lib/CodeGen/AtomicExpandPass.cpp

   1 //===- AtomicExpandPass.cpp - Expand atomic instructions ------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains a pass (at IR level) to replace atomic instructions with
  10 // __atomic_* library calls, or target specific instruction which implement the
  11 // same semantics in a way which better fits the target backend.  This can
  12 // include the use of (intrinsic-based) load-linked/store-conditional loops,
  13 // AtomicCmpXchg, or type coercions.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "llvm/ADT/ArrayRef.h"
  18 #include "llvm/ADT/STLExtras.h"
  19 #include "llvm/ADT/SmallVector.h"
  20 #include "llvm/CodeGen/AtomicExpandUtils.h"
  21 #include "llvm/CodeGen/RuntimeLibcalls.h"
  22 #include "llvm/CodeGen/TargetLowering.h"
  23 #include "llvm/CodeGen/TargetPassConfig.h"
  24 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  25 #include "llvm/CodeGen/ValueTypes.h"
  26 #include "llvm/IR/Attributes.h"
  27 #include "llvm/IR/BasicBlock.h"
  28 #include "llvm/IR/Constant.h"
  29 #include "llvm/IR/Constants.h"
  30 #include "llvm/IR/DataLayout.h"
  31 #include "llvm/IR/DerivedTypes.h"
  32 #include "llvm/IR/Function.h"
  33 #include "llvm/IR/IRBuilder.h"
  34 #include "llvm/IR/InstIterator.h"
  35 #include "llvm/IR/Instruction.h"
  36 #include "llvm/IR/Instructions.h"
  37 #include "llvm/IR/Module.h"
  38 #include "llvm/IR/Type.h"
  39 #include "llvm/IR/User.h"
  40 #include "llvm/IR/Value.h"
  41 #include "llvm/Pass.h"
  42 #include "llvm/Support/AtomicOrdering.h"
  43 #include "llvm/Support/Casting.h"
  44 #include "llvm/Support/Debug.h"
  45 #include "llvm/Support/ErrorHandling.h"
  46 #include "llvm/Support/raw_ostream.h"
  47 #include "llvm/Target/TargetMachine.h"
  48 #include <cassert>
  49 #include <cstdint>
  50 #include <iterator>
  51
  52 using namespace llvm;
  53
  54 #define DEBUG_TYPE "atomic-expand"
  55
  56 namespace {
  57
  58   class AtomicExpand: public FunctionPass {
  59     const TargetLowering *TLI = nullptr;
  60
  61   public:
  62     static char ID; // Pass identification, replacement for typeid
  63
  64     AtomicExpand() : FunctionPass(ID) {
  65       initializeAtomicExpandPass(*PassRegistry::getPassRegistry());
  66     }
  67
  68     bool runOnFunction(Function &F) override;
  69
  70   private:
  71     bool bracketInstWithFences(Instruction *I, AtomicOrdering Order);
  72     IntegerType *getCorrespondingIntegerType(Type *T, const DataLayout &DL);
  73     LoadInst *convertAtomicLoadToIntegerType(LoadInst *LI);
  74     bool tryExpandAtomicLoad(LoadInst *LI);
  75     bool expandAtomicLoadToLL(LoadInst *LI);
  76     bool expandAtomicLoadToCmpXchg(LoadInst *LI);
  77     StoreInst *convertAtomicStoreToIntegerType(StoreInst *SI);
  78     bool expandAtomicStore(StoreInst *SI);
  79     bool tryExpandAtomicRMW(AtomicRMWInst *AI);
  80     Value *
  81     insertRMWLLSCLoop(IRBuilder<> &Builder, Type *ResultTy, Value *Addr,
  82                       AtomicOrdering MemOpOrder,
  83                       function_ref<Value *(IRBuilder<> &, Value *)> PerformOp);
  84     void expandAtomicOpToLLSC(
  85         Instruction *I, Type *ResultTy, Value *Addr, AtomicOrdering MemOpOrder,
  86         function_ref<Value *(IRBuilder<> &, Value *)> PerformOp);
  87     void expandPartwordAtomicRMW(
  88         AtomicRMWInst *I,
  89         TargetLoweringBase::AtomicExpansionKind ExpansionKind);
  90     AtomicRMWInst *widenPartwordAtomicRMW(AtomicRMWInst *AI);
  91     void expandPartwordCmpXchg(AtomicCmpXchgInst *I);
  92     void expandAtomicRMWToMaskedIntrinsic(AtomicRMWInst *AI);
  93     void expandAtomicCmpXchgToMaskedIntrinsic(AtomicCmpXchgInst *CI);
  94
  95     AtomicCmpXchgInst *convertCmpXchgToIntegerType(AtomicCmpXchgInst *CI);
  96     static Value *insertRMWCmpXchgLoop(
  97         IRBuilder<> &Builder, Type *ResultType, Value *Addr,
  98         AtomicOrdering MemOpOrder,
  99         function_ref<Value *(IRBuilder<> &, Value *)> PerformOp,
 100         CreateCmpXchgInstFun CreateCmpXchg);
 101     bool tryExpandAtomicCmpXchg(AtomicCmpXchgInst *CI);
 102
 103     bool expandAtomicCmpXchg(AtomicCmpXchgInst *CI);
 104     bool isIdempotentRMW(AtomicRMWInst *RMWI);
 105     bool simplifyIdempotentRMW(AtomicRMWInst *RMWI);
 106
 107     bool expandAtomicOpToLibcall(Instruction *I, unsigned Size, unsigned Align,
 108                                  Value *PointerOperand, Value *ValueOperand,
 109                                  Value *CASExpected, AtomicOrdering Ordering,
 110                                  AtomicOrdering Ordering2,
 111                                  ArrayRef<RTLIB::Libcall> Libcalls);
 112     void expandAtomicLoadToLibcall(LoadInst *LI);
 113     void expandAtomicStoreToLibcall(StoreInst *LI);
 114     void expandAtomicRMWToLibcall(AtomicRMWInst *I);
 115     void expandAtomicCASToLibcall(AtomicCmpXchgInst *I);
 116
 117     friend bool
 118     llvm::expandAtomicRMWToCmpXchg(AtomicRMWInst *AI,
 119                                    CreateCmpXchgInstFun CreateCmpXchg);
 120   };
 121
 122 } // end anonymous namespace
 123
 124 char AtomicExpand::ID = 0;
 125
 126 char &llvm::AtomicExpandID = AtomicExpand::ID;
 127
 128 INITIALIZE_PASS(AtomicExpand, DEBUG_TYPE, "Expand Atomic instructions",
 129                 false, false)
 130
 131 FunctionPass *llvm::createAtomicExpandPass() { return new AtomicExpand(); }
 132
 133 // Helper functions to retrieve the size of atomic instructions.
 134 static unsigned getAtomicOpSize(LoadInst *LI) {
 135   const DataLayout &DL = LI->getModule()->getDataLayout();
 136   return DL.getTypeStoreSize(LI->getType());
 137 }
 138
 139 static unsigned getAtomicOpSize(StoreInst *SI) {
 140   const DataLayout &DL = SI->getModule()->getDataLayout();
 141   return DL.getTypeStoreSize(SI->getValueOperand()->getType());
 142 }
 143
 144 static unsigned getAtomicOpSize(AtomicRMWInst *RMWI) {
 145   const DataLayout &DL = RMWI->getModule()->getDataLayout();
 146   return DL.getTypeStoreSize(RMWI->getValOperand()->getType());
 147 }
 148
 149 static unsigned getAtomicOpSize(AtomicCmpXchgInst *CASI) {
 150   const DataLayout &DL = CASI->getModule()->getDataLayout();
 151   return DL.getTypeStoreSize(CASI->getCompareOperand()->getType());
 152 }
 153
 154 // Helper functions to retrieve the alignment of atomic instructions.
 155 static unsigned getAtomicOpAlign(LoadInst *LI) {
 156   unsigned Align = LI->getAlignment();
 157   // In the future, if this IR restriction is relaxed, we should
 158   // return DataLayout::getABITypeAlignment when there's no align
 159   // value.
 160   assert(Align != 0 && "An atomic LoadInst always has an explicit alignment");
 161   return Align;
 162 }
 163
 164 static unsigned getAtomicOpAlign(StoreInst *SI) {
 165   unsigned Align = SI->getAlignment();
 166   // In the future, if this IR restriction is relaxed, we should
 167   // return DataLayout::getABITypeAlignment when there's no align
 168   // value.
 169   assert(Align != 0 && "An atomic StoreInst always has an explicit alignment");
 170   return Align;
 171 }
 172
 173 static unsigned getAtomicOpAlign(AtomicRMWInst *RMWI) {
 174   // TODO(PR27168): This instruction has no alignment attribute, but unlike the
 175   // default alignment for load/store, the default here is to assume
 176   // it has NATURAL alignment, not DataLayout-specified alignment.
 177   const DataLayout &DL = RMWI->getModule()->getDataLayout();
 178   return DL.getTypeStoreSize(RMWI->getValOperand()->getType());
 179 }
 180
 181 static unsigned getAtomicOpAlign(AtomicCmpXchgInst *CASI) {
 182   // TODO(PR27168): same comment as above.
 183   const DataLayout &DL = CASI->getModule()->getDataLayout();
 184   return DL.getTypeStoreSize(CASI->getCompareOperand()->getType());
 185 }
 186
 187 // Determine if a particular atomic operation has a supported size,
 188 // and is of appropriate alignment, to be passed through for target
 189 // lowering. (Versus turning into a __atomic libcall)
 190 template <typename Inst>
 191 static bool atomicSizeSupported(const TargetLowering *TLI, Inst *I) {
 192   unsigned Size = getAtomicOpSize(I);
 193   unsigned Align = getAtomicOpAlign(I);
 194   return Align >= Size && Size <= TLI->getMaxAtomicSizeInBitsSupported() / 8;
 195 }
 196
 197 bool AtomicExpand::runOnFunction(Function &F) {
 198   auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
 199   if (!TPC)
 200     return false;
 201
 202   auto &TM = TPC->getTM<TargetMachine>();
 203   if (!TM.getSubtargetImpl(F)->enableAtomicExpand())
 204     return false;
 205   TLI = TM.getSubtargetImpl(F)->getTargetLowering();
 206
 207   SmallVector<Instruction *, 1> AtomicInsts;
 208
 209   // Changing control-flow while iterating through it is a bad idea, so gather a
 210   // list of all atomic instructions before we start.
 211   for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
 212     Instruction *I = &*II;
 213     if (I->isAtomic() && !isa<FenceInst>(I))
 214       AtomicInsts.push_back(I);
 215   }
 216
 217   bool MadeChange = false;
 218   for (auto I : AtomicInsts) {
 219     auto LI = dyn_cast<LoadInst>(I);
 220     auto SI = dyn_cast<StoreInst>(I);
 221     auto RMWI = dyn_cast<AtomicRMWInst>(I);
 222     auto CASI = dyn_cast<AtomicCmpXchgInst>(I);
 223     assert((LI || SI || RMWI || CASI) && "Unknown atomic instruction");
 224
 225     // If the Size/Alignment is not supported, replace with a libcall.
