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//===-- llvm/Instruction.h - Instruction class definition -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the Instruction class, which is the
// base class for all of the LLVM instructions.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_INSTRUCTION_H
#define LLVM_INSTRUCTION_H

#include "llvm/User.h"
#include "llvm/ADT/ilist_node.h"

namespace llvm {

class LLVMContext;

template<typename ValueSubClass, typename ItemParentClass>
  class SymbolTableListTraits;

class Instruction : public User, public ilist_node<Instruction> {
  void operator=(const Instruction &);     // Do not implement
  Instruction(const Instruction &);        // Do not implement

  BasicBlock *Parent;

  friend class SymbolTableListTraits<Instruction, BasicBlock>;
  void setParent(BasicBlock *P);
protected:
  Instruction(const Type *Ty, unsigned iType, Use *Ops, unsigned NumOps,
              Instruction *InsertBefore = 0);
  Instruction(const Type *Ty, unsigned iType, Use *Ops, unsigned NumOps,
              BasicBlock *InsertAtEnd);
public:
  // Out of line virtual method, so the vtable, etc has a home.
  ~Instruction();
  
  /// clone() - Create a copy of 'this' instruction that is identical in all
  /// ways except the following:
  ///   * The instruction has no parent
  ///   * The instruction has no name
  ///
  virtual Instruction *clone(LLVMContext &Context) const = 0;

  /// isIdenticalTo - Return true if the specified instruction is exactly
  /// identical to the current one.  This means that all operands match and any
  /// extra information (e.g. load is volatile) agree.
  bool isIdenticalTo(const Instruction *I) const;

  /// isIdenticalToWhenDefined - This is like isIdenticalTo, except that it
  /// ignores the SubclassOptionalData flags, which specify conditions
  /// under which the instruction's result is undefined.
  bool isIdenticalToWhenDefined(const Instruction *I) const;

  /// This function determines if the specified instruction executes the same
  /// operation as the current one. This means that the opcodes, type, operand
  /// types and any other factors affecting the operation must be the same. This
  /// is similar to isIdenticalTo except the operands themselves don't have to
  /// be identical.
  /// @returns true if the specified instruction is the same operation as
  /// the current one.
  /// @brief Determine if one instruction is the same operation as another.
  bool isSameOperationAs(const Instruction *I) const;

  /// isUsedOutsideOfBlock - Return true if there are any uses of this
  /// instruction in blocks other than the specified block.  Note that PHI nodes
  /// are considered to evaluate their operands in the corresponding predecessor
  /// block.
  bool isUsedOutsideOfBlock(const BasicBlock *BB) const;
  
  
  /// use_back - Specialize the methods defined in Value, as we know that an
  /// instruction can only be used by other instructions.
  Instruction       *use_back()       { return cast<Instruction>(*use_begin());}
  const Instruction *use_back() const { return cast<Instruction>(*use_begin());}
  
  // Accessor methods...
  //
  inline const BasicBlock *getParent() const { return Parent; }
  inline       BasicBlock *getParent()       { return Parent; }

  /// removeFromParent - This method unlinks 'this' from the containing basic
  /// block, but does not delete it.
  ///
  void removeFromParent();

  /// eraseFromParent - This method unlinks 'this' from the containing basic
  /// block and deletes it.
  ///
  void eraseFromParent();

  /// insertBefore - Insert an unlinked instructions into a basic block
  /// immediately before the specified instruction.
  void insertBefore(Instruction *InsertPos);

  /// insertAfter - Insert an unlinked instructions into a basic block
  /// immediately after the specified instruction.
  void insertAfter(Instruction *InsertPos);

  /// moveBefore - Unlink this instruction from its current basic block and
  /// insert it into the basic block that MovePos lives in, right before
  /// MovePos.
  void moveBefore(Instruction *MovePos);

  // ---------------------------------------------------------------------------
  /// Subclass classification... getOpcode() returns a member of
  /// one of the enums that is coming soon (down below)...
  ///
  unsigned getOpcode() const { return getValueID() - InstructionVal; }
  const char *getOpcodeName() const { return getOpcodeName(getOpcode()); }
  bool isTerminator() const { return isTerminator(getOpcode()); }
  bool isBinaryOp() const { return isBinaryOp(getOpcode()); }
  bool isShift() { return isShift(getOpcode()); }
  bool isCast() const { return isCast(getOpcode()); }
  
  
  
  static const char* getOpcodeName(unsigned OpCode);

  static inline bool isTerminator(unsigned OpCode) {
    return OpCode >= TermOpsBegin && OpCode < TermOpsEnd;
  }

  static inline bool isBinaryOp(unsigned Opcode) {
    return Opcode >= BinaryOpsBegin && Opcode < BinaryOpsEnd;
  }

  /// @brief Determine if the Opcode is one of the shift instructions.
  static inline bool isShift(unsigned Opcode) {
    return Opcode >= Shl && Opcode <= AShr;
  }

  /// isLogicalShift - Return true if this is a logical shift left or a logical
  /// shift right.
  inline bool isLogicalShift() const {
    return getOpcode() == Shl || getOpcode() == LShr;
  }

