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diff --git a/llvm/lib/CodeGen/GCRootLowering.cpp b/llvm/lib/CodeGen/GCRootLowering.cpp
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+//===-- GCRootLowering.cpp - Garbage collection infrastructure ------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the lowering for the gc.root mechanism.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/GCMetadata.h"
+#include "llvm/CodeGen/GCStrategy.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/TargetFrameLowering.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+namespace {
+
+/// LowerIntrinsics - This pass rewrites calls to the llvm.gcread or
+/// llvm.gcwrite intrinsics, replacing them with simple loads and stores as
+/// directed by the GCStrategy. It also performs automatic root initialization
+/// and custom intrinsic lowering.
+class LowerIntrinsics : public FunctionPass {
+ bool DoLowering(Function &F, GCStrategy &S);
+
+public:
+ static char ID;
+
+ LowerIntrinsics();
+ StringRef getPassName() const override;
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+ bool doInitialization(Module &M) override;
+ bool runOnFunction(Function &F) override;
+};
+
+/// GCMachineCodeAnalysis - This is a target-independent pass over the machine
+/// function representation to identify safe points for the garbage collector
+/// in the machine code. It inserts labels at safe points and populates a
+/// GCMetadata record for each function.
+class GCMachineCodeAnalysis : public MachineFunctionPass {
+ GCFunctionInfo *FI;
+ MachineModuleInfo *MMI;
+ const TargetInstrInfo *TII;
+
+ void FindSafePoints(MachineFunction &MF);
+ void VisitCallPoint(MachineBasicBlock::iterator CI);
+ MCSymbol *InsertLabel(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+ const DebugLoc &DL) const;
+
+ void FindStackOffsets(MachineFunction &MF);
+
+public:
+ static char ID;
+
+ GCMachineCodeAnalysis();
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+ bool runOnMachineFunction(MachineFunction &MF) override;
+};
+}
+
+// -----------------------------------------------------------------------------
+
+INITIALIZE_PASS_BEGIN(LowerIntrinsics, "gc-lowering", "GC Lowering", false,
+ false)
+INITIALIZE_PASS_DEPENDENCY(GCModuleInfo)
+INITIALIZE_PASS_END(LowerIntrinsics, "gc-lowering", "GC Lowering", false, false)
+
+FunctionPass *llvm::createGCLoweringPass() { return new LowerIntrinsics(); }
+
+char LowerIntrinsics::ID = 0;
+
+LowerIntrinsics::LowerIntrinsics() : FunctionPass(ID) {
+ initializeLowerIntrinsicsPass(*PassRegistry::getPassRegistry());
+}
+
+StringRef LowerIntrinsics::getPassName() const {
+ return "Lower Garbage Collection Instructions";
+}
+
+void LowerIntrinsics::getAnalysisUsage(AnalysisUsage &AU) const {
+ FunctionPass::getAnalysisUsage(AU);
+ AU.addRequired<GCModuleInfo>();
+ AU.addPreserved<DominatorTreeWrapperPass>();
+}
+
+/// doInitialization - If this module uses the GC intrinsics, find them now.
+bool LowerIntrinsics::doInitialization(Module &M) {
+ GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
+ assert(MI && "LowerIntrinsics didn't require GCModuleInfo!?");
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
+ if (!I->isDeclaration() && I->hasGC())
+ MI->getFunctionInfo(*I); // Instantiate the GC strategy.
+
+ return false;
+}
+
+/// CouldBecomeSafePoint - Predicate to conservatively determine whether the
+/// instruction could introduce a safe point.
+static bool CouldBecomeSafePoint(Instruction *I) {
+ // The natural definition of instructions which could introduce safe points
+ // are:
+ //
+ // - call, invoke (AfterCall, BeforeCall)
+ // - phis (Loops)
+ // - invoke, ret, unwind (Exit)
+ //
+ // However, instructions as seemingly inoccuous as arithmetic can become
+ // libcalls upon lowering (e.g., div i64 on a 32-bit platform), so instead
+ // it is necessary to take a conservative approach.
+
+ if (isa<AllocaInst>(I) || isa<GetElementPtrInst>(I) || isa<StoreInst>(I) ||
+ isa<LoadInst>(I))
+ return false;
+
+ // llvm.gcroot is safe because it doesn't do anything at runtime.
