IntrinsicLowering.cpp

//===-- IntrinsicLowering.cpp - Intrinsic Lowering default implementation -===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the default intrinsic lowering implementation.
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/IntrinsicLowering.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Module.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
#include <iostream>

using namespace llvm;

template <class ArgIt>
static Function *EnsureFunctionExists(Module &M, const char *Name,
                                      ArgIt ArgBegin, ArgIt ArgEnd,
                                      const Type *RetTy) {
  if (Function *F = M.getNamedFunction(Name)) return F;
  // It doesn't already exist in the program, insert a new definition now.
  std::vector<const Type *> ParamTys;
  for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
    ParamTys.push_back(I->getType());
  return M.getOrInsertFunction(Name, FunctionType::get(RetTy, ParamTys, false));
}

/// ReplaceCallWith - This function is used when we want to lower an intrinsic
/// call to a call of an external function.  This handles hard cases such as
/// when there was already a prototype for the external function, and if that
/// prototype doesn't match the arguments we expect to pass in.
template <class ArgIt>
static CallInst *ReplaceCallWith(const char *NewFn, CallInst *CI,
                                 ArgIt ArgBegin, ArgIt ArgEnd,
                                 const Type *RetTy, Function *&FCache) {
  if (!FCache) {
    // If we haven't already looked up this function, check to see if the
    // program already contains a function with this name.
    Module *M = CI->getParent()->getParent()->getParent();
    FCache = M->getNamedFunction(NewFn);
    if (!FCache) {
      // It doesn't already exist in the program, insert a new definition now.
      std::vector<const Type *> ParamTys;
      for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
        ParamTys.push_back((*I)->getType());
      FCache = M->getOrInsertFunction(NewFn,
                                     FunctionType::get(RetTy, ParamTys, false));
    }
   }

  const FunctionType *FT = FCache->getFunctionType();
  std::vector<Value*> Operands;
  unsigned ArgNo = 0;
  for (ArgIt I = ArgBegin; I != ArgEnd && ArgNo != FT->getNumParams();
       ++I, ++ArgNo) {
    Value *Arg = *I;
    if (Arg->getType() != FT->getParamType(ArgNo))
      Arg = new CastInst(Arg, FT->getParamType(ArgNo), Arg->getName(), CI);
    Operands.push_back(Arg);
  }
  // Pass nulls into any additional arguments...
  for (; ArgNo != FT->getNumParams(); ++ArgNo)
    Operands.push_back(Constant::getNullValue(FT->getParamType(ArgNo)));

  std::string Name = CI->getName(); CI->setName("");
  if (FT->getReturnType() == Type::VoidTy) Name.clear();
  CallInst *NewCI = new CallInst(FCache, Operands, Name, CI);
  if (!CI->use_empty()) {
    Value *V = NewCI;
    if (CI->getType() != NewCI->getType())
      V = new CastInst(NewCI, CI->getType(), Name, CI);
    CI->replaceAllUsesWith(V);
  }
  return NewCI;
}

void DefaultIntrinsicLowering::AddPrototypes(Module &M) {
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (I->isExternal() && !I->use_empty())
      switch (I->getIntrinsicID()) {
      default: break;
      case Intrinsic::setjmp:
        EnsureFunctionExists(M, "setjmp", I->arg_begin(), I->arg_end(),
                             Type::IntTy);
        break;
      case Intrinsic::longjmp:
        EnsureFunctionExists(M, "longjmp", I->arg_begin(), I->arg_end(),
                             Type::VoidTy);
        break;
      case Intrinsic::siglongjmp:
        EnsureFunctionExists(M, "abort", I->arg_end(), I->arg_end(),
                             Type::VoidTy);
        break;
      case Intrinsic::memcpy:
        EnsureFunctionExists(M, "memcpy", I->arg_begin(), --I->arg_end(),
                             I->arg_begin()->getType());
        break;
      case Intrinsic::memmove:
        EnsureFunctionExists(M, "memmove", I->arg_begin(), --I->arg_end(),
                             I->arg_begin()->getType());
        break;
      case Intrinsic::memset:
        M.getOrInsertFunction("memset", PointerType::get(Type::SByteTy),
                              PointerType::get(Type::SByteTy),
                              Type::IntTy, (--(--I->arg_end()))->getType(),
                              (Type *)0);
        break;
      case Intrinsic::isunordered:
        EnsureFunctionExists(M, "isunordered", I->arg_begin(), I->arg_end(),
                             Type::BoolTy);
        break;
      case Intrinsic::sqrt:
        if(I->arg_begin()->getType() == Type::FloatTy)
          EnsureFunctionExists(M, "sqrtf", I->arg_begin(), I->arg_end(),
                               Type::FloatTy);
        else
          EnsureFunctionExists(M, "sqrt", I->arg_begin(), I->arg_end(),
                               Type::DoubleTy);
        break;
      }
}

