lib/CodeGen/IntrinsicLowering.cpp

   1 //===-- IntrinsicLowering.cpp - Intrinsic Lowering default implementation -===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the IntrinsicLowering class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Constants.h"
  15 #include "llvm/DerivedTypes.h"
  16 #include "llvm/Module.h"
  17 #include "llvm/Type.h"
  18 #include "llvm/CodeGen/IntrinsicLowering.h"
  19 #include "llvm/Support/CallSite.h"
  20 #include "llvm/Support/ErrorHandling.h"
  21 #include "llvm/Support/IRBuilder.h"
  22 #include "llvm/Support/raw_ostream.h"
  23 #include "llvm/Target/TargetData.h"
  24 #include "llvm/ADT/SmallVector.h"
  25 using namespace llvm;
  26
  27 template <class ArgIt>
  28 static void EnsureFunctionExists(Module &M, const char *Name,
  29                                  ArgIt ArgBegin, ArgIt ArgEnd,
  30                                  const Type *RetTy) {
  31   // Insert a correctly-typed definition now.
  32   std::vector<const Type *> ParamTys;
  33   for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
  34     ParamTys.push_back(I->getType());
  35   M.getOrInsertFunction(Name, FunctionType::get(RetTy, ParamTys, false));
  36 }
  37
  38 static void EnsureFPIntrinsicsExist(Module &M, Function *Fn,
  39                                     const char *FName,
  40                                     const char *DName, const char *LDName) {
  41   // Insert definitions for all the floating point types.
  42   switch((int)Fn->arg_begin()->getType()->getTypeID()) {
  43   case Type::FloatTyID:
  44     EnsureFunctionExists(M, FName, Fn->arg_begin(), Fn->arg_end(),
  45                          Type::getFloatTy(M.getContext()));
  46     break;
  47   case Type::DoubleTyID:
  48     EnsureFunctionExists(M, DName, Fn->arg_begin(), Fn->arg_end(),
  49                          Type::getDoubleTy(M.getContext()));
  50     break;
  51   case Type::X86_FP80TyID:
  52   case Type::FP128TyID:
  53   case Type::PPC_FP128TyID:
  54     EnsureFunctionExists(M, LDName, Fn->arg_begin(), Fn->arg_end(),
  55                          Fn->arg_begin()->getType());
  56     break;
  57   }
  58 }
  59
  60 /// ReplaceCallWith - This function is used when we want to lower an intrinsic
  61 /// call to a call of an external function.  This handles hard cases such as
  62 /// when there was already a prototype for the external function, and if that
  63 /// prototype doesn't match the arguments we expect to pass in.
  64 template <class ArgIt>
  65 static CallInst *ReplaceCallWith(const char *NewFn, CallInst *CI,
  66                                  ArgIt ArgBegin, ArgIt ArgEnd,
  67                                  const Type *RetTy) {
  68   // If we haven't already looked up this function, check to see if the
  69   // program already contains a function with this name.
  70   Module *M = CI->getParent()->getParent()->getParent();
  71   // Get or insert the definition now.