 226     if (LI) {
 227       if (!atomicSizeSupported(TLI, LI)) {
 228         expandAtomicLoadToLibcall(LI);
 229         MadeChange = true;
 230         continue;
 231       }
 232     } else if (SI) {
 233       if (!atomicSizeSupported(TLI, SI)) {
 234         expandAtomicStoreToLibcall(SI);
 235         MadeChange = true;
 236         continue;
 237       }
 238     } else if (RMWI) {
 239       if (!atomicSizeSupported(TLI, RMWI)) {
 240         expandAtomicRMWToLibcall(RMWI);
 241         MadeChange = true;
 242         continue;
 243       }
 244     } else if (CASI) {
 245       if (!atomicSizeSupported(TLI, CASI)) {
 246         expandAtomicCASToLibcall(CASI);
 247         MadeChange = true;
 248         continue;
 249       }
 250     }
 251
 252     if (TLI->shouldInsertFencesForAtomic(I)) {
 253       auto FenceOrdering = AtomicOrdering::Monotonic;
 254       if (LI && isAcquireOrStronger(LI->getOrdering())) {
 255         FenceOrdering = LI->getOrdering();
 256         LI->setOrdering(AtomicOrdering::Monotonic);
 257       } else if (SI && isReleaseOrStronger(SI->getOrdering())) {
 258         FenceOrdering = SI->getOrdering();
 259         SI->setOrdering(AtomicOrdering::Monotonic);
 260       } else if (RMWI && (isReleaseOrStronger(RMWI->getOrdering()) ||
 261                           isAcquireOrStronger(RMWI->getOrdering()))) {
 262         FenceOrdering = RMWI->getOrdering();
 263         RMWI->setOrdering(AtomicOrdering::Monotonic);
 264       } else if (CASI &&
 265                  TLI->shouldExpandAtomicCmpXchgInIR(CASI) ==
 266                      TargetLoweringBase::AtomicExpansionKind::None &&
 267                  (isReleaseOrStronger(CASI->getSuccessOrdering()) ||
 268                   isAcquireOrStronger(CASI->getSuccessOrdering()))) {
 269         // If a compare and swap is lowered to LL/SC, we can do smarter fence
 270         // insertion, with a stronger one on the success path than on the
 271         // failure path. As a result, fence insertion is directly done by
 272         // expandAtomicCmpXchg in that case.
 273         FenceOrdering = CASI->getSuccessOrdering();
 274         CASI->setSuccessOrdering(AtomicOrdering::Monotonic);
 275         CASI->setFailureOrdering(AtomicOrdering::Monotonic);
 276       }
 277
 278       if (FenceOrdering != AtomicOrdering::Monotonic) {
 279         MadeChange |= bracketInstWithFences(I, FenceOrdering);
 280       }
 281     }
 282
 283     if (LI) {
 284       if (LI->getType()->isFloatingPointTy()) {
 285         // TODO: add a TLI hook to control this so that each target can
 286         // convert to lowering the original type one at a time.
 287         LI = convertAtomicLoadToIntegerType(LI);
 288         assert(LI->getType()->isIntegerTy() && "invariant broken");
 289         MadeChange = true;
 290       }
 291
 292       MadeChange |= tryExpandAtomicLoad(LI);
 293     } else if (SI) {
 294       if (SI->getValueOperand()->getType()->isFloatingPointTy()) {
 295         // TODO: add a TLI hook to control this so that each target can
 296         // convert to lowering the original type one at a time.
 297         SI = convertAtomicStoreToIntegerType(SI);
 298         assert(SI->getValueOperand()->getType()->isIntegerTy() &&
 299                "invariant broken");
 300         MadeChange = true;
 301       }
 302
 303       if (TLI->shouldExpandAtomicStoreInIR(SI))
 304         MadeChange |= expandAtomicStore(SI);
 305     } else if (RMWI) {
 306       // There are two different ways of expanding RMW instructions:
 307       // - into a load if it is idempotent
 308       // - into a Cmpxchg/LL-SC loop otherwise
 309       // we try them in that order.
 310
 311       if (isIdempotentRMW(RMWI) && simplifyIdempotentRMW(RMWI)) {
 312         MadeChange = true;
 313       } else {
 314         unsigned MinCASSize = TLI->getMinCmpXchgSizeInBits() / 8;
 315         unsigned ValueSize = getAtomicOpSize(RMWI);
 316         AtomicRMWInst::BinOp Op = RMWI->getOperation();
 317         if (ValueSize < MinCASSize &&
 318             (Op == AtomicRMWInst::Or || Op == AtomicRMWInst::Xor ||
 319              Op == AtomicRMWInst::And)) {
 320           RMWI = widenPartwordAtomicRMW(RMWI);
 321           MadeChange = true;
 322         }
 323
 324         MadeChange |= tryExpandAtomicRMW(RMWI);
 325       }
 326     } else if (CASI) {
 327       // TODO: when we're ready to make the change at the IR level, we can
 328       // extend convertCmpXchgToInteger for floating point too.
 329       assert(!CASI->getCompareOperand()->getType()->isFloatingPointTy() &&
 330              "unimplemented - floating point not legal at IR level");
 331       if (CASI->getCompareOperand()->getType()->isPointerTy() ) {
 332         // TODO: add a TLI hook to control this so that each target can
 333         // convert to lowering the original type one at a time.
 334         CASI = convertCmpXchgToIntegerType(CASI);
 335         assert(CASI->getCompareOperand()->getType()->isIntegerTy() &&
 336                "invariant broken");
 337         MadeChange = true;
 338       }
 339
 340       MadeChange |= tryExpandAtomicCmpXchg(CASI);
 341     }
 342   }
 343   return MadeChange;
 344 }
 345
 346 bool AtomicExpand::bracketInstWithFences(Instruction *I, AtomicOrdering Order) {
 347   IRBuilder<> Builder(I);
 348
 349   auto LeadingFence = TLI->emitLeadingFence(Builder, I, Order);
 350
 351   auto TrailingFence = TLI->emitTrailingFence(Builder, I, Order);
 352   // We have a guard here because not every atomic operation generates a
 353   // trailing fence.
 354   if (TrailingFence)
 355     TrailingFence->moveAfter(I);
 356
 357   return (LeadingFence || TrailingFence);
 358 }
 359
 360 /// Get the iX type with the same bitwidth as T.
 361 IntegerType *AtomicExpand::getCorrespondingIntegerType(Type *T,
 362                                                        const DataLayout &DL) {
 363   EVT VT = TLI->getMemValueType(DL, T);
 364   unsigned BitWidth = VT.getStoreSizeInBits();
 365   assert(BitWidth == VT.getSizeInBits() && "must be a power of two");
 366   return IntegerType::get(T->getContext(), BitWidth);
 367 }
 368
 369 /// Convert an atomic load of a non-integral type to an integer load of the
 370 /// equivalent bitwidth.  See the function comment on
 371 /// convertAtomicStoreToIntegerType for background.
 372 LoadInst *AtomicExpand::convertAtomicLoadToIntegerType(LoadInst *LI) {
 373   auto *M = LI->getModule();
 374   Type *NewTy = getCorrespondingIntegerType(LI->getType(),
 375                                             M->getDataLayout());
 376
 377   IRBuilder<> Builder(LI);
 378
 379   Value *Addr = LI->getPointerOperand();
 380   Type *PT = PointerType::get(NewTy,
 381                               Addr->getType()->getPointerAddressSpace());
 382   Value *NewAddr = Builder.CreateBitCast(Addr, PT);
 383
 384   auto *NewLI = Builder.CreateLoad(NewTy, NewAddr);
 385   NewLI->setAlignment(MaybeAlign(LI->getAlignment()));
 386   NewLI->setVolatile(LI->isVolatile());
 387   NewLI->setAtomic(LI->getOrdering(), LI->getSyncScopeID());
 388   LLVM_DEBUG(dbgs() << "Replaced " << *LI << " with " << *NewLI << "\n");
 389
 390   Value *NewVal = Builder.CreateBitCast(NewLI, LI->getType());
 391   LI->replaceAllUsesWith(NewVal);
 392   LI->eraseFromParent();
 393   return NewLI;
 394 }
 395
 396 bool AtomicExpand::tryExpandAtomicLoad(LoadInst *LI) {
 397   switch (TLI->shouldExpandAtomicLoadInIR(LI)) {
 398   case TargetLoweringBase::AtomicExpansionKind::None:
 399     return false;
 400   case TargetLoweringBase::AtomicExpansionKind::LLSC:
 401     expandAtomicOpToLLSC(
 402         LI, LI->getType(), LI->getPointerOperand(), LI->getOrdering(),
 403         [](IRBuilder<> &Builder, Value *Loaded) { return Loaded; });
 404     return true;
 405   case TargetLoweringBase::AtomicExpansionKind::LLOnly:
 406     return expandAtomicLoadToLL(LI);
 407   case TargetLoweringBase::AtomicExpansionKind::CmpXChg:
 408     return expandAtomicLoadToCmpXchg(LI);
 409   default:
 410     llvm_unreachable("Unhandled case in tryExpandAtomicLoad");
 411   }
 412 }
 413
 414 bool AtomicExpand::expandAtomicLoadToLL(LoadInst *LI) {
 415   IRBuilder<> Builder(LI);
 416
 417   // On some architectures, load-linked instructions are atomic for larger
 418   // sizes than normal loads. For example, the only 64-bit load guaranteed
 419   // to be single-copy atomic by ARM is an ldrexd (A3.5.3).
 420   Value *Val =
 421       TLI->emitLoadLinked(Builder, LI->getPointerOperand(), LI->getOrdering());
 422   TLI->emitAtomicCmpXchgNoStoreLLBalance(Builder);
 423
 424   LI->replaceAllUsesWith(Val);
 425   LI->eraseFromParent();
 426
 427   return true;
 428 }
 429
 430 bool AtomicExpand::expandAtomicLoadToCmpXchg(LoadInst *LI) {
 431   IRBuilder<> Builder(LI);
 432   AtomicOrdering Order = LI->getOrdering();
 433   if (Order == AtomicOrdering::Unordered)
 434     Order = AtomicOrdering::Monotonic;
 435
 436   Value *Addr = LI->getPointerOperand();
 437   Type *Ty = cast<PointerType>(Addr->getType())->getElementType();
 438   Constant *DummyVal = Constant::getNullValue(Ty);
 439
 440   Value *Pair = Builder.CreateAtomicCmpXchg(
 441       Addr, DummyVal, DummyVal, Order,
 442       AtomicCmpXchgInst::getStrongestFailureOrdering(Order));
 443   Value *Loaded = Builder.CreateExtractValue(Pair, 0, "loaded");
 444
 445   LI->replaceAllUsesWith(Loaded);
 446   LI->eraseFromParent();
 447
 448   return true;
 449 }
 450
 451 /// Convert an atomic store of a non-integral type to an integer store of the
 452 /// equivalent bitwidth.  We used to not support floating point or vector
 453 /// atomics in the IR at all.  The backends learned to deal with the bitcast
 454 /// idiom because that was the only way of expressing the notion of a atomic
 455 /// float or vector store.  The long term plan is to teach each backend to
 456 /// instruction select from the original atomic store, but as a migration
 457 /// mechanism, we convert back to the old format which the backends understand.
 458 /// Each backend will need individual work to recognize the new format.
 459 StoreInst *AtomicExpand::convertAtomicStoreToIntegerType(StoreInst *SI) {
 460   IRBuilder<> Builder(SI);
 461   auto *M = SI->getModule();
 462   Type *NewTy = getCorrespondingIntegerType(SI->getValueOperand()->getType(),
 463                                             M->getDataLayout());
 464   Value *NewVal = Builder.CreateBitCast(SI->getValueOperand(), NewTy);
 465
 466   Value *Addr = SI->getPointerOperand();
 467   Type *PT = PointerType::get(NewTy,
 468                               Addr->getType()->getPointerAddressSpace());
 469   Value *NewAddr = Builder.CreateBitCast(Addr, PT);
 470
 471   StoreInst *NewSI = Builder.CreateStore(NewVal, NewAddr);
 472   NewSI->setAlignment(MaybeAlign(SI->getAlignment()));
 473   NewSI->setVolatile(SI->isVolatile());
 474   NewSI->setAtomic(SI->getOrdering(), SI->getSyncScopeID());
 475   LLVM_DEBUG(dbgs() << "Replaced " << *SI << " with " << *NewSI << "\n");
 476   SI->eraseFromParent();
 477   return NewSI;
 478 }
 479
 480 bool AtomicExpand::expandAtomicStore(StoreInst *SI) {
 481   // This function is only called on atomic stores that are too large to be
 482   // atomic if implemented as a native store. So we replace them by an
 483   // atomic swap, that can be implemented for example as a ldrex/strex on ARM
 484   // or lock cmpxchg8/16b on X86, as these are atomic for larger sizes.
 485   // It is the responsibility of the target to only signal expansion via
 486   // shouldExpandAtomicRMW in cases where this is required and possible.
 487   IRBuilder<> Builder(SI);
 488   AtomicRMWInst *AI =
 489       Builder.CreateAtomicRMW(AtomicRMWInst::Xchg, SI->getPointerOperand(),
 490                               SI->getValueOperand(), SI->getOrdering());
 491   SI->eraseFromParent();
 492
 493   // Now we have an appropriate swap instruction, lower it as usual.