/// LowerCTPOP - Emit the code to lower ctpop of V before the specified
/// instruction.
static Value *LowerCTPOP(Value *V, Instruction *IP) {
  assert(V->getType()->isInteger() && "Can't ctpop a non-integer type!");

  static const uint64_t MaskValues[6] = {
    0x5555555555555555ULL, 0x3333333333333333ULL,
    0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
    0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL
  };

  const Type *DestTy = V->getType();

  // Force to unsigned so that the shift rights are logical.
  if (DestTy->isSigned())
    V = new CastInst(V, DestTy->getUnsignedVersion(), V->getName(), IP);

  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
  for (unsigned i = 1, ct = 0; i != BitSize; i <<= 1, ++ct) {
    Value *MaskCst =
      ConstantExpr::getCast(ConstantUInt::get(Type::ULongTy,
                                              MaskValues[ct]), V->getType());
    Value *LHS = BinaryOperator::createAnd(V, MaskCst, "cppop.and1", IP);
    Value *VShift = new ShiftInst(Instruction::Shr, V,
                      ConstantInt::get(Type::UByteTy, i), "ctpop.sh", IP);
    Value *RHS = BinaryOperator::createAnd(VShift, MaskCst, "cppop.and2", IP);
    V = BinaryOperator::createAdd(LHS, RHS, "ctpop.step", IP);
  }

  if (V->getType() != DestTy)
    V = new CastInst(V, DestTy, V->getName(), IP);
  return V;
}

/// LowerCTLZ - Emit the code to lower ctlz of V before the specified
/// instruction.
static Value *LowerCTLZ(Value *V, Instruction *IP) {
  const Type *DestTy = V->getType();

  // Force to unsigned so that the shift rights are logical.
  if (DestTy->isSigned())
    V = new CastInst(V, DestTy->getUnsignedVersion(), V->getName(), IP);

  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
  for (unsigned i = 1; i != BitSize; i <<= 1) {
    Value *ShVal = ConstantInt::get(Type::UByteTy, i);
    ShVal = new ShiftInst(Instruction::Shr, V, ShVal, "ctlz.sh", IP);
    V = BinaryOperator::createOr(V, ShVal, "ctlz.step", IP);
  }

  if (V->getType() != DestTy)
    V = new CastInst(V, DestTy, V->getName(), IP);

  V = BinaryOperator::createNot(V, "", IP);
  return LowerCTPOP(V, IP);
}

void DefaultIntrinsicLowering::LowerIntrinsicCall(CallInst *CI) {
  Function *Callee = CI->getCalledFunction();
  assert(Callee && "Cannot lower an indirect call!");

  switch (Callee->getIntrinsicID()) {
  case Intrinsic::not_intrinsic:
    std::cerr << "Cannot lower a call to a non-intrinsic function '"
              << Callee->getName() << "'!\n";
    abort();
  default:
    std::cerr << "Error: Code generator does not support intrinsic function '"
              << Callee->getName() << "'!\n";
    abort();

    // The setjmp/longjmp intrinsics should only exist in the code if it was
    // never optimized (ie, right out of the CFE), or if it has been hacked on
    // by the lowerinvoke pass.  In both cases, the right thing to do is to
    // convert the call to an explicit setjmp or longjmp call.
  case Intrinsic::setjmp: {
    static Function *SetjmpFCache = 0;
    Value *V = ReplaceCallWith("setjmp", CI, CI->op_begin()+1, CI->op_end(),
                               Type::IntTy, SetjmpFCache);
    if (CI->getType() != Type::VoidTy)
      CI->replaceAllUsesWith(V);
    break;
  }
  case Intrinsic::sigsetjmp:
     if (CI->getType() != Type::VoidTy)
       CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
     break;

  case Intrinsic::longjmp: {
    static Function *LongjmpFCache = 0;
    ReplaceCallWith("longjmp", CI, CI->op_begin()+1, CI->op_end(),
                    Type::VoidTy, LongjmpFCache);
    break;
  }

  case Intrinsic::siglongjmp: {
    // Insert the call to abort
    static Function *AbortFCache = 0;
    ReplaceCallWith("abort", CI, CI->op_end(), CI->op_end(), Type::VoidTy,
                    AbortFCache);
    break;
  }
  case Intrinsic::ctpop:
    CI->replaceAllUsesWith(LowerCTPOP(CI->getOperand(1), CI));
    break;

