1 //===- CoroCleanup.cpp - Coroutine Cleanup 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/CoroCleanup.h"
10 #include "CoroInternal.h"
11 #include "llvm/IR/IRBuilder.h"
12 #include "llvm/IR/InstIterator.h"
13 #include "llvm/IR/LegacyPassManager.h"
14 #include "llvm/Pass.h"
15 #include "llvm/Transforms/Scalar.h"
16 
17 using namespace llvm;
18 
19 #define DEBUG_TYPE "coro-cleanup"
20 
21 namespace {
22 // Created on demand if CoroCleanup pass has work to do.
23 struct Lowerer : coro::LowererBase {
24   IRBuilder<> Builder;
25   Lowerer(Module &M) : LowererBase(M), Builder(Context) {}
26   bool lowerRemainingCoroIntrinsics(Function &F);
27 };
28 }
29 
30 static void simplifyCFG(Function &F) {
31   llvm::legacy::FunctionPassManager FPM(F.getParent());
32   FPM.add(createCFGSimplificationPass());
33 
34   FPM.doInitialization();
35   FPM.run(F);
36   FPM.doFinalization();
37 }
38 
39 static void lowerSubFn(IRBuilder<> &Builder, CoroSubFnInst *SubFn) {
40   Builder.SetInsertPoint(SubFn);
41   Value *FrameRaw = SubFn->getFrame();
42   int Index = SubFn->getIndex();
43 
44   auto *FrameTy = StructType::get(
45       SubFn->getContext(), {Builder.getInt8PtrTy(), Builder.getInt8PtrTy()});
46   PointerType *FramePtrTy = FrameTy->getPointerTo();
47 
48   Builder.SetInsertPoint(SubFn);
49   auto *FramePtr = Builder.CreateBitCast(FrameRaw, FramePtrTy);
50   auto *Gep = Builder.CreateConstInBoundsGEP2_32(FrameTy, FramePtr, 0, Index);
51   auto *Load = Builder.CreateLoad(FrameTy->getElementType(Index), Gep);
52 
53   SubFn->replaceAllUsesWith(Load);
54 }
55 
56 bool Lowerer::lowerRemainingCoroIntrinsics(Function &F) {
57   bool Changed = false;
58 
59   for (Instruction &I : llvm::make_early_inc_range(instructions(F))) {
60     if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
61       switch (II->getIntrinsicID()) {
62       default:
63         continue;
64       case Intrinsic::coro_begin:
65         II->replaceAllUsesWith(II->getArgOperand(1));
66         break;
67       case Intrinsic::coro_free:
68         II->replaceAllUsesWith(II->getArgOperand(1));
69         break;
70       case Intrinsic::coro_alloc:
71         II->replaceAllUsesWith(ConstantInt::getTrue(Context));
72         break;
73       case Intrinsic::coro_async_resume:
74         II->replaceAllUsesWith(
75             ConstantPointerNull::get(cast<PointerType>(I.getType())));
76         break;
77       case Intrinsic::coro_id:
78       case Intrinsic::coro_id_retcon:
79       case Intrinsic::coro_id_retcon_once:
80       case Intrinsic::coro_id_async:
81         II->replaceAllUsesWith(ConstantTokenNone::get(Context));
82         break;
83       case Intrinsic::coro_subfn_addr:
84         lowerSubFn(Builder, cast<CoroSubFnInst>(II));
85         break;
86       case Intrinsic::coro_async_size_replace:
87         auto *Target = cast<ConstantStruct>(
88             cast<GlobalVariable>(II->getArgOperand(0)->stripPointerCasts())
89                 ->getInitializer());
90         auto *Source = cast<ConstantStruct>(
91             cast<GlobalVariable>(II->getArgOperand(1)->stripPointerCasts())
92                 ->getInitializer());
93         auto *TargetSize = Target->getOperand(1);
94         auto *SourceSize = Source->getOperand(1);
95         if (TargetSize->isElementWiseEqual(SourceSize)) {
96           break;
97         }
98         auto *TargetRelativeFunOffset = Target->getOperand(0);
99         auto *NewFuncPtrStruct = ConstantStruct::get(
100             Target->getType(), TargetRelativeFunOffset, SourceSize);
101         Target->replaceAllUsesWith(NewFuncPtrStruct);
102         break;
103       }
104       II->eraseFromParent();
105       Changed = true;
106     }
107   }
108 
109   if (Changed) {
110     // After replacement were made we can cleanup the function body a little.
111     simplifyCFG(F);
112   }
113 
114   return Changed;
115 }
116 
117 static bool declaresCoroCleanupIntrinsics(const Module &M) {
118   return coro::declaresIntrinsics(
119       M, {"llvm.coro.alloc", "llvm.coro.begin", "llvm.coro.subfn.addr",
120           "llvm.coro.free", "llvm.coro.id", "llvm.coro.id.retcon",
121           "llvm.coro.id.retcon.once", "llvm.coro.async.size.replace",
122           "llvm.coro.async.resume"});
123 }
124 
125 PreservedAnalyses CoroCleanupPass::run(Function &F,
126                                        FunctionAnalysisManager &AM) {
127   auto &M = *F.getParent();
128   if (!declaresCoroCleanupIntrinsics(M) ||
129       !Lowerer(M).lowerRemainingCoroIntrinsics(F))
130     return PreservedAnalyses::all();
131 
132   return PreservedAnalyses::none();
133 }
134 
135 namespace {
136 
137 struct CoroCleanupLegacy : FunctionPass {
138   static char ID; // Pass identification, replacement for typeid
139 
140   CoroCleanupLegacy() : FunctionPass(ID) {
141     initializeCoroCleanupLegacyPass(*PassRegistry::getPassRegistry());
142   }
143 
144   std::unique_ptr<Lowerer> L;
145 
146   // This pass has work to do only if we find intrinsics we are going to lower
147   // in the module.
148   bool doInitialization(Module &M) override {
149     if (declaresCoroCleanupIntrinsics(M))
150       L = std::make_unique<Lowerer>(M);
151     return false;
152   }
153 
154   bool runOnFunction(Function &F) override {
155     if (L)
156       return L->lowerRemainingCoroIntrinsics(F);
157     return false;
158   }
159   void getAnalysisUsage(AnalysisUsage &AU) const override {
160     if (!L)
161       AU.setPreservesAll();
162   }
163   StringRef getPassName() const override { return "Coroutine Cleanup"; }
164 };
165 }
166 
167 char CoroCleanupLegacy::ID = 0;
168 INITIALIZE_PASS(CoroCleanupLegacy, "coro-cleanup",
169                 "Lower all coroutine related intrinsics", false, false)
170 
171 Pass *llvm::createCoroCleanupLegacyPass() { return new CoroCleanupLegacy(); }
172