X86ISelLowering.cpp

/// constraint it is for this target.
X86TargetLowering::ConstraintType
X86TargetLowering::getConstraintType(const std::string &Constraint) const {
  if (Constraint.size() == 1) {
    switch (Constraint[0]) {
    case 'R':
    case 'q':
    case 'Q':
    case 'f':
    case 't':
    case 'u':
    case 'y':
    case 'x':
    case 'Y':
    case 'l':
      return C_RegisterClass;
    case 'a':
    case 'b':
    case 'c':
    case 'd':
    case 'S':
    case 'D':
    case 'A':
      return C_Register;
    case 'I':
    case 'J':
    case 'K':
    case 'L':
    case 'M':
    case 'N':
    case 'G':
    case 'C':
    case 'e':
    case 'Z':
      return C_Other;
    default:
      break;
    }
  }
  return TargetLowering::getConstraintType(Constraint);
}

/// Examine constraint type and operand type and determine a weight value.
/// This object must already have been set up with the operand type
/// and the current alternative constraint selected.
TargetLowering::ConstraintWeight
  X86TargetLowering::getSingleConstraintMatchWeight(
    AsmOperandInfo &info, const char *constraint) const {
  ConstraintWeight weight = CW_Invalid;
  Value *CallOperandVal = info.CallOperandVal;
    // If we don't have a value, we can't do a match,
    // but allow it at the lowest weight.
  if (CallOperandVal == NULL)
    return CW_Default;
  Type *type = CallOperandVal->getType();
  // Look at the constraint type.
  switch (*constraint) {
  default:
    weight = TargetLowering::getSingleConstraintMatchWeight(info, constraint);
  case 'R':
  case 'q':
  case 'Q':
  case 'a':
  case 'b':
  case 'c':
  case 'd':
  case 'S':
  case 'D':
  case 'A':
    if (CallOperandVal->getType()->isIntegerTy())
      weight = CW_SpecificReg;
    break;
  case 'f':
  case 't':
  case 'u':
      if (type->isFloatingPointTy())
        weight = CW_SpecificReg;
      break;
  case 'y':
      if (type->isX86_MMXTy() && Subtarget->hasMMX())
        weight = CW_SpecificReg;
      break;
  case 'x':
  case 'Y':
    if ((type->getPrimitiveSizeInBits() == 128) && Subtarget->hasXMM())
      weight = CW_Register;
    break;
  case 'I':
    if (ConstantInt *C = dyn_cast<ConstantInt>(info.CallOperandVal)) {
      if (C->getZExtValue() <= 31)
        weight = CW_Constant;
    }
    break;
  case 'J':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if (C->getZExtValue() <= 63)
        weight = CW_Constant;
    }
    break;
  case 'K':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if ((C->getSExtValue() >= -0x80) && (C->getSExtValue() <= 0x7f))
        weight = CW_Constant;
    }
    break;
  case 'L':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if ((C->getZExtValue() == 0xff) || (C->getZExtValue() == 0xffff))
        weight = CW_Constant;
    }
    break;
  case 'M':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if (C->getZExtValue() <= 3)
        weight = CW_Constant;
    }
    break;
  case 'N':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if (C->getZExtValue() <= 0xff)
        weight = CW_Constant;
    }
    break;
  case 'G':
  case 'C':
    if (dyn_cast<ConstantFP>(CallOperandVal)) {
      weight = CW_Constant;
    }
    break;
  case 'e':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if ((C->getSExtValue() >= -0x80000000LL) &&
          (C->getSExtValue() <= 0x7fffffffLL))
        weight = CW_Constant;
    }
    break;
  case 'Z':
    if (ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
      if (C->getZExtValue() <= 0xffffffff)
        weight = CW_Constant;
    }
    break;
  }
  return weight;
}

/// LowerXConstraint - try to replace an X constraint, which matches anything,
/// with another that has more specific requirements based on the type of the
/// corresponding operand.
const char *X86TargetLowering::
LowerXConstraint(EVT ConstraintVT) const {
  // FP X constraints get lowered to SSE1/2 registers if available, otherwise
  // 'f' like normal targets.
  if (ConstraintVT.isFloatingPoint()) {
    if (Subtarget->hasXMMInt())
      return "Y";
    if (Subtarget->hasXMM())
      return "x";
  }

  return TargetLowering::LowerXConstraint(ConstraintVT);
}

/// LowerAsmOperandForConstraint - Lower the specified operand into the Ops
/// vector.  If it is invalid, don't add anything to Ops.
void X86TargetLowering::LowerAsmOperandForConstraint(SDValue Op,
                                                     std::string &Constraint,
                                                     std::vector<SDValue>&Ops,
                                                     SelectionDAG &DAG) const {
  SDValue Result(0, 0);

