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