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#ifndef SRC_TINT_LANG_CORE_IR_INSTRUCTION_H_
#define SRC_TINT_LANG_CORE_IR_INSTRUCTION_H_

#include <string>

#include "src/tint/lang/core/ir/instruction_result.h"
#include "src/tint/lang/core/ir/value.h"
#include "src/tint/utils/containers/const_propagating_ptr.h"
#include "src/tint/utils/containers/enum_set.h"
#include "src/tint/utils/rtti/castable.h"

// Forward declarations
namespace tint::core::ir {
class Block;
class CloneContext;
}  // namespace tint::core::ir

namespace tint::core::ir {

/// An instruction in the IR.
class Instruction : public Castable<Instruction> {
  public:
    /// Destructor
    ~Instruction() override;

    /// Set an operand at a given index.
    /// @param index the operand index
    /// @param value the value to use
    virtual void SetOperand(size_t index, ir::Value* value) = 0;

    /// @returns the operands of the instruction
    virtual VectorRef<ir::Value*> Operands() = 0;

    /// @returns the operands of the instruction
    virtual VectorRef<const ir::Value*> Operands() const = 0;

    /// Replaces the operands of the instruction
    /// @param operands the new operands of the instruction
    virtual void SetOperands(VectorRef<ir::Value*> operands) = 0;

    /// Replaces the results of the instruction
    /// @param results the new results of the instruction
    virtual void SetResults(VectorRef<ir::InstructionResult*> results) = 0;

    /// @returns the result values for this instruction
    virtual VectorRef<InstructionResult*> Results() = 0;

    /// @returns the result values for this instruction
    virtual VectorRef<const InstructionResult*> Results() const = 0;

    /// Removes the instruction from the block, and destroys all the result values.
    /// The result values must not be in use.
    virtual void Destroy();

    /// @returns the friendly name for the instruction
    virtual std::string FriendlyName() const = 0;

    /// @param ctx the CloneContext used to clone this instruction
    /// @returns a clone of this instruction
    virtual Instruction* Clone(CloneContext& ctx) = 0;

    /// @returns true if the Instruction has not been destroyed with Destroy()
    bool Alive() const { return !flags_.Contains(Flag::kDead); }

    /// @returns true if the Instruction is sequenced. Sequenced instructions cannot be implicitly
    /// reordered with other sequenced instructions.
    bool Sequenced() const { return flags_.Contains(Flag::kSequenced); }

    /// Sets the block that owns this instruction
    /// @param block the new owner block
    void SetBlock(ir::Block* block) { block_ = block; }

    /// @returns the block that owns this instruction
    ir::Block* Block() { return block_; }

    /// @returns the block that owns this instruction
    const ir::Block* Block() const { return block_; }

    /// Adds the new instruction before the given instruction in the owning block
    /// @param before the instruction to insert before
    void InsertBefore(Instruction* before);
    /// Adds the new instruction after the given instruction in the owning block
    /// @param after the instruction to insert after
    void InsertAfter(Instruction* after);
    /// Replaces this instruction with @p replacement in the owning block owning this instruction
    /// @param replacement the instruction to replace with
    void ReplaceWith(Instruction* replacement);
    /// Removes this instruction from the owning block
    void Remove();

    /// @param idx the index of the operand
    /// @returns the operand with index @p idx, or `nullptr` if there are no operands or the index
    /// is out of bounds.
    Value* Operand(size_t idx) {
        auto res = Operands();
        return idx < res.Length() ? res[idx] : nullptr;
    }

    /// @param idx the index of the operand
    /// @returns the operand with index @p idx, or `nullptr` if there are no operands or the index
    /// is out of bounds.
    const Value* Operand(size_t idx) const {
        auto res = Operands();
        return idx < res.Length() ? res[idx] : nullptr;
    }

    /// @param idx the index of the result
    /// @returns the result with index @p idx, or `nullptr` if there are no results or the index is
    /// out of bounds.
    InstructionResult* Result(size_t idx) {
        auto res = Results();
        return idx < res.Length() ? res[idx] : nullptr;
    }

    /// @param idx the index of the result
    /// @returns the result with index @p idx, or `nullptr` if there are no results or the index is
    /// out of bounds.
    const InstructionResult* Result(size_t idx) const {
        auto res = Results();
        return idx < res.Length() ? res[idx] : nullptr;
    }

    /// Pointer to the next instruction in the list
    ConstPropagatingPtr<Instruction> next;
    /// Pointer to the previous instruction in the list
    ConstPropagatingPtr<Instruction> prev;

  protected:
    /// Flags applied to an Instruction
    enum class Flag {
        /// The instruction has been destroyed
        kDead,
        /// The instruction must not be reordered with another sequenced instruction
        kSequenced,
    };

    /// Constructor
    Instruction();

    /// The block that owns this instruction
    ConstPropagatingPtr<ir::Block> block_;

    /// Bitset of instruction flags
    tint::EnumSet<Flag> flags_;
};

}  // namespace tint::core::ir

#endif  // SRC_TINT_LANG_CORE_IR_INSTRUCTION_H_