+ if (CallInst *CI = dyn_cast<CallInst>(I))
+ if (Function *F = CI->getCalledFunction())
+ if (Intrinsic::ID IID = F->getIntrinsicID())
+ if (IID == Intrinsic::gcroot)
+ return false;
+
+ return true;
+}
+
+static bool InsertRootInitializers(Function &F, ArrayRef<AllocaInst *> Roots) {
+ // Scroll past alloca instructions.
+ BasicBlock::iterator IP = F.getEntryBlock().begin();
+ while (isa<AllocaInst>(IP))
+ ++IP;
+
+ // Search for initializers in the initial BB.
+ SmallPtrSet<AllocaInst *, 16> InitedRoots;
+ for (; !CouldBecomeSafePoint(&*IP); ++IP)
+ if (StoreInst *SI = dyn_cast<StoreInst>(IP))
+ if (AllocaInst *AI =
+ dyn_cast<AllocaInst>(SI->getOperand(1)->stripPointerCasts()))
+ InitedRoots.insert(AI);
+
+ // Add root initializers.
+ bool MadeChange = false;
+
+ for (AllocaInst *Root : Roots)
+ if (!InitedRoots.count(Root)) {
+ StoreInst *SI = new StoreInst(
+ ConstantPointerNull::get(cast<PointerType>(Root->getAllocatedType())),
+ Root);
+ SI->insertAfter(Root);
+ MadeChange = true;
+ }
+
+ return MadeChange;
+}
+
+/// runOnFunction - Replace gcread/gcwrite intrinsics with loads and stores.
+/// Leave gcroot intrinsics; the code generator needs to see those.
+bool LowerIntrinsics::runOnFunction(Function &F) {
+ // Quick exit for functions that do not use GC.
+ if (!F.hasGC())
+ return false;
+
+ GCFunctionInfo &FI = getAnalysis<GCModuleInfo>().getFunctionInfo(F);
+ GCStrategy &S = FI.getStrategy();
+
+ return DoLowering(F, S);
+}
+
+/// Lower barriers out of existance (if the associated GCStrategy hasn't
+/// already done so...), and insert initializing stores to roots as a defensive
+/// measure. Given we're going to report all roots live at all safepoints, we
+/// need to be able to ensure each root has been initialized by the point the
+/// first safepoint is reached. This really should have been done by the
+/// frontend, but the old API made this non-obvious, so we do a potentially
+/// redundant store just in case.
+bool LowerIntrinsics::DoLowering(Function &F, GCStrategy &S) {
+ SmallVector<AllocaInst *, 32> Roots;
+
+ bool MadeChange = false;
+ for (BasicBlock &BB : F)
+ for (BasicBlock::iterator II = BB.begin(), E = BB.end(); II != E;) {
+ IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++);
+ if (!CI)
+ continue;
+
+ Function *F = CI->getCalledFunction();
+ switch (F->getIntrinsicID()) {
+ default: break;
+ case Intrinsic::gcwrite: {
+ // Replace a write barrier with a simple store.
+ Value *St = new StoreInst(CI->getArgOperand(0),
+ CI->getArgOperand(2), CI);
+ CI->replaceAllUsesWith(St);
+ CI->eraseFromParent();
+ MadeChange = true;
+ break;
+ }
+ case Intrinsic::gcread: {
+ // Replace a read barrier with a simple load.
+ Value *Ld = new LoadInst(CI->getType(), CI->getArgOperand(1), "", CI);
+ Ld->takeName(CI);
+ CI->replaceAllUsesWith(Ld);
+ CI->eraseFromParent();
+ MadeChange = true;
+ break;
+ }
+ case Intrinsic::gcroot: {
+ // Initialize the GC root, but do not delete the intrinsic. The
+ // backend needs the intrinsic to flag the stack slot.
