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                          !defined(setjmp_undefined_for_msvc)
  90 #  pragma push_macro("setjmp")
  91 #  undef setjmp
  92 #  define setjmp_undefined_for_msvc
  93 #endif
  94
  95 void IntrinsicLowering::AddPrototypes(Module &M) {
  96   LLVMContext &Context = M.getContext();
  97   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  98     if (I->isDeclaration() && !I->use_empty())
  99       switch (I->getIntrinsicID()) {
 100       default: break;
 101       case Intrinsic::setjmp:
 102         EnsureFunctionExists(M, "setjmp", I->arg_begin(), I->arg_end(),
 103                              Type::getInt32Ty(M.getContext()));
 104         break;
 105       case Intrinsic::longjmp:
 106         EnsureFunctionExists(M, "longjmp", I->arg_begin(), I->arg_end(),
 107                              Type::getVoidTy(M.getContext()));
 108         break;
 109       case Intrinsic::siglongjmp:
 110         EnsureFunctionExists(M, "abort", I->arg_end(), I->arg_end(),
 111                              Type::getVoidTy(M.getContext()));
 112         break;
 113       case Intrinsic::memcpy:
 114         M.getOrInsertFunction("memcpy",
 115           Type::getInt8PtrTy(Context),
 116                               Type::getInt8PtrTy(Context),
 117                               Type::getInt8PtrTy(Context),
 118                               TD.getIntPtrType(Context), (Type *)0);
 119         break;
 120       case Intrinsic::memmove:
 121         M.getOrInsertFunction("memmove",
 122           Type::getInt8PtrTy(Context),
 123                               Type::getInt8PtrTy(Context),
 124                               Type::getInt8PtrTy(Context),
 125                               TD.getIntPtrType(Context), (Type *)0);
 126         break;
 127       case Intrinsic::memset:
 128         M.getOrInsertFunction("memset",
 129           Type::getInt8PtrTy(Context),
 130                               Type::getInt8PtrTy(Context),
 131                               Type::getInt32Ty(M.getContext()),
 132                               TD.getIntPtrType(Context), (Type *)0);
 133         break;
 134       case Intrinsic::sqrt:
 135         EnsureFPIntrinsicsExist(M, I, "sqrtf", "sqrt", "sqrtl");
 136         break;
 137       case Intrinsic::sin:
 138         EnsureFPIntrinsicsExist(M, I, "sinf", "sin", "sinl");
 139         break;
 140       case Intrinsic::cos:
 141         EnsureFPIntrinsicsExist(M, I, "cosf", "cos", "cosl");
 142         break;
 143       case Intrinsic::pow:
 144         EnsureFPIntrinsicsExist(M, I, "powf", "pow", "powl");
 145         break;
 146       case Intrinsic::log:
 147         EnsureFPIntrinsicsExist(M, I, "logf", "log", "logl");
 148         break;
 149       case Intrinsic::log2:
 150         EnsureFPIntrinsicsExist(M, I, "log2f", "log2", "log2l");
 151         break;
 152       case Intrinsic::log10:
 153         EnsureFPIntrinsicsExist(M, I, "log10f", "log10", "log10l");
 154         break;
 155       case Intrinsic::exp:
 156         EnsureFPIntrinsicsExist(M, I, "expf", "exp", "expl");
 157         break;
 158       case Intrinsic::exp2:
 159         EnsureFPIntrinsicsExist(M, I, "exp2f", "exp2", "exp2l");
 160         break;
 161       }
 162 }
 163
 164 /// LowerBSWAP - Emit the code to lower bswap of V before the specified
 165 /// instruction IP.
