1 //===- CoroEarly.cpp - Coroutine Early Function Pass ----------------------===// 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 #include "llvm/Transforms/Coroutines/CoroEarly.h" 10 #include "CoroInternal.h" 11 #include "llvm/IR/Function.h" 12 #include "llvm/IR/IRBuilder.h" 13 #include "llvm/IR/InstIterator.h" 14 #include "llvm/IR/Module.h" 15 16 using namespace llvm; 17 18 #define DEBUG_TYPE "coro-early" 19 20 namespace { 21 // Created on demand if the coro-early pass has work to do. 22 class Lowerer : public coro::LowererBase { 23 IRBuilder<> Builder; 24 PointerType *const AnyResumeFnPtrTy; 25 Constant *NoopCoro = nullptr; 26 27 void lowerResumeOrDestroy(CallBase &CB, CoroSubFnInst::ResumeKind); 28 void lowerCoroPromise(CoroPromiseInst *Intrin); 29 void lowerCoroDone(IntrinsicInst *II); 30 void lowerCoroNoop(IntrinsicInst *II); 31 32 public: 33 Lowerer(Module &M) 34 : LowererBase(M), Builder(Context), 35 AnyResumeFnPtrTy(FunctionType::get(Type::getVoidTy(Context), Int8Ptr, 36 /*isVarArg=*/false) 37 ->getPointerTo()) {} 38 void lowerEarlyIntrinsics(Function &F); 39 }; 40 } 41 42 // Replace a direct call to coro.resume or coro.destroy with an indirect call to 43 // an address returned by coro.subfn.addr intrinsic. This is done so that 44 // CGPassManager recognizes devirtualization when CoroElide pass replaces a call 45 // to coro.subfn.addr with an appropriate function address. 46 void Lowerer::lowerResumeOrDestroy(CallBase &CB, 47 CoroSubFnInst::ResumeKind Index) { 48 Value *ResumeAddr = makeSubFnCall(CB.getArgOperand(0), Index, &CB); 49 CB.setCalledOperand(ResumeAddr); 50 CB.setCallingConv(CallingConv::Fast); 51 } 52 53 // Coroutine promise field is always at the fixed offset from the beginning of 54 // the coroutine frame. i8* coro.promise(i8*, i1 from) intrinsic adds an offset 55 // to a passed pointer to move from coroutine frame to coroutine promise and 56 // vice versa. Since we don't know exactly which coroutine frame it is, we build 57 // a coroutine frame mock up starting with two function pointers, followed by a 58 // properly aligned coroutine promise field. 59 // TODO: Handle the case when coroutine promise alloca has align override. 60 void Lowerer::lowerCoroPromise(CoroPromiseInst *Intrin) { 61 Value *Operand = Intrin->getArgOperand(0); 62 Align Alignment = Intrin->getAlignment(); 63 Type *Int8Ty = Builder.getInt8Ty(); 64 65 auto *SampleStruct = 66 StructType::get(Context, {AnyResumeFnPtrTy, AnyResumeFnPtrTy, Int8Ty}); 67 const DataLayout &DL = TheModule.getDataLayout(); 68 int64_t Offset = alignTo( 69 DL.getStructLayout(SampleStruct)->getElementOffset(2), Alignment); 70 if (Intrin->isFromPromise()) 71 Offset = -Offset; 72 73 Builder.SetInsertPoint(Intrin); 74 Value *Replacement = 75 Builder.CreateConstInBoundsGEP1_32(Int8Ty, Operand, Offset); 76 77 Intrin->replaceAllUsesWith(Replacement); 78 Intrin->eraseFromParent(); 79 } 80 81 // When a coroutine reaches final suspend point, it zeros out ResumeFnAddr in 82 // the coroutine frame (it is UB to resume from a final suspend point). 