vendor/llvm/llvm-r72732

1 files changed, 892 insertions, 0 deletions

diff --git a/lib/CodeGen/IntrinsicLowering.cpp b/lib/CodeGen/IntrinsicLowering.cpp
new file mode 100644
index 0000000000000..e6912b82c38f9
--- /dev/null
+++ b/lib/CodeGen/IntrinsicLowering.cpp
@@ -0,0 +1,892 @@
+//===-- IntrinsicLowering.cpp - Intrinsic Lowering default implementation -===//
+//
+//                     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 IntrinsicLowering class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Module.h"
+#include "llvm/Type.h"
+#include "llvm/CodeGen/IntrinsicLowering.h"
+#include "llvm/Support/IRBuilder.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/SmallVector.h"
+using namespace llvm;
+
+template <class ArgIt>
+static void EnsureFunctionExists(Module &M, const char *Name,
+                                 ArgIt ArgBegin, ArgIt ArgEnd,
+                                 const Type *RetTy) {
+  // Insert a correctly-typed definition now.
+  std::vector<const Type *> ParamTys;
+  for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
+    ParamTys.push_back(I->getType());
+  M.getOrInsertFunction(Name, FunctionType::get(RetTy, ParamTys, false));
+}
+
+static void EnsureFPIntrinsicsExist(Module &M, Function *Fn,
+                                    const char *FName,
+                                    const char *DName, const char *LDName) {
+  // Insert definitions for all the floating point types.
+  switch((int)Fn->arg_begin()->getType()->getTypeID()) {
+  case Type::FloatTyID:
+    EnsureFunctionExists(M, FName, Fn->arg_begin(), Fn->arg_end(),
+                         Type::FloatTy);
+    break;
+  case Type::DoubleTyID:
+    EnsureFunctionExists(M, DName, Fn->arg_begin(), Fn->arg_end(),
+                         Type::DoubleTy);
+    break;
+  case Type::X86_FP80TyID:
+  case Type::FP128TyID:
+  case Type::PPC_FP128TyID:
+    EnsureFunctionExists(M, LDName, Fn->arg_begin(), Fn->arg_end(),
+                         Fn->arg_begin()->getType());
+    break;
+  }
+}
+
+/// 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, Constant *&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();
+    // Get or insert the 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));
+  }
+
+  IRBuilder<> Builder(CI->getParent(), CI);
+  SmallVector<Value *, 8> Args(ArgBegin, ArgEnd);
+  CallInst *NewCI = Builder.CreateCall(FCache, Args.begin(), Args.end());
+  NewCI->setName(CI->getName());
+  if (!CI->use_empty())
+    CI->replaceAllUsesWith(NewCI);
+  return NewCI;
+}
+
+void IntrinsicLowering::AddPrototypes(Module &M) {
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
+    if (I->isDeclaration() && !I->use_empty())
+      switch (I->getIntrinsicID()) {
+      default: break;
+      case Intrinsic::setjmp:
+        EnsureFunctionExists(M, "setjmp", I->arg_begin(), I->arg_end(),
+                             Type::Int32Ty);
+        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:
+        M.getOrInsertFunction("memcpy", PointerType::getUnqual(Type::Int8Ty),
+                              PointerType::getUnqual(Type::Int8Ty), 
+                              PointerType::getUnqual(Type::Int8Ty), 
+                              TD.getIntPtrType(), (Type *)0);
+        break;
+      case Intrinsic::memmove:
+        M.getOrInsertFunction("memmove", PointerType::getUnqual(Type::Int8Ty),
+                              PointerType::getUnqual(Type::Int8Ty), 
+                              PointerType::getUnqual(Type::Int8Ty), 
+                              TD.getIntPtrType(), (Type *)0);
+        break;
+      case Intrinsic::memset:
+        M.getOrInsertFunction("memset", PointerType::getUnqual(Type::Int8Ty),
+                              PointerType::getUnqual(Type::Int8Ty), 
+                              Type::Int32Ty, 
+                              TD.getIntPtrType(), (Type *)0);
+        break;
+      case Intrinsic::sqrt:
+        EnsureFPIntrinsicsExist(M, I, "sqrtf", "sqrt", "sqrtl");
+        break;
+      case Intrinsic::sin:
+        EnsureFPIntrinsicsExist(M, I, "sinf", "sin", "sinl");
+        break;
+      case Intrinsic::cos:
+        EnsureFPIntrinsicsExist(M, I, "cosf", "cos", "cosl");
+        break;
+      case Intrinsic::pow:
+        EnsureFPIntrinsicsExist(M, I, "powf", "pow", "powl");
+        break;
+      case Intrinsic::log:
+        EnsureFPIntrinsicsExist(M, I, "logf", "log", "logl");
+        break;
+      case Intrinsic::log2:
+        EnsureFPIntrinsicsExist(M, I, "log2f", "log2", "log2l");
+        break;
+      case Intrinsic::log10:
+        EnsureFPIntrinsicsExist(M, I, "log10f", "log10", "log10l");
+        break;
+      case Intrinsic::exp:
+        EnsureFPIntrinsicsExist(M, I, "expf", "exp", "expl");
+        break;
+      case Intrinsic::exp2:
+        EnsureFPIntrinsicsExist(M, I, "exp2f", "exp2", "exp2l");
+        break;
+      }
+}
+
+/// LowerBSWAP - Emit the code to lower bswap of V before the specified
+/// instruction IP.