 494   return tryExpandAtomicRMW(AI);
 495 }
 496
 497 static void createCmpXchgInstFun(IRBuilder<> &Builder, Value *Addr,
 498                                  Value *Loaded, Value *NewVal,
 499                                  AtomicOrdering MemOpOrder,
 500                                  Value *&Success, Value *&NewLoaded) {
 501   Type *OrigTy = NewVal->getType();
 502
 503   // This code can go away when cmpxchg supports FP types.
 504   bool NeedBitcast = OrigTy->isFloatingPointTy();
 505   if (NeedBitcast) {
 506     IntegerType *IntTy = Builder.getIntNTy(OrigTy->getPrimitiveSizeInBits());
 507     unsigned AS = Addr->getType()->getPointerAddressSpace();
 508     Addr = Builder.CreateBitCast(Addr, IntTy->getPointerTo(AS));
 509     NewVal = Builder.CreateBitCast(NewVal, IntTy);
 510     Loaded = Builder.CreateBitCast(Loaded, IntTy);
 511   }
 512
 513   Value* Pair = Builder.CreateAtomicCmpXchg(
 514       Addr, Loaded, NewVal, MemOpOrder,
 515       AtomicCmpXchgInst::getStrongestFailureOrdering(MemOpOrder));
 516   Success = Builder.CreateExtractValue(Pair, 1, "success");
 517   NewLoaded = Builder.CreateExtractValue(Pair, 0, "newloaded");
 518
 519   if (NeedBitcast)
 520     NewLoaded = Builder.CreateBitCast(NewLoaded, OrigTy);
 521 }
 522
 523 /// Emit IR to implement the given atomicrmw operation on values in registers,
 524 /// returning the new value.
 525 static Value *performAtomicOp(AtomicRMWInst::BinOp Op, IRBuilder<> &Builder,
 526                               Value *Loaded, Value *Inc) {
 527   Value *NewVal;
 528   switch (Op) {
 529   case AtomicRMWInst::Xchg:
 530     return Inc;
 531   case AtomicRMWInst::Add:
 532     return Builder.CreateAdd(Loaded, Inc, "new");
 533   case AtomicRMWInst::Sub:
 534     return Builder.CreateSub(Loaded, Inc, "new");
 535   case AtomicRMWInst::And:
 536     return Builder.CreateAnd(Loaded, Inc, "new");
 537   case AtomicRMWInst::Nand:
 538     return Builder.CreateNot(Builder.CreateAnd(Loaded, Inc), "new");
 539   case AtomicRMWInst::Or:
 540     return Builder.CreateOr(Loaded, Inc, "new");
 541   case AtomicRMWInst::Xor:
 542     return Builder.CreateXor(Loaded, Inc, "new");
 543   case AtomicRMWInst::Max:
 544     NewVal = Builder.CreateICmpSGT(Loaded, Inc);
 545     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
 546   case AtomicRMWInst::Min:
 547     NewVal = Builder.CreateICmpSLE(Loaded, Inc);
 548     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
 549   case AtomicRMWInst::UMax:
 550     NewVal = Builder.CreateICmpUGT(Loaded, Inc);
 551     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
 552   case AtomicRMWInst::UMin:
 553     NewVal = Builder.CreateICmpULE(Loaded, Inc);
 554     return Builder.CreateSelect(NewVal, Loaded, Inc, "new");
 555   case AtomicRMWInst::FAdd:
 556     return Builder.CreateFAdd(Loaded, Inc, "new");
 557   case AtomicRMWInst::FSub:
 558     return Builder.CreateFSub(Loaded, Inc, "new");
 559   default:
 560     llvm_unreachable("Unknown atomic op");
 561   }
 562 }
 563
 564 bool AtomicExpand::tryExpandAtomicRMW(AtomicRMWInst *AI) {
 565   switch (TLI->shouldExpandAtomicRMWInIR(AI)) {
 566   case TargetLoweringBase::AtomicExpansionKind::None:
 567     return false;
 568   case TargetLoweringBase::AtomicExpansionKind::LLSC: {
 569     unsigned MinCASSize = TLI->getMinCmpXchgSizeInBits() / 8;
 570     unsigned ValueSize = getAtomicOpSize(AI);
 571     if (ValueSize < MinCASSize) {
 572       llvm_unreachable(
 573           "MinCmpXchgSizeInBits not yet supported for LL/SC architectures.");
 574     } else {
 575       auto PerformOp = [&](IRBuilder<> &Builder, Value *Loaded) {
 576         return performAtomicOp(AI->getOperation(), Builder, Loaded,
 577                                AI->getValOperand());
 578       };
 579       expandAtomicOpToLLSC(AI, AI->getType(), AI->getPointerOperand(),
 580                            AI->getOrdering(), PerformOp);
 581     }
 582     return true;
 583   }
 584   case TargetLoweringBase::AtomicExpansionKind::CmpXChg: {
 585     unsigned MinCASSize = TLI->getMinCmpXchgSizeInBits() / 8;
 586     unsigned ValueSize = getAtomicOpSize(AI);
 587     if (ValueSize < MinCASSize) {
 588       // TODO: Handle atomicrmw fadd/fsub
 589       if (AI->getType()->isFloatingPointTy())
 590         return false;
 591
 592       expandPartwordAtomicRMW(AI,
 593                               TargetLoweringBase::AtomicExpansionKind::CmpXChg);
 594     } else {
 595       expandAtomicRMWToCmpXchg(AI, createCmpXchgInstFun);
 596     }
 597     return true;
 598   }
 599   case TargetLoweringBase::AtomicExpansionKind::MaskedIntrinsic: {
 600     expandAtomicRMWToMaskedIntrinsic(AI);
 601     return true;
 602   }
 603   default:
 604     llvm_unreachable("Unhandled case in tryExpandAtomicRMW");
 605   }
 606 }
 607
 608 namespace {
 609
 610 /// Result values from createMaskInstrs helper.
 611 struct PartwordMaskValues {
 612   Type *WordType;
 613   Type *ValueType;
 614   Value *AlignedAddr;
 615   Value *ShiftAmt;
 616   Value *Mask;
 617   Value *Inv_Mask;
 618 };
 619
 620 } // end anonymous namespace
 621
 622 /// This is a helper function which builds instructions to provide
 623 /// values necessary for partword atomic operations. It takes an
 624 /// incoming address, Addr, and ValueType, and constructs the address,
 625 /// shift-amounts and masks needed to work with a larger value of size
 626 /// WordSize.
 627 ///
 628 /// AlignedAddr: Addr rounded down to a multiple of WordSize
 629 ///
 630 /// ShiftAmt: Number of bits to right-shift a WordSize value loaded
 631 ///           from AlignAddr for it to have the same value as if
 632 ///           ValueType was loaded from Addr.
 633 ///
 634 /// Mask: Value to mask with the value loaded from AlignAddr to
 635 ///       include only the part that would've been loaded from Addr.
 636 ///
 637 /// Inv_Mask: The inverse of Mask.
 638 static PartwordMaskValues createMaskInstrs(IRBuilder<> &Builder, Instruction *I,
 639                                            Type *ValueType, Value *Addr,
 640                                            unsigned WordSize) {
 641   PartwordMaskValues Ret;
 642
 643   BasicBlock *BB = I->getParent();
 644   Function *F = BB->getParent();
 645   Module *M = I->getModule();
 646
 647   LLVMContext &Ctx = F->getContext();
 648   const DataLayout &DL = M->getDataLayout();
 649
 650   unsigned ValueSize = DL.getTypeStoreSize(ValueType);
 651
 652   assert(ValueSize < WordSize);
 653
 654   Ret.ValueType = ValueType;
 655   Ret.WordType = Type::getIntNTy(Ctx, WordSize * 8);
 656
 657   Type *WordPtrType =
 658       Ret.WordType->getPointerTo(Addr->getType()->getPointerAddressSpace());
 659
 660   Value *AddrInt = Builder.CreatePtrToInt(Addr, DL.getIntPtrType(Ctx));
 661   Ret.AlignedAddr = Builder.CreateIntToPtr(
 662       Builder.CreateAnd(AddrInt, ~(uint64_t)(WordSize - 1)), WordPtrType,
 663       "AlignedAddr");
 664
 665   Value *PtrLSB = Builder.CreateAnd(AddrInt, WordSize - 1, "PtrLSB");
 666   if (DL.isLittleEndian()) {
 667     // turn bytes into bits
 668     Ret.ShiftAmt = Builder.CreateShl(PtrLSB, 3);
 669   } else {
 670     // turn bytes into bits, and count from the other side.
 671     Ret.ShiftAmt =
 672         Builder.CreateShl(Builder.CreateXor(PtrLSB, WordSize - ValueSize), 3);
 673   }
 674
 675   Ret.ShiftAmt = Builder.CreateTrunc(Ret.ShiftAmt, Ret.WordType, "ShiftAmt");
 676   Ret.Mask = Builder.CreateShl(
 677       ConstantInt::get(Ret.WordType, (1 << ValueSize * 8) - 1), Ret.ShiftAmt,
 678       "Mask");
 679   Ret.Inv_Mask = Builder.CreateNot(Ret.Mask, "Inv_Mask");
 680
 681   return Ret;
 682 }
 683
 684 /// Emit IR to implement a masked version of a given atomicrmw
 685 /// operation. (That is, only the bits under the Mask should be
 686 /// affected by the operation)
 687 static Value *performMaskedAtomicOp(AtomicRMWInst::BinOp Op,
 688                                     IRBuilder<> &Builder, Value *Loaded,
 689                                     Value *Shifted_Inc, Value *Inc,
 690                                     const PartwordMaskValues &PMV) {
 691   // TODO: update to use
 692   // https://graphics.stanford.edu/~seander/bithacks.html#MaskedMerge in order
 693   // to merge bits from two values without requiring PMV.Inv_Mask.
 694   switch (Op) {
 695   case AtomicRMWInst::Xchg: {
 696     Value *Loaded_MaskOut = Builder.CreateAnd(Loaded, PMV.Inv_Mask);
 697     Value *FinalVal = Builder.CreateOr(Loaded_MaskOut, Shifted_Inc);
 698     return FinalVal;
 699   }
 700   case AtomicRMWInst::Or:
 701   case AtomicRMWInst::Xor:
 702   case AtomicRMWInst::And:
 703     llvm_unreachable("Or/Xor/And handled by widenPartwordAtomicRMW");
 704   case AtomicRMWInst::Add:
 705   case AtomicRMWInst::Sub:
 706   case AtomicRMWInst::Nand: {
 707     // The other arithmetic ops need to be masked into place.
 708     Value *NewVal = performAtomicOp(Op, Builder, Loaded, Shifted_Inc);
 709     Value *NewVal_Masked = Builder.CreateAnd(NewVal, PMV.Mask);
 710     Value *Loaded_MaskOut = Builder.CreateAnd(Loaded, PMV.Inv_Mask);
 711     Value *FinalVal = Builder.CreateOr(Loaded_MaskOut, NewVal_Masked);
 712     return FinalVal;
 713   }
 714   case AtomicRMWInst::Max:
 715   case AtomicRMWInst::Min:
 716   case AtomicRMWInst::UMax:
 717   case AtomicRMWInst::UMin: {
 718     // Finally, comparison ops will operate on the full value, so
 719     // truncate down to the original size, and expand out again after
 720     // doing the operation.
 721     Value *Loaded_Shiftdown = Builder.CreateTrunc(
 722         Builder.CreateLShr(Loaded, PMV.ShiftAmt), PMV.ValueType);
 723     Value *NewVal = performAtomicOp(Op, Builder, Loaded_Shiftdown, Inc);
 724     Value *NewVal_Shiftup = Builder.CreateShl(
 725         Builder.CreateZExt(NewVal, PMV.WordType), PMV.ShiftAmt);
 726     Value *Loaded_MaskOut = Builder.CreateAnd(Loaded, PMV.Inv_Mask);
 727     Value *FinalVal = Builder.CreateOr(Loaded_MaskOut, NewVal_Shiftup);
 728     return FinalVal;
 729   }
 730   default:
 731     llvm_unreachable("Unknown atomic op");
 732   }
 733 }
 734
 735 /// Expand a sub-word atomicrmw operation into an appropriate
 736 /// word-sized operation.