83 // The llvm.coro.done intrinsic is used to check whether a coroutine is 84 // suspended at the final suspend point or not. 85 void Lowerer::lowerCoroDone(IntrinsicInst *II) { 86 Value *Operand = II->getArgOperand(0); 87 88 // ResumeFnAddr is the first pointer sized element of the coroutine frame. 89 static_assert(coro::Shape::SwitchFieldIndex::Resume == 0, 90 "resume function not at offset zero"); 91 auto *FrameTy = Int8Ptr; 92 PointerType *FramePtrTy = FrameTy->getPointerTo(); 93 94 Builder.SetInsertPoint(II); 95 auto *BCI = Builder.CreateBitCast(Operand, FramePtrTy); 96 auto *Load = Builder.CreateLoad(FrameTy, BCI); 97 auto *Cond = Builder.CreateICmpEQ(Load, NullPtr); 98 99 II->replaceAllUsesWith(Cond); 100 II->eraseFromParent(); 101 } 102 103 void Lowerer::lowerCoroNoop(IntrinsicInst *II) { 104 if (!NoopCoro) { 105 LLVMContext &C = Builder.getContext(); 106 Module &M = *II->getModule(); 107 108 // Create a noop.frame struct type. 109 StructType *FrameTy = StructType::create(C, "NoopCoro.Frame"); 110 auto *FramePtrTy = FrameTy->getPointerTo(); 111 auto *FnTy = FunctionType::get(Type::getVoidTy(C), FramePtrTy, 112 /*isVarArg=*/false); 113 auto *FnPtrTy = FnTy->getPointerTo(); 114 FrameTy->setBody({FnPtrTy, FnPtrTy}); 115 116 // Create a Noop function that does nothing. 117 Function *NoopFn = 118 Function::Create(FnTy, GlobalValue::LinkageTypes::PrivateLinkage, 119 "NoopCoro.ResumeDestroy", &M); 120 NoopFn->setCallingConv(CallingConv::Fast); 121 auto *Entry = BasicBlock::Create(C, "entry", NoopFn); 122 ReturnInst::Create(C, Entry); 123 124 // Create a constant struct for the frame. 125 Constant* Values[] = {NoopFn, NoopFn}; 126 Constant* NoopCoroConst = ConstantStruct::get(FrameTy, Values); 127 NoopCoro = new GlobalVariable(M, NoopCoroConst->getType(), /*isConstant=*/true, 128 GlobalVariable::PrivateLinkage, NoopCoroConst, 129 "NoopCoro.Frame.Const"); 130 } 131 132 Builder.SetInsertPoint(II); 133 auto *NoopCoroVoidPtr = Builder.CreateBitCast(NoopCoro, Int8Ptr); 134 II->replaceAllUsesWith(NoopCoroVoidPtr); 135 II->eraseFromParent(); 136 } 137 138 // Prior to CoroSplit, calls to coro.begin needs to be marked as NoDuplicate, 139 // as CoroSplit assumes there is exactly one coro.begin. After CoroSplit, 140 // NoDuplicate attribute will be removed from coro.begin otherwise, it will 141 // interfere with inlining. 142 static void setCannotDuplicate(CoroIdInst *CoroId) { 143 for (User *U : CoroId->users()) 144 if (auto *CB = dyn_cast<CoroBeginInst>(U)) 145 CB->setCannotDuplicate(); 146 } 147 148 void Lowerer::lowerEarlyIntrinsics(Function &F) { 149 CoroIdInst *CoroId = nullptr; 150 SmallVector<CoroFreeInst *, 4> CoroFrees; 151 bool HasCoroSuspend = false; 152 for (Instruction &I : llvm::make_early_inc_range(instructions(F))) { 153 auto *CB = dyn_cast<CallBase>(&I); 154 if (!CB) 155 continue; 156 157 switch (CB->getIntrinsicID()) { 158 default: 159 continue; 160 case Intrinsic::coro_free: 161 CoroFrees.push_back(cast<CoroFreeInst>(&I)); 162 break; 163 case Intrinsic::coro_suspend: 164 // Make sure that final suspend point is not duplicated as CoroSplit 165 // pass expects that there is at most one final suspend point. 