+static Value *LowerBSWAP(Value *V, Instruction *IP) {
+  assert(V->getType()->isInteger() && "Can't bswap a non-integer type!");
+
+  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
+  
+  IRBuilder<> Builder(IP->getParent(), IP);
+
+  switch(BitSize) {
+  default: assert(0 && "Unhandled type size of value to byteswap!");
+  case 16: {
+    Value *Tmp1 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
+                                    "bswap.2");
+    Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
+                                     "bswap.1");
+    V = Builder.CreateOr(Tmp1, Tmp2, "bswap.i16");
+    break;
+  }
+  case 32: {
+    Value *Tmp4 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
+                                    "bswap.4");
+    Value *Tmp3 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
+                                    "bswap.3");
+    Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
+                                     "bswap.2");
+    Value *Tmp1 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 24),
+                                     "bswap.1");
+    Tmp3 = Builder.CreateAnd(Tmp3, ConstantInt::get(Type::Int32Ty, 0xFF0000),
+                             "bswap.and3");
+    Tmp2 = Builder.CreateAnd(Tmp2, ConstantInt::get(Type::Int32Ty, 0xFF00),
+                             "bswap.and2");
+    Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or1");
+    Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or2");
+    V = Builder.CreateOr(Tmp4, Tmp2, "bswap.i32");
+    break;
+  }
+  case 64: {
+    Value *Tmp8 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 56),
+                                    "bswap.8");
+    Value *Tmp7 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 40),
+                                    "bswap.7");
+    Value *Tmp6 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
+                                    "bswap.6");
+    Value *Tmp5 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
+                                    "bswap.5");
+    Value* Tmp4 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
+                                     "bswap.4");
+    Value* Tmp3 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 24),
+                                     "bswap.3");
+    Value* Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 40),
+                                     "bswap.2");
+    Value* Tmp1 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 56),
+                                     "bswap.1");
+    Tmp7 = Builder.CreateAnd(Tmp7,
+                             ConstantInt::get(Type::Int64Ty,
+                                              0xFF000000000000ULL),
+                             "bswap.and7");
+    Tmp6 = Builder.CreateAnd(Tmp6,
+                             ConstantInt::get(Type::Int64Ty,
+                                              0xFF0000000000ULL),
+                             "bswap.and6");
+    Tmp5 = Builder.CreateAnd(Tmp5,
+                             ConstantInt::get(Type::Int64Ty, 0xFF00000000ULL),
+                             "bswap.and5");
+    Tmp4 = Builder.CreateAnd(Tmp4,
+                             ConstantInt::get(Type::Int64Ty, 0xFF000000ULL),
+                             "bswap.and4");
+    Tmp3 = Builder.CreateAnd(Tmp3,
+                             ConstantInt::get(Type::Int64Ty, 0xFF0000ULL),
+                             "bswap.and3");
+    Tmp2 = Builder.CreateAnd(Tmp2,
+                             ConstantInt::get(Type::Int64Ty, 0xFF00ULL),
+                             "bswap.and2");
+    Tmp8 = Builder.CreateOr(Tmp8, Tmp7, "bswap.or1");
+    Tmp6 = Builder.CreateOr(Tmp6, Tmp5, "bswap.or2");
+    Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or3");
+    Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or4");
+    Tmp8 = Builder.CreateOr(Tmp8, Tmp6, "bswap.or5");
+    Tmp4 = Builder.CreateOr(Tmp4, Tmp2, "bswap.or6");
+    V = Builder.CreateOr(Tmp8, Tmp4, "bswap.i64");
+    break;
+  }
+  }
+  return V;
+}
+
+/// LowerCTPOP - Emit the code to lower ctpop of V before the specified
+/// instruction IP.