 737 ///
 738 /// It will create an LL/SC or cmpxchg loop, as appropriate, the same
 739 /// way as a typical atomicrmw expansion. The only difference here is
 740 /// that the operation inside of the loop must operate only upon a
 741 /// part of the value.
 742 void AtomicExpand::expandPartwordAtomicRMW(
 743     AtomicRMWInst *AI, TargetLoweringBase::AtomicExpansionKind ExpansionKind) {
 744   assert(ExpansionKind == TargetLoweringBase::AtomicExpansionKind::CmpXChg);
 745
 746   AtomicOrdering MemOpOrder = AI->getOrdering();
 747
 748   IRBuilder<> Builder(AI);
 749
 750   PartwordMaskValues PMV =
 751       createMaskInstrs(Builder, AI, AI->getType(), AI->getPointerOperand(),
 752                        TLI->getMinCmpXchgSizeInBits() / 8);
 753
 754   Value *ValOperand_Shifted =
 755       Builder.CreateShl(Builder.CreateZExt(AI->getValOperand(), PMV.WordType),
 756                         PMV.ShiftAmt, "ValOperand_Shifted");
 757
 758   auto PerformPartwordOp = [&](IRBuilder<> &Builder, Value *Loaded) {
 759     return performMaskedAtomicOp(AI->getOperation(), Builder, Loaded,
 760                                  ValOperand_Shifted, AI->getValOperand(), PMV);
 761   };
 762
 763   // TODO: When we're ready to support LLSC conversions too, use
 764   // insertRMWLLSCLoop here for ExpansionKind==LLSC.
 765   Value *OldResult =
 766       insertRMWCmpXchgLoop(Builder, PMV.WordType, PMV.AlignedAddr, MemOpOrder,
 767                            PerformPartwordOp, createCmpXchgInstFun);
 768   Value *FinalOldResult = Builder.CreateTrunc(
 769       Builder.CreateLShr(OldResult, PMV.ShiftAmt), PMV.ValueType);
 770   AI->replaceAllUsesWith(FinalOldResult);
 771   AI->eraseFromParent();
 772 }
 773
 774 // Widen the bitwise atomicrmw (or/xor/and) to the minimum supported width.
 775 AtomicRMWInst *AtomicExpand::widenPartwordAtomicRMW(AtomicRMWInst *AI) {
 776   IRBuilder<> Builder(AI);
 777   AtomicRMWInst::BinOp Op = AI->getOperation();
 778
 779   assert((Op == AtomicRMWInst::Or || Op == AtomicRMWInst::Xor ||
 780           Op == AtomicRMWInst::And) &&
 781          "Unable to widen operation");
 782
 783   PartwordMaskValues PMV =
 784       createMaskInstrs(Builder, AI, AI->getType(), AI->getPointerOperand(),
 785                        TLI->getMinCmpXchgSizeInBits() / 8);
 786
 787   Value *ValOperand_Shifted =
 788       Builder.CreateShl(Builder.CreateZExt(AI->getValOperand(), PMV.WordType),
 789                         PMV.ShiftAmt, "ValOperand_Shifted");
 790
 791   Value *NewOperand;
 792
 793   if (Op == AtomicRMWInst::And)
 794     NewOperand =
 795         Builder.CreateOr(PMV.Inv_Mask, ValOperand_Shifted, "AndOperand");
 796   else
 797     NewOperand = ValOperand_Shifted;
 798
 799   AtomicRMWInst *NewAI = Builder.CreateAtomicRMW(Op, PMV.AlignedAddr,
 800                                                  NewOperand, AI->getOrdering());
 801
 802   Value *FinalOldResult = Builder.CreateTrunc(
 803       Builder.CreateLShr(NewAI, PMV.ShiftAmt), PMV.ValueType);
 804   AI->replaceAllUsesWith(FinalOldResult);
 805   AI->eraseFromParent();
 806   return NewAI;
 807 }
 808
 809 void AtomicExpand::expandPartwordCmpXchg(AtomicCmpXchgInst *CI) {
 810   // The basic idea here is that we're expanding a cmpxchg of a
 811   // smaller memory size up to a word-sized cmpxchg. To do this, we
 812   // need to add a retry-loop for strong cmpxchg, so that
 813   // modifications to other parts of the word don't cause a spurious
 814   // failure.
 815
 816   // This generates code like the following:
 817   //     [[Setup mask values PMV.*]]
 818   //     %NewVal_Shifted = shl i32 %NewVal, %PMV.ShiftAmt
 819   //     %Cmp_Shifted = shl i32 %Cmp, %PMV.ShiftAmt
 820   //     %InitLoaded = load i32* %addr
 821   //     %InitLoaded_MaskOut = and i32 %InitLoaded, %PMV.Inv_Mask
 822   //     br partword.cmpxchg.loop
 823   // partword.cmpxchg.loop:
 824   //     %Loaded_MaskOut = phi i32 [ %InitLoaded_MaskOut, %entry ],
 825   //        [ %OldVal_MaskOut, %partword.cmpxchg.failure ]
 826   //     %FullWord_NewVal = or i32 %Loaded_MaskOut, %NewVal_Shifted
 827   //     %FullWord_Cmp = or i32 %Loaded_MaskOut, %Cmp_Shifted
 828   //     %NewCI = cmpxchg i32* %PMV.AlignedAddr, i32 %FullWord_Cmp,
 829   //        i32 %FullWord_NewVal success_ordering failure_ordering
 830   //     %OldVal = extractvalue { i32, i1 } %NewCI, 0
 831   //     %Success = extractvalue { i32, i1 } %NewCI, 1
 832   //     br i1 %Success, label %partword.cmpxchg.end,
 833   //        label %partword.cmpxchg.failure
 834   // partword.cmpxchg.failure:
 835   //     %OldVal_MaskOut = and i32 %OldVal, %PMV.Inv_Mask
 836   //     %ShouldContinue = icmp ne i32 %Loaded_MaskOut, %OldVal_MaskOut
 837   //     br i1 %ShouldContinue, label %partword.cmpxchg.loop,
 838   //         label %partword.cmpxchg.end
 839   // partword.cmpxchg.end:
 840   //    %tmp1 = lshr i32 %OldVal, %PMV.ShiftAmt
 841   //    %FinalOldVal = trunc i32 %tmp1 to i8
 842   //    %tmp2 = insertvalue { i8, i1 } undef, i8 %FinalOldVal, 0
 843   //    %Res = insertvalue { i8, i1 } %25, i1 %Success, 1
 844
 845   Value *Addr = CI->getPointerOperand();
 846   Value *Cmp = CI->getCompareOperand();
 847   Value *NewVal = CI->getNewValOperand();
 848
 849   BasicBlock *BB = CI->getParent();
 850   Function *F = BB->getParent();
 851   IRBuilder<> Builder(CI);
 852   LLVMContext &Ctx = Builder.getContext();
 853
 854   const int WordSize = TLI->getMinCmpXchgSizeInBits() / 8;
 855
 856   BasicBlock *EndBB =
 857       BB->splitBasicBlock(CI->getIterator(), "partword.cmpxchg.end");
 858   auto FailureBB =
 859       BasicBlock::Create(Ctx, "partword.cmpxchg.failure", F, EndBB);
 860   auto LoopBB = BasicBlock::Create(Ctx, "partword.cmpxchg.loop", F, FailureBB);
 861
 862   // The split call above "helpfully" added a branch at the end of BB
 863   // (to the wrong place).
 864   std::prev(BB->end())->eraseFromParent();
 865   Builder.SetInsertPoint(BB);
 866
 867   PartwordMaskValues PMV = createMaskInstrs(
 868       Builder, CI, CI->getCompareOperand()->getType(), Addr, WordSize);
 869
 870   // Shift the incoming values over, into the right location in the word.
 871   Value *NewVal_Shifted =
 872       Builder.CreateShl(Builder.CreateZExt(NewVal, PMV.WordType), PMV.ShiftAmt);
 873   Value *Cmp_Shifted =
 874       Builder.CreateShl(Builder.CreateZExt(Cmp, PMV.WordType), PMV.ShiftAmt);
 875
 876   // Load the entire current word, and mask into place the expected and new
 877   // values
 878   LoadInst *InitLoaded = Builder.CreateLoad(PMV.WordType, PMV.AlignedAddr);
 879   InitLoaded->setVolatile(CI->isVolatile());
 880   Value *InitLoaded_MaskOut = Builder.CreateAnd(InitLoaded, PMV.Inv_Mask);
 881   Builder.CreateBr(LoopBB);
 882
 883   // partword.cmpxchg.loop:
 884   Builder.SetInsertPoint(LoopBB);
 885   PHINode *Loaded_MaskOut = Builder.CreatePHI(PMV.WordType, 2);
 886   Loaded_MaskOut->addIncoming(InitLoaded_MaskOut, BB);
 887
 888   // Mask/Or the expected and new values into place in the loaded word.
 889   Value *FullWord_NewVal = Builder.CreateOr(Loaded_MaskOut, NewVal_Shifted);
 890   Value *FullWord_Cmp = Builder.CreateOr(Loaded_MaskOut, Cmp_Shifted);
 891   AtomicCmpXchgInst *NewCI = Builder.CreateAtomicCmpXchg(
 892       PMV.AlignedAddr, FullWord_Cmp, FullWord_NewVal, CI->getSuccessOrdering(),
 893       CI->getFailureOrdering(), CI->getSyncScopeID());
 894   NewCI->setVolatile(CI->isVolatile());
 895   // When we're building a strong cmpxchg, we need a loop, so you
 896   // might think we could use a weak cmpxchg inside. But, using strong
 897   // allows the below comparison for ShouldContinue, and we're
 898   // expecting the underlying cmpxchg to be a machine instruction,
 899   // which is strong anyways.
 900   NewCI->setWeak(CI->isWeak());
 901
 902   Value *OldVal = Builder.CreateExtractValue(NewCI, 0);
 903   Value *Success = Builder.CreateExtractValue(NewCI, 1);
 904
 905   if (CI->isWeak())
 906     Builder.CreateBr(EndBB);
 907   else
 908     Builder.CreateCondBr(Success, EndBB, FailureBB);
 909
 910   // partword.cmpxchg.failure:
 911   Builder.SetInsertPoint(FailureBB);
 912   // Upon failure, verify that the masked-out part of the loaded value
 913   // has been modified.  If it didn't, abort the cmpxchg, since the
 914   // masked-in part must've.
 915   Value *OldVal_MaskOut = Builder.CreateAnd(OldVal, PMV.Inv_Mask);
 916   Value *ShouldContinue = Builder.CreateICmpNE(Loaded_MaskOut, OldVal_MaskOut);
 917   Builder.CreateCondBr(ShouldContinue, LoopBB, EndBB);
 918
 919   // Add the second value to the phi from above
 920   Loaded_MaskOut->addIncoming(OldVal_MaskOut, FailureBB);
 921
 922   // partword.cmpxchg.end:
 923   Builder.SetInsertPoint(CI);
 924
 925   Value *FinalOldVal = Builder.CreateTrunc(
 926       Builder.CreateLShr(OldVal, PMV.ShiftAmt), PMV.ValueType);
 927   Value *Res = UndefValue::get(CI->getType());
 928   Res = Builder.CreateInsertValue(Res, FinalOldVal, 0);
 929   Res = Builder.CreateInsertValue(Res, Success, 1);
 930
 931   CI->replaceAllUsesWith(Res);
 932   CI->eraseFromParent();
 933 }
 934
 935 void AtomicExpand::expandAtomicOpToLLSC(
 936     Instruction *I, Type *ResultType, Value *Addr, AtomicOrdering MemOpOrder,
 937     function_ref<Value *(IRBuilder<> &, Value *)> PerformOp) {
 938   IRBuilder<> Builder(I);
 939   Value *Loaded =
 940       insertRMWLLSCLoop(Builder, ResultType, Addr, MemOpOrder, PerformOp);
 941
 942   I->replaceAllUsesWith(Loaded);
 943   I->eraseFromParent();
 944 }
 945
 946 void AtomicExpand::expandAtomicRMWToMaskedIntrinsic(AtomicRMWInst *AI) {
 947   IRBuilder<> Builder(AI);
 948
 949   PartwordMaskValues PMV =
 950       createMaskInstrs(Builder, AI, AI->getType(), AI->getPointerOperand(),
 951                        TLI->getMinCmpXchgSizeInBits() / 8);
 952
 953   // The value operand must be sign-extended for signed min/max so that the
 954   // target's signed comparison instructions can be used. Otherwise, just
 955   // zero-ext.
