C++ TargetRegisterInfo::getMinimalPhysRegClass方法代码示例

/// Get the size in bits of the \p Reg.
///
/// \pre \p Reg != 0 (NoRegister).
static unsigned getSizeInBits(unsigned Reg, const MachineRegisterInfo &MRI,
                              const TargetRegisterInfo &TRI) {
  const TargetRegisterClass *RC = nullptr;
  if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
    // The size is not directly available for physical registers.
    // Instead, we need to access a register class that contains Reg and
    // get the size of that register class.
    RC = TRI.getMinimalPhysRegClass(Reg);
  } else {
    unsigned RegSize = MRI.getSize(Reg);
    // If Reg is not a generic register, query the register class to
    // get its size.
    if (RegSize)
      return RegSize;
    // Since Reg is not a generic register, it must have a register class.
    RC = MRI.getRegClass(Reg);
  }
  assert(RC && "Unable to deduce the register class");
  return RC->getSize() * 8;
}

bool DwarfExpression::addMachineReg(const TargetRegisterInfo &TRI,
                                    unsigned MachineReg, unsigned MaxSize) {
  if (!TRI.isPhysicalRegister(MachineReg)) {
    if (isFrameRegister(TRI, MachineReg)) {
      DwarfRegs.push_back({-1, 0, nullptr});
      return true;
    }
    return false;
  }

  int Reg = TRI.getDwarfRegNum(MachineReg, false);

  // If this is a valid register number, emit it.
  if (Reg >= 0) {
    DwarfRegs.push_back({Reg, 0, nullptr});
    return true;
  }

  // Walk up the super-register chain until we find a valid number.
  // For example, EAX on x86_64 is a 32-bit fragment of RAX with offset 0.
  for (MCSuperRegIterator SR(MachineReg, &TRI); SR.isValid(); ++SR) {
    Reg = TRI.getDwarfRegNum(*SR, false);
    if (Reg >= 0) {
      unsigned Idx = TRI.getSubRegIndex(*SR, MachineReg);
      unsigned Size = TRI.getSubRegIdxSize(Idx);
      unsigned RegOffset = TRI.getSubRegIdxOffset(Idx);
      DwarfRegs.push_back({Reg, 0, "super-register"});
      // Use a DW_OP_bit_piece to describe the sub-register.
      setSubRegisterPiece(Size, RegOffset);
      return true;
    }
  }

  // Otherwise, attempt to find a covering set of sub-register numbers.
  // For example, Q0 on ARM is a composition of D0+D1.
  unsigned CurPos = 0;
  // The size of the register in bits, assuming 8 bits per byte.
  unsigned RegSize = TRI.getMinimalPhysRegClass(MachineReg)->getSize() * 8;
  // Keep track of the bits in the register we already emitted, so we
  // can avoid emitting redundant aliasing subregs.
  SmallBitVector Coverage(RegSize, false);
  for (MCSubRegIterator SR(MachineReg, &TRI); SR.isValid(); ++SR) {
    unsigned Idx = TRI.getSubRegIndex(MachineReg, *SR);
    unsigned Size = TRI.getSubRegIdxSize(Idx);
    unsigned Offset = TRI.getSubRegIdxOffset(Idx);
    Reg = TRI.getDwarfRegNum(*SR, false);

    // Intersection between the bits we already emitted and the bits
    // covered by this subregister.
    SmallBitVector Intersection(RegSize, false);
    Intersection.set(Offset, Offset + Size);
    Intersection ^= Coverage;

    // If this sub-register has a DWARF number and we haven't covered
    // its range, emit a DWARF piece for it.
    if (Reg >= 0 && Intersection.any()) {
      // Emit a piece for any gap in the coverage.
      if (Offset > CurPos)
        DwarfRegs.push_back({-1, Offset - CurPos, nullptr});
      DwarfRegs.push_back(
          {Reg, std::min<unsigned>(Size, MaxSize - Offset), "sub-register"});
      if (Offset >= MaxSize)
	break;