  72   std::vector<const Type *> ParamTys;
  73   for (ArgIt I = ArgBegin; I != ArgEnd; ++I)
  74     ParamTys.push_back((*I)->getType());
  75   Constant* FCache = M->getOrInsertFunction(NewFn,
  76                                   FunctionType::get(RetTy, ParamTys, false));
  77
  78   IRBuilder<> Builder(CI->getParent(), CI);
  79   SmallVector<Value *, 8> Args(ArgBegin, ArgEnd);
  80   CallInst *NewCI = Builder.CreateCall(FCache, Args.begin(), Args.end());
  81   NewCI->setName(CI->getName());
  82   if (!CI->use_empty())
  83     CI->replaceAllUsesWith(NewCI);
  84   return NewCI;
  85 }
  86
  87 // VisualStudio defines setjmp as _setjmp
  88 #if defined(_MSC_VER) && defined(setjmp)
  89 #define setjmp_undefined_for_visual_studio
  90 #undef setjmp
  91 #endif
  92
  93 void IntrinsicLowering::AddPrototypes(Module &M) {
  94   LLVMContext &Context = M.getContext();
  95   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  96     if (I->isDeclaration() && !I->use_empty())
  97       switch (I->getIntrinsicID()) {
  98       default: break;
  99       case Intrinsic::setjmp:
 100         EnsureFunctionExists(M, "setjmp", I->arg_begin(), I->arg_end(),
 101                              Type::getInt32Ty(M.getContext()));
 102         break;
 103       case Intrinsic::longjmp:
 104         EnsureFunctionExists(M, "longjmp", I->arg_begin(), I->arg_end(),
 105                              Type::getVoidTy(M.getContext()));
 106         break;
 107       case Intrinsic::siglongjmp:
 108         EnsureFunctionExists(M, "abort", I->arg_end(), I->arg_end(),
 109                              Type::getVoidTy(M.getContext()));
 110         break;
 111       case Intrinsic::memcpy:
 112         M.getOrInsertFunction("memcpy",
 113           Type::getInt8PtrTy(Context),
 114                               Type::getInt8PtrTy(Context),
 115                               Type::getInt8PtrTy(Context),
 116                               TD.getIntPtrType(Context), (Type *)0);
 117         break;
 118       case Intrinsic::memmove:
 119         M.getOrInsertFunction("memmove",
 120           Type::getInt8PtrTy(Context),
 121                               Type::getInt8PtrTy(Context),
 122                               Type::getInt8PtrTy(Context),
 123                               TD.getIntPtrType(Context), (Type *)0);
 124         break;
 125       case Intrinsic::memset:
 126         M.getOrInsertFunction("memset",
 127           Type::getInt8PtrTy(Context),
 128                               Type::getInt8PtrTy(Context),
 129                               Type::getInt32Ty(M.getContext()),
 130                               TD.getIntPtrType(Context), (Type *)0);
 131         break;
 132       case Intrinsic::sqrt:
 133         EnsureFPIntrinsicsExist(M, I, "sqrtf", "sqrt", "sqrtl");
 134         break;
 135       case Intrinsic::sin:
 136         EnsureFPIntrinsicsExist(M, I, "sinf", "sin", "sinl");
 137         break;
 138       case Intrinsic::cos:
 139         EnsureFPIntrinsicsExist(M, I, "cosf", "cos", "cosl");
 140         break;
 141       case Intrinsic::pow:
 142         EnsureFPIntrinsicsExist(M, I, "powf", "pow", "powl");
 143         break;
 144       case Intrinsic::log:
 145         EnsureFPIntrinsicsExist(M, I, "logf", "log", "logl");
 146         break;
 147       case Intrinsic::log2:
 148         EnsureFPIntrinsicsExist(M, I, "log2f", "log2", "log2l");
 149         break;
 150       case Intrinsic::log10:
 151         EnsureFPIntrinsicsExist(M, I, "log10f", "log10", "log10l");
 152         break;
 153       case Intrinsic::exp:
 154         EnsureFPIntrinsicsExist(M, I, "expf", "exp", "expl");
 155         break;
 156       case Intrinsic::exp2:
 157         EnsureFPIntrinsicsExist(M, I, "exp2f", "exp2", "exp2l");
 158         break;
 159       }
 160 }
 161
 162 /// LowerBSWAP - Emit the code to lower bswap of V before the specified
 163 /// instruction IP.