  // Only support length 1 constraints for now.
  if (Constraint.length() > 1) return;

  char ConstraintLetter = Constraint[0];
  switch (ConstraintLetter) {
  default: break;
  case 'I':
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
      if (C->getZExtValue() <= 31) {
        Result = DAG.getTargetConstant(C->getZExtValue(), Op.getValueType());
        break;
      }
    }
    return;
  case 'J':
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
      if (C->getZExtValue() <= 63) {
        Result = DAG.getTargetConstant(C->getZExtValue(), Op.getValueType());
        break;
      }
    }
    return;
  case 'K':
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
      if ((int8_t)C->getSExtValue() == C->getSExtValue()) {
        Result = DAG.getTargetConstant(C->getZExtValue(), Op.getValueType());
        break;
      }
    }
    return;
  case 'N':
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
      if (C->getZExtValue() <= 255) {
        Result = DAG.getTargetConstant(C->getZExtValue(), Op.getValueType());
        break;
      }
    }
    return;
  case 'e': {
    // 32-bit signed value
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
      if (ConstantInt::isValueValidForType(Type::getInt32Ty(*DAG.getContext()),
                                           C->getSExtValue())) {
        // Widen to 64 bits here to get it sign extended.
        Result = DAG.getTargetConstant(C->getSExtValue(), MVT::i64);
        break;
      }
    // FIXME gcc accepts some relocatable values here too, but only in certain
    // memory models; it's complicated.
    }
    return;
  }
  case 'Z': {
    // 32-bit unsigned value
    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op)) {
      if (ConstantInt::isValueValidForType(Type::getInt32Ty(*DAG.getContext()),
                                           C->getZExtValue())) {
        Result = DAG.getTargetConstant(C->getZExtValue(), Op.getValueType());
        break;
      }
    }
    // FIXME gcc accepts some relocatable values here too, but only in certain
    // memory models; it's complicated.
    return;
  }
  case 'i': {
    // Literal immediates are always ok.
    if (ConstantSDNode *CST = dyn_cast<ConstantSDNode>(Op)) {
      // Widen to 64 bits here to get it sign extended.
      Result = DAG.getTargetConstant(CST->getSExtValue(), MVT::i64);
      break;
    }

    // In any sort of PIC mode addresses need to be computed at runtime by
    // adding in a register or some sort of table lookup.  These can't
    // be used as immediates.
    if (Subtarget->isPICStyleGOT() || Subtarget->isPICStyleStubPIC())
      return;

    // If we are in non-pic codegen mode, we allow the address of a global (with
    // an optional displacement) to be used with 'i'.
    GlobalAddressSDNode *GA = 0;
    int64_t Offset = 0;

    // Match either (GA), (GA+C), (GA+C1+C2), etc.
    while (1) {
      if ((GA = dyn_cast<GlobalAddressSDNode>(Op))) {
        Offset += GA->getOffset();
        break;
      } else if (Op.getOpcode() == ISD::ADD) {
        if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
          Offset += C->getZExtValue();
          Op = Op.getOperand(0);
          continue;
        }
      } else if (Op.getOpcode() == ISD::SUB) {
        if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
          Offset += -C->getZExtValue();
          Op = Op.getOperand(0);
          continue;
        }
      }

      // Otherwise, this isn't something we can handle, reject it.
      return;
    }

    const GlobalValue *GV = GA->getGlobal();
    // If we require an extra load to get this address, as in PIC mode, we
    // can't accept it.
    if (isGlobalStubReference(Subtarget->ClassifyGlobalReference(GV,
                                                        getTargetMachine())))
      return;