+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
+  };
+
+  IRBuilder<> Builder(IP->getParent(), IP);
+
+  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
+  unsigned WordSize = (BitSize + 63) / 64;
+  Value *Count = ConstantInt::get(V->getType(), 0);
+
+  for (unsigned n = 0; n < WordSize; ++n) {
+    Value *PartValue = V;
+    for (unsigned i = 1, ct = 0; i < (BitSize>64 ? 64 : BitSize); 
+         i <<= 1, ++ct) {
+      Value *MaskCst = ConstantInt::get(V->getType(), MaskValues[ct]);
+      Value *LHS = Builder.CreateAnd(PartValue, MaskCst, "cppop.and1");
+      Value *VShift = Builder.CreateLShr(PartValue,
+                                         ConstantInt::get(V->getType(), i),
+                                         "ctpop.sh");
+      Value *RHS = Builder.CreateAnd(VShift, MaskCst, "cppop.and2");
+      PartValue = Builder.CreateAdd(LHS, RHS, "ctpop.step");
+    }
+    Count = Builder.CreateAdd(PartValue, Count, "ctpop.part");
+    if (BitSize > 64) {
+      V = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 64),
+                             "ctpop.part.sh");
+      BitSize -= 64;
+    }
+  }
+
+  return Count;
+}
+
+/// LowerCTLZ - Emit the code to lower ctlz of V before the specified
+/// instruction IP.
+static Value *LowerCTLZ(Value *V, Instruction *IP) {
+
+  IRBuilder<> Builder(IP->getParent(), IP);
+
+  unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
+  for (unsigned i = 1; i < BitSize; i <<= 1) {
+    Value *ShVal = ConstantInt::get(V->getType(), i);
+    ShVal = Builder.CreateLShr(V, ShVal, "ctlz.sh");
+    V = Builder.CreateOr(V, ShVal, "ctlz.step");
+  }
+
+  V = Builder.CreateNot(V);
+  return LowerCTPOP(V, IP);
+}
+
+/// Convert the llvm.part.select.iX.iY intrinsic. This intrinsic takes 
+/// three integer arguments. The first argument is the Value from which the
+/// bits will be selected. It may be of any bit width. The second and third
+/// arguments specify a range of bits to select with the second argument 
+/// specifying the low bit and the third argument specifying the high bit. Both
+/// must be type i32. The result is the corresponding selected bits from the
+/// Value in the same width as the Value (first argument). If the low bit index
+/// is higher than the high bit index then the inverse selection is done and 
+/// the bits are returned in inverse order. 
+/// @brief Lowering of llvm.part.select intrinsic.
+static Instruction *LowerPartSelect(CallInst *CI) {
+  IRBuilder<> Builder;
+
+  // Make sure we're dealing with a part select intrinsic here
+  Function *F = CI->getCalledFunction();
+  const FunctionType *FT = F->getFunctionType();
+  if (!F->isDeclaration() || !FT->getReturnType()->isInteger() ||
+      FT->getNumParams() != 3 || !FT->getParamType(0)->isInteger() ||
+      !FT->getParamType(1)->isInteger() || !FT->getParamType(2)->isInteger())
+    return CI;
+
+  // Get the intrinsic implementation function by converting all the . to _
+  // in the intrinsic's function name and then reconstructing the function
+  // declaration.
+  std::string Name(F->getName());
+  for (unsigned i = 4; i < Name.length(); ++i)
+    if (Name[i] == '.')
+      Name[i] = '_';
+  Module* M = F->getParent();
+  F = cast<Function>(M->getOrInsertFunction(Name, FT));
+  F->setLinkage(GlobalValue::WeakAnyLinkage);
+
+  // If we haven't defined the impl function yet, do so now
+  if (F->isDeclaration()) {
+
+    // Get the arguments to the function
+    Function::arg_iterator args = F->arg_begin();
+    Value* Val = args++; Val->setName("Val");
+    Value* Lo = args++; Lo->setName("Lo");
+    Value* Hi = args++; Hi->setName("High");
+
+    // We want to select a range of bits here such that [Hi, Lo] is shifted
+    // down to the low bits. However, it is quite possible that Hi is smaller
+    // than Lo in which case the bits have to be reversed. 