 164 static Value *LowerBSWAP(LLVMContext &Context, Value *V, Instruction *IP) {
 165   assert(V->getType()->isIntegerTy() && "Can't bswap a non-integer type!");
 166
 167   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
 168
 169   IRBuilder<> Builder(IP->getParent(), IP);
 170
 171   switch(BitSize) {
 172   default: llvm_unreachable("Unhandled type size of value to byteswap!");
 173   case 16: {
 174     Value *Tmp1 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
 175                                     "bswap.2");
 176     Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
 177                                      "bswap.1");
 178     V = Builder.CreateOr(Tmp1, Tmp2, "bswap.i16");
 179     break;
 180   }
 181   case 32: {
 182     Value *Tmp4 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
 183                                     "bswap.4");
 184     Value *Tmp3 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
 185                                     "bswap.3");
 186     Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
 187                                      "bswap.2");
 188     Value *Tmp1 = Builder.CreateLShr(V,ConstantInt::get(V->getType(), 24),
 189                                      "bswap.1");
 190     Tmp3 = Builder.CreateAnd(Tmp3,
 191                          ConstantInt::get(Type::getInt32Ty(Context), 0xFF0000),
 192                              "bswap.and3");
 193     Tmp2 = Builder.CreateAnd(Tmp2,
 194                            ConstantInt::get(Type::getInt32Ty(Context), 0xFF00),
 195                              "bswap.and2");
 196     Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or1");
 197     Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or2");
 198     V = Builder.CreateOr(Tmp4, Tmp2, "bswap.i32");
 199     break;
 200   }
 201   case 64: {
 202     Value *Tmp8 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 56),
 203                                     "bswap.8");
 204     Value *Tmp7 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 40),
 205                                     "bswap.7");
 206     Value *Tmp6 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
 207                                     "bswap.6");
 208     Value *Tmp5 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
 209                                     "bswap.5");
 210     Value* Tmp4 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
 211                                      "bswap.4");
 212     Value* Tmp3 = Builder.CreateLShr(V,
 213                                      ConstantInt::get(V->getType(), 24),
 214                                      "bswap.3");
 215     Value* Tmp2 = Builder.CreateLShr(V,
 216                                      ConstantInt::get(V->getType(), 40),
 217                                      "bswap.2");
 218     Value* Tmp1 = Builder.CreateLShr(V,
 219                                      ConstantInt::get(V->getType(), 56),
 220                                      "bswap.1");
 221     Tmp7 = Builder.CreateAnd(Tmp7,
 222                              ConstantInt::get(Type::getInt64Ty(Context),
 223                                               0xFF000000000000ULL),
 224                              "bswap.and7");
 225     Tmp6 = Builder.CreateAnd(Tmp6,
 226                              ConstantInt::get(Type::getInt64Ty(Context),
 227                                               0xFF0000000000ULL),
 228                              "bswap.and6");
 229     Tmp5 = Builder.CreateAnd(Tmp5,
 230                         ConstantInt::get(Type::getInt64Ty(Context),
 231                              0xFF00000000ULL),
 232                              "bswap.and5");
 233     Tmp4 = Builder.CreateAnd(Tmp4,
 234                         ConstantInt::get(Type::getInt64Ty(Context),
 235                              0xFF000000ULL),
 236                              "bswap.and4");
 237     Tmp3 = Builder.CreateAnd(Tmp3,
 238                              ConstantInt::get(Type::getInt64Ty(Context),
 239                              0xFF0000ULL),
 240                              "bswap.and3");
 241     Tmp2 = Builder.CreateAnd(Tmp2,
 242                              ConstantInt::get(Type::getInt64Ty(Context),
 243                              0xFF00ULL),
 244                              "bswap.and2");
 245     Tmp8 = Builder.CreateOr(Tmp8, Tmp7, "bswap.or1");
 246     Tmp6 = Builder.CreateOr(Tmp6, Tmp5, "bswap.or2");
 247     Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or3");
 248     Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or4");
 249     Tmp8 = Builder.CreateOr(Tmp8, Tmp6, "bswap.or5");
 250     Tmp4 = Builder.CreateOr(Tmp4, Tmp2, "bswap.or6");
 251     V = Builder.CreateOr(Tmp8, Tmp4, "bswap.i64");
 252     break;
 253   }
 254   }
 255   return V;
 256 }
 257
 258 /// LowerCTPOP - Emit the code to lower ctpop of V before the specified
 259 /// instruction IP.
