lib/Transforms/Coroutines/CoroCleanup.cpp

   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(); }