// Copyright (c) 2015-2016 The Khronos Group 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_VAL_FUNCTION_H_
#define LIBSPIRV_VAL_FUNCTION_H_

#include <functional>
#include <list>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "latest_version_spirv_header.h"
#include "spirv-tools/libspirv.h"
#include "val/basic_block.h"
#include "val/construct.h"

namespace libspirv {

struct bb_constr_type_pair_hash {
  std::size_t operator()(
      const std::pair<const BasicBlock*, ConstructType>& p) const {
    auto h1 = std::hash<const BasicBlock*>{}(p.first);
    auto h2 = std::hash<std::underlying_type<ConstructType>::type>{}(
        static_cast<std::underlying_type<ConstructType>::type>(p.second));
    return (h1 ^ h2);
  }
};

enum class FunctionDecl {
  kFunctionDeclUnknown,      /// < Unknown function declaration
  kFunctionDeclDeclaration,  /// < Function declaration
  kFunctionDeclDefinition    /// < Function definition
};

/// This class manages all function declaration and definitions in a module. It
/// handles the state and id information while parsing a function in the SPIR-V
/// binary.
class Function {
 public:
  Function(uint32_t id, uint32_t result_type_id,
           SpvFunctionControlMask function_control, uint32_t function_type_id);

  /// Registers a function parameter in the current function
  /// @return Returns SPV_SUCCESS if the call was successful
  spv_result_t RegisterFunctionParameter(uint32_t id, uint32_t type_id);

  /// Sets the declaration type of the current function
  /// @return Returns SPV_SUCCESS if the call was successful
  spv_result_t RegisterSetFunctionDeclType(FunctionDecl type);

  /// Registers a block in the current function. Subsequent block instructions
  /// will target this block
  /// @param id The ID of the label of the block
  /// @return Returns SPV_SUCCESS if the call was successful
  spv_result_t RegisterBlock(uint32_t id, bool is_definition = true);

  /// Registers a variable in the current block
  ///
  /// @param[in] type_id The type ID of the varaible
  /// @param[in] id      The ID of the varaible
  /// @param[in] storage The storage of the variable
  /// @param[in] init_id The initializer ID of the variable
  ///
  /// @return Returns SPV_SUCCESS if the call was successful
  spv_result_t RegisterBlockVariable(uint32_t type_id, uint32_t id,
                                     SpvStorageClass storage, uint32_t init_id);

  /// Registers a loop merge construct in the function
  ///
  /// @param[in] merge_id The merge block ID of the loop
  /// @param[in] continue_id The continue block ID of the loop
  ///
  /// @return Returns SPV_SUCCESS if the call was successful
  spv_result_t RegisterLoopMerge(uint32_t merge_id, uint32_t continue_id);

  /// Registers a selection merge construct in the function
  /// @return Returns SPV_SUCCESS if the call was successful
  spv_result_t RegisterSelectionMerge(uint32_t merge_id);

  /// Registers the end of the block
  ///
  /// @param[in] successors_list A list of ids to the block's successors
  /// @param[in] branch_instruction the branch instruction that ended the block
  void RegisterBlockEnd(std::vector<uint32_t> successors_list,
                        SpvOp branch_instruction);

  /// Registers the end of the function.  This is idempotent.
  void RegisterFunctionEnd();

  /// Returns true if the \p id block is the first block of this function
  bool IsFirstBlock(uint32_t id) const;

  /// Returns true if the \p merge_block_id is a BlockType of \p type
  bool IsBlockType(uint32_t merge_block_id, BlockType type) const;

  /// Returns a pair consisting of the BasicBlock with \p id and a bool
  /// which is true if the block has been defined, and false if it is
  /// declared but not defined. This function will return nullptr if the
  /// \p id was not declared and not defined at the current point in the binary
  std::pair<const BasicBlock*, bool> GetBlock(uint32_t id) const;
  std::pair<BasicBlock*, bool> GetBlock(uint32_t id);

  /// Returns the first block of the current function
  const BasicBlock* first_block() const;

  /// Returns the first block of the current function
  BasicBlock* first_block();

  /// Returns a vector of all the blocks in the function
  const std::vector<BasicBlock*>& ordered_blocks() const;

  /// Returns a vector of all the blocks in the function
  std::vector<BasicBlock*>& ordered_blocks();

  /// Returns a list of all the cfg constructs in the function
  const std::list<Construct>& constructs() const;