 956   Instruction::CastOps CastOp = Instruction::ZExt;
 957   AtomicRMWInst::BinOp RMWOp = AI->getOperation();
 958   if (RMWOp == AtomicRMWInst::Max || RMWOp == AtomicRMWInst::Min)
 959     CastOp = Instruction::SExt;
 960
 961   Value *ValOperand_Shifted = Builder.CreateShl(
 962       Builder.CreateCast(CastOp, AI->getValOperand(), PMV.WordType),
 963       PMV.ShiftAmt, "ValOperand_Shifted");
 964   Value *OldResult = TLI->emitMaskedAtomicRMWIntrinsic(
 965       Builder, AI, PMV.AlignedAddr, ValOperand_Shifted, PMV.Mask, PMV.ShiftAmt,
 966       AI->getOrdering());
 967   Value *FinalOldResult = Builder.CreateTrunc(
 968       Builder.CreateLShr(OldResult, PMV.ShiftAmt), PMV.ValueType);
 969   AI->replaceAllUsesWith(FinalOldResult);
 970   AI->eraseFromParent();
 971 }
 972
 973 void AtomicExpand::expandAtomicCmpXchgToMaskedIntrinsic(AtomicCmpXchgInst *CI) {
 974   IRBuilder<> Builder(CI);
 975
 976   PartwordMaskValues PMV = createMaskInstrs(
 977       Builder, CI, CI->getCompareOperand()->getType(), CI->getPointerOperand(),
 978       TLI->getMinCmpXchgSizeInBits() / 8);
 979
 980   Value *CmpVal_Shifted = Builder.CreateShl(
 981       Builder.CreateZExt(CI->getCompareOperand(), PMV.WordType), PMV.ShiftAmt,
 982       "CmpVal_Shifted");
 983   Value *NewVal_Shifted = Builder.CreateShl(
 984       Builder.CreateZExt(CI->getNewValOperand(), PMV.WordType), PMV.ShiftAmt,
 985       "NewVal_Shifted");
 986   Value *OldVal = TLI->emitMaskedAtomicCmpXchgIntrinsic(
 987       Builder, CI, PMV.AlignedAddr, CmpVal_Shifted, NewVal_Shifted, PMV.Mask,
 988       CI->getSuccessOrdering());
 989   Value *FinalOldVal = Builder.CreateTrunc(
 990       Builder.CreateLShr(OldVal, PMV.ShiftAmt), PMV.ValueType);
 991
 992   Value *Res = UndefValue::get(CI->getType());
 993   Res = Builder.CreateInsertValue(Res, FinalOldVal, 0);
 994   Value *Success = Builder.CreateICmpEQ(
 995       CmpVal_Shifted, Builder.CreateAnd(OldVal, PMV.Mask), "Success");
 996   Res = Builder.CreateInsertValue(Res, Success, 1);
 997
 998   CI->replaceAllUsesWith(Res);
 999   CI->eraseFromParent();
1000 }
1001
1002 Value *AtomicExpand::insertRMWLLSCLoop(
1003     IRBuilder<> &Builder, Type *ResultTy, Value *Addr,
1004     AtomicOrdering MemOpOrder,
1005     function_ref<Value *(IRBuilder<> &, Value *)> PerformOp) {
1006   LLVMContext &Ctx = Builder.getContext();
1007   BasicBlock *BB = Builder.GetInsertBlock();
1008   Function *F = BB->getParent();
1009
1010   // Given: atomicrmw some_op iN* %addr, iN %incr ordering
1011   //
1012   // The standard expansion we produce is:
1013   //     [...]
1014   // atomicrmw.start:
1015   //     %loaded = @load.linked(%addr)
1016   //     %new = some_op iN %loaded, %incr
1017   //     %stored = @store_conditional(%new, %addr)
1018   //     %try_again = icmp i32 ne %stored, 0
1019   //     br i1 %try_again, label %loop, label %atomicrmw.end
1020   // atomicrmw.end:
1021   //     [...]
1022   BasicBlock *ExitBB =
1023       BB->splitBasicBlock(Builder.GetInsertPoint(), "atomicrmw.end");
1024   BasicBlock *LoopBB =  BasicBlock::Create(Ctx, "atomicrmw.start", F, ExitBB);
1025
1026   // The split call above "helpfully" added a branch at the end of BB (to the
1027   // wrong place).
1028   std::prev(BB->end())->eraseFromParent();
1029   Builder.SetInsertPoint(BB);
1030   Builder.CreateBr(LoopBB);
1031
1032   // Start the main loop block now that we've taken care of the preliminaries.
1033   Builder.SetInsertPoint(LoopBB);
1034   Value *Loaded = TLI->emitLoadLinked(Builder, Addr, MemOpOrder);
1035
1036   Value *NewVal = PerformOp(Builder, Loaded);
1037
1038   Value *StoreSuccess =
1039       TLI->emitStoreConditional(Builder, NewVal, Addr, MemOpOrder);
1040   Value *TryAgain = Builder.CreateICmpNE(
1041       StoreSuccess, ConstantInt::get(IntegerType::get(Ctx, 32), 0), "tryagain");
1042   Builder.CreateCondBr(TryAgain, LoopBB, ExitBB);
1043
1044   Builder.SetInsertPoint(ExitBB, ExitBB->begin());
1045   return Loaded;
1046 }
1047
1048 /// Convert an atomic cmpxchg of a non-integral type to an integer cmpxchg of
1049 /// the equivalent bitwidth.  We used to not support pointer cmpxchg in the
1050 /// IR.  As a migration step, we convert back to what use to be the standard
1051 /// way to represent a pointer cmpxchg so that we can update backends one by
1052 /// one.
1053 AtomicCmpXchgInst *AtomicExpand::convertCmpXchgToIntegerType(AtomicCmpXchgInst *CI) {
1054   auto *M = CI->getModule();
1055   Type *NewTy = getCorrespondingIntegerType(CI->getCompareOperand()->getType(),
1056                                             M->getDataLayout());
1057
1058   IRBuilder<> Builder(CI);
1059
1060   Value *Addr = CI->getPointerOperand();
1061   Type *PT = PointerType::get(NewTy,
1062                               Addr->getType()->getPointerAddressSpace());
1063   Value *NewAddr = Builder.CreateBitCast(Addr, PT);
1064
1065   Value *NewCmp = Builder.CreatePtrToInt(CI->getCompareOperand(), NewTy);
1066   Value *NewNewVal = Builder.CreatePtrToInt(CI->getNewValOperand(), NewTy);
1067
1068
1069   auto *NewCI = Builder.CreateAtomicCmpXchg(NewAddr, NewCmp, NewNewVal,
1070                                             CI->getSuccessOrdering(),
1071                                             CI->getFailureOrdering(),
1072                                             CI->getSyncScopeID());
1073   NewCI->setVolatile(CI->isVolatile());
1074   NewCI->setWeak(CI->isWeak());
1075   LLVM_DEBUG(dbgs() << "Replaced " << *CI << " with " << *NewCI << "\n");
1076
1077   Value *OldVal = Builder.CreateExtractValue(NewCI, 0);
1078   Value *Succ = Builder.CreateExtractValue(NewCI, 1);
1079
1080   OldVal = Builder.CreateIntToPtr(OldVal, CI->getCompareOperand()->getType());
1081
1082   Value *Res = UndefValue::get(CI->getType());
1083   Res = Builder.CreateInsertValue(Res, OldVal, 0);
1084   Res = Builder.CreateInsertValue(Res, Succ, 1);
1085
1086   CI->replaceAllUsesWith(Res);
1087   CI->eraseFromParent();
1088   return NewCI;
1089 }
1090
1091 bool AtomicExpand::expandAtomicCmpXchg(AtomicCmpXchgInst *CI) {
1092   AtomicOrdering SuccessOrder = CI->getSuccessOrdering();
1093   AtomicOrdering FailureOrder = CI->getFailureOrdering();
1094   Value *Addr = CI->getPointerOperand();
1095   BasicBlock *BB = CI->getParent();
1096   Function *F = BB->getParent();
1097   LLVMContext &Ctx = F->getContext();
1098   // If shouldInsertFencesForAtomic() returns true, then the target does not
1099   // want to deal with memory orders, and emitLeading/TrailingFence should take
1100   // care of everything. Otherwise, emitLeading/TrailingFence are no-op and we
1101   // should preserve the ordering.
1102   bool ShouldInsertFencesForAtomic = TLI->shouldInsertFencesForAtomic(CI);
1103   AtomicOrdering MemOpOrder =
1104       ShouldInsertFencesForAtomic ? AtomicOrdering::Monotonic : SuccessOrder;
1105
1106   // In implementations which use a barrier to achieve release semantics, we can
1107   // delay emitting this barrier until we know a store is actually going to be
1108   // attempted. The cost of this delay is that we need 2 copies of the block
1109   // emitting the load-linked, affecting code size.
1110   //
1111   // Ideally, this logic would be unconditional except for the minsize check
1112   // since in other cases the extra blocks naturally collapse down to the
1113   // minimal loop. Unfortunately, this puts too much stress on later
1114   // optimisations so we avoid emitting the extra logic in those cases too.
1115   bool HasReleasedLoadBB = !CI->isWeak() && ShouldInsertFencesForAtomic &&
1116                            SuccessOrder != AtomicOrdering::Monotonic &&
1117                            SuccessOrder != AtomicOrdering::Acquire &&
1118                            !F->hasMinSize();
1119
1120   // There's no overhead for sinking the release barrier in a weak cmpxchg, so
1121   // do it even on minsize.
1122   bool UseUnconditionalReleaseBarrier = F->hasMinSize() && !CI->isWeak();
1123
1124   // Given: cmpxchg some_op iN* %addr, iN %desired, iN %new success_ord fail_ord
1125   //
1126   // The full expansion we produce is:
1127   //     [...]
1128   // cmpxchg.start:
1129   //     %unreleasedload = @load.linked(%addr)
1130   //     %should_store = icmp eq %unreleasedload, %desired
1131   //     br i1 %should_store, label %cmpxchg.fencedstore,
1132   //                          label %cmpxchg.nostore
1133   // cmpxchg.releasingstore:
1134   //     fence?
1135   //     br label cmpxchg.trystore
1136   // cmpxchg.trystore:
1137   //     %loaded.trystore = phi [%unreleasedload, %releasingstore],
1138   //                            [%releasedload, %cmpxchg.releasedload]
1139   //     %stored = @store_conditional(%new, %addr)
1140   //     %success = icmp eq i32 %stored, 0
1141   //     br i1 %success, label %cmpxchg.success,
1142   //                     label %cmpxchg.releasedload/%cmpxchg.failure
1143   // cmpxchg.releasedload:
1144   //     %releasedload = @load.linked(%addr)
1145   //     %should_store = icmp eq %releasedload, %desired
1146   //     br i1 %should_store, label %cmpxchg.trystore,
1147   //                          label %cmpxchg.failure
1148   // cmpxchg.success:
1149   //     fence?
1150   //     br label %cmpxchg.end
1151   // cmpxchg.nostore:
1152   //     %loaded.nostore = phi [%unreleasedload, %cmpxchg.start],
1153   //                           [%releasedload,
1154   //                               %cmpxchg.releasedload/%cmpxchg.trystore]
1155   //     @load_linked_fail_balance()?
1156   //     br label %cmpxchg.failure
1157   // cmpxchg.failure:
1158   //     fence?
