// 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_FOLD_H_

#define SOURCE_OPT_FOLD_H_

#include <cstdint>

#include <vector>

#include "source/opt/const_folding_rules.h"

#include "source/opt/constants.h"

#include "source/opt/def_use_manager.h"

#include "source/opt/folding_rules.h"

namespace spvtools {

namespace opt {

class InstructionFolder {

 public:

  explicit InstructionFolder(IRContext* context)

      : context_(context),

        const_folding_rules_(new ConstantFoldingRules(context)),

        folding_rules_(new FoldingRules(context)) {

    folding_rules_->AddFoldingRules();

    const_folding_rules_->AddFoldingRules();

  }

  explicit InstructionFolder(

      IRContext* context, std::unique_ptr<FoldingRules>&& folding_rules,

      std::unique_ptr<ConstantFoldingRules>&& constant_folding_rules)

      : context_(context),

        const_folding_rules_(std::move(constant_folding_rules)),

        folding_rules_(std::move(folding_rules)) {

    folding_rules_->AddFoldingRules();

    const_folding_rules_->AddFoldingRules();

  }

  // Returns the result of folding a scalar instruction with the given |opcode|

  // and |operands|. Each entry in |operands| is a pointer to an

  // analysis::Constant instance, which should've been created with the constant

  // manager (See IRContext::get_constant_mgr).

  //

  // It is an error to call this function with an opcode that does not pass the

  // IsFoldableOpcode test. If any error occurs during folding, the folder will

  // fail with a call to assert.

  uint32_t FoldScalars(

      spv::Op opcode,

      const std::vector<const analysis::Constant*>& operands) const;

  // Returns the result of performing an operation with the given |opcode| over

  // constant vectors with |num_dims| dimensions.  Each entry in |operands| is a

  // pointer to an analysis::Constant instance, which should've been created

  // with the constant manager (See IRContext::get_constant_mgr).

  //

  // This function iterates through the given vector type constant operands and

  // calculates the result for each element of the result vector to return.

  // Vectors with longer than 32-bit scalar components are not accepted in this

  // function.

  //

  // It is an error to call this function with an opcode that does not pass the

  // IsFoldableOpcode test. If any error occurs during folding, the folder will

  // fail with a call to assert.

  std::vector<uint32_t> FoldVectors(

      spv::Op opcode, uint32_t num_dims,

      const std::vector<const analysis::Constant*>& operands) const;

  // Returns true if |opcode| represents an operation handled by FoldScalars or

  // FoldVectors.

  bool IsFoldableOpcode(spv::Op opcode) const;

  // Returns true if |cst| is supported by FoldScalars and FoldVectors.

  bool IsFoldableConstant(const analysis::Constant* cst) const;

  // Returns true if |FoldInstructionToConstant| could fold an instruction whose

  // result type is |type_inst|.

  bool IsFoldableType(Instruction* type_inst) const;

  // Returns true if |FoldInstructionToConstant| could fold an instruction whose

  // result type is |type_inst|.

  bool IsFoldableScalarType(Instruction* type_inst) const;

  // Returns true if |FoldInstructionToConstant| could fold an instruction whose

  // result type is |type_inst|.

  bool IsFoldableVectorType(Instruction* type_inst) const;

  // Tries to fold |inst| to a single constant, when the input ids to |inst|

  // have been substituted using |id_map|.  Returns a pointer to the OpConstant*

  // instruction if successful.  If necessary, a new constant instruction is

  // created and placed in the global values section.

  //

  // |id_map| is a function that takes one result id and returns another.  It

  // can be used for things like CCP where it is known that some ids contain a

  // constant, but the instruction itself has not been updated yet.  This can

  // map those ids to the appropriate constants.

  Instruction* FoldInstructionToConstant(

      Instruction* inst, std::function<uint32_t(uint32_t)> id_map) const;

  // Returns true if |inst| can be folded into a simpler instruction.

  // If |inst| can be simplified, |inst| is overwritten with the simplified

  // instruction reusing the same result id.

  //

  // If |inst| is simplified, it is possible that the resulting code in invalid

  // because the instruction is in a bad location.  Callers of this function

  // have to handle the following cases:

  //

  // 1) An OpPhi becomes and OpCopyObject - If there are OpPhi instruction after

  //    |inst| in a basic block then this is invalid.  The caller must fix this

  //    up.

  bool FoldInstruction(Instruction* inst) const;

  // Return true if this opcode has a const folding rule associtated with it.

  bool HasConstFoldingRule(const Instruction* inst) const {

    return GetConstantFoldingRules().HasFoldingRule(inst);

  }

 private:

  // Returns a reference to the ConstnatFoldingRules instance.

  const ConstantFoldingRules& GetConstantFoldingRules() const {

    return *const_folding_rules_;

  }

  // Returns a reference to the FoldingRules instance.

  const FoldingRules& GetFoldingRules() const { return *folding_rules_; }

  // Returns the single-word result from performing the given unary operation on

  // the operand value which is passed in as a 32-bit word.

  uint32_t UnaryOperate(spv::Op opcode, uint32_t operand) const;

  // Returns the single-word result from performing the given binary operation

  // on the operand values which are passed in as two 32-bit word.

  uint32_t BinaryOperate(spv::Op opcode, uint32_t a, uint32_t b) const;

  // Returns the single-word result from performing the given ternary operation

  // on the operand values which are passed in as three 32-bit word.

  uint32_t TernaryOperate(spv::Op opcode, uint32_t a, uint32_t b,

                          uint32_t c) const;

  // Returns the single-word result from performing the given operation on the

  // operand words. This only works with 32-bit operations and uses boolean

  // convention that 0u is false, and anything else is boolean true.

  // TODO(qining): Support operands other than 32-bit wide.

  uint32_t OperateWords(spv::Op opcode,

                        const std::vector<uint32_t>& operand_words) const;

  bool FoldInstructionInternal(Instruction* inst) const;

  // Returns true if |inst| is a binary operation that takes two integers as

  // parameters and folds to a constant that can be represented as an unsigned

  // 32-bit value when the ids have been replaced by |id_map|.  If |inst| can be

  // folded, the resulting value is returned in |*result|.  Valid result types

  // for the instruction are any integer (signed or unsigned) with 32-bits or

  // less, or a boolean value.

  bool FoldBinaryIntegerOpToConstant(

      Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map,

      uint32_t* result) const;

  // Returns true if |inst| is a binary operation on two boolean values, and

  // folds

  // to a constant boolean value when the ids have been replaced using |id_map|.

  // If |inst| can be folded, the result value is returned in |*result|.

  bool FoldBinaryBooleanOpToConstant(

      Instruction* inst, const std::function<uint32_t(uint32_t)>& id_map,

      uint32_t* result) const;

  // Returns true if |inst| can be folded to an constant when the ids have been

  // substituted using id_map.  If it can, the value is returned in |result|. If

  // not, |result| is unchanged.  It is assumed that not all operands are

  // constant.  Those cases are handled by |FoldScalar|.

  bool FoldIntegerOpToConstant(Instruction* inst,

                               const std::function<uint32_t(uint32_t)>& id_map,

                               uint32_t* result) const;

  IRContext* context_;

  // Folding rules used by |FoldInstructionToConstant| and |FoldInstruction|.

  std::unique_ptr<ConstantFoldingRules> const_folding_rules_;

  // Folding rules used by |FoldInstruction|.

  std::unique_ptr<FoldingRules> folding_rules_;

};

}  // namespace opt

}  // namespace spvtools

#endif  // SOURCE_OPT_FOLD_H_