-//===-- GCStrategy.cpp - Garbage collection infrastructure -----------------===//
+//===-- GCStrategy.cpp - Garbage Collector Description --------------------===//
//
// The LLVM Compiler Infrastructure
//
//
//===----------------------------------------------------------------------===//
//
-// This file implements target- and collector-independent garbage collection
-// infrastructure.
-//
-// MachineCodeAnalysis identifies the GC safe points in the machine code. Roots
-// are identified in SelectionDAGISel.
+// This file implements the policy object GCStrategy which describes the
+// behavior of a given garbage collector.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GCStrategy.h"
-#include "llvm/CodeGen/Passes.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Module.h"
-#include "llvm/CodeGen/MachineFrameInfo.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineModuleInfo.h"
-#include "llvm/Target/TargetFrameInfo.h"
-#include "llvm/Target/TargetInstrInfo.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/Target/TargetRegisterInfo.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 {
- static bool NeedsDefaultLoweringPass(const GCStrategy &C);
- static bool NeedsCustomLoweringPass(const GCStrategy &C);
- static bool CouldBecomeSafePoint(Instruction *I);
- bool PerformDefaultLowering(Function &F, GCStrategy &Coll);
- static bool InsertRootInitializers(Function &F,
- AllocaInst **Roots, unsigned Count);
-
- public:
- static char ID;
-
- LowerIntrinsics();
- const char *getPassName() const;
- void getAnalysisUsage(AnalysisUsage &AU) const;
-
- bool doInitialization(Module &M);
- bool runOnFunction(Function &F);
- };
-
-
- /// MachineCodeAnalysis - 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 MachineCodeAnalysis : public MachineFunctionPass {
- const TargetMachine *TM;
- GCFunctionInfo *FI;
- MachineModuleInfo *MMI;
- const TargetInstrInfo *TII;
-
- void FindSafePoints(MachineFunction &MF);
- void VisitCallPoint(MachineBasicBlock::iterator MI);
- MCSymbol *InsertLabel(MachineBasicBlock &MBB,
- MachineBasicBlock::iterator MI,
- DebugLoc DL) const;
-
- void FindStackOffsets(MachineFunction &MF);
-
- public:
- static char ID;
-
- MachineCodeAnalysis();
- const char *getPassName() const;
- void getAnalysisUsage(AnalysisUsage &AU) const;
-
- bool runOnMachineFunction(MachineFunction &MF);
- };
-
-}
-
-// -----------------------------------------------------------------------------
-
-GCStrategy::GCStrategy() :
- NeededSafePoints(0),
- CustomReadBarriers(false),
- CustomWriteBarriers(false),
- CustomRoots(false),
- InitRoots(true),
- UsesMetadata(false)
-{}
-
-GCStrategy::~GCStrategy() {
- for (iterator I = begin(), E = end(); I != E; ++I)
- delete *I;
-
- Functions.clear();
-}
-
-bool GCStrategy::initializeCustomLowering(Module &M) { return false; }
-
-bool GCStrategy::performCustomLowering(Function &F) {
- dbgs() << "gc " << getName() << " must override performCustomLowering.\n";
- llvm_unreachable(0);
- return 0;
-}
-
-GCFunctionInfo *GCStrategy::insertFunctionInfo(const Function &F) {
- GCFunctionInfo *FI = new GCFunctionInfo(F, *this);
- Functions.push_back(FI);
- return FI;
-}
-
-// -----------------------------------------------------------------------------
-
-FunctionPass *llvm::createGCLoweringPass() {
- return new LowerIntrinsics();
-}
-
-char LowerIntrinsics::ID = 0;
-
-LowerIntrinsics::LowerIntrinsics()
- : FunctionPass(ID) {}
-
-const char *LowerIntrinsics::getPassName() const {
- return "Lower Garbage Collection Instructions";
-}
-
-void LowerIntrinsics::getAnalysisUsage(AnalysisUsage &AU) const {
- FunctionPass::getAnalysisUsage(AU);
- AU.addRequired<GCModuleInfo>();
-}
-
-/// doInitialization - If this module uses the GC intrinsics, find them now.
