GCRootLowering.cpp [plain text]
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/GCStrategy.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 {
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;
};
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) {
return !C.customWriteBarrier() || !C.customReadBarrier() ||
C.initializeRoots();
}
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);
return false;
}
static bool CouldBecomeSafePoint(Instruction *I) {
if (isa<AllocaInst>(I) || isa<GetElementPtrInst>(I) || isa<StoreInst>(I) ||
isa<LoadInst>(I))
return false;
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;
}
static bool InsertRootInitializers(Function &F, AllocaInst **Roots,
unsigned Count) {
BasicBlock::iterator IP = F.getEntryBlock().begin();
while (isa<AllocaInst>(IP))
++IP;
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);
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::runOnFunction(Function &F) {
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) {
Value *St =
new StoreInst(CI->getArgOperand(0), CI->getArgOperand(2), CI);
CI->replaceAllUsesWith(St);
CI->eraseFromParent();
}
break;
case Intrinsic::gcread:
if (LowerRd) {
Value *Ld = new LoadInst(CI->getArgOperand(1), "", CI);
Ld->takeName(CI);
CI->replaceAllUsesWith(Ld);
CI->eraseFromParent();
}
break;
case Intrinsic::gcroot:
if (InitRoots) {
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) {
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()) {
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 (MF.getFrameInfo()->isDeadObjectIndex(RI->Num)) {
RI = FI->removeStackRoot(RI);
} else {
RI->StackOffset = TFI->getFrameIndexOffset(MF, RI->Num);
++RI;
}
}
}
bool GCMachineCodeAnalysis::runOnMachineFunction(MachineFunction &MF) {
if (!MF.getFunction()->hasGC())
return false;
FI = &getAnalysis<GCModuleInfo>().getFunctionInfo(*MF.getFunction());
if (!FI->getStrategy().needsSafePoints())
return false;
MMI = &getAnalysis<MachineModuleInfo>();
TII = MF.getSubtarget().getInstrInfo();
FI->setFrameSize(MF.getFrameInfo()->getStackSize());
FindSafePoints(MF);
FindStackOffsets(MF);
return false;
}