  /// Returns a list of all the cfg constructs in the function
  std::list<Construct>& constructs();

  /// Returns the number of blocks in the current function being parsed
  size_t block_count() const;

  /// Returns the id of the function
  uint32_t id() const { return id_; }

  /// Returns return type id of the function
  uint32_t GetResultTypeId() const { return result_type_id_; }

  /// Returns the number of blocks in the current function being parsed
  size_t undefined_block_count() const;
  const std::unordered_set<uint32_t>& undefined_blocks() const {
    return undefined_blocks_;
  }

  /// Returns the block that is currently being parsed in the binary
  BasicBlock* current_block();

  /// Returns the block that is currently being parsed in the binary
  const BasicBlock* current_block() const;

  // For dominance calculations, we want to analyze all the
  // blocks in the function, even in degenerate control flow cases
  // including unreachable blocks.  We therefore make an "augmented CFG"
  // which is the same as the ordinary CFG but adds:
  //  - A pseudo-entry node.
  //  - A pseudo-exit node.
  //  - A minimal set of edges so that a forward traversal from the
  //    pseudo-entry node will visit all nodes.
  //  - A minimal set of edges so that a backward traversal from the
  //    pseudo-exit node will visit all nodes.
  // In particular, the pseudo-entry node is the unique source of the
  // augmented CFG, and the psueo-exit node is the unique sink of the
  // augmented CFG.

  /// Returns the pseudo exit block
  BasicBlock* pseudo_entry_block() { return &pseudo_entry_block_; }

  /// Returns the pseudo exit block
  const BasicBlock* pseudo_entry_block() const { return &pseudo_entry_block_; }

  /// Returns the pseudo exit block
  BasicBlock* pseudo_exit_block() { return &pseudo_exit_block_; }

  /// Returns the pseudo exit block
  const BasicBlock* pseudo_exit_block() const { return &pseudo_exit_block_; }

  using GetBlocksFunction =
      std::function<const std::vector<BasicBlock*>*(const BasicBlock*)>;
  /// Returns the block successors function for the augmented CFG.
  GetBlocksFunction AugmentedCFGSuccessorsFunction() const;
  /// Like AugmentedCFGSuccessorsFunction, but also includes a forward edge from
  /// a loop header block to its continue target, if they are different blocks.
  GetBlocksFunction
  AugmentedCFGSuccessorsFunctionIncludingHeaderToContinueEdge() const;
  /// Returns the block predecessors function for the augmented CFG.
  GetBlocksFunction AugmentedCFGPredecessorsFunction() const;

  /// Returns the control flow nesting depth of the given basic block.
  /// This function only works when you have structured control flow.
  /// This function should only be called after the control flow constructs have
  /// been identified and dominators have been computed.
  int GetBlockDepth(BasicBlock* bb);

  /// Prints a GraphViz digraph of the CFG of the current funciton
  void PrintDotGraph() const;

  /// Prints a directed graph of the CFG of the current funciton
  void PrintBlocks() const;

  /// Registers execution model limitation such as "Feature X is only available
  /// with Execution Model Y".
  void RegisterExecutionModelLimitation(SpvExecutionModel model,
                                        const std::string& message);

  /// Registers execution model limitation with an |is_compatible| functor.
  void RegisterExecutionModelLimitation(
      std::function<bool(SpvExecutionModel, std::string*)> is_compatible) {
    execution_model_limitations_.push_back(is_compatible);
  }

  /// Returns true if the given execution model passes the limitations stored in
  /// execution_model_limitations_. Returns false otherwise and fills optional
  /// |reason| parameter.
  bool IsCompatibleWithExecutionModel(SpvExecutionModel model,
                                      std::string* reason = nullptr) const;

  // Inserts id to the set of functions called from this function.
  void AddFunctionCallTarget(uint32_t call_target_id) {
    function_call_targets_.insert(call_target_id);
  }

  // Returns a set with ids of all functions called from this function.
  const std::set<uint32_t> function_call_targets() const {
    return function_call_targets_;
  }

 private:
  // Computes the representation of the augmented CFG.
  // Populates augmented_successors_map_ and augmented_predecessors_map_.
  void ComputeAugmentedCFG();

  // Adds a copy of the given Construct, and tracks it by its entry block.
  // Returns a reference to the stored construct.
  Construct& AddConstruct(const Construct& new_construct);