 260 static Value *LowerCTPOP(LLVMContext &Context, Value *V, Instruction *IP) {
 261   assert(V->getType()->isIntegerTy() && "Can't ctpop a non-integer type!");
 262
 263   static const uint64_t MaskValues[6] = {
 264     0x5555555555555555ULL, 0x3333333333333333ULL,
 265     0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
 266     0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL
 267   };
 268
 269   IRBuilder<> Builder(IP->getParent(), IP);
 270
 271   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
 272   unsigned WordSize = (BitSize + 63) / 64;
 273   Value *Count = ConstantInt::get(V->getType(), 0);
 274
 275   for (unsigned n = 0; n < WordSize; ++n) {
 276     Value *PartValue = V;
 277     for (unsigned i = 1, ct = 0; i < (BitSize>64 ? 64 : BitSize);
 278          i <<= 1, ++ct) {
 279       Value *MaskCst = ConstantInt::get(V->getType(), MaskValues[ct]);
 280       Value *LHS = Builder.CreateAnd(PartValue, MaskCst, "cppop.and1");
 281       Value *VShift = Builder.CreateLShr(PartValue,
 282                                         ConstantInt::get(V->getType(), i),
 283                                          "ctpop.sh");
 284       Value *RHS = Builder.CreateAnd(VShift, MaskCst, "cppop.and2");
 285       PartValue = Builder.CreateAdd(LHS, RHS, "ctpop.step");
 286     }
 287     Count = Builder.CreateAdd(PartValue, Count, "ctpop.part");
 288     if (BitSize > 64) {
 289       V = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 64),
 290                              "ctpop.part.sh");
 291       BitSize -= 64;
 292     }
 293   }
 294
 295   return Count;
 296 }
 297
 298 /// LowerCTLZ - Emit the code to lower ctlz of V before the specified
 299 /// instruction IP.
 300 static Value *LowerCTLZ(LLVMContext &Context, Value *V, Instruction *IP) {
 301
 302   IRBuilder<> Builder(IP->getParent(), IP);
 303
 304   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
 305   for (unsigned i = 1; i < BitSize; i <<= 1) {
 306     Value *ShVal = ConstantInt::get(V->getType(), i);
 307     ShVal = Builder.CreateLShr(V, ShVal, "ctlz.sh");
 308     V = Builder.CreateOr(V, ShVal, "ctlz.step");
 309   }
 310
 311   V = Builder.CreateNot(V);
 312   return LowerCTPOP(Context, V, IP);
 313 }
 314
 315 static void ReplaceFPIntrinsicWithCall(CallInst *CI, const char *Fname,
 316                                        const char *Dname,
 317                                        const char *LDname) {
 318   CallSite CS(CI);
 319   switch (CI->getArgOperand(0)->getType()->getTypeID()) {
 320   default: llvm_unreachable("Invalid type in intrinsic");
 321   case Type::FloatTyID:
 322     ReplaceCallWith(Fname, CI, CS.arg_begin(), CS.arg_end(),
 323                   Type::getFloatTy(CI->getContext()));
 324     break;
 325   case Type::DoubleTyID:
 326     ReplaceCallWith(Dname, CI, CS.arg_begin(), CS.arg_end(),
 327                   Type::getDoubleTy(CI->getContext()));
 328     break;
 329   case Type::X86_FP80TyID:
 330   case Type::FP128TyID:
 331   case Type::PPC_FP128TyID:
 332     ReplaceCallWith(LDname, CI, CS.arg_begin(), CS.arg_end(),
 333                   CI->getArgOperand(0)->getType());
 334     break;
 335   }
 336 }
 337
 338 void IntrinsicLowering::LowerIntrinsicCall(CallInst *CI) {
 339   IRBuilder<> Builder(CI->getParent(), CI);
 340   LLVMContext &Context = CI->getContext();
 341
 342   const Function *Callee = CI->getCalledFunction();
 343   assert(Callee && "Cannot lower an indirect call!");
 344
 345   CallSite CS(CI);
 346   switch (Callee->getIntrinsicID()) {
 347   case Intrinsic::not_intrinsic:
 348     report_fatal_error("Cannot lower a call to a non-intrinsic function '"+
 349                       Callee->getName() + "'!");
 350   default:
 351     report_fatal_error("Code generator does not support intrinsic function '"+
 352                       Callee->getName()+"'!");
 353
 354     // The setjmp/longjmp intrinsics should only exist in the code if it was
 355     // never optimized (ie, right out of the CFE), or if it has been hacked on
 356     // by the lowerinvoke pass.  In both cases, the right thing to do is to
 357     // convert the call to an explicit setjmp or longjmp call.