  /// isArithmeticShift - Return true if this is an arithmetic shift right.
  inline bool isArithmeticShift() const {
    return getOpcode() == AShr;
  }

  /// @brief Determine if the OpCode is one of the CastInst instructions.
  static inline bool isCast(unsigned OpCode) {
    return OpCode >= CastOpsBegin && OpCode < CastOpsEnd;
  }

  /// isAssociative - Return true if the instruction is associative:
  ///
  ///   Associative operators satisfy:  x op (y op z) === (x op y) op z
  ///
  /// In LLVM, the Add, Mul, And, Or, and Xor operators are associative, when
  /// not applied to floating point types.
  ///
  bool isAssociative() const { return isAssociative(getOpcode(), getType()); }
  static bool isAssociative(unsigned op, const Type *Ty);

  /// isCommutative - Return true if the instruction is commutative:
  ///
  ///   Commutative operators satisfy: (x op y) === (y op x)
  ///
  /// In LLVM, these are the associative operators, plus SetEQ and SetNE, when
  /// applied to any type.
  ///
  bool isCommutative() const { return isCommutative(getOpcode()); }
  static bool isCommutative(unsigned op);

  /// mayWriteToMemory - Return true if this instruction may modify memory.
  ///
  bool mayWriteToMemory() const;

  /// mayReadFromMemory - Return true if this instruction may read memory.
  ///
  bool mayReadFromMemory() const;

  /// mayThrow - Return true if this instruction may throw an exception.
  ///
  bool mayThrow() const;

  /// mayHaveSideEffects - Return true if the instruction may have side effects.
  ///
  /// Note that this does not consider malloc and alloca to have side
  /// effects because the newly allocated memory is completely invisible to
  /// instructions which don't used the returned value.  For cases where this
  /// matters, isSafeToSpeculativelyExecute may be more appropriate.
  bool mayHaveSideEffects() const {
    return mayWriteToMemory() || mayThrow();
  }

  /// isSafeToSpeculativelyExecute - Return true if the instruction does not
  /// have any effects besides calculating the result and does not have
  /// undefined behavior.
  ///
  /// This method never returns true for an instruction that returns true for
  /// mayHaveSideEffects; however, this method also does some other checks in
  /// addition. It checks for undefined behavior, like dividing by zero or
  /// loading from an invalid pointer (but not for undefined results, like a
  /// shift with a shift amount larger than the width of the result). It checks
  /// for malloc and alloca because speculatively executing them might cause a
  /// memory leak. It also returns false for instructions related to control
  /// flow, specifically terminators and PHI nodes.
  ///
  /// This method only looks at the instruction itself and its operands, so if
  /// this method returns true, it is safe to move the instruction as long as
  /// the correct dominance relationships for the operands and users hold.
  /// However, this method can return true for instructions that read memory;
  /// for such instructions, moving them may change the resulting value.
  bool isSafeToSpeculativelyExecute() const;

  /// Methods for support type inquiry through isa, cast, and dyn_cast:
  static inline bool classof(const Instruction *) { return true; }
  static inline bool classof(const Value *V) {
    return V->getValueID() >= Value::InstructionVal;
  }

  //----------------------------------------------------------------------
  // Exported enumerations...
  //
  enum TermOps {       // These terminate basic blocks
#define  FIRST_TERM_INST(N)             TermOpsBegin = N,
#define HANDLE_TERM_INST(N, OPC, CLASS) OPC = N,
#define   LAST_TERM_INST(N)             TermOpsEnd = N+1
#include "llvm/Instruction.def"
  };

  enum BinaryOps {
#define  FIRST_BINARY_INST(N)             BinaryOpsBegin = N,
#define HANDLE_BINARY_INST(N, OPC, CLASS) OPC = N,
#define   LAST_BINARY_INST(N)             BinaryOpsEnd = N+1
#include "llvm/Instruction.def"
  };

  enum MemoryOps {
#define  FIRST_MEMORY_INST(N)             MemoryOpsBegin = N,
#define HANDLE_MEMORY_INST(N, OPC, CLASS) OPC = N,
#define   LAST_MEMORY_INST(N)             MemoryOpsEnd = N+1
#include "llvm/Instruction.def"
  };

  enum CastOps {
#define  FIRST_CAST_INST(N)             CastOpsBegin = N,
#define HANDLE_CAST_INST(N, OPC, CLASS) OPC = N,
#define   LAST_CAST_INST(N)             CastOpsEnd = N+1
#include "llvm/Instruction.def"
  };

  enum OtherOps {
#define  FIRST_OTHER_INST(N)             OtherOpsBegin = N,
#define HANDLE_OTHER_INST(N, OPC, CLASS) OPC = N,
#define   LAST_OTHER_INST(N)             OtherOpsEnd = N+1
#include "llvm/Instruction.def"
  };
};

// Instruction* is only 4-byte aligned.
template<>
class PointerLikeTypeTraits<Instruction*> {
  typedef Instruction* PT;
public:
  static inline void *getAsVoidPointer(PT P) { return P; }
  static inline PT getFromVoidPointer(void *P) {
    return static_cast<PT>(P);
  }
  enum { NumLowBitsAvailable = 2 };
};
  
} // End llvm namespace

#endif