1159   //     br label %cmpxchg.end
1160   // cmpxchg.end:
1161   //     %loaded = phi [%loaded.nostore, %cmpxchg.failure],
1162   //                   [%loaded.trystore, %cmpxchg.trystore]
1163   //     %success = phi i1 [true, %cmpxchg.success], [false, %cmpxchg.failure]
1164   //     %restmp = insertvalue { iN, i1 } undef, iN %loaded, 0
1165   //     %res = insertvalue { iN, i1 } %restmp, i1 %success, 1
1166   //     [...]
1167   BasicBlock *ExitBB = BB->splitBasicBlock(CI->getIterator(), "cmpxchg.end");
1168   auto FailureBB = BasicBlock::Create(Ctx, "cmpxchg.failure", F, ExitBB);
1169   auto NoStoreBB = BasicBlock::Create(Ctx, "cmpxchg.nostore", F, FailureBB);
1170   auto SuccessBB = BasicBlock::Create(Ctx, "cmpxchg.success", F, NoStoreBB);
1171   auto ReleasedLoadBB =
1172       BasicBlock::Create(Ctx, "cmpxchg.releasedload", F, SuccessBB);
1173   auto TryStoreBB =
1174       BasicBlock::Create(Ctx, "cmpxchg.trystore", F, ReleasedLoadBB);
1175   auto ReleasingStoreBB =
1176       BasicBlock::Create(Ctx, "cmpxchg.fencedstore", F, TryStoreBB);
1177   auto StartBB = BasicBlock::Create(Ctx, "cmpxchg.start", F, ReleasingStoreBB);
1178
1179   // This grabs the DebugLoc from CI
1180   IRBuilder<> Builder(CI);
1181
1182   // The split call above "helpfully" added a branch at the end of BB (to the
1183   // wrong place), but we might want a fence too. It's easiest to just remove
1184   // the branch entirely.
1185   std::prev(BB->end())->eraseFromParent();
1186   Builder.SetInsertPoint(BB);
1187   if (ShouldInsertFencesForAtomic && UseUnconditionalReleaseBarrier)
1188     TLI->emitLeadingFence(Builder, CI, SuccessOrder);
1189   Builder.CreateBr(StartBB);
1190
1191   // Start the main loop block now that we've taken care of the preliminaries.
1192   Builder.SetInsertPoint(StartBB);
1193   Value *UnreleasedLoad = TLI->emitLoadLinked(Builder, Addr, MemOpOrder);
1194   Value *ShouldStore = Builder.CreateICmpEQ(
1195       UnreleasedLoad, CI->getCompareOperand(), "should_store");
1196
1197   // If the cmpxchg doesn't actually need any ordering when it fails, we can
1198   // jump straight past that fence instruction (if it exists).
1199   Builder.CreateCondBr(ShouldStore, ReleasingStoreBB, NoStoreBB);
1200
1201   Builder.SetInsertPoint(ReleasingStoreBB);
1202   if (ShouldInsertFencesForAtomic && !UseUnconditionalReleaseBarrier)
1203     TLI->emitLeadingFence(Builder, CI, SuccessOrder);
1204   Builder.CreateBr(TryStoreBB);
1205
1206   Builder.SetInsertPoint(TryStoreBB);
1207   Value *StoreSuccess = TLI->emitStoreConditional(
1208       Builder, CI->getNewValOperand(), Addr, MemOpOrder);
1209   StoreSuccess = Builder.CreateICmpEQ(
1210       StoreSuccess, ConstantInt::get(Type::getInt32Ty(Ctx), 0), "success");
1211   BasicBlock *RetryBB = HasReleasedLoadBB ? ReleasedLoadBB : StartBB;
1212   Builder.CreateCondBr(StoreSuccess, SuccessBB,
1213                        CI->isWeak() ? FailureBB : RetryBB);
1214
1215   Builder.SetInsertPoint(ReleasedLoadBB);
1216   Value *SecondLoad;
1217   if (HasReleasedLoadBB) {
1218     SecondLoad = TLI->emitLoadLinked(Builder, Addr, MemOpOrder);
1219     ShouldStore = Builder.CreateICmpEQ(SecondLoad, CI->getCompareOperand(),
1220                                        "should_store");
1221
1222     // If the cmpxchg doesn't actually need any ordering when it fails, we can
1223     // jump straight past that fence instruction (if it exists).
1224     Builder.CreateCondBr(ShouldStore, TryStoreBB, NoStoreBB);
1225   } else
1226     Builder.CreateUnreachable();
1227
1228   // Make sure later instructions don't get reordered with a fence if
1229   // necessary.
1230   Builder.SetInsertPoint(SuccessBB);
1231   if (ShouldInsertFencesForAtomic)
1232     TLI->emitTrailingFence(Builder, CI, SuccessOrder);
1233   Builder.CreateBr(ExitBB);
1234
1235   Builder.SetInsertPoint(NoStoreBB);
1236   // In the failing case, where we don't execute the store-conditional, the
1237   // target might want to balance out the load-linked with a dedicated
1238   // instruction (e.g., on ARM, clearing the exclusive monitor).
1239   TLI->emitAtomicCmpXchgNoStoreLLBalance(Builder);
1240   Builder.CreateBr(FailureBB);
1241
1242   Builder.SetInsertPoint(FailureBB);
1243   if (ShouldInsertFencesForAtomic)
1244     TLI->emitTrailingFence(Builder, CI, FailureOrder);
1245   Builder.CreateBr(ExitBB);
1246
1247   // Finally, we have control-flow based knowledge of whether the cmpxchg
1248   // succeeded or not. We expose this to later passes by converting any
1249   // subsequent "icmp eq/ne %loaded, %oldval" into a use of an appropriate
1250   // PHI.
1251   Builder.SetInsertPoint(ExitBB, ExitBB->begin());
1252   PHINode *Success = Builder.CreatePHI(Type::getInt1Ty(Ctx), 2);
1253   Success->addIncoming(ConstantInt::getTrue(Ctx), SuccessBB);
1254   Success->addIncoming(ConstantInt::getFalse(Ctx), FailureBB);
1255
1256   // Setup the builder so we can create any PHIs we need.
1257   Value *Loaded;
1258   if (!HasReleasedLoadBB)
1259     Loaded = UnreleasedLoad;
1260   else {
1261     Builder.SetInsertPoint(TryStoreBB, TryStoreBB->begin());
1262     PHINode *TryStoreLoaded = Builder.CreatePHI(UnreleasedLoad->getType(), 2);
1263     TryStoreLoaded->addIncoming(UnreleasedLoad, ReleasingStoreBB);
1264     TryStoreLoaded->addIncoming(SecondLoad, ReleasedLoadBB);
1265
1266     Builder.SetInsertPoint(NoStoreBB, NoStoreBB->begin());
1267     PHINode *NoStoreLoaded = Builder.CreatePHI(UnreleasedLoad->getType(), 2);
1268     NoStoreLoaded->addIncoming(UnreleasedLoad, StartBB);
1269     NoStoreLoaded->addIncoming(SecondLoad, ReleasedLoadBB);
1270
1271     Builder.SetInsertPoint(ExitBB, ++ExitBB->begin());
1272     PHINode *ExitLoaded = Builder.CreatePHI(UnreleasedLoad->getType(), 2);
1273     ExitLoaded->addIncoming(TryStoreLoaded, SuccessBB);
1274     ExitLoaded->addIncoming(NoStoreLoaded, FailureBB);
1275
1276     Loaded = ExitLoaded;
1277   }
1278
1279   // Look for any users of the cmpxchg that are just comparing the loaded value
1280   // against the desired one, and replace them with the CFG-derived version.
1281   SmallVector<ExtractValueInst *, 2> PrunedInsts;
1282   for (auto User : CI->users()) {
1283     ExtractValueInst *EV = dyn_cast<ExtractValueInst>(User);
1284     if (!EV)
1285       continue;
1286
1287     assert(EV->getNumIndices() == 1 && EV->getIndices()[0] <= 1 &&
1288            "weird extraction from { iN, i1 }");
1289
1290     if (EV->getIndices()[0] == 0)
1291       EV->replaceAllUsesWith(Loaded);
1292     else
1293       EV->replaceAllUsesWith(Success);
1294
1295     PrunedInsts.push_back(EV);
1296   }
1297
1298   // We can remove the instructions now we're no longer iterating through them.
1299   for (auto EV : PrunedInsts)
1300     EV->eraseFromParent();
1301
1302   if (!CI->use_empty()) {
1303     // Some use of the full struct return that we don't understand has happened,
1304     // so we've got to reconstruct it properly.
1305     Value *Res;
1306     Res = Builder.CreateInsertValue(UndefValue::get(CI->getType()), Loaded, 0);
1307     Res = Builder.CreateInsertValue(Res, Success, 1);
1308
1309     CI->replaceAllUsesWith(Res);
1310   }
1311
1312   CI->eraseFromParent();
1313   return true;
1314 }
1315
1316 bool AtomicExpand::isIdempotentRMW(AtomicRMWInst* RMWI) {
1317   auto C = dyn_cast<ConstantInt>(RMWI->getValOperand());
1318   if(!C)
1319     return false;
1320
1321   AtomicRMWInst::BinOp Op = RMWI->getOperation();
1322   switch(Op) {
1323     case AtomicRMWInst::Add:
1324     case AtomicRMWInst::Sub:
1325     case AtomicRMWInst::Or:
1326     case AtomicRMWInst::Xor:
1327       return C->isZero();
1328     case AtomicRMWInst::And:
1329       return C->isMinusOne();
1330     // FIXME: we could also treat Min/Max/UMin/UMax by the INT_MIN/INT_MAX/...
1331     default:
1332       return false;
1333   }
1334 }
1335
1336 bool AtomicExpand::simplifyIdempotentRMW(AtomicRMWInst* RMWI) {
1337   if (auto ResultingLoad = TLI->lowerIdempotentRMWIntoFencedLoad(RMWI)) {
1338     tryExpandAtomicLoad(ResultingLoad);
1339     return true;
1340   }
1341   return false;
1342 }
1343
1344 Value *AtomicExpand::insertRMWCmpXchgLoop(
1345     IRBuilder<> &Builder, Type *ResultTy, Value *Addr,
1346     AtomicOrdering MemOpOrder,
1347     function_ref<Value *(IRBuilder<> &, Value *)> PerformOp,
1348     CreateCmpXchgInstFun CreateCmpXchg) {
1349   LLVMContext &Ctx = Builder.getContext();
1350   BasicBlock *BB = Builder.GetInsertBlock();
1351   Function *F = BB->getParent();
1352
1353   // Given: atomicrmw some_op iN* %addr, iN %incr ordering
1354   //
1355   // The standard expansion we produce is:
1356   //     [...]
1357   //     %init_loaded = load atomic iN* %addr
1358   //     br label %loop
1359   // loop:
1360   //     %loaded = phi iN [ %init_loaded, %entry ], [ %new_loaded, %loop ]
1361   //     %new = some_op iN %loaded, %incr
1362   //     %pair = cmpxchg iN* %addr, iN %loaded, iN %new
1363   //     %new_loaded = extractvalue { iN, i1 } %pair, 0
1364   //     %success = extractvalue { iN, i1 } %pair, 1
1365   //     br i1 %success, label %atomicrmw.end, label %loop
1366   // atomicrmw.end:
1367   //     [...]
1368   BasicBlock *ExitBB =
1369       BB->splitBasicBlock(Builder.GetInsertPoint(), "atomicrmw.end");
1370   BasicBlock *LoopBB = BasicBlock::Create(Ctx, "atomicrmw.start", F, ExitBB);
1371
1372   // The split call above "helpfully" added a branch at the end of BB (to the
1373   // wrong place), but we want a load. It's easiest to just remove
1374   // the branch entirely.
1375   std::prev(BB->end())->eraseFromParent();
1376   Builder.SetInsertPoint(BB);
1377   LoadInst *InitLoaded = Builder.CreateLoad(ResultTy, Addr);
1378   // Atomics require at least natural alignment.
1379   InitLoaded->setAlignment(MaybeAlign(ResultTy->getPrimitiveSizeInBits() / 8));
1380   Builder.CreateBr(LoopBB);
1381
1382   // Start the main loop block now that we've taken care of the preliminaries.
