// Copyright (c) 2018 Google LLC.

//

// 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 SOURCE_OPT_LICM_PASS_H_

#define SOURCE_OPT_LICM_PASS_H_

#include <queue>

#include <vector>

#include "source/opt/basic_block.h"

#include "source/opt/instruction.h"

#include "source/opt/loop_descriptor.h"

#include "source/opt/pass.h"

namespace spvtools {

namespace opt {

class LICMPass : public Pass {

 public:

  LICMPass() {}

  const char* name() const override { return "loop-invariant-code-motion"; }

  Status Process() override;

 private:

  // Searches the IRContext for functions and processes each, moving invariants

  // outside loops within the function where possible.

  // Returns the status depending on whether or not there was a failure or

  // change.

  Pass::Status ProcessIRContext();

  // Checks the function for loops, calling ProcessLoop on each one found.

  // Returns the status depending on whether or not there was a failure or

  // change.

  Pass::Status ProcessFunction(Function* f);

  // Checks for invariants in the loop and attempts to move them to the loops

  // preheader. Works from inner loop to outer when nested loops are found.

  // Returns the status depending on whether or not there was a failure or

  // change.

  Pass::Status ProcessLoop(Loop* loop, Function* f);

  // Analyses each instruction in |bb|, hoisting invariants to |pre_header_bb|.

  // Each child of |bb| wrt to |dom_tree| is pushed to |loop_bbs|

  // Returns the status depending on whether or not there was a failure or

  // change.

  Pass::Status AnalyseAndHoistFromBB(Loop* loop, Function* f, BasicBlock* bb,

                                     std::vector<BasicBlock*>* loop_bbs);

  // Returns true if |bb| is immediately contained in |loop|

  bool IsImmediatelyContainedInLoop(Loop* loop, Function* f, BasicBlock* bb);

  // Move the instruction to the preheader of |loop|.

  // This method will update the instruction to block mapping for the context

  bool HoistInstruction(Loop* loop, Instruction* inst);

};

}  // namespace opt

}  // namespace spvtools

#endif  // SOURCE_OPT_LICM_PASS_H_