 166 static Value *LowerBSWAP(LLVMContext &Context, Value *V, Instruction *IP) {
 167   assert(V->getType()->isIntegerTy() && "Can't bswap a non-integer type!");
 168
 169   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
 170
 171   IRBuilder<> Builder(IP->getParent(), IP);
 172
 173   switch(BitSize) {
 174   default: llvm_unreachable("Unhandled type size of value to byteswap!");
 175   case 16: {
 176     Value *Tmp1 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
 177                                     "bswap.2");
 178     Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
 179                                      "bswap.1");
 180     V = Builder.CreateOr(Tmp1, Tmp2, "bswap.i16");
 181     break;
 182   }
 183   case 32: {
 184     Value *Tmp4 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
 185                                     "bswap.4");
 186     Value *Tmp3 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
 187                                     "bswap.3");
 188     Value *Tmp2 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
 189                                      "bswap.2");
 190     Value *Tmp1 = Builder.CreateLShr(V,ConstantInt::get(V->getType(), 24),
 191                                      "bswap.1");
 192     Tmp3 = Builder.CreateAnd(Tmp3,
 193                          ConstantInt::get(Type::getInt32Ty(Context), 0xFF0000),
 194                              "bswap.and3");
 195     Tmp2 = Builder.CreateAnd(Tmp2,
 196                            ConstantInt::get(Type::getInt32Ty(Context), 0xFF00),
 197                              "bswap.and2");
 198     Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or1");
 199     Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or2");
 200     V = Builder.CreateOr(Tmp4, Tmp2, "bswap.i32");
 201     break;
 202   }
 203   case 64: {
 204     Value *Tmp8 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 56),
 205                                     "bswap.8");
 206     Value *Tmp7 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 40),
 207                                     "bswap.7");
 208     Value *Tmp6 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 24),
 209                                     "bswap.6");
 210     Value *Tmp5 = Builder.CreateShl(V, ConstantInt::get(V->getType(), 8),
 211                                     "bswap.5");
 212     Value* Tmp4 = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 8),
 213                                      "bswap.4");
 214     Value* Tmp3 = Builder.CreateLShr(V,
 215                                      ConstantInt::get(V->getType(), 24),
 216                                      "bswap.3");
 217     Value* Tmp2 = Builder.CreateLShr(V,
 218                                      ConstantInt::get(V->getType(), 40),
 219                                      "bswap.2");
 220     Value* Tmp1 = Builder.CreateLShr(V,
 221                                      ConstantInt::get(V->getType(), 56),
 222                                      "bswap.1");
 223     Tmp7 = Builder.CreateAnd(Tmp7,
 224                              ConstantInt::get(Type::getInt64Ty(Context),
 225                                               0xFF000000000000ULL),
 226                              "bswap.and7");
 227     Tmp6 = Builder.CreateAnd(Tmp6,
 228                              ConstantInt::get(Type::getInt64Ty(Context),
 229                                               0xFF0000000000ULL),
 230                              "bswap.and6");
 231     Tmp5 = Builder.CreateAnd(Tmp5,
 232                         ConstantInt::get(Type::getInt64Ty(Context),
 233                              0xFF00000000ULL),
 234                              "bswap.and5");
 235     Tmp4 = Builder.CreateAnd(Tmp4,
 236                         ConstantInt::get(Type::getInt64Ty(Context),
 237                              0xFF000000ULL),
 238                              "bswap.and4");
 239     Tmp3 = Builder.CreateAnd(Tmp3,
 240                              ConstantInt::get(Type::getInt64Ty(Context),
 241                              0xFF0000ULL),
 242                              "bswap.and3");
 243     Tmp2 = Builder.CreateAnd(Tmp2,
 244                              ConstantInt::get(Type::getInt64Ty(Context),
 245                              0xFF00ULL),
 246                              "bswap.and2");
 247     Tmp8 = Builder.CreateOr(Tmp8, Tmp7, "bswap.or1");
 248     Tmp6 = Builder.CreateOr(Tmp6, Tmp5, "bswap.or2");
 249     Tmp4 = Builder.CreateOr(Tmp4, Tmp3, "bswap.or3");
 250     Tmp2 = Builder.CreateOr(Tmp2, Tmp1, "bswap.or4");
 251     Tmp8 = Builder.CreateOr(Tmp8, Tmp6, "bswap.or5");
 252     Tmp4 = Builder.CreateOr(Tmp4, Tmp2, "bswap.or6");
 253     V = Builder.CreateOr(Tmp8, Tmp4, "bswap.i64");
 254     break;
 255   }
 256   }
 257   return V;
 258 }
 259
 260 /// LowerCTPOP - Emit the code to lower ctpop of V before the specified
 261 /// instruction IP.