1383   Builder.SetInsertPoint(LoopBB);
1384   PHINode *Loaded = Builder.CreatePHI(ResultTy, 2, "loaded");
1385   Loaded->addIncoming(InitLoaded, BB);
1386
1387   Value *NewVal = PerformOp(Builder, Loaded);
1388
1389   Value *NewLoaded = nullptr;
1390   Value *Success = nullptr;
1391
1392   CreateCmpXchg(Builder, Addr, Loaded, NewVal,
1393                 MemOpOrder == AtomicOrdering::Unordered
1394                     ? AtomicOrdering::Monotonic
1395                     : MemOpOrder,
1396                 Success, NewLoaded);
1397   assert(Success && NewLoaded);
1398
1399   Loaded->addIncoming(NewLoaded, LoopBB);
1400
1401   Builder.CreateCondBr(Success, ExitBB, LoopBB);
1402
1403   Builder.SetInsertPoint(ExitBB, ExitBB->begin());
1404   return NewLoaded;
1405 }
1406
1407 bool AtomicExpand::tryExpandAtomicCmpXchg(AtomicCmpXchgInst *CI) {
1408   unsigned MinCASSize = TLI->getMinCmpXchgSizeInBits() / 8;
1409   unsigned ValueSize = getAtomicOpSize(CI);
1410
1411   switch (TLI->shouldExpandAtomicCmpXchgInIR(CI)) {
1412   default:
1413     llvm_unreachable("Unhandled case in tryExpandAtomicCmpXchg");
1414   case TargetLoweringBase::AtomicExpansionKind::None:
1415     if (ValueSize < MinCASSize)
1416       expandPartwordCmpXchg(CI);
1417     return false;
1418   case TargetLoweringBase::AtomicExpansionKind::LLSC: {
1419     assert(ValueSize >= MinCASSize &&
1420            "MinCmpXchgSizeInBits not yet supported for LL/SC expansions.");
1421     return expandAtomicCmpXchg(CI);
1422   }
1423   case TargetLoweringBase::AtomicExpansionKind::MaskedIntrinsic:
1424     expandAtomicCmpXchgToMaskedIntrinsic(CI);
1425     return true;
1426   }
1427 }
1428
1429 // Note: This function is exposed externally by AtomicExpandUtils.h
1430 bool llvm::expandAtomicRMWToCmpXchg(AtomicRMWInst *AI,
1431                                     CreateCmpXchgInstFun CreateCmpXchg) {
1432   IRBuilder<> Builder(AI);
1433   Value *Loaded = AtomicExpand::insertRMWCmpXchgLoop(
1434       Builder, AI->getType(), AI->getPointerOperand(), AI->getOrdering(),
1435       [&](IRBuilder<> &Builder, Value *Loaded) {
1436         return performAtomicOp(AI->getOperation(), Builder, Loaded,
1437                                AI->getValOperand());
1438       },
1439       CreateCmpXchg);
1440
1441   AI->replaceAllUsesWith(Loaded);
1442   AI->eraseFromParent();
1443   return true;
1444 }
1445
1446 // In order to use one of the sized library calls such as
1447 // __atomic_fetch_add_4, the alignment must be sufficient, the size
1448 // must be one of the potentially-specialized sizes, and the value
1449 // type must actually exist in C on the target (otherwise, the
1450 // function wouldn't actually be defined.)
1451 static bool canUseSizedAtomicCall(unsigned Size, unsigned Align,
1452                                   const DataLayout &DL) {
1453   // TODO: "LargestSize" is an approximation for "largest type that
1454   // you can express in C". It seems to be the case that int128 is
1455   // supported on all 64-bit platforms, otherwise only up to 64-bit
1456   // integers are supported. If we get this wrong, then we'll try to
1457   // call a sized libcall that doesn't actually exist. There should
1458   // really be some more reliable way in LLVM of determining integer
1459   // sizes which are valid in the target's C ABI...
1460   unsigned LargestSize = DL.getLargestLegalIntTypeSizeInBits() >= 64 ? 16 : 8;
1461   return Align >= Size &&
1462          (Size == 1 || Size == 2 || Size == 4 || Size == 8 || Size == 16) &&
1463          Size <= LargestSize;
1464 }
1465
1466 void AtomicExpand::expandAtomicLoadToLibcall(LoadInst *I) {
1467   static const RTLIB::Libcall Libcalls[6] = {
1468       RTLIB::ATOMIC_LOAD,   RTLIB::ATOMIC_LOAD_1, RTLIB::ATOMIC_LOAD_2,
1469       RTLIB::ATOMIC_LOAD_4, RTLIB::ATOMIC_LOAD_8, RTLIB::ATOMIC_LOAD_16};
1470   unsigned Size = getAtomicOpSize(I);
1471   unsigned Align = getAtomicOpAlign(I);
1472
1473   bool expanded = expandAtomicOpToLibcall(
1474       I, Size, Align, I->getPointerOperand(), nullptr, nullptr,
1475       I->getOrdering(), AtomicOrdering::NotAtomic, Libcalls);
1476   (void)expanded;
1477   assert(expanded && "expandAtomicOpToLibcall shouldn't fail tor Load");
1478 }
1479
1480 void AtomicExpand::expandAtomicStoreToLibcall(StoreInst *I) {
1481   static const RTLIB::Libcall Libcalls[6] = {
1482       RTLIB::ATOMIC_STORE,   RTLIB::ATOMIC_STORE_1, RTLIB::ATOMIC_STORE_2,
1483       RTLIB::ATOMIC_STORE_4, RTLIB::ATOMIC_STORE_8, RTLIB::ATOMIC_STORE_16};
1484   unsigned Size = getAtomicOpSize(I);
1485   unsigned Align = getAtomicOpAlign(I);
1486
1487   bool expanded = expandAtomicOpToLibcall(
1488       I, Size, Align, I->getPointerOperand(), I->getValueOperand(), nullptr,
1489       I->getOrdering(), AtomicOrdering::NotAtomic, Libcalls);
1490   (void)expanded;
1491   assert(expanded && "expandAtomicOpToLibcall shouldn't fail tor Store");
1492 }
1493
1494 void AtomicExpand::expandAtomicCASToLibcall(AtomicCmpXchgInst *I) {
1495   static const RTLIB::Libcall Libcalls[6] = {
1496       RTLIB::ATOMIC_COMPARE_EXCHANGE,   RTLIB::ATOMIC_COMPARE_EXCHANGE_1,
1497       RTLIB::ATOMIC_COMPARE_EXCHANGE_2, RTLIB::ATOMIC_COMPARE_EXCHANGE_4,
1498       RTLIB::ATOMIC_COMPARE_EXCHANGE_8, RTLIB::ATOMIC_COMPARE_EXCHANGE_16};
1499   unsigned Size = getAtomicOpSize(I);
1500   unsigned Align = getAtomicOpAlign(I);
1501
1502   bool expanded = expandAtomicOpToLibcall(
1503       I, Size, Align, I->getPointerOperand(), I->getNewValOperand(),
1504       I->getCompareOperand(), I->getSuccessOrdering(), I->getFailureOrdering(),
1505       Libcalls);
1506   (void)expanded;
1507   assert(expanded && "expandAtomicOpToLibcall shouldn't fail tor CAS");
1508 }
1509
1510 static ArrayRef<RTLIB::Libcall> GetRMWLibcall(AtomicRMWInst::BinOp Op) {
1511   static const RTLIB::Libcall LibcallsXchg[6] = {
1512       RTLIB::ATOMIC_EXCHANGE,   RTLIB::ATOMIC_EXCHANGE_1,
1513       RTLIB::ATOMIC_EXCHANGE_2, RTLIB::ATOMIC_EXCHANGE_4,
1514       RTLIB::ATOMIC_EXCHANGE_8, RTLIB::ATOMIC_EXCHANGE_16};
1515   static const RTLIB::Libcall LibcallsAdd[6] = {
1516       RTLIB::UNKNOWN_LIBCALL,    RTLIB::ATOMIC_FETCH_ADD_1,
1517       RTLIB::ATOMIC_FETCH_ADD_2, RTLIB::ATOMIC_FETCH_ADD_4,
1518       RTLIB::ATOMIC_FETCH_ADD_8, RTLIB::ATOMIC_FETCH_ADD_16};
1519   static const RTLIB::Libcall LibcallsSub[6] = {
1520       RTLIB::UNKNOWN_LIBCALL,    RTLIB::ATOMIC_FETCH_SUB_1,
1521       RTLIB::ATOMIC_FETCH_SUB_2, RTLIB::ATOMIC_FETCH_SUB_4,
1522       RTLIB::ATOMIC_FETCH_SUB_8, RTLIB::ATOMIC_FETCH_SUB_16};
1523   static const RTLIB::Libcall LibcallsAnd[6] = {
1524       RTLIB::UNKNOWN_LIBCALL,    RTLIB::ATOMIC_FETCH_AND_1,
1525       RTLIB::ATOMIC_FETCH_AND_2, RTLIB::ATOMIC_FETCH_AND_4,
1526       RTLIB::ATOMIC_FETCH_AND_8, RTLIB::ATOMIC_FETCH_AND_16};
1527   static const RTLIB::Libcall LibcallsOr[6] = {
1528       RTLIB::UNKNOWN_LIBCALL,   RTLIB::ATOMIC_FETCH_OR_1,
1529       RTLIB::ATOMIC_FETCH_OR_2, RTLIB::ATOMIC_FETCH_OR_4,
1530       RTLIB::ATOMIC_FETCH_OR_8, RTLIB::ATOMIC_FETCH_OR_16};
1531   static const RTLIB::Libcall LibcallsXor[6] = {
1532       RTLIB::UNKNOWN_LIBCALL,    RTLIB::ATOMIC_FETCH_XOR_1,
1533       RTLIB::ATOMIC_FETCH_XOR_2, RTLIB::ATOMIC_FETCH_XOR_4,
1534       RTLIB::ATOMIC_FETCH_XOR_8, RTLIB::ATOMIC_FETCH_XOR_16};
1535   static const RTLIB::Libcall LibcallsNand[6] = {
1536       RTLIB::UNKNOWN_LIBCALL,     RTLIB::ATOMIC_FETCH_NAND_1,
1537       RTLIB::ATOMIC_FETCH_NAND_2, RTLIB::ATOMIC_FETCH_NAND_4,
1538       RTLIB::ATOMIC_FETCH_NAND_8, RTLIB::ATOMIC_FETCH_NAND_16};
1539
1540   switch (Op) {
1541   case AtomicRMWInst::BAD_BINOP:
1542     llvm_unreachable("Should not have BAD_BINOP.");
1543   case AtomicRMWInst::Xchg:
1544     return makeArrayRef(LibcallsXchg);
1545   case AtomicRMWInst::Add:
1546     return makeArrayRef(LibcallsAdd);
1547   case AtomicRMWInst::Sub:
1548     return makeArrayRef(LibcallsSub);
1549   case AtomicRMWInst::And:
1550     return makeArrayRef(LibcallsAnd);
1551   case AtomicRMWInst::Or:
1552     return makeArrayRef(LibcallsOr);
1553   case AtomicRMWInst::Xor:
1554     return makeArrayRef(LibcallsXor);
1555   case AtomicRMWInst::Nand:
1556     return makeArrayRef(LibcallsNand);
1557   case AtomicRMWInst::Max:
1558   case AtomicRMWInst::Min:
1559   case AtomicRMWInst::UMax:
1560   case AtomicRMWInst::UMin:
1561   case AtomicRMWInst::FAdd:
1562   case AtomicRMWInst::FSub:
1563     // No atomic libcalls are available for max/min/umax/umin.
1564     return {};
1565   }
1566   llvm_unreachable("Unexpected AtomicRMW operation.");
1567 }
1568
1569 void AtomicExpand::expandAtomicRMWToLibcall(AtomicRMWInst *I) {
1570   ArrayRef<RTLIB::Libcall> Libcalls = GetRMWLibcall(I->getOperation());
1571
1572   unsigned Size = getAtomicOpSize(I);
1573   unsigned Align = getAtomicOpAlign(I);
1574
1575   bool Success = false;
1576   if (!Libcalls.empty())
1577     Success = expandAtomicOpToLibcall(
1578         I, Size, Align, I->getPointerOperand(), I->getValOperand(), nullptr,
1579         I->getOrdering(), AtomicOrdering::NotAtomic, Libcalls);
1580
1581   // The expansion failed: either there were no libcalls at all for
1582   // the operation (min/max), or there were only size-specialized
1583   // libcalls (add/sub/etc) and we needed a generic. So, expand to a
1584   // CAS libcall, via a CAS loop, instead.
