Factor GC metadata table assembly generation out of Collector in preparation for splitting AsmPrinter into its own library.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54881 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/GCStrategy.cpp

@@ -0,0 +1,389 @@
+//===-- Collector.cpp - Garbage collection infrastructure -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements target- and collector-independent garbage collection
+// infrastructure.
+//
+//===----------------------------------------------------------------------===//
+
+#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/Support/Compiler.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 Collector. It also performs automatic root initialization
+  /// and custom intrinsic lowering.
+  class VISIBILITY_HIDDEN LowerIntrinsics : public FunctionPass {
+    static bool NeedsDefaultLoweringPass(const Collector &C);
+    static bool NeedsCustomLoweringPass(const Collector &C);
+    static bool CouldBecomeSafePoint(Instruction *I);
+    bool PerformDefaultLowering(Function &F, Collector &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
+  /// CollectorMetadata record for each function.
+  class VISIBILITY_HIDDEN MachineCodeAnalysis : public MachineFunctionPass {
+    const TargetMachine *TM;
+    CollectorMetadata *MD;
+    MachineModuleInfo *MMI;
+    const TargetInstrInfo *TII;
+    MachineFrameInfo *MFI;
+    
+    void FindSafePoints(MachineFunction &MF);
+    void VisitCallPoint(MachineBasicBlock::iterator MI);
+    unsigned InsertLabel(MachineBasicBlock &MBB, 
+                         MachineBasicBlock::iterator MI) const;
+    
+    void FindStackOffsets(MachineFunction &MF);
+    
+  public:
+    static char ID;
+    
+    MachineCodeAnalysis();
+    const char *getPassName() const;
+    void getAnalysisUsage(AnalysisUsage &AU) const;
+    
+    bool runOnMachineFunction(MachineFunction &MF);
+  };
+  
+}
+
+// -----------------------------------------------------------------------------
+
+Collector::Collector() :
+  NeededSafePoints(0),
+  CustomReadBarriers(false),
+  CustomWriteBarriers(false),
+  CustomRoots(false),
+  InitRoots(true),
+  UsesMetadata(false)
+{}
+
+Collector::~Collector() {
+  for (iterator I = begin(), E = end(); I != E; ++I)
+    delete *I;
+  
+  Functions.clear();
+}
+ 
+bool Collector::initializeCustomLowering(Module &M) { return false; }
+ 
+bool Collector::performCustomLowering(Function &F) {
+  cerr << "gc " << getName() << " must override performCustomLowering.\n";
+  abort();
+  return 0;
+}
+    
+CollectorMetadata *Collector::insertFunctionMetadata(const Function &F) {
+  CollectorMetadata *CM = new CollectorMetadata(F, *this);
+  Functions.push_back(CM);
+  return CM;
+} 
+
+// -----------------------------------------------------------------------------
+
+FunctionPass *llvm::createGCLoweringPass() {
+  return new LowerIntrinsics();
+}
+ 
+char LowerIntrinsics::ID = 0;
+
+LowerIntrinsics::LowerIntrinsics()
+  : FunctionPass((intptr_t)&ID) {}
+
+const char *LowerIntrinsics::getPassName() const {
+  return "Lower Garbage Collection Instructions";
+}
+    
+void LowerIntrinsics::getAnalysisUsage(AnalysisUsage &AU) const {
+  FunctionPass::getAnalysisUsage(AU);
+  AU.addRequired<CollectorModuleMetadata>();
+}
+
+/// 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).
+  CollectorModuleMetadata *CMM = getAnalysisToUpdate<CollectorModuleMetadata>();
+  assert(CMM && "LowerIntrinsics didn't require CollectorModuleMetadata!?");
+  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
+    if (I->hasCollector())
+      CMM->get(*I); // Instantiate the Collector.
+  
+  bool MadeChange = false;
+  for (CollectorModuleMetadata::iterator I = CMM->begin(),
+                                         E = CMM->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)) {
+      new StoreInst(ConstantPointerNull::get(cast<PointerType>(
+                      cast<PointerType>((*I)->getType())->getElementType())),
+                    *I, IP);
+      MadeChange = true;
+    }
+  
+  return MadeChange;
+}
+
+bool LowerIntrinsics::NeedsDefaultLoweringPass(const Collector &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 Collector &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.hasCollector()) return false;
+  
+  CollectorMetadata &MD = getAnalysis<CollectorModuleMetadata>().get(F);
+  Collector &Coll = MD.getCollector();
+  
+  bool MadeChange = false;
+  
+  if (NeedsDefaultLoweringPass(Coll))
+    MadeChange |= PerformDefaultLowering(F, Coll);
+  
+  if (NeedsCustomLoweringPass(Coll))
+    MadeChange |= Coll.performCustomLowering(F);
+  
+  return MadeChange;
+}
+
+bool LowerIntrinsics::PerformDefaultLowering(Function &F, Collector &Coll) {
+  bool LowerWr = !Coll.customWriteBarrier();
+  bool LowerRd = !Coll.customReadBarrier();
+  bool InitRoots = Coll.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->getOperand(1), CI->getOperand(3), 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->getOperand(2), "", 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->getOperand(1)->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(intptr_t(&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<CollectorModuleMetadata>();
+}
+
+unsigned MachineCodeAnalysis::InsertLabel(MachineBasicBlock &MBB, 
+                                     MachineBasicBlock::iterator MI) const {
+  unsigned Label = MMI->NextLabelID();
+  BuildMI(MBB, MI, TII->get(TargetInstrInfo::GC_LABEL)).addImm(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 (MD->getCollector().needsSafePoint(GC::PreCall))
+    MD->addSafePoint(GC::PreCall, InsertLabel(*CI->getParent(), CI));
+  
+  if (MD->getCollector().needsSafePoint(GC::PostCall))
+    MD->addSafePoint(GC::PostCall, InsertLabel(*CI->getParent(), RAI));
+}
+
+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) {
+  uint64_t StackSize = MFI->getStackSize();
+  uint64_t OffsetAdjustment = MFI->getOffsetAdjustment();
+  uint64_t OffsetOfLocalArea = TM->getFrameInfo()->getOffsetOfLocalArea();
+  
+  for (CollectorMetadata::roots_iterator RI = MD->roots_begin(),
+                                         RE = MD->roots_end(); RI != RE; ++RI)
+    RI->StackOffset = MFI->getObjectOffset(RI->Num) + StackSize
+                      - OffsetOfLocalArea + OffsetAdjustment;
+}
+
+bool MachineCodeAnalysis::runOnMachineFunction(MachineFunction &MF) {
+  // Quick exit for functions that do not use GC.
+  if (!MF.getFunction()->hasCollector()) return false;
+  
+  MD = &getAnalysis<CollectorModuleMetadata>().get(*MF.getFunction());
+  if (!MD->getCollector().needsSafePoints())
+    return false;
+  
+  TM = &MF.getTarget();
+  MMI = &getAnalysis<MachineModuleInfo>();
+  TII = TM->getInstrInfo();
+  MFI = MF.getFrameInfo();
+  
+  // Find the size of the stack frame.
+  MD->setFrameSize(MFI->getStackSize());
+  
+  // Find all safe points.
+  FindSafePoints(MF);
+  
+  // Find the stack offsets for all roots.
+  FindStackOffsets(MF);
+  
+  return false;
+}