 358   case Intrinsic::setjmp: {
 359     Value *V = ReplaceCallWith("setjmp", CI, CS.arg_begin(), CS.arg_end(),
 360                                Type::getInt32Ty(Context));
 361     if (!CI->getType()->isVoidTy())
 362       CI->replaceAllUsesWith(V);
 363     break;
 364   }
 365   case Intrinsic::sigsetjmp:
 366      if (!CI->getType()->isVoidTy())
 367        CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
 368      break;
 369
 370   case Intrinsic::longjmp: {
 371     ReplaceCallWith("longjmp", CI, CS.arg_begin(), CS.arg_end(),
 372                     Type::getVoidTy(Context));
 373     break;
 374   }
 375
 376   case Intrinsic::siglongjmp: {
 377     // Insert the call to abort
 378     ReplaceCallWith("abort", CI, CS.arg_end(), CS.arg_end(),
 379                     Type::getVoidTy(Context));
 380     break;
 381   }
 382   case Intrinsic::ctpop:
 383     CI->replaceAllUsesWith(LowerCTPOP(Context, CI->getArgOperand(0), CI));
 384     break;
 385
 386   case Intrinsic::bswap:
 387     CI->replaceAllUsesWith(LowerBSWAP(Context, CI->getArgOperand(0), CI));
 388     break;
 389
 390   case Intrinsic::ctlz:
 391     CI->replaceAllUsesWith(LowerCTLZ(Context, CI->getArgOperand(0), CI));
 392     break;
 393
 394   case Intrinsic::cttz: {
 395     // cttz(x) -> ctpop(~X & (X-1))
 396     Value *Src = CI->getArgOperand(0);
 397     Value *NotSrc = Builder.CreateNot(Src);
 398     NotSrc->setName(Src->getName() + ".not");
 399     Value *SrcM1 = ConstantInt::get(Src->getType(), 1);
 400     SrcM1 = Builder.CreateSub(Src, SrcM1);
 401     Src = LowerCTPOP(Context, Builder.CreateAnd(NotSrc, SrcM1), CI);
 402     CI->replaceAllUsesWith(Src);
 403     break;
 404   }
 405
 406   case Intrinsic::stacksave:
 407   case Intrinsic::stackrestore: {
 408     if (!Warned)
 409       errs() << "WARNING: this target does not support the llvm.stack"
 410              << (Callee->getIntrinsicID() == Intrinsic::stacksave ?
 411                "save" : "restore") << " intrinsic.\n";
 412     Warned = true;
 413     if (Callee->getIntrinsicID() == Intrinsic::stacksave)
 414       CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
 415     break;
 416   }
 417
 418   case Intrinsic::returnaddress:
 419   case Intrinsic::frameaddress:
 420     errs() << "WARNING: this target does not support the llvm."
 421            << (Callee->getIntrinsicID() == Intrinsic::returnaddress ?
