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| 1 | +//===--- Atomic.h - Shared codegen of atomic operations -------------------===// |
| 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 | +#ifndef LLVM_FRONTEND_ATOMIC_ATOMIC_H |
| 10 | +#define LLVM_FRONTEND_ATOMIC_ATOMIC_H |
| 11 | + |
| 12 | +#include "llvm/ADT/DenseMap.h" |
| 13 | +#include "llvm/CodeGen/RuntimeLibcalls.h" |
| 14 | +#include "llvm/IR/DataLayout.h" |
| 15 | +#include "llvm/IR/Instructions.h" |
| 16 | +#include "llvm/IR/Intrinsics.h" |
| 17 | +#include "llvm/IR/Module.h" |
| 18 | +#include "llvm/IR/Operator.h" |
| 19 | + |
| 20 | +namespace llvm { |
| 21 | + |
| 22 | +template <typename IRBuilderTy> struct AtomicInfo { |
| 23 | + IRBuilderTy *Builder; |
| 24 | + |
| 25 | + Type *Ty; |
| 26 | + uint64_t AtomicSizeInBits; |
| 27 | + uint64_t ValueSizeInBits; |
| 28 | + llvm::Align AtomicAlign; |
| 29 | + llvm::Align ValueAlign; |
| 30 | + bool UseLibcall; |
| 31 | + |
| 32 | +public: |
| 33 | + AtomicInfo(IRBuilderTy *Builder, Type *Ty, uint64_t AtomicSizeInBits, |
| 34 | + uint64_t ValueSizeInBits, llvm::Align AtomicAlign, |
| 35 | + llvm::Align ValueAlign, bool UseLibcall) |
| 36 | + : Builder(Builder), Ty(Ty), AtomicSizeInBits(AtomicSizeInBits), |
| 37 | + ValueSizeInBits(ValueSizeInBits), AtomicAlign(AtomicAlign), |
| 38 | + ValueAlign(ValueAlign), UseLibcall(UseLibcall) {} |
| 39 | + |
| 40 | + virtual ~AtomicInfo() = default; |
| 41 | + |
| 42 | + llvm::Align getAtomicAlignment() const { return AtomicAlign; } |
| 43 | + uint64_t getAtomicSizeInBits() const { return AtomicSizeInBits; } |
| 44 | + uint64_t getValueSizeInBits() const { return ValueSizeInBits; } |
| 45 | + bool shouldUseLibcall() const { return UseLibcall; } |
| 46 | + llvm::Type *getAtomicTy() const { return Ty; } |
| 47 | + |
| 48 | + virtual llvm::Value *getAtomicPointer() const = 0; |
| 49 | + virtual void decorateWithTBAA(Instruction *I) {} |
| 50 | + virtual llvm::AllocaInst *CreateAlloca(llvm::Type *Ty, |
| 51 | + const llvm::Twine &Name) = 0; |
| 52 | + |
| 53 | + /// Is the atomic size larger than the underlying value type? |
| 54 | + /// |
| 55 | + /// Note that the absence of padding does not mean that atomic |
| 56 | + /// objects are completely interchangeable with non-atomic |
| 57 | + /// objects: we might have promoted the alignment of a type |
| 58 | + /// without making it bigger. |
| 59 | + bool hasPadding() const { return (ValueSizeInBits != AtomicSizeInBits); } |
| 60 | + |
| 61 | + LLVMContext &getLLVMContext() const { return Builder->getContext(); } |
| 62 | + |
| 63 | + static bool shouldCastToInt(llvm::Type *ValTy, bool CmpXchg) { |
| 64 | + if (ValTy->isFloatingPointTy()) |
| 65 | + return ValTy->isX86_FP80Ty() || CmpXchg; |
| 66 | + return !ValTy->isIntegerTy() && !ValTy->isPointerTy(); |
| 67 | + } |
| 68 | + |
| 69 | + llvm::Value *EmitAtomicLoadOp(llvm::AtomicOrdering AO, bool IsVolatile, |
| 70 | + bool CmpXchg = false) { |
| 71 | + Value *Ptr = getAtomicPointer(); |
| 72 | + Type *AtomicTy = Ty; |
| 73 | + if (shouldCastToInt(Ty, CmpXchg)) |
| 74 | + AtomicTy = llvm::IntegerType::get(getLLVMContext(), AtomicSizeInBits); |
| 75 | + LoadInst *Load = |
| 76 | + Builder->CreateAlignedLoad(AtomicTy, Ptr, AtomicAlign, "atomic-load"); |
| 77 | + Load->setAtomic(AO); |
| 78 | + |
| 79 | + // Other decoration. |
| 80 | + if (IsVolatile) |
| 81 | + Load->setVolatile(true); |
| 82 | + decorateWithTBAA(Load); |
| 83 | + return Load; |
| 84 | + } |
| 85 | + |