  case Intrinsic::ctlz:
    CI->replaceAllUsesWith(LowerCTLZ(CI->getOperand(1), CI));
    break;
  case Intrinsic::cttz: {
    // cttz(x) -> ctpop(~X & (X-1))
    Value *Src = CI->getOperand(1);
    Value *NotSrc = BinaryOperator::createNot(Src, Src->getName()+".not", CI);
    Value *SrcM1  = ConstantInt::get(Src->getType(), 1);
    SrcM1 = BinaryOperator::createSub(Src, SrcM1, "", CI);
    Src = LowerCTPOP(BinaryOperator::createAnd(NotSrc, SrcM1, "", CI), CI);
    CI->replaceAllUsesWith(Src);
    break;
  }

  case Intrinsic::stacksave:
  case Intrinsic::stackrestore: {
    static bool Warned = false;
    if (!Warned)
      std::cerr << "WARNING: this target does not support the llvm.stack"
       << (Callee->getIntrinsicID() == Intrinsic::stacksave ?
           "save" : "restore") << " intrinsic.\n";
    Warned = true;
    if (Callee->getIntrinsicID() == Intrinsic::stacksave)
      CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
    break;
  }
    
  case Intrinsic::returnaddress:
  case Intrinsic::frameaddress:
    std::cerr << "WARNING: this target does not support the llvm."
              << (Callee->getIntrinsicID() == Intrinsic::returnaddress ?
                  "return" : "frame") << "address intrinsic.\n";
    CI->replaceAllUsesWith(ConstantPointerNull::get(
                                            cast<PointerType>(CI->getType())));
    break;

  case Intrinsic::prefetch:
    break;    // Simply strip out prefetches on unsupported architectures

  case Intrinsic::pcmarker:
    break;    // Simply strip out pcmarker on unsupported architectures
  case Intrinsic::readcyclecounter: {
    std::cerr << "WARNING: this target does not support the llvm.readcyclecoun"
              << "ter intrinsic.  It is being lowered to a constant 0\n";
    CI->replaceAllUsesWith(ConstantUInt::get(Type::ULongTy, 0));
    break;
  }

  case Intrinsic::dbg_stoppoint:
  case Intrinsic::dbg_region_start:
  case Intrinsic::dbg_region_end:
  case Intrinsic::dbg_declare:
  case Intrinsic::dbg_func_start:
    if (CI->getType() != Type::VoidTy)
      CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
    break;    // Simply strip out debugging intrinsics

  case Intrinsic::memcpy: {
    // The memcpy intrinsic take an extra alignment argument that the memcpy
    // libc function does not.
    static Function *MemcpyFCache = 0;
    ReplaceCallWith("memcpy", CI, CI->op_begin()+1, CI->op_end()-1,
                    (*(CI->op_begin()+1))->getType(), MemcpyFCache);
    break;
  }
  case Intrinsic::memmove: {
    // The memmove intrinsic take an extra alignment argument that the memmove
    // libc function does not.
    static Function *MemmoveFCache = 0;
    ReplaceCallWith("memmove", CI, CI->op_begin()+1, CI->op_end()-1,
                    (*(CI->op_begin()+1))->getType(), MemmoveFCache);
    break;
  }
  case Intrinsic::memset: {
    // The memset intrinsic take an extra alignment argument that the memset
    // libc function does not.
    static Function *MemsetFCache = 0;
    ReplaceCallWith("memset", CI, CI->op_begin()+1, CI->op_end()-1,
                    (*(CI->op_begin()+1))->getType(), MemsetFCache);
    break;
  }
  case Intrinsic::isunordered: {
    Value *L = CI->getOperand(1);
    Value *R = CI->getOperand(2);

    Value *LIsNan = new SetCondInst(Instruction::SetNE, L, L, "LIsNan", CI);
    Value *RIsNan = new SetCondInst(Instruction::SetNE, R, R, "RIsNan", CI);
    CI->replaceAllUsesWith(
      BinaryOperator::create(Instruction::Or, LIsNan, RIsNan,
                             "isunordered", CI));
    break;
  }
  case Intrinsic::sqrt: {
    static Function *sqrtFCache = 0;
    static Function *sqrtfFCache = 0;
    if(CI->getType() == Type::FloatTy)
      ReplaceCallWith("sqrtf", CI, CI->op_begin()+1, CI->op_end(),
                      Type::FloatTy, sqrtfFCache);
    else
      ReplaceCallWith("sqrt", CI, CI->op_begin()+1, CI->op_end(),
                      Type::DoubleTy, sqrtFCache);
    break;
  }
  }

  assert(CI->use_empty() &&
         "Lowering should have eliminated any uses of the intrinsic call!");
  CI->eraseFromParent();
}