  // Returns a reference to the construct corresponding to the given entry
  // block.
  Construct& FindConstructForEntryBlock(const BasicBlock* entry_block,
                                        ConstructType t);

  /// The result id of the OpLabel that defined this block
  uint32_t id_;

  /// The type of the function
  uint32_t function_type_id_;

  /// The type of the return value
  uint32_t result_type_id_;

  /// The control fo the funciton
  SpvFunctionControlMask function_control_;

  /// The type of declaration of each function
  FunctionDecl declaration_type_;

  // Have we finished parsing this function?
  bool end_has_been_registered_;

  /// The blocks in the function mapped by block ID
  std::unordered_map<uint32_t, BasicBlock> blocks_;

  /// A list of blocks in the order they appeared in the binary
  std::vector<BasicBlock*> ordered_blocks_;

  /// Blocks which are forward referenced by blocks but not defined
  std::unordered_set<uint32_t> undefined_blocks_;

  /// The block that is currently being parsed
  BasicBlock* current_block_;

  /// A pseudo entry node used in dominance analysis.
  /// After the function end has been registered, the successor list of the
  /// pseudo entry node is the minimal set of nodes such that all nodes in the
  /// CFG can be reached by following successor lists.  That is, the successors
  /// will be:
  ///   - Any basic block without predecessors.  This includes the entry
  ///     block to the function.
  ///   - A single node from each otherwise unreachable cycle in the CFG, if
  ///     such cycles exist.
  /// The pseudo entry node does not appear in the predecessor or successor
  /// list of any ordinary block.
  /// It has no predecessors.
  /// It has Id 0.
  BasicBlock pseudo_entry_block_;

  /// A pseudo exit block used in dominance analysis.
  /// After the function end has been registered, the predecessor list of the
  /// pseudo exit node is the minimal set of nodes such that all nodes in the
  /// CFG can be reached by following predecessor lists.  That is, the
  /// predecessors will be:
  ///   - Any basic block without successors.  This includes any basic block
  ///     ending with an OpReturn, OpReturnValue or similar instructions.
  ///   - A single node from each otherwise unreachable cycle in the CFG, if
  ///     such cycles exist.
  /// The pseudo exit node does not appear in the predecessor or successor
  /// list of any ordinary block.
  /// It has no successors.
  BasicBlock pseudo_exit_block_;

  // Maps a block to its successors in the augmented CFG, if that set is
  // different from its successors in the ordinary CFG.
  std::unordered_map<const BasicBlock*, std::vector<BasicBlock*>>
      augmented_successors_map_;
  // Maps a block to its predecessors in the augmented CFG, if that set is
  // different from its predecessors in the ordinary CFG.
  std::unordered_map<const BasicBlock*, std::vector<BasicBlock*>>
      augmented_predecessors_map_;

  // Maps a structured loop header to its CFG successors and also its
  // continue target if that continue target is not the loop header
  // itself. This might have duplicates.
  std::unordered_map<const BasicBlock*, std::vector<BasicBlock*>>
      loop_header_successors_plus_continue_target_map_;

  /// The constructs that are available in this function
  std::list<Construct> cfg_constructs_;

  /// The variable IDs of the functions
  std::vector<uint32_t> variable_ids_;

  /// The function parameter ids of the functions
  std::vector<uint32_t> parameter_ids_;

  /// Maps a construct's entry block to the construct(s).
  /// Since a basic block may be the entry block of different types of
  /// constructs, the type of the construct should also be specified in order to
  /// get the unique construct.
  std::unordered_map<std::pair<const BasicBlock*, ConstructType>, Construct*,
                     libspirv::bb_constr_type_pair_hash>
      entry_block_to_construct_;

  /// This map provides the header block for a given merge block.
  std::unordered_map<BasicBlock*, BasicBlock*> merge_block_header_;

  /// Stores the control flow nesting depth of a given basic block
  std::unordered_map<BasicBlock*, int> block_depth_;

  /// Stores execution model limitations imposed by instructions used within the
  /// function. The functor stored in the list return true if execution model
  /// is compatible, false otherwise. If the functor returns false, it can also
  /// optionally fill the string parameter with the reason for incompatibility.
  std::list<std::function<bool(SpvExecutionModel, std::string*)>>
      execution_model_limitations_;

  /// Stores ids of all functions called from this function.
  std::set<uint32_t> function_call_targets_;
};

}  // namespace libspirv

#endif  /// LIBSPIRV_VAL_FUNCTION_H_