diff options
author | Dimitry Andric <dim@FreeBSD.org> | 2017-04-16 16:02:28 +0000 |
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committer | Dimitry Andric <dim@FreeBSD.org> | 2017-04-16 16:02:28 +0000 |
commit | 7442d6faa2719e4e7d33a7021c406c5a4facd74d (patch) | |
tree | c72b9241553fc9966179aba84f90f17bfa9235c3 /lib/CodeGen/CGCoroutine.cpp | |
parent | b52119637f743680a99710ce5fdb6646da2772af (diff) |
Notes
Diffstat (limited to 'lib/CodeGen/CGCoroutine.cpp')
-rw-r--r-- | lib/CodeGen/CGCoroutine.cpp | 277 |
1 files changed, 269 insertions, 8 deletions
diff --git a/lib/CodeGen/CGCoroutine.cpp b/lib/CodeGen/CGCoroutine.cpp index 2fdb1279ece97..0ef680ef66092 100644 --- a/lib/CodeGen/CGCoroutine.cpp +++ b/lib/CodeGen/CGCoroutine.cpp @@ -12,28 +12,58 @@ //===----------------------------------------------------------------------===// #include "CodeGenFunction.h" +#include "llvm/ADT/ScopeExit.h" #include "clang/AST/StmtCXX.h" using namespace clang; using namespace CodeGen; -namespace clang { -namespace CodeGen { +using llvm::Value; +using llvm::BasicBlock; + +namespace { +enum class AwaitKind { Init, Normal, Yield, Final }; +static constexpr llvm::StringLiteral AwaitKindStr[] = {"init", "await", "yield", + "final"}; +} + +struct clang::CodeGen::CGCoroData { + // What is the current await expression kind and how many + // await/yield expressions were encountered so far. + // These are used to generate pretty labels for await expressions in LLVM IR. + AwaitKind CurrentAwaitKind = AwaitKind::Init; + unsigned AwaitNum = 0; + unsigned YieldNum = 0; + + // How many co_return statements are in the coroutine. Used to decide whether + // we need to add co_return; equivalent at the end of the user authored body. + unsigned CoreturnCount = 0; + + // A branch to this block is emitted when coroutine needs to suspend. + llvm::BasicBlock *SuspendBB = nullptr; + + // Stores the jump destination just before the coroutine memory is freed. + // This is the destination that every suspend point jumps to for the cleanup + // branch. + CodeGenFunction::JumpDest CleanupJD; + + // Stores the jump destination just before the final suspend. The co_return + // statements jumps to this point after calling return_xxx promise member. + CodeGenFunction::JumpDest FinalJD; -struct CGCoroData { // Stores the llvm.coro.id emitted in the function so that we can supply it // as the first argument to coro.begin, coro.alloc and coro.free intrinsics. // Note: llvm.coro.id returns a token that cannot be directly expressed in a // builtin. llvm::CallInst *CoroId = nullptr; + // If coro.id came from the builtin, remember the expression to give better // diagnostic. If CoroIdExpr is nullptr, the coro.id was created by // EmitCoroutineBody. CallExpr const *CoroIdExpr = nullptr; }; -} -} +// Defining these here allows to keep CGCoroData private to this file. clang::CodeGen::CodeGenFunction::CGCoroInfo::CGCoroInfo() {} CodeGenFunction::CGCoroInfo::~CGCoroInfo() {} @@ -59,19 +89,250 @@ static void createCoroData(CodeGenFunction &CGF, CurCoro.Data->CoroIdExpr = CoroIdExpr; } +// Synthesize a pretty name for a suspend point. +static SmallString<32> buildSuspendPrefixStr(CGCoroData &Coro, AwaitKind Kind) { + unsigned No = 0; + switch (Kind) { + case AwaitKind::Init: + case AwaitKind::Final: + break; + case AwaitKind::Normal: + No = ++Coro.AwaitNum; + break; + case AwaitKind::Yield: + No = ++Coro.YieldNum; + break; + } + SmallString<32> Prefix(AwaitKindStr[static_cast<unsigned>(Kind)]); + if (No > 1) { + Twine(No).toVector(Prefix); + } + return Prefix; +} + +// Emit suspend expression which roughly looks like: +// +// auto && x = CommonExpr(); +// if (!x.await_ready()) { +// llvm_coro_save(); +// x.await_suspend(...); (*) +// llvm_coro_suspend(); (**) +// } +// x.await_resume(); +// +// where the result of the entire expression is the result of x.await_resume() +// +// (*) If x.await_suspend return type is bool, it allows to veto a suspend: +// if (x.await_suspend(...)) +// llvm_coro_suspend(); +// +// (**) llvm_coro_suspend() encodes