C++ ConstraintInfo类代码示例

InlineAsm::ConstraintInfoVector
InlineAsm::ParseConstraints(StringRef Constraints) {
  ConstraintInfoVector Result;
  
  // Scan the constraints string.
  for (StringRef::iterator I = Constraints.begin(),
         E = Constraints.end(); I != E; ) {
    ConstraintInfo Info;

    // Find the end of this constraint.
    StringRef::iterator ConstraintEnd = std::find(I, E, ',');

    if (ConstraintEnd == I ||  // Empty constraint like ",,"
        Info.Parse(StringRef(I, ConstraintEnd-I), Result)) {
      Result.clear();          // Erroneous constraint?
      break;
    }

    Result.push_back(Info);
    
    // ConstraintEnd may be either the next comma or the end of the string.  In
    // the former case, we skip the comma.
    I = ConstraintEnd;
    if (I != E) {
      ++I;
      if (I == E) {
        Result.clear();
        break;
      } // don't allow "xyz,"
    }
  }
  
  return Result;
}

bool TargetInfo::validateOutputConstraint(ConstraintInfo &Info) const {
  const char *Name = Info.getConstraintStr().c_str();
  // An output constraint must start with '=' or '+'
  if (*Name != '=' && *Name != '+')
    return false;

  if (*Name == '+')
    Info.setIsReadWrite();

  Name++;
  while (*Name) {
    switch (*Name) {
    default:
      if (!validateAsmConstraint(Name, Info)) {
        // FIXME: We temporarily return false
        // so we can add more constraints as we hit it.
        // Eventually, an unknown constraint should just be treated as 'g'.
        return false;
      }
    case '&': // early clobber.
      break;
    case '%': // commutative.
      // FIXME: Check that there is a another register after this one.
      break;
    case 'r': // general register.
      Info.setAllowsRegister();
      break;
    case 'm': // memory operand.
    case 'o': // offsetable memory operand.
    case 'V': // non-offsetable memory operand.
    case '<': // autodecrement memory operand.
    case '>': // autoincrement memory operand.
      Info.setAllowsMemory();
      break;
    case 'g': // general register, memory operand or immediate integer.
    case 'X': // any operand.
      Info.setAllowsRegister();
      Info.setAllowsMemory();
      break;
    case ',': // multiple alternative constraint.  Pass it.
      // Handle additional optional '=' or '+' modifiers.
      if (Name[1] == '=' || Name[1] == '+')
        Name++;
      break;
    case '?': // Disparage slightly code.
    case '!': // Disparage severely.
    case '#': // Ignore as constraint.
    case '*': // Ignore for choosing register preferences.
      break;  // Pass them.
    }

    Name++;
  }

  // If a constraint allows neither memory nor register operands it contains
  // only modifiers. Reject it.
  return Info.allowsMemory() || Info.allowsRegister();
}

bool TargetInfo::validateInputConstraint(
                              MutableArrayRef<ConstraintInfo> OutputConstraints,
                              ConstraintInfo &Info) const {
  const char *Name = Info.ConstraintStr.c_str();

  if (!*Name)
    return false;

  while (*Name) {
    switch (*Name) {
    default:
      // Check if we have a matching constraint
      if (*Name >= '0' && *Name <= '9') {
        const char *DigitStart = Name;
        while (Name[1] >= '0' && Name[1] <= '9')
          Name++;
        const char *DigitEnd = Name;
        unsigned i;
        if (StringRef(DigitStart, DigitEnd - DigitStart + 1)
                .getAsInteger(10, i))
          return false;

        // Check if matching constraint is out of bounds.
        if (i >= OutputConstraints.size()) return false;

        // A number must refer to an output only operand.
        if (OutputConstraints[i].isReadWrite())
          return false;

        // If the constraint is already tied, it must be tied to the
        // same operand referenced to by the number.
        if (Info.hasTiedOperand() && Info.getTiedOperand() != i)
          return false;

        // The constraint should have the same info as the respective
        // output constraint.
        Info.setTiedOperand(i, OutputConstraints[i]);
      } else if (!validateAsmConstraint(Name, Info)) {
        // FIXME: This error return is in place temporarily so we can
        // add more constraints as we hit it.  Eventually, an unknown
        // constraint should just be treated as 'g'.
        return false;
      }
      break;
    case '[': {
      unsigned Index = 0;
      if (!resolveSymbolicName(Name, OutputConstraints, Index))
        return false;

      // If the constraint is already tied, it must be tied to the
      // same operand referenced to by the number.
      if (Info.hasTiedOperand() && Info.getTiedOperand() != Index)
        return false;

      // A number must refer to an output only operand.
      if (OutputConstraints[Index].isReadWrite())
        return false;

      Info.setTiedOperand(Index, OutputConstraints[Index]);
      break;
    }
    case '%': // commutative
      // FIXME: Fail if % is used with the last operand.
      break;
    case 'i': // immediate integer.
    case 'n': // immediate integer with a known value.
      break;
    case 'I':  // Various constant constraints with target-specific meanings.
    case 'J':
    case 'K':
    case 'L':
    case 'M':
    case 'N':
    case 'O':
    case 'P':
      if (!validateAsmConstraint(Name, Info))
        return false;
      break;
    case 'r': // general register.
      Info.setAllowsRegister();
      break;
    case 'm': // memory operand.
    case 'o': // offsettable memory operand.
    case 'V': // non-offsettable memory operand.
    case '<': // autodecrement memory operand.
    case '>': // autoincrement memory operand.
      Info.setAllowsMemory();
      break;
    case 'g': // general register, memory operand or immediate integer.
    case 'X': // any operand.
      Info.setAllowsRegister();
      Info.setAllowsMemory();
      break;
    case 'E': // immediate floating point.
    case 'F': // immediate floating point.
    case 'p': // address operand.
      break;
    case ',': // multiple alternative constraint.  Ignore comma.
      break;
    case '#': // Ignore as constraint.
//.........这里部分代码省略.........