path: root/include/llvm/Target/TargetInstrInfo.h

//===-- llvm/Target/TargetInstrInfo.h - Instruction Info --------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file describes the target machine instructions to the code generator.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_TARGET_TARGETINSTRINFO_H
#define LLVM_TARGET_TARGETINSTRINFO_H

#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/Support/DataTypes.h"
#include <vector>
#include <cassert>

namespace llvm {

class MachineInstr;
class TargetMachine;
class TargetRegisterClass;
class LiveVariables;
class CalleeSavedInfo;

template<class T> class SmallVectorImpl;

//---------------------------------------------------------------------------
// Data types used to define information about a single machine instruction
//---------------------------------------------------------------------------

typedef short MachineOpCode;
typedef unsigned InstrSchedClass;

//---------------------------------------------------------------------------
// struct TargetInstrDescriptor:
//  Predefined information about each machine instruction.
//  Designed to initialized statically.
//

const unsigned M_BRANCH_FLAG           = 1 << 0;
const unsigned M_CALL_FLAG             = 1 << 1;
const unsigned M_RET_FLAG              = 1 << 2;
const unsigned M_BARRIER_FLAG          = 1 << 3;
const unsigned M_DELAY_SLOT_FLAG       = 1 << 4;
  
/// M_SIMPLE_LOAD_FLAG - This flag is set for instructions that are simple loads
/// from memory.  This should only be set on instructions that load a value from
/// memory and return it in their only virtual register definition.
const unsigned M_SIMPLE_LOAD_FLAG      = 1 << 5;
  
/// M_MAY_STORE_FLAG - This flag is set to any instruction that could possibly
/// modify memory.  Instructions with this flag set are not necessarily simple
/// store instructions, they may store a modified value based on their operands,
/// or may not actually modify anything, for example.
const unsigned M_MAY_STORE_FLAG        = 1 << 6;
  
const unsigned M_INDIRECT_FLAG         = 1 << 7;
const unsigned M_IMPLICIT_DEF_FLAG     = 1 << 8;

// M_CONVERTIBLE_TO_3_ADDR - This is a 2-address instruction which can be
// changed into a 3-address instruction if the first two operands cannot be
// assigned to the same register.  The target must implement the
// TargetInstrInfo::convertToThreeAddress method for this instruction.
const unsigned M_CONVERTIBLE_TO_3_ADDR = 1 << 9;

// This M_COMMUTABLE - is a 2- or 3-address instruction (of the form X = op Y,
// Z), which produces the same result if Y and Z are exchanged.
const unsigned M_COMMUTABLE            = 1 << 10;

// M_TERMINATOR_FLAG - Is this instruction part of the terminator for a basic
// block?  Typically this is things like return and branch instructions.
// Various passes use this to insert code into the bottom of a basic block, but
// before control flow occurs.
const unsigned M_TERMINATOR_FLAG       = 1 << 11;

// M_USES_CUSTOM_DAG_SCHED_INSERTION - Set if this instruction requires custom
// insertion support when the DAG scheduler is inserting it into a machine basic
// block.
const unsigned M_USES_CUSTOM_DAG_SCHED_INSERTION = 1 << 12;

// M_VARIABLE_OPS - Set if this instruction can have a variable number of extra
// operands in addition to the minimum number operands specified.
const unsigned M_VARIABLE_OPS          = 1 << 13;

// M_PREDICABLE - Set if this instruction has a predicate operand that
// controls execution. It may be set to 'always'.
const unsigned M_PREDICABLE            = 1 << 14;

// M_REMATERIALIZIBLE - Set if this instruction can be trivally re-materialized
// at any time, e.g. constant generation, load from constant pool.
const unsigned M_REMATERIALIZIBLE      = 1 << 15;

// M_NOT_DUPLICABLE - Set if this instruction cannot be safely duplicated.
// (e.g. instructions with unique labels attached).
const unsigned M_NOT_DUPLICABLE        = 1 << 16;

// M_HAS_OPTIONAL_DEF - Set if this instruction has an optional definition, e.g.
// ARM instructions which can set condition code if 's' bit is set.
const unsigned M_HAS_OPTIONAL_DEF      = 1 << 17;

// M_NEVER_HAS_SIDE_EFFECTS - Set if this instruction has no side effects that
// are not captured by any operands of the instruction or other flags, and when
// *all* instances of the instruction of that opcode have no side effects.
//
// Note: This and M_MAY_HAVE_SIDE_EFFECTS are mutually exclusive. You can't set
// both! If neither flag is set, then the instruction *always* has side effects.
const unsigned M_NEVER_HAS_SIDE_EFFECTS = 1 << 18;

// M_MAY_HAVE_SIDE_EFFECTS - Set if some instances of this instruction can have
// side effects. The virtual method "isReallySideEffectFree" is called to
// determine this. Load instructions are an example of where this is useful. In
// general, loads always have side effects. However, loads from constant pools
// don't. We let the specific back end make this determination.
//
// Note: This and M_NEVER_HAS_SIDE_EFFECTS are mutually exclusive. You can't set
// both! If neither flag is set, then the instruction *always* has side effects.
const unsigned M_MAY_HAVE_SIDE_EFFECTS = 1 << 19;