 262 static Value *LowerCTPOP(LLVMContext &Context, Value *V, Instruction *IP) {
 263   assert(V->getType()->isIntegerTy() && "Can't ctpop a non-integer type!");
 264
 265   static const uint64_t MaskValues[6] = {
 266     0x5555555555555555ULL, 0x3333333333333333ULL,
 267     0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
 268     0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL
 269   };
 270
 271   IRBuilder<> Builder(IP->getParent(), IP);
 272
 273   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
 274   unsigned WordSize = (BitSize + 63) / 64;
 275   Value *Count = ConstantInt::get(V->getType(), 0);
 276
 277   for (unsigned n = 0; n < WordSize; ++n) {
 278     Value *PartValue = V;
 279     for (unsigned i = 1, ct = 0; i < (BitSize>64 ? 64 : BitSize);
 280          i <<= 1, ++ct) {
 281       Value *MaskCst = ConstantInt::get(V->getType(), MaskValues[ct]);
 282       Value *LHS = Builder.CreateAnd(PartValue, MaskCst, "cppop.and1");
 283       Value *VShift = Builder.CreateLShr(PartValue,
 284                                         ConstantInt::get(V->getType(), i),
 285                                          "ctpop.sh");
 286       Value *RHS = Builder.CreateAnd(VShift, MaskCst, "cppop.and2");
 287       PartValue = Builder.CreateAdd(LHS, RHS, "ctpop.step");
 288     }
 289     Count = Builder.CreateAdd(PartValue, Count, "ctpop.part");
 290     if (BitSize > 64) {
 291       V = Builder.CreateLShr(V, ConstantInt::get(V->getType(), 64),
 292                              "ctpop.part.sh");
 293       BitSize -= 64;
 294     }
 295   }
 296
 297   return Count;
 298 }
 299
 300 /// LowerCTLZ - Emit the code to lower ctlz of V before the specified
 301 /// instruction IP.
 302 static Value *LowerCTLZ(LLVMContext &Context, Value *V, Instruction *IP) {
 303
 304   IRBuilder<> Builder(IP->getParent(), IP);
 305
 306   unsigned BitSize = V->getType()->getPrimitiveSizeInBits();
 307   for (unsigned i = 1; i < BitSize; i <<= 1) {
 308     Value *ShVal = ConstantInt::get(V->getType(), i);
 309     ShVal = Builder.CreateLShr(V, ShVal, "ctlz.sh");
 310     V = Builder.CreateOr(V, ShVal, "ctlz.step");
 311   }
 312
 313   V = Builder.CreateNot(V);
 314   return LowerCTPOP(Context, V, IP);
 315 }
 316
 317 static void ReplaceFPIntrinsicWithCall(CallInst *CI, const char *Fname,
 318                                        const char *Dname,
 319                                        const char *LDname) {
 320   CallSite CS(CI);
 321   switch (CI->getArgOperand(0)->getType()->getTypeID()) {
 322   default: llvm_unreachable("Invalid type in intrinsic");
 323   case Type::FloatTyID:
 324     ReplaceCallWith(Fname, CI, CS.arg_begin(), CS.arg_end(),
 325                   Type::getFloatTy(CI->getContext()));
 326     break;
 327   case Type::DoubleTyID:
 328     ReplaceCallWith(Dname, CI, CS.arg_begin(), CS.arg_end(),
 329                   Type::getDoubleTy(CI->getContext()));
 330     break;
 331   case Type::X86_FP80TyID:
 332   case Type::FP128TyID:
 333   case Type::PPC_FP128TyID:
 334     ReplaceCallWith(LDname, CI, CS.arg_begin(), CS.arg_end(),
 335                   CI->getArgOperand(0)->getType());
 336     break;
 337   }
 338 }
 339
 340 void IntrinsicLowering::LowerIntrinsicCall(CallInst *CI) {
 341   IRBuilder<> Builder(CI->getParent(), CI);
 342   LLVMContext &Context = CI->getContext();
 343
 344   const Function *Callee = CI->getCalledFunction();
 345   assert(Callee && "Cannot lower an indirect call!");
 346
 347   CallSite CS(CI);
 348   switch (Callee->getIntrinsicID()) {
 349   case Intrinsic::not_intrinsic:
 350     report_fatal_error("Cannot lower a call to a non-intrinsic function '"+
 351                       Callee->getName() + "'!");
 352   default:
 353     report_fatal_error("Code generator does not support intrinsic function '"+
 354                       Callee->getName()+"'!");
 355
 356   case Intrinsic::expect: {
 357     // Just replace __builtin_expect(exp, c) with EXP.
 358     Value *V = CI->getArgOperand(0);
 359     CI->replaceAllUsesWith(V);
 360     break;
 361   }
 362
 363     // The setjmp/longjmp intrinsics should only exist in the code if it was
 364     // never optimized (ie, right out of the CFE), or if it has been hacked on
 365     // by the lowerinvoke pass.  In both cases, the right thing to do is to
 366     // convert the call to an explicit setjmp or longjmp call.