1585   if (!Success) {
1586     expandAtomicRMWToCmpXchg(I, [this](IRBuilder<> &Builder, Value *Addr,
1587                                        Value *Loaded, Value *NewVal,
1588                                        AtomicOrdering MemOpOrder,
1589                                        Value *&Success, Value *&NewLoaded) {
1590       // Create the CAS instruction normally...
1591       AtomicCmpXchgInst *Pair = Builder.CreateAtomicCmpXchg(
1592           Addr, Loaded, NewVal, MemOpOrder,
1593           AtomicCmpXchgInst::getStrongestFailureOrdering(MemOpOrder));
1594       Success = Builder.CreateExtractValue(Pair, 1, "success");
1595       NewLoaded = Builder.CreateExtractValue(Pair, 0, "newloaded");
1596
1597       // ...and then expand the CAS into a libcall.
1598       expandAtomicCASToLibcall(Pair);
1599     });
1600   }
1601 }
1602
1603 // A helper routine for the above expandAtomic*ToLibcall functions.
1604 //
1605 // 'Libcalls' contains an array of enum values for the particular
1606 // ATOMIC libcalls to be emitted. All of the other arguments besides
1607 // 'I' are extracted from the Instruction subclass by the
1608 // caller. Depending on the particular call, some will be null.
1609 bool AtomicExpand::expandAtomicOpToLibcall(
1610     Instruction *I, unsigned Size, unsigned Align, Value *PointerOperand,
1611     Value *ValueOperand, Value *CASExpected, AtomicOrdering Ordering,
1612     AtomicOrdering Ordering2, ArrayRef<RTLIB::Libcall> Libcalls) {
1613   assert(Libcalls.size() == 6);
1614
1615   LLVMContext &Ctx = I->getContext();
1616   Module *M = I->getModule();
1617   const DataLayout &DL = M->getDataLayout();
1618   IRBuilder<> Builder(I);
1619   IRBuilder<> AllocaBuilder(&I->getFunction()->getEntryBlock().front());
1620
1621   bool UseSizedLibcall = canUseSizedAtomicCall(Size, Align, DL);
1622   Type *SizedIntTy = Type::getIntNTy(Ctx, Size * 8);
1623
1624   unsigned AllocaAlignment = DL.getPrefTypeAlignment(SizedIntTy);
1625
1626   // TODO: the "order" argument type is "int", not int32. So
1627   // getInt32Ty may be wrong if the arch uses e.g. 16-bit ints.
1628   ConstantInt *SizeVal64 = ConstantInt::get(Type::getInt64Ty(Ctx), Size);
1629   assert(Ordering != AtomicOrdering::NotAtomic && "expect atomic MO");
1630   Constant *OrderingVal =
1631       ConstantInt::get(Type::getInt32Ty(Ctx), (int)toCABI(Ordering));
1632   Constant *Ordering2Val = nullptr;
1633   if (CASExpected) {
1634     assert(Ordering2 != AtomicOrdering::NotAtomic && "expect atomic MO");
1635     Ordering2Val =
1636         ConstantInt::get(Type::getInt32Ty(Ctx), (int)toCABI(Ordering2));
1637   }
1638   bool HasResult = I->getType() != Type::getVoidTy(Ctx);
1639
1640   RTLIB::Libcall RTLibType;
1641   if (UseSizedLibcall) {
1642     switch (Size) {
1643     case 1: RTLibType = Libcalls[1]; break;
1644     case 2: RTLibType = Libcalls[2]; break;
1645     case 4: RTLibType = Libcalls[3]; break;
1646     case 8: RTLibType = Libcalls[4]; break;
1647     case 16: RTLibType = Libcalls[5]; break;
1648     }
1649   } else if (Libcalls[0] != RTLIB::UNKNOWN_LIBCALL) {
1650     RTLibType = Libcalls[0];
1651   } else {
1652     // Can't use sized function, and there's no generic for this
1653     // operation, so give up.
1654     return false;
1655   }
1656
1657   // Build up the function call. There's two kinds. First, the sized
1658   // variants.  These calls are going to be one of the following (with
1659   // N=1,2,4,8,16):
1660   //  iN    __atomic_load_N(iN *ptr, int ordering)
1661   //  void  __atomic_store_N(iN *ptr, iN val, int ordering)
1662   //  iN    __atomic_{exchange|fetch_*}_N(iN *ptr, iN val, int ordering)
1663   //  bool  __atomic_compare_exchange_N(iN *ptr, iN *expected, iN desired,
1664   //                                    int success_order, int failure_order)
1665   //
1666   // Note that these functions can be used for non-integer atomic
1667   // operations, the values just need to be bitcast to integers on the
1668   // way in and out.
1669   //
1670   // And, then, the generic variants. They look like the following:
1671   //  void  __atomic_load(size_t size, void *ptr, void *ret, int ordering)
1672   //  void  __atomic_store(size_t size, void *ptr, void *val, int ordering)
1673   //  void  __atomic_exchange(size_t size, void *ptr, void *val, void *ret,
1674   //                          int ordering)
1675   //  bool  __atomic_compare_exchange(size_t size, void *ptr, void *expected,
1676   //                                  void *desired, int success_order,
1677   //                                  int failure_order)
1678   //
1679   // The different signatures are built up depending on the
1680   // 'UseSizedLibcall', 'CASExpected', 'ValueOperand', and 'HasResult'
1681   // variables.
1682
1683   AllocaInst *AllocaCASExpected = nullptr;
1684   Value *AllocaCASExpected_i8 = nullptr;
1685   AllocaInst *AllocaValue = nullptr;
1686   Value *AllocaValue_i8 = nullptr;
1687   AllocaInst *AllocaResult = nullptr;
1688   Value *AllocaResult_i8 = nullptr;
1689
1690   Type *ResultTy;
1691   SmallVector<Value *, 6> Args;
1692   AttributeList Attr;
1693
1694   // 'size' argument.
1695   if (!UseSizedLibcall) {
1696     // Note, getIntPtrType is assumed equivalent to size_t.
1697     Args.push_back(ConstantInt::get(DL.getIntPtrType(Ctx), Size));
1698   }
1699
1700   // 'ptr' argument.
1701   // note: This assumes all address spaces share a common libfunc
1702   // implementation and that addresses are convertable.  For systems without
1703   // that property, we'd need to extend this mechanism to support AS-specific
1704   // families of atomic intrinsics.
1705   auto PtrTypeAS = PointerOperand->getType()->getPointerAddressSpace();
1706   Value *PtrVal = Builder.CreateBitCast(PointerOperand,
1707                                         Type::getInt8PtrTy(Ctx, PtrTypeAS));
1708   PtrVal = Builder.CreateAddrSpaceCast(PtrVal, Type::getInt8PtrTy(Ctx));
1709   Args.push_back(PtrVal);
1710
1711   // 'expected' argument, if present.
1712   if (CASExpected) {
1713     AllocaCASExpected = AllocaBuilder.CreateAlloca(CASExpected->getType());
1714     AllocaCASExpected->setAlignment(MaybeAlign(AllocaAlignment));
1715     unsigned AllocaAS =  AllocaCASExpected->getType()->getPointerAddressSpace();
1716
1717     AllocaCASExpected_i8 =
1718       Builder.CreateBitCast(AllocaCASExpected,
1719                             Type::getInt8PtrTy(Ctx, AllocaAS));
1720     Builder.CreateLifetimeStart(AllocaCASExpected_i8, SizeVal64);
1721     Builder.CreateAlignedStore(CASExpected, AllocaCASExpected, AllocaAlignment);
1722     Args.push_back(AllocaCASExpected_i8);
1723   }
1724
1725   // 'val' argument ('desired' for cas), if present.
1726   if (ValueOperand) {
1727     if (UseSizedLibcall) {
1728       Value *IntValue =
1729           Builder.CreateBitOrPointerCast(ValueOperand, SizedIntTy);
1730       Args.push_back(IntValue);
1731     } else {
1732       AllocaValue = AllocaBuilder.CreateAlloca(ValueOperand->getType());
1733       AllocaValue->setAlignment(MaybeAlign(AllocaAlignment));
1734       AllocaValue_i8 =
1735           Builder.CreateBitCast(AllocaValue, Type::getInt8PtrTy(Ctx));
1736       Builder.CreateLifetimeStart(AllocaValue_i8, SizeVal64);
1737       Builder.CreateAlignedStore(ValueOperand, AllocaValue, AllocaAlignment);
1738       Args.push_back(AllocaValue_i8);
1739     }
1740   }
1741
1742   // 'ret' argument.
1743   if (!CASExpected && HasResult && !UseSizedLibcall) {
1744     AllocaResult = AllocaBuilder.CreateAlloca(I->getType());
1745     AllocaResult->setAlignment(MaybeAlign(AllocaAlignment));
1746     unsigned AllocaAS =  AllocaResult->getType()->getPointerAddressSpace();
1747     AllocaResult_i8 =
1748       Builder.CreateBitCast(AllocaResult, Type::getInt8PtrTy(Ctx, AllocaAS));
1749     Builder.CreateLifetimeStart(AllocaResult_i8, SizeVal64);
1750     Args.push_back(AllocaResult_i8);
1751   }
1752
1753   // 'ordering' ('success_order' for cas) argument.
1754   Args.push_back(OrderingVal);
1755
1756   // 'failure_order' argument, if present.
1757   if (Ordering2Val)
1758     Args.push_back(Ordering2Val);
1759
1760   // Now, the return type.
1761   if (CASExpected) {
1762     ResultTy = Type::getInt1Ty(Ctx);
1763     Attr = Attr.addAttribute(Ctx, AttributeList::ReturnIndex, Attribute::ZExt);
1764   } else if (HasResult && UseSizedLibcall)
1765     ResultTy = SizedIntTy;
1766   else
1767     ResultTy = Type::getVoidTy(Ctx);
1768
1769   // Done with setting up arguments and return types, create the call:
1770   SmallVector<Type *, 6> ArgTys;
1771   for (Value *Arg : Args)
1772     ArgTys.push_back(Arg->getType());
1773   FunctionType *FnType = FunctionType::get(ResultTy, ArgTys, false);
1774   FunctionCallee LibcallFn =
1775       M->getOrInsertFunction(TLI->getLibcallName(RTLibType), FnType, Attr);
1776   CallInst *Call = Builder.CreateCall(LibcallFn, Args);
1777   Call->setAttributes(Attr);
1778   Value *Result = Call;
1779
1780   // And then, extract the results...
1781   if (ValueOperand && !UseSizedLibcall)
1782     Builder.CreateLifetimeEnd(AllocaValue_i8, SizeVal64);
1783
1784   if (CASExpected) {
1785     // The final result from the CAS is {load of 'expected' alloca, bool result
1786     // from call}
1787     Type *FinalResultTy = I->getType();
1788     Value *V = UndefValue::get(FinalResultTy);
1789     Value *ExpectedOut = Builder.CreateAlignedLoad(
1790         CASExpected->getType(), AllocaCASExpected, AllocaAlignment);
1791     Builder.CreateLifetimeEnd(AllocaCASExpected_i8, SizeVal64);
1792     V = Builder.CreateInsertValue(V, ExpectedOut, 0);
1793     V = Builder.CreateInsertValue(V, Result, 1);
1794     I->replaceAllUsesWith(V);
1795   } else if (HasResult) {
1796     Value *V;
1797     if (UseSizedLibcall)
1798       V = Builder.CreateBitOrPointerCast(Result, I->getType());
1799     else {
1800       V = Builder.CreateAlignedLoad(I->getType(), AllocaResult,
1801                                     AllocaAlignment);
1802       Builder.CreateLifetimeEnd(AllocaResult_i8, SizeVal64);
1803     }
1804     I->replaceAllUsesWith(V);
1805   }
1806   I->eraseFromParent();
1807   return true;
1808 }