    Result = DAG.getTargetGlobalAddress(GV, Op.getDebugLoc(),
                                        GA->getValueType(0), Offset);
    break;
  }
  }

  if (Result.getNode()) {
    Ops.push_back(Result);
    return;
  }
  return TargetLowering::LowerAsmOperandForConstraint(Op, Constraint, Ops, DAG);
}

std::pair<unsigned, const TargetRegisterClass*>
X86TargetLowering::getRegForInlineAsmConstraint(const std::string &Constraint,
                                                EVT VT) const {
  // First, see if this is a constraint that directly corresponds to an LLVM
  // register class.
  if (Constraint.size() == 1) {
    // GCC Constraint Letters
    switch (Constraint[0]) {
    default: break;
      // TODO: Slight differences here in allocation order and leaving
      // RIP in the class. Do they matter any more here than they do
      // in the normal allocation?
    case 'q':   // GENERAL_REGS in 64-bit mode, Q_REGS in 32-bit mode.
      if (Subtarget->is64Bit()) {
	if (VT == MVT::i32 || VT == MVT::f32)
	  return std::make_pair(0U, X86::GR32RegisterClass);
	else if (VT == MVT::i16)
	  return std::make_pair(0U, X86::GR16RegisterClass);
	else if (VT == MVT::i8 || VT == MVT::i1)
	  return std::make_pair(0U, X86::GR8RegisterClass);
	else if (VT == MVT::i64 || VT == MVT::f64)
	  return std::make_pair(0U, X86::GR64RegisterClass);
	break;
      }
      // 32-bit fallthrough
    case 'Q':   // Q_REGS
      if (VT == MVT::i32 || VT == MVT::f32)
	return std::make_pair(0U, X86::GR32_ABCDRegisterClass);
      else if (VT == MVT::i16)
	return std::make_pair(0U, X86::GR16_ABCDRegisterClass);
      else if (VT == MVT::i8 || VT == MVT::i1)
	return std::make_pair(0U, X86::GR8_ABCD_LRegisterClass);
      else if (VT == MVT::i64)
	return std::make_pair(0U, X86::GR64_ABCDRegisterClass);
      break;
    case 'r':   // GENERAL_REGS
    case 'l':   // INDEX_REGS
      if (VT == MVT::i8 || VT == MVT::i1)
        return std::make_pair(0U, X86::GR8RegisterClass);
      if (VT == MVT::i16)
        return std::make_pair(0U, X86::GR16RegisterClass);
      if (VT == MVT::i32 || VT == MVT::f32 || !Subtarget->is64Bit())
        return std::make_pair(0U, X86::GR32RegisterClass);
      return std::make_pair(0U, X86::GR64RegisterClass);
    case 'R':   // LEGACY_REGS
      if (VT == MVT::i8 || VT == MVT::i1)
        return std::make_pair(0U, X86::GR8_NOREXRegisterClass);
      if (VT == MVT::i16)
        return std::make_pair(0U, X86::GR16_NOREXRegisterClass);
      if (VT == MVT::i32 || !Subtarget->is64Bit())
        return std::make_pair(0U, X86::GR32_NOREXRegisterClass);
      return std::make_pair(0U, X86::GR64_NOREXRegisterClass);
    case 'f':  // FP Stack registers.
      // If SSE is enabled for this VT, use f80 to ensure the isel moves the
      // value to the correct fpstack register class.
      if (VT == MVT::f32 && !isScalarFPTypeInSSEReg(VT))
        return std::make_pair(0U, X86::RFP32RegisterClass);
      if (VT == MVT::f64 && !isScalarFPTypeInSSEReg(VT))
        return std::make_pair(0U, X86::RFP64RegisterClass);
      return std::make_pair(0U, X86::RFP80RegisterClass);
    case 'y':   // MMX_REGS if MMX allowed.
      if (!Subtarget->hasMMX()) break;
      return std::make_pair(0U, X86::VR64RegisterClass);
    case 'Y':   // SSE_REGS if SSE2 allowed
      if (!Subtarget->hasXMMInt()) break;
      // FALL THROUGH.
    case 'x':   // SSE_REGS if SSE1 allowed
      if (!Subtarget->hasXMM()) break;

      switch (VT.getSimpleVT().SimpleTy) {
      default: break;
      // Scalar SSE types.
      case MVT::f32:
      case MVT::i32:
        return std::make_pair(0U, X86::FR32RegisterClass);
      case MVT::f64:
      case MVT::i64:
        return std::make_pair(0U, X86::FR64RegisterClass);
      // Vector types.
      case MVT::v16i8:
      case MVT::v8i16:
      case MVT::v4i32:
      case MVT::v2i64:
      case MVT::v4f32:
      case MVT::v2f64:
        return std::make_pair(0U, X86::VR128RegisterClass);
      }
      break;
    }
  }

  // Use the default implementation in TargetLowering to convert the register
  // constraint into a member of a register class.
  std::pair<unsigned, const TargetRegisterClass*> Res;
  Res = TargetLowering::getRegForInlineAsmConstraint(Constraint, VT);