| 86 | + static CallInst *emitAtomicLibcalls2(IRBuilderTy *Builder, StringRef fnName, |
| 87 | + Type *ResultType, |
| 88 | + ArrayRef<Value *> Args) { |
| 89 | + auto &C = Builder->getContext(); |
| 90 | + |
| 91 | + SmallVector<Type *, 6> ArgTys; |
| 92 | + for (Value *Arg : Args) |
| 93 | + ArgTys.push_back(Arg->getType()); |
| 94 | + FunctionType *FnType = FunctionType::get(ResultType, ArgTys, false); |
| 95 | + Module *M = Builder->GetInsertBlock()->getModule(); |
| 96 | + |
| 97 | + // TODO: Use llvm::TargetLowering for Libcall ABI |
| 98 | + llvm::AttrBuilder fnAttrB(C); |
| 99 | + fnAttrB.addAttribute(llvm::Attribute::NoUnwind); |
| 100 | + fnAttrB.addAttribute(llvm::Attribute::WillReturn); |
| 101 | + llvm::AttributeList fnAttrs = llvm::AttributeList::get( |
| 102 | + C, llvm::AttributeList::FunctionIndex, fnAttrB); |
| 103 | + FunctionCallee LibcallFn = M->getOrInsertFunction(fnName, FnType, fnAttrs); |
| 104 | + CallInst *Call = Builder->CreateCall(LibcallFn, Args); |
| 105 | + |
| 106 | + return Call; |
| 107 | + } |
| 108 | + |
| 109 | + llvm::Value *getAtomicSizeValue() const { |
| 110 | + auto &C = getLLVMContext(); |
| 111 | + |
| 112 | + // TODO: Get from llvm::TargetMachine / clang::TargetInfo |
| 113 | + uint16_t SizeTBits = 64; |
| 114 | + uint16_t BitsPerByte = 8; |
| 115 | + return llvm::ConstantInt::get(llvm::IntegerType::get(C, SizeTBits), |
| 116 | + AtomicSizeInBits / BitsPerByte); |
| 117 | + } |
| 118 | + |
| 119 | + std::pair<llvm::Value *, llvm::Value *> EmitAtomicCompareExchangeLibcall( |
| 120 | + llvm::Value *ExpectedVal, llvm::Value *DesiredVal, |
| 121 | + llvm::AtomicOrdering Success, llvm::AtomicOrdering Failure) { |
| 122 | + auto &C = getLLVMContext(); |
| 123 | + |
| 124 | + // __atomic_compare_exchange's expected and desired are passed by pointers |
| 125 | + // FIXME: types |
| 126 | + |
| 127 | + // TODO: Get from llvm::TargetMachine / clang::TargetInfo |
| 128 | + uint64_t IntBits = 32; |
| 129 | + |
| 130 | + // bool __atomic_compare_exchange(size_t size, void *obj, void *expected, |
| 131 | + // void *desired, int success, int failure); |
| 132 | + llvm::Value *Args[6] = { |
| 133 | + getAtomicSizeValue(), |
| 134 | + getAtomicPointer(), |
| 135 | + ExpectedVal, |
| 136 | + DesiredVal, |
| 137 | + llvm::Constant::getIntegerValue( |
| 138 | + llvm::IntegerType::get(C, IntBits), |
| 139 | + llvm::APInt(IntBits, (uint64_t)Success, /*signed=*/true)), |
| 140 | + llvm::Constant::getIntegerValue( |
| 141 | + llvm::IntegerType::get(C, IntBits), |
| 142 | + llvm::APInt(IntBits, (uint64_t)Failure, /*signed=*/true)), |
| 143 | + }; |
| 144 | + auto Res = emitAtomicLibcalls2(Builder, "__atomic_compare_exchange", |
| 145 | + llvm::IntegerType::getInt1Ty(C), Args); |
| 146 | + return std::make_pair(ExpectedVal, Res); |
| 147 | + } |
| 148 | + |
| 149 | + Value *castToAtomicIntPointer(Value *addr) const { |
| 150 | + return addr; // opaque pointer |
| 151 | + } |
| 152 | + |
| 153 | + Value *getAtomicAddressAsAtomicIntPointer() const { |
| 154 | + return castToAtomicIntPointer(getAtomicPointer()); |
| 155 | + } |
| 156 | + |
| 157 | + std::pair<llvm::Value *, llvm::Value *> |
| 158 | + EmitAtomicCompareExchangeOp(llvm::Value *ExpectedVal, llvm::Value *DesiredVal, |
| 159 | + llvm::AtomicOrdering Success, |
| 160 | + llvm::AtomicOrdering Failure, |
| 161 | + bool IsVolatile = false, bool IsWeak = false) { |
| 162 | + // Do the atomic store. |
| 163 | + Value *Addr = getAtomicAddressAsAtomicIntPointer(); |
