llvm/lib/VMCore/InlineAsm.cpp

//===-- InlineAsm.cpp - Implement the InlineAsm class ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the InlineAsm class.
//
//===----------------------------------------------------------------------===//

#include "llvm/InlineAsm.h"
#include "llvm/DerivedTypes.h"
#include <algorithm>
#include <cctype>
using namespace llvm;

// Implement the first virtual method in this class in this file so the
// InlineAsm vtable is emitted here.
InlineAsm::~InlineAsm() {
}


// NOTE: when memoizing the function type, we have to be careful to handle the
// case when the type gets refined.

InlineAsm *InlineAsm::get(const FunctionType *Ty, const StringRef &AsmString,
                          const StringRef &Constraints, bool hasSideEffects,
                          bool isMsAsm) {
  // FIXME: memoize!
  return new InlineAsm(Ty, AsmString, Constraints, hasSideEffects, isMsAsm);  
}

InlineAsm::InlineAsm(const FunctionType *Ty, const StringRef &asmString,
                     const StringRef &constraints, bool hasSideEffects,
                     bool isMsAsm)
  : Value(PointerType::getUnqual(Ty), 
          Value::InlineAsmVal), 
    AsmString(asmString), 
    Constraints(constraints), HasSideEffects(hasSideEffects), IsMsAsm(isMsAsm) {

  // Do various checks on the constraint string and type.
  assert(Verify(Ty, constraints) && "Function type not legal for constraints!");
}

const FunctionType *InlineAsm::getFunctionType() const {
  return cast<FunctionType>(getType()->getElementType());
}

/// Parse - Analyze the specified string (e.g. "==&{eax}") and fill in the
/// fields in this structure.  If the constraint string is not understood,
/// return true, otherwise return false.
bool InlineAsm::ConstraintInfo::Parse(const StringRef &Str,
                     std::vector<InlineAsm::ConstraintInfo> &ConstraintsSoFar) {
  StringRef::iterator I = Str.begin(), E = Str.end();
  
  // Initialize
  Type = isInput;
  isEarlyClobber = false;
  MatchingInput = -1;
  isCommutative = false;
  isIndirect = false;
  
  // Parse prefixes.
  if (*I == '~') {
    Type = isClobber;
    ++I;
  } else if (*I == '=') {
    ++I;
    Type = isOutput;
  }
  
  if (*I == '*') {
    isIndirect = true;
    ++I;
  }
  
  if (I == E) return true;  // Just a prefix, like "==" or "~".
  
  // Parse the modifiers.
  bool DoneWithModifiers = false;
  while (!DoneWithModifiers) {
    switch (*I) {
    default:
      DoneWithModifiers = true;
      break;
    case '&':     // Early clobber.
      if (Type != isOutput ||      // Cannot early clobber anything but output.
          isEarlyClobber)          // Reject &&&&&&
        return true;
      isEarlyClobber = true;
      break;
    case '%':     // Commutative.
      if (Type == isClobber ||     // Cannot commute clobbers.
          isCommutative)           // Reject %%%%%
        return true;
      isCommutative = true;
      break;
    case '#':     // Comment.
    case '*':     // Register preferencing.
      return true;     // Not supported.
    }
    
    if (!DoneWithModifiers) {
      ++I;
      if (I == E) return true;   // Just prefixes and modifiers!
    }
  }
  
  // Parse the various constraints.
  while (I != E) {
    if (*I == '{') {   // Physical register reference.
      // Find the end of the register name.
      StringRef::iterator ConstraintEnd = std::find(I+1, E, '}');
      if (ConstraintEnd == E) return true;  // "{foo"
      Codes.push_back(std::string(I, ConstraintEnd+1));
      I = ConstraintEnd+1;
    } else if (isdigit(*I)) {     // Matching Constraint
      // Maximal munch numbers.
      StringRef::iterator NumStart = I;
      while (I != E && isdigit(*I))
        ++I;
      Codes.push_back(std::string(NumStart, I));
      unsigned N = atoi(Codes.back().c_str());
      // Check that this is a valid matching constraint!
      if (N >= ConstraintsSoFar.size() || ConstraintsSoFar[N].Type != isOutput||
          Type != isInput)
        return true;  // Invalid constraint number.
      
      // If Operand N already has a matching input, reject this.  An output
      // can't be constrained to the same value as multiple inputs.
      if (ConstraintsSoFar[N].hasMatchingInput())
        return true;
      
      // Note that operand #n has a matching input.
      ConstraintsSoFar[N].MatchingInput = ConstraintsSoFar.size();
    } else {
      // Single letter constraint.
      Codes.push_back(std::string(I, I+1));
      ++I;
    }
  }

  return false;
}

std::vector<InlineAsm::ConstraintInfo>
InlineAsm::ParseConstraints(const StringRef &Constraints) {
  std::vector<ConstraintInfo> 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(std::string(I, ConstraintEnd), 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;
}


/// Verify - Verify that the specified constraint string is reasonable for the
/// specified function type, and otherwise validate the constraint string.
bool InlineAsm::Verify(const FunctionType *Ty, const StringRef &ConstStr) {
  if (Ty->isVarArg()) return false;
  
  std::vector<ConstraintInfo> Constraints = ParseConstraints(ConstStr);
  
  // Error parsing constraints.
  if (Constraints.empty() && !ConstStr.empty()) return false;
  
  unsigned NumOutputs = 0, NumInputs = 0, NumClobbers = 0;
  unsigned NumIndirect = 0;
  
  for (unsigned i = 0, e = Constraints.size(); i != e; ++i) {
    switch (Constraints[i].Type) {
    case InlineAsm::isOutput:
      if ((NumInputs-NumIndirect) != 0 || NumClobbers != 0)
        return false;  // outputs before inputs and clobbers.
      if (!Constraints[i].isIndirect) {
        ++NumOutputs;
        break;
      }
      ++NumIndirect;
      // FALLTHROUGH for Indirect Outputs.
    case InlineAsm::isInput:
      if (NumClobbers) return false;               // inputs before clobbers.
      ++NumInputs;
      break;
    case InlineAsm::isClobber:
      ++NumClobbers;
      break;
    }
  }
  
  switch (NumOutputs) {
  case 0:
    if (Ty->getReturnType() != Type::getVoidTy(Ty->getContext())) return false;
    break;
  case 1:
    if (isa<StructType>(Ty->getReturnType())) return false;
    break;
  default:
    const StructType *STy = dyn_cast<StructType>(Ty->getReturnType());
    if (STy == 0 || STy->getNumElements() != NumOutputs)
      return false;
    break;
  }      
  
  if (Ty->getNumParams() != NumInputs) return false;
  return true;
}