three possible continuations as +// a switch instruction: +// +// %where-to = call i8 @llvm.coro.suspend(...) +// switch i8 %where-to, label %coro.ret [ ; jump to epilogue to suspend +// i8 0, label %yield.ready ; go here when resumed +// i8 1, label %yield.cleanup ; go here when destroyed +// ] +// +// See llvm's docs/Coroutines.rst for more details. +// +static RValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Coro, + CoroutineSuspendExpr const &S, + AwaitKind Kind, AggValueSlot aggSlot, + bool ignoreResult) { + auto *E = S.getCommonExpr(); + auto Binder = + CodeGenFunction::OpaqueValueMappingData::bind(CGF, S.getOpaqueValue(), E); + auto UnbindOnExit = llvm::make_scope_exit([&] { Binder.unbind(CGF); }); + + auto Prefix = buildSuspendPrefixStr(Coro, Kind); + BasicBlock *ReadyBlock = CGF.createBasicBlock(Prefix + Twine(".ready")); + BasicBlock *SuspendBlock = CGF.createBasicBlock(Prefix + Twine(".suspend")); + BasicBlock *CleanupBlock = CGF.createBasicBlock(Prefix + Twine(".cleanup")); + + // If expression is ready, no need to suspend. + CGF.EmitBranchOnBoolExpr(S.getReadyExpr(), ReadyBlock, SuspendBlock, 0); + + // Otherwise, emit suspend logic. + CGF.EmitBlock(SuspendBlock); + + auto &Builder = CGF.Builder; + llvm::Function *CoroSave = CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_save); + auto *NullPtr = llvm::ConstantPointerNull::get(CGF.CGM.Int8PtrTy); + auto *SaveCall = Builder.CreateCall(CoroSave, {NullPtr}); + + auto *SuspendRet = CGF.EmitScalarExpr(S.getSuspendExpr()); + if (SuspendRet != nullptr) { + // Veto suspension if requested by bool returning await_suspend. + assert(SuspendRet->getType()->isIntegerTy(1) && + "Sema should have already checked that it is void or bool"); + BasicBlock *RealSuspendBlock = + CGF.createBasicBlock(Prefix + Twine(".suspend.bool")); + CGF.Builder.CreateCondBr(SuspendRet, RealSuspendBlock, ReadyBlock); + SuspendBlock = RealSuspendBlock; + CGF.EmitBlock(RealSuspendBlock); + } + + // Emit the suspend point. + const bool IsFinalSuspend = (Kind == AwaitKind::Final); + llvm::Function *CoroSuspend = + CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_suspend); + auto *SuspendResult = Builder.CreateCall( + CoroSuspend, {SaveCall, Builder.getInt1(IsFinalSuspend)}); + + // Create a switch capturing three possible continuations. + auto *Switch = Builder.CreateSwitch(SuspendResult, Coro.SuspendBB, 2); + Switch->addCase(Builder.getInt8(0), ReadyBlock); + Switch->addCase(Builder.getInt8(1), CleanupBlock); + + // Emit cleanup for this suspend point. + CGF.EmitBlock(CleanupBlock); + CGF.EmitBranchThroughCleanup(Coro.CleanupJD); + + // Emit await_resume expression. + CGF.EmitBlock(ReadyBlock); + return CGF.EmitAnyExpr(S.getResumeExpr(), aggSlot, ignoreResult); +} + +RValue CodeGenFunction::EmitCoawaitExpr(const CoawaitExpr &E, + AggValueSlot aggSlot, + bool ignoreResult) { + return emitSuspendExpression(*this, *CurCoro.Data, E, + CurCoro.Data->CurrentAwaitKind, aggSlot, + ignoreResult); +} +RValue CodeGenFunction::EmitCoyieldExpr(const CoyieldExpr &E, + AggValueSlot aggSlot, + bool ignoreResult) { + return emitSuspendExpression(*this, *CurCoro.Data, E, AwaitKind::Yield, + aggSlot, ignoreResult); +} + +void CodeGenFunction::EmitCoreturnStmt(CoreturnStmt const &S) { + ++CurCoro.Data->CoreturnCount; + EmitStmt(S.getPromiseCall()); + EmitBranchThroughCleanup(CurCoro.Data->FinalJD); +} + +// For WinEH exception representation backend need to know what funclet coro.end +// belongs to. That information is passed in a funclet bundle. +static SmallVector<llvm::OperandBundleDef, 1> +getBundlesForCoroEnd(CodeGenFunction &CGF) { + SmallVector<llvm::OperandBundleDef, 1> BundleList; + + if (llvm::Instruction *EHPad = CGF.CurrentFuncletPad) + BundleList.emplace_back("funclet", EHPad); + + return BundleList; +} + +namespace { +// We will insert coro.end to cut any of the destructors for objects that +// do not need to be destroyed once the coroutine is resumed. +// See llvm/docs/Coroutines.rst