llvm-6502/lib/CodeGen/Collector.cpp
Dan Gohman 4406604047 Split ISD::LABEL into ISD::DBG_LABEL and ISD::EH_LABEL, eliminating
the need for a flavor operand, and add a new SDNode subclass,
LabelSDNode, for use with them to eliminate the need for a label id
operand.

Change instruction selection to let these label nodes through
unmodified instead of creating copies of them. Teach the MachineInstr
emitter how to emit a MachineInstr directly from an ISD label node.

This avoids the need for allocating SDNodes for the label id and
flavor value, as well as SDNodes for each of the post-isel label,
label id, and label flavor.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52943 91177308-0d34-0410-b5e6-96231b3b80d8
2008-07-01 00:05:16 +00:00

401 lines
13 KiB
C++

//===-- 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/Collector.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/ADT/SmallPtrSet.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)
{}
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;
}
void Collector::beginAssembly(std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI) {
// Default is no action.
}
void Collector::finishAssembly(std::ostream &OS, AsmPrinter &AP,
const TargetAsmInfo &TAI) {
// Default is no action.
}
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;
}