Vendor import of llvm trunk r238337:vendor/llvm/llvm-trunk-r238337

https://llvm.org/svn/llvm-project/llvm/trunk@238337

1 files changed, 354 insertions, 0 deletions

diff --git a/lib/CodeGen/GCRootLowering.cpp b/lib/CodeGen/GCRootLowering.cpp
new file mode 100644
index 000000000000..d8edd7e4063f
--- /dev/null
+++ b/lib/CodeGen/GCRootLowering.cpp
@@ -0,0 +1,354 @@
+//===-- GCRootLowering.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 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/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"
+#include "llvm/Target/TargetFrameLowering.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.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 PerformDefaultLowering(Function &F, GCStrategy &Coll);
+
+public:
+  static char ID;
+
+  LowerIntrinsics();
+  const char *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 MI);
+  MCSymbol *InsertLabel(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+                        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());
+}
+
+const char *LowerIntrinsics::getPassName() const {
+  return "Lower Garbage Collection Instructions";
+}
+
+void LowerIntrinsics::getAnalysisUsage(AnalysisUsage &AU) const {
+  FunctionPass::getAnalysisUsage(AU);
+  AU.addRequired<GCModuleInfo>();
+  AU.addPreserved<DominatorTreeWrapperPass>();
+}
+
+static bool 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();
+}
+
+/// 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, 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;
+}
+
+/// 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);
+
+  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;
+}
+
+// -----------------------------------------------------------------------------
+
+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<MachineModuleInfo>();
+  AU.addRequired<GCModuleInfo>();
+}
+
+MCSymbol *GCMachineCodeAnalysis::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 GCMachineCodeAnalysis::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)) {
+    MCSymbol *Label = InsertLabel(*CI->getParent(), CI, CI->getDebugLoc());
+    FI->addSafePoint(GC::PreCall, Label, CI->getDebugLoc());
+  }
+
+  if (FI->getStrategy().needsSafePoint(GC::PostCall)) {
+    MCSymbol *Label = InsertLabel(*CI->getParent(), RAI, CI->getDebugLoc());
+    FI->addSafePoint(GC::PostCall, Label, CI->getDebugLoc());
+  }
+}
+
+void GCMachineCodeAnalysis::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->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 {
+      RI->StackOffset = TFI->getFrameIndexOffset(MF, RI->Num);
+      ++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<MachineModuleInfo>();
+  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;
+}