| 164 | + auto *Inst = Builder->CreateAtomicCmpXchg(Addr, ExpectedVal, DesiredVal, |
| 165 | + getAtomicAlignment(), Success, |
| 166 | + Failure, llvm::SyncScope::System); |
| 167 | + // Other decoration. |
| 168 | + Inst->setVolatile(IsVolatile); |
| 169 | + Inst->setWeak(IsWeak); |
| 170 | + |
| 171 | + // Okay, turn that back into the original value type. |
| 172 | + auto *PreviousVal = Builder->CreateExtractValue(Inst, /*Idxs=*/0); |
| 173 | + auto *SuccessFailureVal = Builder->CreateExtractValue(Inst, /*Idxs=*/1); |
| 174 | + return std::make_pair(PreviousVal, SuccessFailureVal); |
| 175 | + } |
| 176 | + |
| 177 | + std::pair<llvm::Value *, llvm::Value *> |
| 178 | + EmitAtomicCompareExchange(llvm::Value *ExpectedVal, llvm::Value *DesiredVal, |
| 179 | + llvm::AtomicOrdering Success, |
| 180 | + llvm::AtomicOrdering Failure, bool IsVolatile, |
| 181 | + bool IsWeak) { |
| 182 | + |
| 183 | + // Check whether we should use a library call. |
| 184 | + if (shouldUseLibcall()) { |
| 185 | + return EmitAtomicCompareExchangeLibcall(ExpectedVal, DesiredVal, Success, |
| 186 | + Failure); |
| 187 | + } |
| 188 | + |
| 189 | + // If we've got a scalar value of the right size, try to avoid going |
| 190 | + // through memory. |
| 191 | + auto Res = EmitAtomicCompareExchangeOp(ExpectedVal, DesiredVal, Success, |
| 192 | + Failure, IsVolatile, IsWeak); |
| 193 | + return Res; |
| 194 | + } |
| 195 | + |
| 196 | + // void __atomic_load(size_t size, void *mem, void *return, int order); |
| 197 | + std::pair<llvm::LoadInst *, llvm::AllocaInst *> |
| 198 | + EmitAtomicLoadLibcall(llvm::AtomicOrdering AO) { |
| 199 | + LLVMContext &Ctx = getLLVMContext(); |
| 200 | + Type *SizedIntTy = Type::getIntNTy(Ctx, getAtomicSizeInBits() * 8); |
| 201 | + Type *ResultTy; |
| 202 | + SmallVector<Value *, 6> Args; |
| 203 | + AttributeList Attr; |
| 204 | + Module *M = Builder->GetInsertBlock()->getModule(); |
| 205 | + const DataLayout &DL = M->getDataLayout(); |
| 206 | + Args.push_back(ConstantInt::get(DL.getIntPtrType(Ctx), |
| 207 | + this->getAtomicSizeInBits() / 8)); |
| 208 | + Value *PtrVal = getAtomicPointer(); |
| 209 | + PtrVal = Builder->CreateAddrSpaceCast(PtrVal, PointerType::getUnqual(Ctx)); |
| 210 | + Args.push_back(PtrVal); |
| 211 | + AllocaInst *AllocaResult = |
| 212 | + CreateAlloca(Ty, getAtomicPointer()->getName() + "atomic.temp.load"); |
| 213 | + const Align AllocaAlignment = DL.getPrefTypeAlign(SizedIntTy); |
| 214 | + AllocaResult->setAlignment(AllocaAlignment); |
| 215 | + Args.push_back(AllocaResult); |
| 216 | + Constant *OrderingVal = |
| 217 | + ConstantInt::get(Type::getInt32Ty(Ctx), (int)toCABI(AO)); |
| 218 | + Args.push_back(OrderingVal); |
| 219 | + ResultTy = Type::getVoidTy(Ctx); |
| 220 | + SmallVector<Type *, 6> ArgTys; |
| 221 | + for (Value *Arg : Args) |
| 222 | + ArgTys.push_back(Arg->getType()); |
| 223 | + FunctionType *FnType = FunctionType::get(ResultTy, ArgTys, false); |
| 224 | + FunctionCallee LibcallFn = |
| 225 | + M->getOrInsertFunction("__atomic_load", FnType, Attr); |
| 226 | + CallInst *Call = Builder->CreateCall(LibcallFn, Args); |
| 227 | + Call->setAttributes(Attr); |
| 228 | + return std::make_pair( |
| 229 | + Builder->CreateAlignedLoad(Ty, AllocaResult, AllocaAlignment), |
| 230 | + AllocaResult); |
| 231 | + } |
| 232 | +}; |
| 233 | +} // end namespace llvm |
| 234 | + |
| 235 | +#endif /* LLVM_FRONTEND_ATOMIC_ATOMIC_H */ |
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