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 (auto IB = inst_begin(F), E = inst_end(F); IB != E;) {
60     Instruction &I = *IB++;
61     if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
62       switch (II->getIntrinsicID()) {
63       default:
64         continue;
65       case Intrinsic::coro_begin:
66         II->replaceAllUsesWith(II->getArgOperand(1));
67         break;
68       case Intrinsic::coro_free:
69         II->replaceAllUsesWith(II->getArgOperand(1));
70         break;
71       case Intrinsic::coro_alloc:
72         II->replaceAllUsesWith(ConstantInt::getTrue(Context));
73         break;
74       case Intrinsic::coro_id:
75       case Intrinsic::coro_id_retcon:
76       case Intrinsic::coro_id_retcon_once:
77       case Intrinsic::coro_id_async:
78         II->replaceAllUsesWith(ConstantTokenNone::get(Context));
79         break;
80       case Intrinsic::coro_subfn_addr:
81         lowerSubFn(Builder, cast<CoroSubFnInst>(II));
82         break;
83       case Intrinsic::coro_async_size_replace:
84         auto *Target = cast<ConstantStruct>(
85             cast<GlobalVariable>(II->getArgOperand(0)->stripPointerCasts())
86                 ->getInitializer());
87         auto *Source = cast<ConstantStruct>(
88             cast<GlobalVariable>(II->getArgOperand(1)->stripPointerCasts())
89                 ->getInitializer());
90         auto *TargetSize = Target->getOperand(1);
91         auto *SourceSize = Source->getOperand(1);
92         if (TargetSize->isElementWiseEqual(SourceSize)) {
93           break;
94         }
95         auto *TargetRelativeFunOffset = Target->getOperand(0);
96         auto *NewFuncPtrStruct = ConstantStruct::get(
97             Target->getType(), TargetRelativeFunOffset, SourceSize);
98         Target->replaceAllUsesWith(NewFuncPtrStruct);
99         break;
100       }
101       II->eraseFromParent();
102       Changed = true;
103     }
104   }
105 
106   if (Changed) {
107     // After replacement were made we can cleanup the function body a little.
108     simplifyCFG(F);
109   }
110 
111   return Changed;
112 }
113 
114 static bool declaresCoroCleanupIntrinsics(const Module &M) {
115   return coro::declaresIntrinsics(
116       M, {"llvm.coro.alloc", "llvm.coro.begin", "llvm.coro.subfn.addr",
117           "llvm.coro.free", "llvm.coro.id", "llvm.coro.id.retcon",
118           "llvm.coro.id.retcon.once", "llvm.coro.async.size.replace"});
119 }
120 
121 PreservedAnalyses CoroCleanupPass::run(Function &F,
122                                        FunctionAnalysisManager &AM) {
123   auto &M = *F.getParent();
124   if (!declaresCoroCleanupIntrinsics(M) ||
125       !Lowerer(M).lowerRemainingCoroIntrinsics(F))
126     return PreservedAnalyses::all();
127 
128   return PreservedAnalyses::none();
129 }
130 
131 namespace {
132 
133 struct CoroCleanupLegacy : FunctionPass {
134   static char ID; // Pass identification, replacement for typeid
135 
136   CoroCleanupLegacy() : FunctionPass(ID) {
137     initializeCoroCleanupLegacyPass(*PassRegistry::getPassRegistry());
138   }
139 
140   std::unique_ptr<Lowerer> L;
141 
142   // This pass has work to do only if we find intrinsics we are going to lower
143   // in the module.
144   bool doInitialization(Module &M) override {
145     if (declaresCoroCleanupIntrinsics(M))
146       L = std::make_unique<Lowerer>(M);
147     return false;
148   }
149 
150   bool runOnFunction(Function &F) override {
151     if (L)
152       return L->lowerRemainingCoroIntrinsics(F);
153     return false;
154   }
155   void getAnalysisUsage(AnalysisUsage &AU) const override {
156     if (!L)
157       AU.setPreservesAll();
158   }
159   StringRef getPassName() const override { return "Coroutine Cleanup"; }
160 };
161 }
162 
163 char CoroCleanupLegacy::ID = 0;
164 INITIALIZE_PASS(CoroCleanupLegacy, "coro-cleanup",
165                 "Lower all coroutine related intrinsics", false, false)
166 
167 Pass *llvm::createCoroCleanupLegacyPass() { return new CoroCleanupLegacy(); }
168