Module*) override;
+
+ private:
+  // Return true if |block_ptr| is loop header block
+  bool IsLoopHeader(ir::BasicBlock* block_ptr);
+
+  // Return true if |labId| has multiple refs. Do not count OpName.
+  bool HasMultipleRefs(uint32_t labId);
+
+  // Kill any OpName instruction referencing |inst|, then kill |inst|.
+  void KillInstAndName(ir::Instruction* inst);
+
+  // Search |func| for blocks which have a single Branch to a block
+  // with no other predecessors. Merge these blocks into a single block.
+  bool MergeBlocks(ir::Function* func);
+
+  // Initialize extensions whitelist
+  void InitExtensions();
+
+  // Return true if all extensions in this module are allowed by this pass.
+  bool AllExtensionsSupported() const;
+
+  void Initialize(ir::Module* module);
+  Pass::Status ProcessImpl();
+
+  // Module this pass is processing
+  ir::Module* module_;
+
+  // Def-Uses for the module we are processing
+  std::unique_ptr<analysis::DefUseManager> def_use_mgr_;
+
+  // Map from function's result id to function
+  std::unordered_map<uint32_t, ir::Function*> id2function_;
+
+  // Extensions supported by this pass.
+  std::unordered_set<std::string> extensions_whitelist_;
+};
+
+}  // namespace opt
+}  // namespace spvtools
+
+#endif  // LIBSPIRV_OPT_BLOCK_MERGE_PASS_H_
+