 367   case Intrinsic::setjmp: {
 368     Value *V = ReplaceCallWith("setjmp", CI, CS.arg_begin(), CS.arg_end(),
 369                                Type::getInt32Ty(Context));
 370     if (!CI->getType()->isVoidTy())
 371       CI->replaceAllUsesWith(V);
 372     break;
 373   }
 374   case Intrinsic::sigsetjmp:
 375      if (!CI->getType()->isVoidTy())
 376        CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
 377      break;
 378
 379   case Intrinsic::longjmp: {
 380     ReplaceCallWith("longjmp", CI, CS.arg_begin(), CS.arg_end(),
 381                     Type::getVoidTy(Context));
 382     break;
 383   }
 384
 385   case Intrinsic::siglongjmp: {
 386     // Insert the call to abort
 387     ReplaceCallWith("abort", CI, CS.arg_end(), CS.arg_end(),
 388                     Type::getVoidTy(Context));
 389     break;
 390   }
 391   case Intrinsic::ctpop:
 392     CI->replaceAllUsesWith(LowerCTPOP(Context, CI->getArgOperand(0), CI));
 393     break;
 394
 395   case Intrinsic::bswap:
 396     CI->replaceAllUsesWith(LowerBSWAP(Context, CI->getArgOperand(0), CI));
 397     break;
 398
 399   case Intrinsic::ctlz:
 400     CI->replaceAllUsesWith(LowerCTLZ(Context, CI->getArgOperand(0), CI));
 401     break;
 402
 403   case Intrinsic::cttz: {
 404     // cttz(x) -> ctpop(~X & (X-1))
 405     Value *Src = CI->getArgOperand(0);
 406     Value *NotSrc = Builder.CreateNot(Src);
 407     NotSrc->setName(Src->getName() + ".not");
 408     Value *SrcM1 = ConstantInt::get(Src->getType(), 1);
 409     SrcM1 = Builder.CreateSub(Src, SrcM1);
 410     Src = LowerCTPOP(Context, Builder.CreateAnd(NotSrc, SrcM1), CI);
 411     CI->replaceAllUsesWith(Src);
 412     break;
 413   }
 414
 415   case Intrinsic::stacksave:
 416   case Intrinsic::stackrestore: {
 417     if (!Warned)
 418       errs() << "WARNING: this target does not support the llvm.stack"
 419              << (Callee->getIntrinsicID() == Intrinsic::stacksave ?
 420                "save" : "restore") << " intrinsic.\n";
 421     Warned = true;
 422     if (Callee->getIntrinsicID() == Intrinsic::stacksave)
 423       CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
 424     break;
 425   }
 426
 427   case Intrinsic::returnaddress:
 428   case Intrinsic::frameaddress:
 429     errs() << "WARNING: this target does not support the llvm."
 430            << (Callee->getIntrinsicID() == Intrinsic::returnaddress ?
 431              "return" : "frame") << "address intrinsic.\n";
 432     CI->replaceAllUsesWith(ConstantPointerNull::get(
 433                                             cast<PointerType>(CI->getType())));
 434     break;
 435
 436   case Intrinsic::prefetch:
 437     break;    // Simply strip out prefetches on unsupported architectures
 438
 439   case Intrinsic::pcmarker:
 440     break;    // Simply strip out pcmarker on unsupported architectures
 441   case Intrinsic::readcyclecounter: {
 442     errs() << "WARNING: this target does not support the llvm.readcyclecoun"
 443            << "ter intrinsic.  It is being lowered to a constant 0\n";
 444     CI->replaceAllUsesWith(ConstantInt::get(Type::getInt64Ty(Context), 0));
 445     break;
 446   }
 447
 448   case Intrinsic::dbg_declare:
 449     break;    // Simply strip out debugging intrinsics
 450
 451   case Intrinsic::eh_exception:
 452   case Intrinsic::eh_selector:
 453     CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
 454     break;
 455
 456   case Intrinsic::eh_typeid_for:
 457     // Return something different to eh_selector.