// Machine operand flags
// M_LOOK_UP_PTR_REG_CLASS - Set if this operand is a pointer value and it
// requires a callback to look up its register class.
const unsigned M_LOOK_UP_PTR_REG_CLASS = 1 << 0;

/// M_PREDICATE_OPERAND - Set if this is one of the operands that made up of the
/// predicate operand that controls an M_PREDICATED instruction.
const unsigned M_PREDICATE_OPERAND = 1 << 1;

/// M_OPTIONAL_DEF_OPERAND - Set if this operand is a optional def.
///
const unsigned M_OPTIONAL_DEF_OPERAND = 1 << 2;

namespace TOI {
  // Operand constraints: only "tied_to" for now.
  enum OperandConstraint {
    TIED_TO = 0  // Must be allocated the same register as.
  };
}

/// TargetOperandInfo - This holds information about one operand of a machine
/// instruction, indicating the register class for register operands, etc.
///
class TargetOperandInfo {
public:
  /// RegClass - This specifies the register class enumeration of the operand 
  /// if the operand is a register.  If not, this contains 0.
  unsigned short RegClass;
  unsigned short Flags;
  /// Lower 16 bits are used to specify which constraints are set. The higher 16
  /// bits are used to specify the value of constraints (4 bits each).
  unsigned int Constraints;
  /// Currently no other information.
};


class TargetInstrDescriptor {
public:
  MachineOpCode   Opcode;        // The opcode.
  unsigned short  numOperands;   // Num of args (may be more if variable_ops).
  unsigned short  numDefs;       // Num of args that are definitions.
  const char *    Name;          // Assembly language mnemonic for the opcode.
  InstrSchedClass schedClass;    // enum  identifying instr sched class
  unsigned        Flags;         // flags identifying machine instr class
  unsigned        TSFlags;       // Target Specific Flag values
  const unsigned *ImplicitUses;  // Registers implicitly read by this instr
  const unsigned *ImplicitDefs;  // Registers implicitly defined by this instr
  const TargetOperandInfo *OpInfo; // 'numOperands' entries about operands.

  /// getOperandConstraint - Returns the value of the specific constraint if
  /// it is set. Returns -1 if it is not set.
  int getOperandConstraint(unsigned OpNum,
                           TOI::OperandConstraint Constraint) const {
    assert((OpNum < numOperands || (Flags & M_VARIABLE_OPS)) &&
           "Invalid operand # of TargetInstrInfo");
    if (OpNum < numOperands &&
        (OpInfo[OpNum].Constraints & (1 << Constraint))) {
      unsigned Pos = 16 + Constraint * 4;
      return (int)(OpInfo[OpNum].Constraints >> Pos) & 0xf;
    }
    return -1;
  }

  /// findTiedToSrcOperand - Returns the operand that is tied to the specified
  /// dest operand. Returns -1 if there isn't one.
  int findTiedToSrcOperand(unsigned OpNum) const;
  
  
  /// isSimpleLoad - Return true for instructions that are simple loads from
  /// memory.  This should only be set on instructions that load a value from
  /// memory and return it in their only virtual register definition.
  /// Instructions that return a value loaded from memory and then modified in
  /// some way should not return true for this.
  bool isSimpleLoad() const {
    return Flags & M_SIMPLE_LOAD_FLAG;
  }
  
};


//---------------------------------------------------------------------------
///
/// TargetInstrInfo - Interface to description of machine instructions
///
class TargetInstrInfo {
  const TargetInstrDescriptor* desc;    // raw array to allow static init'n
  unsigned NumOpcodes;                  // number of entries in the desc array
  unsigned numRealOpCodes;              // number of non-dummy op codes

  TargetInstrInfo(const TargetInstrInfo &);  // DO NOT IMPLEMENT
  void operator=(const TargetInstrInfo &);   // DO NOT IMPLEMENT
public:
  TargetInstrInfo(const TargetInstrDescriptor *desc, unsigned NumOpcodes);
  virtual ~TargetInstrInfo();

  // Invariant opcodes: All instruction sets have these as their low opcodes.
  enum { 
    PHI = 0,
    INLINEASM = 1,
    LABEL = 2,
    EXTRACT_SUBREG = 3,
    INSERT_SUBREG = 4
  };

  unsigned getNumOpcodes() const { return NumOpcodes; }

  /// get - Return the machine instruction descriptor that corresponds to the
  /// specified instruction opcode.
  ///
  const TargetInstrDescriptor& get(MachineOpCode Opcode) const {
    assert((unsigned)Opcode < NumOpcodes);
    return desc[Opcode];
  }

  const char *getName(MachineOpCode Opcode) const {
    return get(Opcode).Name;
  }

  int getNumOperands(MachineOpCode Opcode) const {
    return get(Opcode).numOperands;
  }

  int getNumDefs(MachineOpCode Opcode) const {
    return get(Opcode).numDefs;
  }

  InstrSchedClass getSchedClass(MachineOpCode Opcode) const {
    return get(Opcode).schedClass;
  }