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 // This pass lowers all remaining coroutine intrinsics.
9 //===----------------------------------------------------------------------===//
10 
11 #include "CoroInternal.h"
12 #include "llvm/IR/IRBuilder.h"
13 #include "llvm/IR/InstIterator.h"
14 #include "llvm/IR/LegacyPassManager.h"
15 #include "llvm/Pass.h"
16 #include "llvm/Transforms/Scalar.h"
17 
18 using namespace llvm;
19 
20 #define DEBUG_TYPE "coro-cleanup"
21 
22 namespace {
23 // Created on demand if CoroCleanup pass has work to do.
24 struct Lowerer : coro::LowererBase {
25   IRBuilder<> Builder;
26   Lowerer(Module &M) : LowererBase(M), Builder(Context) {}
27   bool lowerRemainingCoroIntrinsics(Function &F);
28 };
29 }
30 
31 static void simplifyCFG(Function &F) {
32   llvm::legacy::FunctionPassManager FPM(F.getParent());
33   FPM.add(createCFGSimplificationPass());
34 
35   FPM.doInitialization();
36   FPM.run(F);
37   FPM.doFinalization();
38 }
39 
40 static void lowerSubFn(IRBuilder<> &Builder, CoroSubFnInst *SubFn) {
41   Builder.SetInsertPoint(SubFn);
42   Value *FrameRaw = SubFn->getFrame();
43   int Index = SubFn->getIndex();
44 
45   auto *FrameTy = StructType::get(
46       SubFn->getContext(), {Builder.getInt8PtrTy(), Builder.getInt8PtrTy()});
47   PointerType *FramePtrTy = FrameTy->getPointerTo();
48 
49   Builder.SetInsertPoint(SubFn);
50   auto *FramePtr = Builder.CreateBitCast(FrameRaw, FramePtrTy);
51   auto *Gep = Builder.CreateConstInBoundsGEP2_32(FrameTy, FramePtr, 0, Index);
52   auto *Load = Builder.CreateLoad(FrameTy->getElementType(Index), Gep);
53 
54   SubFn->replaceAllUsesWith(Load);
55 }
56 
57 bool Lowerer::lowerRemainingCoroIntrinsics(Function &F) {
58   bool Changed = false;
59 
60   for (auto IB = inst_begin(F), E = inst_end(F); IB != E;) {
61     Instruction &I = *IB++;
62     if (auto *II = dyn_cast<IntrinsicInst>(&I)) {
63       switch (II->getIntrinsicID()) {
64       default:
65         continue;
66       case Intrinsic::coro_begin:
67         II->replaceAllUsesWith(II->getArgOperand(1));
68         break;
69       case Intrinsic::coro_free:
70         II->replaceAllUsesWith(II->getArgOperand(1));
71         break;
72       case Intrinsic::coro_alloc:
73         II->replaceAllUsesWith(ConstantInt::getTrue(Context));
74         break;
75       case Intrinsic::coro_id:
76         II->replaceAllUsesWith(ConstantTokenNone::get(Context));
77         break;
78       case Intrinsic::coro_subfn_addr:
79         lowerSubFn(Builder, cast<CoroSubFnInst>(II));
80         break;
81       }
82       II->eraseFromParent();
83       Changed = true;
84     }
85   }
86 
87   if (Changed) {
88     // After replacement were made we can cleanup the function body a little.
89     simplifyCFG(F);
90   }
91   return Changed;
92 }
93 
94 //===----------------------------------------------------------------------===//
95 //                              Top Level Driver
96 //===----------------------------------------------------------------------===//
97 
98 namespace {
99 
100 struct CoroCleanup : FunctionPass {
101   static char ID; // Pass identification, replacement for typeid
102 
103   CoroCleanup() : FunctionPass(ID) {
104     initializeCoroCleanupPass(*PassRegistry::getPassRegistry());
105   }
106 
107   std::unique_ptr<Lowerer> L;
108 
109   // This pass has work to do only if we find intrinsics we are going to lower
110   // in the module.
111   bool doInitialization(Module &M) override {
112     if (coro::declaresIntrinsics(M, {"llvm.coro.alloc", "llvm.coro.begin",
113                                      "llvm.coro.subfn.addr", "llvm.coro.free",
114                                      "llvm.coro.id"}))
115       L = llvm::make_unique<Lowerer>(M);
116     return false;
117   }
118 
119   bool runOnFunction(Function &F) override {
120     if (L)
121       return L->lowerRemainingCoroIntrinsics(F);
122     return false;
123   }
124   void getAnalysisUsage(AnalysisUsage &AU) const override {
125     if (!L)
126       AU.setPreservesAll();
127   }
128   StringRef getPassName() const override { return "Coroutine Cleanup"; }
129 };
130 }
131 
132 char CoroCleanup::ID = 0;
133 INITIALIZE_PASS(CoroCleanup, "coro-cleanup",
134                 "Lower all coroutine related intrinsics", false, false)
135 
136 Pass *llvm::createCoroCleanupPass() { return new CoroCleanup(); }
137