 458     CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
 459     break;
 460
 461   case Intrinsic::var_annotation:
 462     break;   // Strip out annotate intrinsic
 463
 464   case Intrinsic::memcpy: {
 465     const IntegerType *IntPtr = TD.getIntPtrType(Context);
 466     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
 467                                         /* isSigned */ false);
 468     Value *Ops[3];
 469     Ops[0] = CI->getArgOperand(0);
 470     Ops[1] = CI->getArgOperand(1);
 471     Ops[2] = Size;
 472     ReplaceCallWith("memcpy", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
 473     break;
 474   }
 475   case Intrinsic::memmove: {
 476     const IntegerType *IntPtr = TD.getIntPtrType(Context);
 477     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
 478                                         /* isSigned */ false);
 479     Value *Ops[3];
 480     Ops[0] = CI->getArgOperand(0);
 481     Ops[1] = CI->getArgOperand(1);
 482     Ops[2] = Size;
 483     ReplaceCallWith("memmove", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
 484     break;
 485   }
 486   case Intrinsic::memset: {
 487     const IntegerType *IntPtr = TD.getIntPtrType(Context);
 488     Value *Size = Builder.CreateIntCast(CI->getArgOperand(2), IntPtr,
 489                                         /* isSigned */ false);
 490     Value *Ops[3];
 491     Ops[0] = CI->getArgOperand(0);
 492     // Extend the amount to i32.
 493     Ops[1] = Builder.CreateIntCast(CI->getArgOperand(1),
 494                                    Type::getInt32Ty(Context),
 495                                    /* isSigned */ false);
 496     Ops[2] = Size;
 497     ReplaceCallWith("memset", CI, Ops, Ops+3, CI->getArgOperand(0)->getType());
 498     break;
 499   }
 500   case Intrinsic::sqrt: {
 501     ReplaceFPIntrinsicWithCall(CI, "sqrtf", "sqrt", "sqrtl");
 502     break;
 503   }
 504   case Intrinsic::log: {
 505     ReplaceFPIntrinsicWithCall(CI, "logf", "log", "logl");
 506     break;
 507   }
 508   case Intrinsic::log2: {
 509     ReplaceFPIntrinsicWithCall(CI, "log2f", "log2", "log2l");
 510     break;
 511   }
 512   case Intrinsic::log10: {
 513     ReplaceFPIntrinsicWithCall(CI, "log10f", "log10", "log10l");
 514     break;
 515   }
 516   case Intrinsic::exp: {
 517     ReplaceFPIntrinsicWithCall(CI, "expf", "exp", "expl");
 518     break;
 519   }
 520   case Intrinsic::exp2: {
 521     ReplaceFPIntrinsicWithCall(CI, "exp2f", "exp2", "exp2l");
 522     break;
 523   }
 524   case Intrinsic::pow: {
 525     ReplaceFPIntrinsicWithCall(CI, "powf", "pow", "powl");
 526     break;
 527   }
 528   case Intrinsic::flt_rounds:
 529      // Lower to "round to the nearest"
 530      if (!CI->getType()->isVoidTy())
 531        CI->replaceAllUsesWith(ConstantInt::get(CI->getType(), 1));
 532      break;
 533   case Intrinsic::invariant_start:
 534   case Intrinsic::lifetime_start:
 535     // Discard region information.
 536     CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
 537     break;
 538   case Intrinsic::invariant_end:
 539   case Intrinsic::lifetime_end:
 540     // Discard region information.
 541     break;
 542   }
 543
 544   assert(CI->use_empty() &&
 545          "Lowering should have eliminated any uses of the intrinsic call!");
 546   CI->eraseFromParent();
 547 }
 548
 549 bool IntrinsicLowering::LowerToByteSwap(CallInst *CI) {
 550   // Verify this is a simple bswap.
 551   if (CI->getNumArgOperands() != 1 ||
 552       CI->getType() != CI->getArgOperand(0)->getType() ||
 553       !CI->getType()->isIntegerTy())
 554     return false;
 555
 556   const IntegerType *Ty = dyn_cast<IntegerType>(CI->getType());
 557   if (!Ty)
 558     return false;
 559
 560   // Okay, we can do this xform, do so now.
 561   const Type *Tys[] = { Ty };
 562   Module *M = CI->getParent()->getParent()->getParent();
 563   Constant *Int = Intrinsic::getDeclaration(M, Intrinsic::bswap, Tys, 1);
 564
 565   Value *Op = CI->getArgOperand(0);
 566   Op = CallInst::Create(Int, Op, CI->getName(), CI);
 567
 568   CI->replaceAllUsesWith(Op);
 569   CI->eraseFromParent();
 570   return true;
 571 }