for more details about coro.end. +struct CallCoroEnd final : public EHScopeStack::Cleanup { + void Emit(CodeGenFunction &CGF, Flags flags) override { + auto &CGM = CGF.CGM; + auto *NullPtr = llvm::ConstantPointerNull::get(CGF.Int8PtrTy); + llvm::Function *CoroEndFn = CGM.getIntrinsic(llvm::Intrinsic::coro_end); + // See if we have a funclet bundle to associate coro.end with. (WinEH) + auto Bundles = getBundlesForCoroEnd(CGF); + auto *CoroEnd = CGF.Builder.CreateCall( + CoroEndFn, {NullPtr, CGF.Builder.getTrue()}, Bundles); + if (Bundles.empty()) { + // Otherwise, (landingpad model), create a conditional branch that leads + // either to a cleanup block or a block with EH resume instruction. + auto *ResumeBB = CGF.getEHResumeBlock(/*cleanup=*/true); + auto *CleanupContBB = CGF.createBasicBlock("cleanup.cont"); + CGF.Builder.CreateCondBr(CoroEnd, ResumeBB, CleanupContBB); + CGF.EmitBlock(CleanupContBB); + } + } +}; +} + +namespace { +// Make sure to call coro.delete on scope exit. +struct CallCoroDelete final : public EHScopeStack::Cleanup { + Stmt *Deallocate; + + // TODO: Wrap deallocate in if(coro.free(...)) Deallocate. + void Emit(CodeGenFunction &CGF, Flags) override { + // Note: That deallocation will be emitted twice: once for a normal exit and + // once for exceptional exit. This usage is safe because Deallocate does not + // contain any declarations. The SubStmtBuilder::makeNewAndDeleteExpr() + // builds a single call to a deallocation function which is safe to emit + // multiple times. + CGF.EmitStmt(Deallocate); + } + explicit CallCoroDelete(Stmt *DeallocStmt) : Deallocate(DeallocStmt) {} +}; +} + void CodeGenFunction::EmitCoroutineBody(const CoroutineBodyStmt &S) { auto *NullPtr = llvm::ConstantPointerNull::get(Builder.getInt8PtrTy()); auto &TI = CGM.getContext().getTargetInfo(); unsigned NewAlign = TI.getNewAlign() / TI.getCharWidth(); + auto *FinalBB = createBasicBlock("coro.final"); + auto *RetBB = createBasicBlock("coro.ret"); + auto *CoroId = Builder.CreateCall( CGM.getIntrinsic(llvm::Intrinsic::coro_id), {Builder.getInt32(NewAlign), NullPtr, NullPtr, NullPtr}); createCoroData(*this, CurCoro, CoroId); + CurCoro.Data->SuspendBB = RetBB; + + auto *AllocateCall = EmitScalarExpr(S.getAllocate()); + + // Handle allocation failure if 'ReturnStmtOnAllocFailure' was provided. + if (auto *RetOnAllocFailure = S.getReturnStmtOnAllocFailure()) { + auto *RetOnFailureBB = createBasicBlock("coro.ret.on.failure"); + auto *InitBB = createBasicBlock("coro.init"); + + // See if allocation was successful. + auto *NullPtr = llvm::ConstantPointerNull::get(Int8PtrTy); + auto *Cond = Builder.CreateICmpNE(AllocateCall, NullPtr); + Builder.CreateCondBr(Cond, InitBB, RetOnFailureBB); + + // If not, return OnAllocFailure object. + EmitBlock(RetOnFailureBB); + EmitStmt(RetOnAllocFailure); + + EmitBlock(InitBB); + } + + CurCoro.Data->CleanupJD = getJumpDestInCurrentScope(RetBB); + { + CodeGenFunction::RunCleanupsScope ResumeScope(*this); + EHStack.pushCleanup<CallCoroDelete>(NormalAndEHCleanup, S.getDeallocate()); + + EmitStmt(S.getPromiseDeclStmt()); + + EHStack.pushCleanup<CallCoroEnd>(EHCleanup); + + CurCoro.Data->FinalJD = getJumpDestInCurrentScope(FinalBB); + + // FIXME: Emit initial suspend and more before the body. + + CurCoro.Data->CurrentAwaitKind = AwaitKind::Normal; + EmitStmt(S.getBody()); + + // See if we need to generate final suspend. + const bool CanFallthrough = Builder.GetInsertBlock(); + const bool HasCoreturns = CurCoro.Data->CoreturnCount > 0; + if (CanFallthrough || HasCoreturns) { + EmitBlock(FinalBB); + // FIXME: Emit final suspend. + } + } + + EmitBlock(RetBB); + llvm::Function *CoroEnd = CGM.getIntrinsic(llvm::Intrinsic::coro_end); + Builder.CreateCall(CoroEnd, {NullPtr, Builder.getFalse()}); - EmitScalarExpr(S.getAllocate()); - // FIXME: Emit the rest of the coroutine. - EmitStmt(S.getDeallocate()); + // FIXME: Emit return for the coroutine return object. } // Emit coroutine intrinsic and patch up arguments of the token type. |