      // Mark it as emitted.
      Coverage.set(Offset, Offset + Size);
      CurPos = Offset + Size;
    }
  }

  return CurPos;
}

bool DwarfExpression::addMachineReg(const TargetRegisterInfo &TRI,
                                    unsigned MachineReg, unsigned MaxSize) {
  if (!TRI.isPhysicalRegister(MachineReg)) {
    if (isFrameRegister(TRI, MachineReg)) {
      DwarfRegs.push_back({-1, 0, nullptr});
      return true;
    }
    return false;
  }

  int Reg = TRI.getDwarfRegNum(MachineReg, false);

  // If this is a valid register number, emit it.
  if (Reg >= 0) {
    DwarfRegs.push_back({Reg, 0, nullptr});
    return true;
  }

  // Walk up the super-register chain until we find a valid number.
  // For example, EAX on x86_64 is a 32-bit fragment of RAX with offset 0.
  for (MCSuperRegIterator SR(MachineReg, &TRI); SR.isValid(); ++SR) {
    Reg = TRI.getDwarfRegNum(*SR, false);
    if (Reg >= 0) {
      unsigned Idx = TRI.getSubRegIndex(*SR, MachineReg);
      unsigned Size = TRI.getSubRegIdxSize(Idx);
      unsigned RegOffset = TRI.getSubRegIdxOffset(Idx);
      DwarfRegs.push_back({Reg, 0, "super-register"});
      // Use a DW_OP_bit_piece to describe the sub-register.
      setSubRegisterPiece(Size, RegOffset);
      return true;
    }
  }

  // Otherwise, attempt to find a covering set of sub-register numbers.
  // For example, Q0 on ARM is a composition of D0+D1.
  unsigned CurPos = 0;
  // The size of the register in bits.
  const TargetRegisterClass *RC = TRI.getMinimalPhysRegClass(MachineReg);
  unsigned RegSize = TRI.getRegSizeInBits(*RC);
  // Keep track of the bits in the register we already emitted, so we
  // can avoid emitting redundant aliasing subregs. Because this is
  // just doing a greedy scan of all subregisters, it is possible that
  // this doesn't find a combination of subregisters that fully cover
  // the register (even though one may exist).
  SmallBitVector Coverage(RegSize, false);
  for (MCSubRegIterator SR(MachineReg, &TRI); SR.isValid(); ++SR) {
    unsigned Idx = TRI.getSubRegIndex(MachineReg, *SR);
    unsigned Size = TRI.getSubRegIdxSize(Idx);
    unsigned Offset = TRI.getSubRegIdxOffset(Idx);
    Reg = TRI.getDwarfRegNum(*SR, false);
    if (Reg < 0)
      continue;

    // Intersection between the bits we already emitted and the bits
    // covered by this subregister.
    SmallBitVector CurSubReg(RegSize, false);
    CurSubReg.set(Offset, Offset + Size);

    // If this sub-register has a DWARF number and we haven't covered
    // its range, emit a DWARF piece for it.
    if (CurSubReg.test(Coverage)) {
      // Emit a piece for any gap in the coverage.
      if (Offset > CurPos)
        DwarfRegs.push_back({-1, Offset - CurPos, "no DWARF register encoding"});
      DwarfRegs.push_back(
          {Reg, std::min<unsigned>(Size, MaxSize - Offset), "sub-register"});
      if (Offset >= MaxSize)
        break;

      // Mark it as emitted.
      Coverage.set(Offset, Offset + Size);
      CurPos = Offset + Size;
    }
  }
  // Failed to find any DWARF encoding.
  if (CurPos == 0)
    return false;
  // Found a partial or complete DWARF encoding.
  if (CurPos < RegSize)
    DwarfRegs.push_back({-1, RegSize - CurPos, "no DWARF register encoding"});
  return true;
}