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_id:
74       case Intrinsic::coro_id_retcon:
75       case Intrinsic::coro_id_retcon_once:
76       case Intrinsic::coro_id_async:
77         II->replaceAllUsesWith(ConstantTokenNone::get(Context));
78         break;
79       case Intrinsic::coro_subfn_addr:
80         lowerSubFn(Builder, cast<CoroSubFnInst>(II));
81         break;
82       case Intrinsic::coro_async_size_replace:
83         auto *Target = cast<ConstantStruct>(
84             cast<GlobalVariable>(II->getArgOperand(0)->stripPointerCasts())
85                 ->getInitializer());
86         auto *Source = cast<ConstantStruct>(
87             cast<GlobalVariable>(II->getArgOperand(1)->stripPointerCasts())
88                 ->getInitializer());
89         auto *TargetSize = Target->getOperand(1);
90         auto *SourceSize = Source->getOperand(1);
91         if (TargetSize->isElementWiseEqual(SourceSize)) {
92           break;
93         }
94         auto *TargetRelativeFunOffset = Target->getOperand(0);
95         auto *NewFuncPtrStruct = ConstantStruct::get(
96             Target->getType(), TargetRelativeFunOffset, SourceSize);
97         Target->replaceAllUsesWith(NewFuncPtrStruct);
98         break;
99       }
100       II->eraseFromParent();
101       Changed = true;
102     }
103   }
104 
105   if (Changed) {
106     // After replacement were made we can cleanup the function body a little.
107     simplifyCFG(F);
108   }
109 
110   return Changed;
111 }
112 
113 static bool declaresCoroCleanupIntrinsics(const Module &M) {
114   return coro::declaresIntrinsics(
115       M, {"llvm.coro.alloc", "llvm.coro.begin", "llvm.coro.subfn.addr",
116           "llvm.coro.free", "llvm.coro.id", "llvm.coro.id.retcon",
117           "llvm.coro.id.retcon.once", "llvm.coro.async.size.replace"});
118 }
119 
120 PreservedAnalyses CoroCleanupPass::run(Function &F,
121                                        FunctionAnalysisManager &AM) {
122   auto &M = *F.getParent();
123   if (!declaresCoroCleanupIntrinsics(M) ||
124       !Lowerer(M).lowerRemainingCoroIntrinsics(F))
125     return PreservedAnalyses::all();
126 
127   return PreservedAnalyses::none();
128 }
129 
130 namespace {
131 
132 struct CoroCleanupLegacy : FunctionPass {
133   static char ID; // Pass identification, replacement for typeid
134 
135   CoroCleanupLegacy() : FunctionPass(ID) {
136     initializeCoroCleanupLegacyPass(*PassRegistry::getPassRegistry());
137   }
138 
139   std::unique_ptr<Lowerer> L;
140 
141   // This pass has work to do only if we find intrinsics we are going to lower
142   // in the module.
143   bool doInitialization(Module &M) override {
144     if (declaresCoroCleanupIntrinsics(M))
145       L = std::make_unique<Lowerer>(M);
146     return false;
147   }
148 
149   bool runOnFunction(Function &F) override {
150     if (L)
151       return L->lowerRemainingCoroIntrinsics(F);
152     return false;
153   }
154   void getAnalysisUsage(AnalysisUsage &AU) const override {
155     if (!L)
156       AU.setPreservesAll();
157   }
158   StringRef getPassName() const override { return "Coroutine Cleanup"; }
159 };
160 }
161 
162 char CoroCleanupLegacy::ID = 0;
163 INITIALIZE_PASS(CoroCleanupLegacy, "coro-cleanup",
164                 "Lower all coroutine related intrinsics", false, false)
165 
166 Pass *llvm::createCoroCleanupLegacyPass() { return new CoroCleanupLegacy(); }
167