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jhuber6jhuber6
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[Clang] Add support for scoped atomic thread fence (#115545)
Summary: Previously we added support for all of the atomic GNU extensions with optional memory scoped except for `__atomic_thread_fence`. This patch adds support for that. This should ideally allow us to generically emit these LLVM scopes.
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‎clang/include/clang/Basic/Builtins.td

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@@ -1995,6 +1995,12 @@ def AtomicThreadFence : Builtin {
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let Prototype = "void(int)";
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}
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def ScopedAtomicThreadFence : Builtin {
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let Spellings = ["__scoped_atomic_thread_fence"];
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let Attributes = [NoThrow];
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let Prototype = "void(int, int)";
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}
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def AtomicSignalFence : Builtin {
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let Spellings = ["__atomic_signal_fence"];
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let Attributes = [NoThrow];

‎clang/lib/CodeGen/CGBuiltin.cpp

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Original file line numberDiff line numberDiff line change
@@ -5213,6 +5213,136 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
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Builder.SetInsertPoint(ContBB);
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return RValue::get(nullptr);
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}
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case Builtin::BI__scoped_atomic_thread_fence: {
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auto ScopeModel = AtomicScopeModel::create(AtomicScopeModelKind::Generic);
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Value *Order = EmitScalarExpr(E->getArg(0));
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Value *Scope = EmitScalarExpr(E->getArg(1));
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auto Ord = dyn_cast<llvm::ConstantInt>(Order);
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auto Scp = dyn_cast<llvm::ConstantInt>(Scope);
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if (Ord && Scp) {
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SyncScope SS = ScopeModel->isValid(Scp->getZExtValue())
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? ScopeModel->map(Scp->getZExtValue())
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: ScopeModel->map(ScopeModel->getFallBackValue());
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switch (Ord->getZExtValue()) {
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case 0: // memory_order_relaxed
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default: // invalid order
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break;
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case 1: // memory_order_consume
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case 2: // memory_order_acquire
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Builder.CreateFence(
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llvm::AtomicOrdering::Acquire,
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getTargetHooks().getLLVMSyncScopeID(getLangOpts(), SS,
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llvm::AtomicOrdering::Acquire,
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getLLVMContext()));
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break;
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case 3: // memory_order_release
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Builder.CreateFence(
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llvm::AtomicOrdering::Release,
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getTargetHooks().getLLVMSyncScopeID(getLangOpts(), SS,
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llvm::AtomicOrdering::Release,
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getLLVMContext()));
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break;
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case 4: // memory_order_acq_rel
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Builder.CreateFence(llvm::AtomicOrdering::AcquireRelease,
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getTargetHooks().getLLVMSyncScopeID(
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getLangOpts(), SS,
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llvm::AtomicOrdering::AcquireRelease,
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getLLVMContext()));
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break;
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case 5: // memory_order_seq_cst
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Builder.CreateFence(llvm::AtomicOrdering::SequentiallyConsistent,
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getTargetHooks().getLLVMSyncScopeID(
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getLangOpts(), SS,
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llvm::AtomicOrdering::SequentiallyConsistent,
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getLLVMContext()));
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break;
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}
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return RValue::get(nullptr);
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}
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llvm::BasicBlock *ContBB = createBasicBlock("atomic.scope.continue", CurFn);
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llvm::SmallVector<std::pair<llvm::BasicBlock *, llvm::AtomicOrdering>>
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OrderBBs;
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if (Ord) {
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switch (Ord->getZExtValue()) {
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case 0: // memory_order_relaxed
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default: // invalid order
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ContBB->eraseFromParent();
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return RValue::get(nullptr);
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case 1: // memory_order_consume
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case 2: // memory_order_acquire
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OrderBBs.emplace_back(Builder.GetInsertBlock(),
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llvm::AtomicOrdering::Acquire);
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break;
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case 3: // memory_order_release
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OrderBBs.emplace_back(Builder.GetInsertBlock(),
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llvm::AtomicOrdering::Release);
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break;
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case 4: // memory_order_acq_rel
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OrderBBs.emplace_back(Builder.GetInsertBlock(),
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llvm::AtomicOrdering::AcquireRelease);
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break;
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case 5: // memory_order_seq_cst
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OrderBBs.emplace_back(Builder.GetInsertBlock(),
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llvm::AtomicOrdering::SequentiallyConsistent);
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break;
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}
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} else {
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llvm::BasicBlock *AcquireBB = createBasicBlock("acquire", CurFn);
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llvm::BasicBlock *ReleaseBB = createBasicBlock("release", CurFn);
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llvm::BasicBlock *AcqRelBB = createBasicBlock("acqrel", CurFn);
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llvm::BasicBlock *SeqCstBB = createBasicBlock("seqcst", CurFn);
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Order = Builder.CreateIntCast(Order, Builder.getInt32Ty(), false);
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llvm::SwitchInst *SI = Builder.CreateSwitch(Order, ContBB);
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SI->addCase(Builder.getInt32(1), AcquireBB);
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SI->addCase(Builder.getInt32(2), AcquireBB);
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SI->addCase(Builder.getInt32(3), ReleaseBB);
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SI->addCase(Builder.getInt32(4), AcqRelBB);
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SI->addCase(Builder.getInt32(5), SeqCstBB);
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OrderBBs.emplace_back(AcquireBB, llvm::AtomicOrdering::Acquire);
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OrderBBs.emplace_back(ReleaseBB, llvm::AtomicOrdering::Release);
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OrderBBs.emplace_back(AcqRelBB, llvm::AtomicOrdering::AcquireRelease);
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OrderBBs.emplace_back(SeqCstBB,
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llvm::AtomicOrdering::SequentiallyConsistent);
5311+
}
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5313+
for (auto &[OrderBB, Ordering] : OrderBBs) {
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Builder.SetInsertPoint(OrderBB);
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if (Scp) {
5316+
SyncScope SS = ScopeModel->isValid(Scp->getZExtValue())
5317+
? ScopeModel->map(Scp->getZExtValue())
5318+
: ScopeModel->map(ScopeModel->getFallBackValue());
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Builder.CreateFence(Ordering,
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getTargetHooks().getLLVMSyncScopeID(
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getLangOpts(), SS, Ordering, getLLVMContext()));
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Builder.CreateBr(ContBB);
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} else {
5324+
llvm::DenseMap<unsigned, llvm::BasicBlock *> BBs;
5325+
for (unsigned Scp : ScopeModel->getRuntimeValues())
5326+
BBs[Scp] = createBasicBlock(getAsString(ScopeModel->map(Scp)), CurFn);
5327+
5328+
auto *SC = Builder.CreateIntCast(Scope, Builder.getInt32Ty(), false);
5329+
llvm::SwitchInst *SI = Builder.CreateSwitch(SC, ContBB);
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for (unsigned Scp : ScopeModel->getRuntimeValues()) {
5331+
auto *B = BBs[Scp];
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SI->addCase(Builder.getInt32(Scp), B);
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5334+
Builder.SetInsertPoint(B);
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Builder.CreateFence(Ordering, getTargetHooks().getLLVMSyncScopeID(
5336+
getLangOpts(), ScopeModel->map(Scp),
5337+
Ordering, getLLVMContext()));
5338+
Builder.CreateBr(ContBB);
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}
5340+
}
5341+
}
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5343+
Builder.SetInsertPoint(ContBB);
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return RValue::get(nullptr);
5345+
}
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case Builtin::BI__builtin_signbit:
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case Builtin::BI__builtin_signbitf:

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