-bool LowerIntrinsics::doInitialization(Module &M) {
- // FIXME: This is rather antisocial in the context of a JIT since it performs
- // work against the entire module. But this cannot be done at
- // runFunction time (initializeCustomLowering likely needs to change
- // the module).
- 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.
-
- bool MadeChange = false;
- for (GCModuleInfo::iterator I = MI->begin(), E = MI->end(); I != E; ++I)
- if (NeedsCustomLoweringPass(**I))
- if ((*I)->initializeCustomLowering(M))
- MadeChange = true;
-
- return MadeChange;
-}
-
-bool LowerIntrinsics::InsertRootInitializers(Function &F, AllocaInst **Roots,
- unsigned Count) {
- // 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 **I = Roots, **E = Roots + Count; I != E; ++I)
- if (!InitedRoots.count(*I)) {
- StoreInst* SI = new StoreInst(ConstantPointerNull::get(cast<PointerType>(
- cast<PointerType>((*I)->getType())->getElementType())),
- *I);
- SI->insertAfter(*I);
- MadeChange = true;
- }
-
- return MadeChange;
-}
-
-bool LowerIntrinsics::NeedsDefaultLoweringPass(const GCStrategy &C) {
- // Default lowering is necessary only if read or write barriers have a default
- // action. The default for roots is no action.
- return !C.customWriteBarrier()
- || !C.customReadBarrier()
- || C.initializeRoots();
-}
-
-bool LowerIntrinsics::NeedsCustomLoweringPass(const GCStrategy &C) {
- // Custom lowering is only necessary if enabled for some action.
- return C.customWriteBarrier()
- || C.customReadBarrier()
- || C.customRoots();
-}
-
-/// CouldBecomeSafePoint - Predicate to conservatively determine whether the
-/// instruction could introduce a safe point.
-bool LowerIntrinsics::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 (unsigned IID = F->getIntrinsicID())
- if (IID == Intrinsic::gcroot)
- return false;
-
- return true;
-}
-
-/// 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();
-
- bool MadeChange = false;
-
- if (NeedsDefaultLoweringPass(S))
- MadeChange |= PerformDefaultLowering(F, S);
-
- if (NeedsCustomLoweringPass(S))
- MadeChange |= S.performCustomLowering(F);
-
- return MadeChange;
-}
-
-bool LowerIntrinsics::PerformDefaultLowering(Function &F, GCStrategy &S) {
- bool LowerWr = !S.customWriteBarrier();
- bool LowerRd = !S.customReadBarrier();
- bool InitRoots = S.initializeRoots();
-
- SmallVector<AllocaInst*, 32> Roots;
-
- bool MadeChange = false;
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
- for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) {
- if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++)) {
- Function *F = CI->getCalledFunction();
- switch (F->getIntrinsicID()) {
- case Intrinsic::gcwrite:
- if (LowerWr) {
- // Replace a write barrier with a simple store.
- Value *St = new StoreInst(CI->getArgOperand(0),
- CI->getArgOperand(2), CI);
- CI->replaceAllUsesWith(St);
- CI->eraseFromParent();
- }
- break;
- case Intrinsic::gcread:
- if (LowerRd) {
- // Replace a read barrier with a simple load.