+    
+    // Create the blocks we will need for the two cases (forward, reverse)
+    BasicBlock* CurBB   = BasicBlock::Create("entry", F);
+    BasicBlock *RevSize = BasicBlock::Create("revsize", CurBB->getParent());
+    BasicBlock *FwdSize = BasicBlock::Create("fwdsize", CurBB->getParent());
+    BasicBlock *Compute = BasicBlock::Create("compute", CurBB->getParent());
+    BasicBlock *Reverse = BasicBlock::Create("reverse", CurBB->getParent());
+    BasicBlock *RsltBlk = BasicBlock::Create("result",  CurBB->getParent());
+
+    Builder.SetInsertPoint(CurBB);
+
+    // Cast Hi and Lo to the size of Val so the widths are all the same
+    if (Hi->getType() != Val->getType())
+      Hi = Builder.CreateIntCast(Hi, Val->getType(), /* isSigned */ false,
+                                 "tmp");
+    if (Lo->getType() != Val->getType())
+      Lo = Builder.CreateIntCast(Lo, Val->getType(), /* isSigned */ false,
+                                 "tmp");
+
+    // Compute a few things that both cases will need, up front.
+    Constant* Zero = ConstantInt::get(Val->getType(), 0);
+    Constant* One = ConstantInt::get(Val->getType(), 1);
+    Constant* AllOnes = ConstantInt::getAllOnesValue(Val->getType());
+
+    // Compare the Hi and Lo bit positions. This is used to determine 
+    // which case we have (forward or reverse)
+    Value *Cmp = Builder.CreateICmpULT(Hi, Lo, "less");
+    Builder.CreateCondBr(Cmp, RevSize, FwdSize);
+
+    // First, compute the number of bits in the forward case.
+    Builder.SetInsertPoint(FwdSize);
+    Value* FBitSize = Builder.CreateSub(Hi, Lo, "fbits");
+    Builder.CreateBr(Compute);
+
+    // Second, compute the number of bits in the reverse case.
+    Builder.SetInsertPoint(RevSize);
+    Value* RBitSize = Builder.CreateSub(Lo, Hi, "rbits");
+    Builder.CreateBr(Compute);
+
+    // Now, compute the bit range. Start by getting the bitsize and the shift
+    // amount (either Hi or Lo) from PHI nodes. Then we compute a mask for 
+    // the number of bits we want in the range. We shift the bits down to the 
+    // least significant bits, apply the mask to zero out unwanted high bits, 
+    // and we have computed the "forward" result. It may still need to be 
+    // reversed.
+    Builder.SetInsertPoint(Compute);
+
+    // Get the BitSize from one of the two subtractions
+    PHINode *BitSize = Builder.CreatePHI(Val->getType(), "bits");
+    BitSize->reserveOperandSpace(2);
+    BitSize->addIncoming(FBitSize, FwdSize);
+    BitSize->addIncoming(RBitSize, RevSize);
+
+    // Get the ShiftAmount as the smaller of Hi/Lo
+    PHINode *ShiftAmt = Builder.CreatePHI(Val->getType(), "shiftamt");
+    ShiftAmt->reserveOperandSpace(2);
+    ShiftAmt->addIncoming(Lo, FwdSize);
+    ShiftAmt->addIncoming(Hi, RevSize);
+
+    // Increment the bit size
+    Value *BitSizePlusOne = Builder.CreateAdd(BitSize, One, "bits");
+
+    // Create a Mask to zero out the high order bits.
+    Value* Mask = Builder.CreateShl(AllOnes, BitSizePlusOne, "mask");
+    Mask = Builder.CreateNot(Mask, "mask");
+
+    // Shift the bits down and apply the mask
+    Value* FRes = Builder.CreateLShr(Val, ShiftAmt, "fres");
+    FRes = Builder.CreateAnd(FRes, Mask, "fres");
+    Builder.CreateCondBr(Cmp, Reverse, RsltBlk);
+
+    // In the Reverse block we have the mask already in FRes but we must reverse
+    // it by shifting FRes bits right and putting them in RRes by shifting them 
+    // in from left.
+    Builder.SetInsertPoint(Reverse);
+
+    // First set up our loop counters
+    PHINode *Count = Builder.CreatePHI(Val->getType(), "count");
+    Count->reserveOperandSpace(2);
+    Count->addIncoming(BitSizePlusOne, Compute);
+
+    // Next, get the value that we are shifting.
+    PHINode *BitsToShift = Builder.CreatePHI(Val->getType(), "val");
+    BitsToShift->reserveOperandSpace(2);
+    BitsToShift->addIncoming(FRes, Compute);
+
+    // Finally, get the result of the last computation
+    PHINode *RRes = Builder.CreatePHI(Val->getType(), "rres");
+    RRes->reserveOperandSpace(2);
+    RRes->addIncoming(Zero, Compute);
+
+    // Decrement the counter
+    Value *Decr = Builder.CreateSub(Count, One, "decr");
+    Count->addIncoming(Decr, Reverse);
+
+    // Compute the Bit that we want to move
+    Value *Bit = Builder.CreateAnd(BitsToShift, One, "bit");
+
+    // Compute the new value for next iteration.