 422              "return" : "frame") << "address intrinsic.\n";
 423     CI->replaceAllUsesWith(ConstantPointerNull::get(
 424                                             cast<PointerType>(CI->getType())));
 425     break;
 426
 427   case Intrinsic::prefetch:
 428     break;    // Simply strip out prefetches on unsupported architectures
 429
 430   case Intrinsic::pcmarker:
 431     break;    // Simply strip out pcmarker on unsupported architectures
 432   case Intrinsic::readcyclecounter: {
 433     errs() << "WARNING: this target does not support the llvm.readcyclecoun"
 434            << "ter intrinsic.  It is being lowered to a constant 0\n";
 435     CI->replaceAllUsesWith(ConstantInt::get(Type::getInt64Ty(Context), 0));
 436     break;
 437   }
 438
 439   case Intrinsic::dbg_declare:
 440     break;    // Simply strip out debugging intrinsics
 441
 442   case Intrinsic::eh_exception:
 443   case Intrinsic::eh_selector:
 444     CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
 445     break;
 446
 447   case Intrinsic::eh_typeid_for:
 448     // Return something different to eh_selector.
 449     CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
 450     break;
 451
 452   case Intrinsic::var_annotation:
 453     break;   // Strip out annotate intrinsic
 454
 455   case Intrinsic::memcpy: {
 456     const IntegerType *IntPtr = TD.getIntPtrType(Context);
 457     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
 458                                         /* isSigned */ false);
 459     Value *Ops[3];
 460     Ops[0] = CI->getArgOperand(0);
 461     Ops[1] = CI->getArgOperand(1);
 462     Ops[2] = Size;
 463     ReplaceCallWith("memcpy", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
 464     break;
 465   }
 466   case Intrinsic::memmove: {
 467     const IntegerType *IntPtr = TD.getIntPtrType(Context);
 468     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
 469                                         /* isSigned */ false);
 470     Value *Ops[3];
 471     Ops[0] = CI->getArgOperand(0);
 472     Ops[1] = CI->getArgOperand(1);
 473     Ops[2] = Size;
 474     ReplaceCallWith("memmove", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
 475     break;
 476   }
 477   case Intrinsic::memset: {
 478     const IntegerType *IntPtr = TD.getIntPtrType(Context);
 479     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
 480                                         /* isSigned */ false);
 481     Value *Ops[3];
 482     Ops[0] = CI->getArgOperand(0);
 483     // Extend the amount to i32.
 484     Ops[1] = Builder.CreateIntCast(CI->getArgOperand(1),
 485                                    Type::getInt32Ty(Context),
 486                                    /* isSigned */ false);
 487     Ops[2] = Size;
 488     ReplaceCallWith("memset", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
 489     break;
 490   }
 491   case Intrinsic::sqrt: {
 492     ReplaceFPIntrinsicWithCall(CI, "sqrtf", "sqrt", "sqrtl");
 493     break;
 494   }
 495   case Intrinsic::log: {
 496     ReplaceFPIntrinsicWithCall(CI, "logf", "log", "logl");
 497     break;
 498   }
 499   case Intrinsic::log2: {
 500     ReplaceFPIntrinsicWithCall(CI, "log2f", "log2", "log2l");
 501     break;
 502   }
 503   case Intrinsic::log10: {
 504     ReplaceFPIntrinsicWithCall(CI, "log10f", "log10", "log10l");
 505     break;
 506   }
 507   case Intrinsic::exp: {
 508     ReplaceFPIntrinsicWithCall(CI, "expf", "exp", "expl");
 509     break;
 510   }
 511   case Intrinsic::exp2: {
 512     ReplaceFPIntrinsicWithCall(CI, "exp2f", "exp2", "exp2l");
 513     break;
 514   }
 515   case Intrinsic::pow: {
 516     ReplaceFPIntrinsicWithCall(CI, "powf", "pow", "powl");
 517     break;
 518   }
 519   case Intrinsic::flt_rounds:
 520      // Lower to "round to the nearest"
 521      if (!CI->getType()->isVoidTy())
 522        CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
 523      break;
 524   case Intrinsic::invariant_start:
 525   case Intrinsic::lifetime_start:
 526     // Discard region information.
 527     CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
 528     break;
 529   case Intrinsic::invariant_end:
 530   case Intrinsic::lifetime_end:
 531     // Discard region information.
 532     break;
 533   }
 534
 535   assert(CI->use_empty() &&
 536          "Lowering should have eliminated any uses of the intrinsic call!");
 537   CI->eraseFromParent();
 538 }