+ Roots.push_back(
+ cast<AllocaInst>(CI->getArgOperand(0)->stripPointerCasts()));
+ break;
+ }
+ }
+ }
+
+ if (Roots.size())
+ MadeChange |= InsertRootInitializers(F, Roots);
+
+ return MadeChange;
+}
+
+// -----------------------------------------------------------------------------
+
+char GCMachineCodeAnalysis::ID = 0;
+char &llvm::GCMachineCodeAnalysisID = GCMachineCodeAnalysis::ID;
+
+INITIALIZE_PASS(GCMachineCodeAnalysis, "gc-analysis",
+ "Analyze Machine Code For Garbage Collection", false, false)
+
+GCMachineCodeAnalysis::GCMachineCodeAnalysis() : MachineFunctionPass(ID) {}
+
+void GCMachineCodeAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+ MachineFunctionPass::getAnalysisUsage(AU);
+ AU.setPreservesAll();
+ AU.addRequired<MachineModuleInfoWrapperPass>();
+ AU.addRequired<GCModuleInfo>();
+}
+
+MCSymbol *GCMachineCodeAnalysis::InsertLabel(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator MI,
+ const DebugLoc &DL) const {
+ MCSymbol *Label = MBB.getParent()->getContext().createTempSymbol();
+ BuildMI(MBB, MI, DL, TII->get(TargetOpcode::GC_LABEL)).addSym(Label);
+ return Label;
+}
+
+void GCMachineCodeAnalysis::VisitCallPoint(MachineBasicBlock::iterator CI) {
+ // Find the return address (next instruction), since that's what will be on
+ // the stack when the call is suspended and we need to inspect the stack.
+ MachineBasicBlock::iterator RAI = CI;
+ ++RAI;
+
+ MCSymbol *Label = InsertLabel(*CI->getParent(), RAI, CI->getDebugLoc());
+ FI->addSafePoint(Label, CI->getDebugLoc());
+}
+
+void GCMachineCodeAnalysis::FindSafePoints(MachineFunction &MF) {
+ for (MachineBasicBlock &MBB : MF)
+ for (MachineBasicBlock::iterator MI = MBB.begin(), ME = MBB.end();
+ MI != ME; ++MI)
+ if (MI->isCall()) {
+ // Do not treat tail or sibling call sites as safe points. This is
+ // legal since any arguments passed to the callee which live in the
+ // remnants of the callers frame will be owned and updated by the
+ // callee if required.
+ if (MI->isTerminator())
+ continue;
+ VisitCallPoint(MI);
+ }
+}
+
+void GCMachineCodeAnalysis::FindStackOffsets(MachineFunction &MF) {
+ const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
+ assert(TFI && "TargetRegisterInfo not available!");
+
+ for (GCFunctionInfo::roots_iterator RI = FI->roots_begin();
+ RI != FI->roots_end();) {
+ // If the root references a dead object, no need to keep it.
+ if (MF.getFrameInfo().isDeadObjectIndex(RI->Num)) {
+ RI = FI->removeStackRoot(RI);
+ } else {
+ unsigned FrameReg; // FIXME: surely GCRoot ought to store the
+ // register that the offset is from?
+ RI->StackOffset = TFI->getFrameIndexReference(MF, RI->Num, FrameReg);
+ ++RI;
+ }
+ }
+}
+
+bool GCMachineCodeAnalysis::runOnMachineFunction(MachineFunction &MF) {
+ // Quick exit for functions that do not use GC.
+ if (!MF.getFunction().hasGC())
+ return false;
+
+ FI = &getAnalysis<GCModuleInfo>().getFunctionInfo(MF.getFunction());
+ MMI = &getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
+ TII = MF.getSubtarget().getInstrInfo();
+
+ // Find the size of the stack frame. There may be no correct static frame
+ // size, we use UINT64_MAX to represent this.
+ const MachineFrameInfo &MFI = MF.getFrameInfo();
+ const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
+ const bool DynamicFrameSize = MFI.hasVarSizedObjects() ||
+ RegInfo->needsStackRealignment(MF);
+ FI->setFrameSize(DynamicFrameSize ? UINT64_MAX : MFI.getStackSize());
+
+ // Find all safe points.
+ if (FI->getStrategy().needsSafePoints())
+ FindSafePoints(MF);
+
+ // Find the concrete stack offsets for all roots (stack slots)
+ FindStackOffsets(MF);
+
+ return false;
+}
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