+    Value *NewVal = Builder.CreateLShr(BitsToShift, One, "rshift");
+    BitsToShift->addIncoming(NewVal, Reverse);
+
+    // Shift the bit into the low bits of the result.
+    Value *NewRes = Builder.CreateShl(RRes, One, "lshift");
+    NewRes = Builder.CreateOr(NewRes, Bit, "addbit");
+    RRes->addIncoming(NewRes, Reverse);
+    
+    // Terminate loop if we've moved all the bits.
+    Value *Cond = Builder.CreateICmpEQ(Decr, Zero, "cond");
+    Builder.CreateCondBr(Cond, RsltBlk, Reverse);
+
+    // Finally, in the result block, select one of the two results with a PHI
+    // node and return the result;
+    Builder.SetInsertPoint(RsltBlk);
+    PHINode *BitSelect = Builder.CreatePHI(Val->getType(), "part_select");
+    BitSelect->reserveOperandSpace(2);
+    BitSelect->addIncoming(FRes, Compute);
+    BitSelect->addIncoming(NewRes, Reverse);
+    Builder.CreateRet(BitSelect);
+  }
+
+  // Return a call to the implementation function
+  Builder.SetInsertPoint(CI->getParent(), CI);
+  CallInst *NewCI = Builder.CreateCall3(F, CI->getOperand(1),
+                                        CI->getOperand(2), CI->getOperand(3));
+  NewCI->setName(CI->getName());
+  return NewCI;
+}
+
+/// Convert the llvm.part.set.iX.iY.iZ intrinsic. This intrinsic takes 
+/// four integer arguments (iAny %Value, iAny %Replacement, i32 %Low, i32 %High)
+/// The first two arguments can be any bit width. The result is the same width
+/// as %Value. The operation replaces bits between %Low and %High with the value
+/// in %Replacement. If %Replacement is not the same width, it is truncated or
+/// zero extended as appropriate to fit the bits being replaced. If %Low is
+/// greater than %High then the inverse set of bits are replaced.
+/// @brief Lowering of llvm.bit.part.set intrinsic.
+static Instruction *LowerPartSet(CallInst *CI) {
+  IRBuilder<> Builder;
+
+  // Make sure we're dealing with a part select intrinsic here
+  Function *F = CI->getCalledFunction();
+  const FunctionType *FT = F->getFunctionType();
+  if (!F->isDeclaration() || !FT->getReturnType()->isInteger() ||
+      FT->getNumParams() != 4 || !FT->getParamType(0)->isInteger() ||
+      !FT->getParamType(1)->isInteger() || !FT->getParamType(2)->isInteger() ||
+      !FT->getParamType(3)->isInteger())
+    return CI;
+
+  // Get the intrinsic implementation function by converting all the . to _
+  // in the intrinsic's function name and then reconstructing the function
+  // declaration.
+  std::string Name(F->getName());
+  for (unsigned i = 4; i < Name.length(); ++i)
+    if (Name[i] == '.')
+      Name[i] = '_';
+  Module* M = F->getParent();
+  F = cast<Function>(M->getOrInsertFunction(Name, FT));
+  F->setLinkage(GlobalValue::WeakAnyLinkage);
+
+  // If we haven't defined the impl function yet, do so now
+  if (F->isDeclaration()) {
+    // Get the arguments for the function.
+    Function::arg_iterator args = F->arg_begin();
+    Value* Val = args++; Val->setName("Val");
+    Value* Rep = args++; Rep->setName("Rep");
+    Value* Lo  = args++; Lo->setName("Lo");
+    Value* Hi  = args++; Hi->setName("Hi");
+
+    // Get some types we need
+    const IntegerType* ValTy = cast<IntegerType>(Val->getType());
+    const IntegerType* RepTy = cast<IntegerType>(Rep->getType());
+    uint32_t RepBits = RepTy->getBitWidth();
+
+    // Constant Definitions
+    ConstantInt* RepBitWidth = ConstantInt::get(Type::Int32Ty, RepBits);
+    ConstantInt* RepMask = ConstantInt::getAllOnesValue(RepTy);
+    ConstantInt* ValMask = ConstantInt::getAllOnesValue(ValTy);
+    ConstantInt* One = ConstantInt::get(Type::Int32Ty, 1);
+    ConstantInt* ValOne = ConstantInt::get(ValTy, 1);
+    ConstantInt* Zero = ConstantInt::get(Type::Int32Ty, 0);
+    ConstantInt* ValZero = ConstantInt::get(ValTy, 0);
+
+    // Basic blocks we fill in below.
