// Copyright (c) 2017 Google 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 SOURCE_OPT_PRIVATE_TO_LOCAL_PASS_H_

#define SOURCE_OPT_PRIVATE_TO_LOCAL_PASS_H_

#include "source/opt/ir_context.h"

#include "source/opt/pass.h"

namespace spvtools {

namespace opt {

// This pass implements total redundancy elimination.  This is the same as

// local redundancy elimination except it looks across basic block boundaries.

// An instruction, inst, is totally redundant if there is another instruction

// that dominates inst, and also computes the same value.

class PrivateToLocalPass : public Pass {

 public:

  const char* name() const override { return "private-to-local"; }

  Status Process() override;

  IRContext::Analysis GetPreservedAnalyses() override {

    return IRContext::kAnalysisDefUse |

           IRContext::kAnalysisInstrToBlockMapping |

           IRContext::kAnalysisDecorations | IRContext::kAnalysisCombinators |

           IRContext::kAnalysisCFG | IRContext::kAnalysisDominatorAnalysis |

           IRContext::kAnalysisNameMap | IRContext::kAnalysisConstants |

           IRContext::kAnalysisTypes;

  }

 private:

  // Moves |variable| from the private storage class to the function storage

  // class of |function|.  Returns false if the variable could not be moved.

  bool MoveVariable(Instruction* variable, Function* function);

  // |inst| is an instruction declaring a variable.  If that variable is

  // referenced in a single function and all of uses are valid as defined by

  // |IsValidUse|, then that function is returned.  Otherwise, the return

  // value is |nullptr|.

  Function* FindLocalFunction(const Instruction& inst) const;

  // Returns true is |inst| is a valid use of a pointer.  In this case, a

  // valid use is one where the transformation is able to rewrite the type to

  // match a change in storage class of the original variable.

  bool IsValidUse(const Instruction* inst, uint32_t private_variable_id) const;

  // Given the result id of a pointer type, |old_type_id|, this function

  // returns the id of a the same pointer type except the storage class has

  // been changed to function.  If the type does not already exist, it will be

  // created.  Returns 0 if the new type could not be found or generated.

  uint32_t GetNewType(uint32_t old_type_id);

  // Updates |inst|, and any instruction dependent on |inst|, to reflect the

  // change of the base pointer now pointing to the function storage class.

  bool UpdateUse(Instruction* inst, Instruction* user);

  bool UpdateUses(Instruction* inst);

};

}  // namespace opt

}  // namespace spvtools

#endif  // SOURCE_OPT_PRIVATE_TO_LOCAL_PASS_H_