166 if (cast<CoroSuspendInst>(&I)->isFinal()) 167 CB->setCannotDuplicate(); 168 HasCoroSuspend = true; 169 break; 170 case Intrinsic::coro_end_async: 171 case Intrinsic::coro_end: 172 // Make sure that fallthrough coro.end is not duplicated as CoroSplit 173 // pass expects that there is at most one fallthrough coro.end. 174 if (cast<AnyCoroEndInst>(&I)->isFallthrough()) 175 CB->setCannotDuplicate(); 176 break; 177 case Intrinsic::coro_noop: 178 lowerCoroNoop(cast<IntrinsicInst>(&I)); 179 break; 180 case Intrinsic::coro_id: 181 if (auto *CII = cast<CoroIdInst>(&I)) { 182 if (CII->getInfo().isPreSplit()) { 183 assert(F.isPresplitCoroutine() && 184 "The frontend uses Swtich-Resumed ABI should emit " 185 "\"coroutine.presplit\" attribute for the coroutine."); 186 setCannotDuplicate(CII); 187 CII->setCoroutineSelf(); 188 CoroId = cast<CoroIdInst>(&I); 189 } 190 } 191 break; 192 case Intrinsic::coro_id_retcon: 193 case Intrinsic::coro_id_retcon_once: 194 case Intrinsic::coro_id_async: 195 F.setPresplitCoroutine(); 196 break; 197 case Intrinsic::coro_resume: 198 lowerResumeOrDestroy(*CB, CoroSubFnInst::ResumeIndex); 199 break; 200 case Intrinsic::coro_destroy: 201 lowerResumeOrDestroy(*CB, CoroSubFnInst::DestroyIndex); 202 break; 203 case Intrinsic::coro_promise: 204 lowerCoroPromise(cast<CoroPromiseInst>(&I)); 205 break; 206 case Intrinsic::coro_done: 207 lowerCoroDone(cast<IntrinsicInst>(&I)); 208 break; 209 } 210 } 211 212 // Make sure that all CoroFree reference the coro.id intrinsic. 213 // Token type is not exposed through coroutine C/C++ builtins to plain C, so 214 // we allow specifying none and fixing it up here. 215 if (CoroId) 216 for (CoroFreeInst *CF : CoroFrees) 217 CF->setArgOperand(0, CoroId); 218 219 // Coroutine suspention could potentially lead to any argument modified 220 // outside of the function, hence arguments should not have noalias 221 // attributes. 222 if (HasCoroSuspend) 223 for (Argument &A : F.args()) 224 if (A.hasNoAliasAttr()) 225 A.removeAttr(Attribute::NoAlias); 226 } 227 228 static bool declaresCoroEarlyIntrinsics(const Module &M) { 229 return coro::declaresIntrinsics( 230 M, {"llvm.coro.id", "llvm.coro.id.retcon", "llvm.coro.id.retcon.once", 231 "llvm.coro.id.async", "llvm.coro.destroy", "llvm.coro.done", 232 "llvm.coro.end", "llvm.coro.end.async", "llvm.coro.noop", 233 "llvm.coro.free", "llvm.coro.promise", "llvm.coro.resume", 234 "llvm.coro.suspend"}); 235 } 236 237 PreservedAnalyses CoroEarlyPass::run(Module &M, ModuleAnalysisManager &) { 238 if (!declaresCoroEarlyIntrinsics(M)) 239 return PreservedAnalyses::all(); 240 241 Lowerer L(M); 242 for (auto &F : M) 243 L.lowerEarlyIntrinsics(F); 244 245 PreservedAnalyses PA; 246 PA.preserveSet<CFGAnalyses>(); 247 return PA; 248 } 249