  // Not found as a standard register?
  if (Res.second == 0) {
    // Map st(0) -> st(7) -> ST0
    if (Constraint.size() == 7 && Constraint[0] == '{' &&
        tolower(Constraint[1]) == 's' &&
        tolower(Constraint[2]) == 't' &&
        Constraint[3] == '(' &&
        (Constraint[4] >= '0' && Constraint[4] <= '7') &&
        Constraint[5] == ')' &&
        Constraint[6] == '}') {

      Res.first = X86::ST0+Constraint[4]-'0';
      Res.second = X86::RFP80RegisterClass;
      return Res;
    }

    // GCC allows "st(0)" to be called just plain "st".
    if (StringRef("{st}").equals_lower(Constraint)) {
      Res.first = X86::ST0;
      Res.second = X86::RFP80RegisterClass;
      return Res;
    }

    // flags -> EFLAGS
    if (StringRef("{flags}").equals_lower(Constraint)) {
      Res.first = X86::EFLAGS;
      Res.second = X86::CCRRegisterClass;
      return Res;
    }

    // 'A' means EAX + EDX.
    if (Constraint == "A") {
      Res.first = X86::EAX;
      Res.second = X86::GR32_ADRegisterClass;
      return Res;
    }
    return Res;
  }

  // Otherwise, check to see if this is a register class of the wrong value
  // type.  For example, we want to map "{ax},i32" -> {eax}, we don't want it to
  // turn into {ax},{dx}.
  if (Res.second->hasType(VT))
    return Res;   // Correct type already, nothing to do.

  // All of the single-register GCC register classes map their values onto
  // 16-bit register pieces "ax","dx","cx","bx","si","di","bp","sp".  If we
  // really want an 8-bit or 32-bit register, map to the appropriate register
  // class and return the appropriate register.
  if (Res.second == X86::GR16RegisterClass) {
    if (VT == MVT::i8) {
      unsigned DestReg = 0;
      switch (Res.first) {
      default: break;
      case X86::AX: DestReg = X86::AL; break;
      case X86::DX: DestReg = X86::DL; break;
      case X86::CX: DestReg = X86::CL; break;
      case X86::BX: DestReg = X86::BL; break;
      }
      if (DestReg) {
        Res.first = DestReg;
        Res.second = X86::GR8RegisterClass;
      }
    } else if (VT == MVT::i32) {
      unsigned DestReg = 0;
      switch (Res.first) {
      default: break;
      case X86::AX: DestReg = X86::EAX; break;
      case X86::DX: DestReg = X86::EDX; break;
      case X86::CX: DestReg = X86::ECX; break;
      case X86::BX: DestReg = X86::EBX; break;
      case X86::SI: DestReg = X86::ESI; break;
      case X86::DI: DestReg = X86::EDI; break;
      case X86::BP: DestReg = X86::EBP; break;
      case X86::SP: DestReg = X86::ESP; break;
      }
      if (DestReg) {
        Res.first = DestReg;
        Res.second = X86::GR32RegisterClass;
      }
    } else if (VT == MVT::i64) {
      unsigned DestReg = 0;
      switch (Res.first) {
      default: break;
      case X86::AX: DestReg = X86::RAX; break;
      case X86::DX: DestReg = X86::RDX; break;
      case X86::CX: DestReg = X86::RCX; break;
      case X86::BX: DestReg = X86::RBX; break;
      case X86::SI: DestReg = X86::RSI; break;
      case X86::DI: DestReg = X86::RDI; break;
      case X86::BP: DestReg = X86::RBP; break;
      case X86::SP: DestReg = X86::RSP; break;
      }
      if (DestReg) {
        Res.first = DestReg;
        Res.second = X86::GR64RegisterClass;
      }
    }
  } else if (Res.second == X86::FR32RegisterClass ||
             Res.second == X86::FR64RegisterClass ||
             Res.second == X86::VR128RegisterClass) {
    // Handle references to XMM physical registers that got mapped into the
    // wrong class.  This can happen with constraints like {xmm0} where the
    // target independent register mapper will just pick the first match it can
    // find, ignoring the required type.
    if (VT == MVT::f32)
      Res.second = X86::FR32RegisterClass;
    else if (VT == MVT::f64)
      Res.second = X86::FR64RegisterClass;
    else if (X86::VR128RegisterClass->hasType(VT))
      Res.second = X86::VR128RegisterClass;
  }

  return Res;
}