- Value *Ld = new LoadInst(CI->getArgOperand(1), "", CI);
- Ld->takeName(CI);
- CI->replaceAllUsesWith(Ld);
- CI->eraseFromParent();
- }
- break;
- case Intrinsic::gcroot:
- if (InitRoots) {
- // 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;
- default:
- continue;
- }
-
- MadeChange = true;
- }
- }
- }
-
- if (Roots.size())
- MadeChange |= InsertRootInitializers(F, Roots.begin(), Roots.size());
-
- return MadeChange;
-}
-
-// -----------------------------------------------------------------------------
-
-FunctionPass *llvm::createGCMachineCodeAnalysisPass() {
- return new MachineCodeAnalysis();
-}
-
-char MachineCodeAnalysis::ID = 0;
-
-MachineCodeAnalysis::MachineCodeAnalysis()
- : MachineFunctionPass(ID) {}
-
-const char *MachineCodeAnalysis::getPassName() const {
- return "Analyze Machine Code For Garbage Collection";
-}
-
-void MachineCodeAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
- MachineFunctionPass::getAnalysisUsage(AU);
- AU.setPreservesAll();
- AU.addRequired<MachineModuleInfo>();
- AU.addRequired<GCModuleInfo>();
-}
-
-MCSymbol *MachineCodeAnalysis::InsertLabel(MachineBasicBlock &MBB,
- MachineBasicBlock::iterator MI,
- DebugLoc DL) const {
- MCSymbol *Label = MBB.getParent()->getContext().CreateTempSymbol();
- BuildMI(MBB, MI, DL, TII->get(TargetOpcode::GC_LABEL)).addSym(Label);
- return Label;
-}
-
-void MachineCodeAnalysis::VisitCallPoint(MachineBasicBlock::iterator CI) {
- // Find the return address (next instruction), too, so as to bracket the call
- // instruction.
- MachineBasicBlock::iterator RAI = CI;
- ++RAI;
-
- if (FI->getStrategy().needsSafePoint(GC::PreCall))
- FI->addSafePoint(GC::PreCall, InsertLabel(*CI->getParent(), CI,
- CI->getDebugLoc()));
-
- if (FI->getStrategy().needsSafePoint(GC::PostCall))
- FI->addSafePoint(GC::PostCall, InsertLabel(*CI->getParent(), RAI,
- CI->getDebugLoc()));
-}
-
-void MachineCodeAnalysis::FindSafePoints(MachineFunction &MF) {
- for (MachineFunction::iterator BBI = MF.begin(),
- BBE = MF.end(); BBI != BBE; ++BBI)
- for (MachineBasicBlock::iterator MI = BBI->begin(),
- ME = BBI->end(); MI != ME; ++MI)
- if (MI->getDesc().isCall())
- VisitCallPoint(MI);
-}
-
-void MachineCodeAnalysis::FindStackOffsets(MachineFunction &MF) {
- const TargetRegisterInfo *TRI = TM->getRegisterInfo();
- assert(TRI && "TargetRegisterInfo not available!");
-
- for (GCFunctionInfo::roots_iterator RI = FI->roots_begin(),
- RE = FI->roots_end(); RI != RE; ++RI)
- RI->StackOffset = TRI->getFrameIndexOffset(MF, RI->Num);
-}
-
-bool MachineCodeAnalysis::runOnMachineFunction(MachineFunction &MF) {
- // Quick exit for functions that do not use GC.
- if (!MF.getFunction()->hasGC())
- return false;
-
- FI = &getAnalysis<GCModuleInfo>().getFunctionInfo(*MF.getFunction());
- if (!FI->getStrategy().needsSafePoints())
- return false;
-
- TM = &MF.getTarget();
- MMI = &getAnalysis<MachineModuleInfo>();
- TII = TM->getInstrInfo();
-
- // Find the size of the stack frame.
- FI->setFrameSize(MF.getFrameInfo()->getStackSize());
-
- // Find all safe points.
- FindSafePoints(MF);
-
- // Find the stack offsets for all roots.
- FindStackOffsets(MF);
-
- return false;
-}
+GCStrategy::GCStrategy()
+ : UseStatepoints(false), NeededSafePoints(0), CustomReadBarriers(false),
+ CustomWriteBarriers(false), CustomRoots(false), InitRoots(true),
+ UsesMetadata(false) {}
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