+    BasicBlock* entry = BasicBlock::Create("entry", F, 0);
+    BasicBlock* large = BasicBlock::Create("large", F, 0);
+    BasicBlock* small = BasicBlock::Create("small", F, 0);
+    BasicBlock* reverse = BasicBlock::Create("reverse", F, 0);
+    BasicBlock* result = BasicBlock::Create("result", F, 0);
+
+    // BASIC BLOCK: entry
+    Builder.SetInsertPoint(entry);
+    // First, get the number of bits that we're placing as an i32
+    Value* is_forward = Builder.CreateICmpULT(Lo, Hi);
+    Value* Hi_pn = Builder.CreateSelect(is_forward, Hi, Lo);
+    Value* Lo_pn = Builder.CreateSelect(is_forward, Lo, Hi);
+    Value* NumBits = Builder.CreateSub(Hi_pn, Lo_pn);
+    NumBits = Builder.CreateAdd(NumBits, One);
+    // Now, convert Lo and Hi to ValTy bit width
+    Lo = Builder.CreateIntCast(Lo_pn, ValTy, /* isSigned */ false);
+    // Determine if the replacement bits are larger than the number of bits we
+    // are replacing and deal with it.
+    Value* is_large = Builder.CreateICmpULT(NumBits, RepBitWidth);
+    Builder.CreateCondBr(is_large, large, small);
+
+    // BASIC BLOCK: large
+    Builder.SetInsertPoint(large);
+    Value* MaskBits = Builder.CreateSub(RepBitWidth, NumBits);
+    MaskBits = Builder.CreateIntCast(MaskBits, RepMask->getType(),
+                                     /* isSigned */ false);
+    Value* Mask1 = Builder.CreateLShr(RepMask, MaskBits);
+    Value* Rep2 = Builder.CreateAnd(Mask1, Rep);
+    Builder.CreateBr(small);
+
+    // BASIC BLOCK: small
+    Builder.SetInsertPoint(small);
+    PHINode* Rep3 = Builder.CreatePHI(RepTy);
+    Rep3->reserveOperandSpace(2);
+    Rep3->addIncoming(Rep2, large);
+    Rep3->addIncoming(Rep, entry);
+    Value* Rep4 = Builder.CreateIntCast(Rep3, ValTy, /* isSigned */ false);
+    Builder.CreateCondBr(is_forward, result, reverse);
+
+    // BASIC BLOCK: reverse (reverses the bits of the replacement)
+    Builder.SetInsertPoint(reverse);
+    // Set up our loop counter as a PHI so we can decrement on each iteration.
+    // We will loop for the number of bits in the replacement value.
+    PHINode *Count = Builder.CreatePHI(Type::Int32Ty, "count");
+    Count->reserveOperandSpace(2);
+    Count->addIncoming(NumBits, small);
+
+    // Get the value that we are shifting bits out of as a PHI because
+    // we'll change this with each iteration.
+    PHINode *BitsToShift = Builder.CreatePHI(Val->getType(), "val");
+    BitsToShift->reserveOperandSpace(2);
+    BitsToShift->addIncoming(Rep4, small);
+
+    // Get the result of the last computation or zero on first iteration
+    PHINode *RRes = Builder.CreatePHI(Val->getType(), "rres");
+    RRes->reserveOperandSpace(2);
+    RRes->addIncoming(ValZero, small);
+
+    // Decrement the loop counter by one
+    Value *Decr = Builder.CreateSub(Count, One);
+    Count->addIncoming(Decr, reverse);
+
+    // Get the bit that we want to move into the result
+    Value *Bit = Builder.CreateAnd(BitsToShift, ValOne);
+
+    // Compute the new value of the bits to shift for the next iteration.
+    Value *NewVal = Builder.CreateLShr(BitsToShift, ValOne);
+    BitsToShift->addIncoming(NewVal, reverse);
+
+    // Shift the bit we extracted into the low bit of the result.
+    Value *NewRes = Builder.CreateShl(RRes, ValOne);
+    NewRes = Builder.CreateOr(NewRes, Bit);
+    RRes->addIncoming(NewRes, reverse);
+    
+    // Terminate loop if we've moved all the bits.
+    Value *Cond = Builder.CreateICmpEQ(Decr, Zero);
+    Builder.CreateCondBr(Cond, result, reverse);
+
+    // BASIC BLOCK: result
+    Builder.SetInsertPoint(result);
+    PHINode *Rplcmnt = Builder.CreatePHI(Val->getType());
+    Rplcmnt->reserveOperandSpace(2);
+    Rplcmnt->addIncoming(NewRes, reverse);
+    Rplcmnt->addIncoming(Rep4, small);
+    Value* t0   = Builder.CreateIntCast(NumBits, ValTy, /* isSigned */ false);
+    Value* t1   = Builder.CreateShl(ValMask, Lo);
+    Value* t2   = Builder.CreateNot(t1);
+    Value* t3   = Builder.CreateShl(t1, t0);
+    Value* t4   = Builder.CreateOr(t2, t3);
+    Value* t5   = Builder.CreateAnd(t4, Val);
+    Value* t6   = Builder.CreateShl(Rplcmnt, Lo);
+    Value* Rslt = Builder.CreateOr(t5, t6, "part_set");
+    Builder.CreateRet(Rslt);
+  }
+
+  // Return a call to the implementation function
+  Builder.SetInsertPoint(CI->getParent(), CI);
+  CallInst *NewCI = Builder.CreateCall4(F, CI->getOperand(1),
+                                        CI->getOperand(2), CI->getOperand(3),
+                                        CI->getOperand(4));
+  NewCI->setName(CI->getName());
+  return NewCI;
+}
+
+static void ReplaceFPIntrinsicWithCall(CallInst *CI, Constant *FCache,
+                                       Constant *DCache, Constant *LDCache,
+                                       const char *Fname, const char *Dname,
+                                       const char *LDname) {
+  switch (CI->getOperand(1)->getType()->getTypeID()) {
+  default: assert(0 && "Invalid type in intrinsic"); abort();
+  case Type::FloatTyID:
+    ReplaceCallWith(Fname, CI, CI->op_begin() + 1, CI->op_end(),
+                  Type::FloatTy, FCache);
+    break;
+  case Type::DoubleTyID:
+    ReplaceCallWith(Dname, CI, CI->op_begin() + 1, CI->op_end(),
+                  Type::DoubleTy, DCache);
+    break;
+  case Type::X86_FP80TyID:
+  case Type::FP128TyID:
+  case Type::PPC_FP128TyID:
+    ReplaceCallWith(LDname, CI, CI->op_begin() + 1, CI->op_end(),
+                  CI->getOperand(1)->getType(), LDCache);
+    break;
+  }
+}
+
+void IntrinsicLowering::LowerIntrinsicCall(CallInst *CI) {
+  IRBuilder<> Builder(CI->getParent(), CI);
+
+  Function *Callee = CI->getCalledFunction();
+  assert(Callee && "Cannot lower an indirect call!");
+
+  switch (Callee->getIntrinsicID()) {
+  case Intrinsic::not_intrinsic:
+    cerr << "Cannot lower a call to a non-intrinsic function '"
+         << Callee->getName() << "'!\n";
+    abort();
+  default:
+    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 Constant *SetjmpFCache = 0;
+    Value *V = ReplaceCallWith("setjmp", CI, CI->op_begin() + 1, CI->op_end(),
+                               Type::Int32Ty, 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 Constant *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 Constant *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::bswap:
+    CI->replaceAllUsesWith(LowerBSWAP(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 = Builder.CreateNot(Src);
+    NotSrc->setName(Src->getName() + ".not");
+    Value *SrcM1 = ConstantInt::get(Src->getType(), 1);
+    SrcM1 = Builder.CreateSub(Src, SrcM1);
+    Src = LowerCTPOP(Builder.CreateAnd(NotSrc, SrcM1), CI);
+    CI->replaceAllUsesWith(Src);
+    break;
+  }
+
+  case Intrinsic::part_select:
+    CI->replaceAllUsesWith(LowerPartSelect(CI));
+    break;
+
+  case Intrinsic::part_set:
+    CI->replaceAllUsesWith(LowerPartSet(CI));
+    break;
+
+  case Intrinsic::stacksave:
+  case Intrinsic::stackrestore: {
+    static bool Warned = false;
+    if (!Warned)
+      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:
+    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: {
+    cerr << "WARNING: this target does not support the llvm.readcyclecoun"
+         << "ter intrinsic.  It is being lowered to a constant 0\n";
+    CI->replaceAllUsesWith(ConstantInt::get(Type::Int64Ty, 0));
+    break;
+  }
+
+  case Intrinsic::dbg_stoppoint:
+  case Intrinsic::dbg_region_start:
+  case Intrinsic::dbg_region_end:
+  case Intrinsic::dbg_func_start:
+  case Intrinsic::dbg_declare:
+    break;    // Simply strip out debugging intrinsics
+
+  case Intrinsic::eh_exception:
+  case Intrinsic::eh_selector_i32:
+  case Intrinsic::eh_selector_i64:
+    CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
+    break;
+
+  case Intrinsic::eh_typeid_for_i32:
+  case Intrinsic::eh_typeid_for_i64:
+    // Return something different to eh_selector.
+    CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
+    break;
+
+  case Intrinsic::var_annotation:
+    break;   // Strip out annotate intrinsic
+    
+  case Intrinsic::memcpy: {
+    static Constant *MemcpyFCache = 0;
+    const IntegerType *IntPtr = TD.getIntPtrType();
+    Value *Size = Builder.CreateIntCast(CI->getOperand(3), IntPtr,
+                                        /* isSigned */ false);
+    Value *Ops[3];
+    Ops[0] = CI->getOperand(1);
+    Ops[1] = CI->getOperand(2);
+    Ops[2] = Size;
+    ReplaceCallWith("memcpy", CI, Ops, Ops+3, CI->getOperand(1)->getType(),
+                    MemcpyFCache);
+    break;
+  }
+  case Intrinsic::memmove: {
+    static Constant *MemmoveFCache = 0;
+    const IntegerType *IntPtr = TD.getIntPtrType();
+    Value *Size = Builder.CreateIntCast(CI->getOperand(3), IntPtr,
+                                        /* isSigned */ false);
+    Value *Ops[3];
+    Ops[0] = CI->getOperand(1);
+    Ops[1] = CI->getOperand(2);
+    Ops[2] = Size;
+    ReplaceCallWith("memmove", CI, Ops, Ops+3, CI->getOperand(1)->getType(),
+                    MemmoveFCache);
+    break;
+  }
+  case Intrinsic::memset: {
+    static Constant *MemsetFCache = 0;
+    const IntegerType *IntPtr = TD.getIntPtrType();
+    Value *Size = Builder.CreateIntCast(CI->getOperand(3), IntPtr,
+                                        /* isSigned */ false);
+    Value *Ops[3];
+    Ops[0] = CI->getOperand(1);
+    // Extend the amount to i32.
+    Ops[1] = Builder.CreateIntCast(CI->getOperand(2), Type::Int32Ty,
+                                   /* isSigned */ false);
+    Ops[2] = Size;
+    ReplaceCallWith("memset", CI, Ops, Ops+3, CI->getOperand(1)->getType(),
+                    MemsetFCache);
+    break;
+  }
+  case Intrinsic::sqrt: {
+    static Constant *sqrtFCache = 0;
+    static Constant *sqrtDCache = 0;
+    static Constant *sqrtLDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, sqrtFCache, sqrtDCache, sqrtLDCache,
+                               "sqrtf", "sqrt", "sqrtl");
+    break;
+  }
+  case Intrinsic::log: {
+    static Constant *logFCache = 0;
+    static Constant *logDCache = 0;
+    static Constant *logLDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, logFCache, logDCache, logLDCache,
+                               "logf", "log", "logl");
+    break;
+  }
+  case Intrinsic::log2: {
+    static Constant *log2FCache = 0;
+    static Constant *log2DCache = 0;
+    static Constant *log2LDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, log2FCache, log2DCache, log2LDCache,
+                               "log2f", "log2", "log2l");
+    break;
+  }
+  case Intrinsic::log10: {
+    static Constant *log10FCache = 0;
+    static Constant *log10DCache = 0;
+    static Constant *log10LDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, log10FCache, log10DCache, log10LDCache,
+                               "log10f", "log10", "log10l");
+    break;
+  }
+  case Intrinsic::exp: {
+    static Constant *expFCache = 0;
+    static Constant *expDCache = 0;
+    static Constant *expLDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, expFCache, expDCache, expLDCache,
+                               "expf", "exp", "expl");
+    break;
+  }
+  case Intrinsic::exp2: {
+    static Constant *exp2FCache = 0;
+    static Constant *exp2DCache = 0;
+    static Constant *exp2LDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, exp2FCache, exp2DCache, exp2LDCache,
+                               "exp2f", "exp2", "exp2l");
+    break;
+  }
+  case Intrinsic::pow: {
+    static Constant *powFCache = 0;
+    static Constant *powDCache = 0;
+    static Constant *powLDCache = 0;
+    ReplaceFPIntrinsicWithCall(CI, powFCache, powDCache, powLDCache,
+                               "powf", "pow", "powl");
+    break;
+  }
+  case Intrinsic::flt_rounds:
+     // Lower to "round to the nearest"
+     if (CI->getType() != Type::VoidTy)
+       CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
+     break;
+  }
+
+  assert(CI->use_empty() &&
+         "Lowering should have eliminated any uses of the intrinsic call!");
+  CI->eraseFromParent();
+}