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https://github.com/c64scene-ar/llvm-6502.git
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22f35ace45
instruction to insert before can be end(). getDebugLoc on end() returns an invalid value, therefore use the debug loc of the call instruction, and give it to InsertLabel. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81207 91177308-0d34-0410-b5e6-96231b3b80d8
400 lines
13 KiB
C++
400 lines
13 KiB
C++
//===-- GCStrategy.cpp - Garbage collection infrastructure -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements target- and collector-independent garbage collection
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// infrastructure.
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//
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// MachineCodeAnalysis identifies the GC safe points in the machine code. Roots
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// are identified in SelectionDAGISel.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/GCStrategy.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Module.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/Target/TargetFrameInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace {
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/// LowerIntrinsics - This pass rewrites calls to the llvm.gcread or
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/// llvm.gcwrite intrinsics, replacing them with simple loads and stores as
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/// directed by the GCStrategy. It also performs automatic root initialization
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/// and custom intrinsic lowering.
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class VISIBILITY_HIDDEN LowerIntrinsics : public FunctionPass {
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static bool NeedsDefaultLoweringPass(const GCStrategy &C);
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static bool NeedsCustomLoweringPass(const GCStrategy &C);
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static bool CouldBecomeSafePoint(Instruction *I);
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bool PerformDefaultLowering(Function &F, GCStrategy &Coll);
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static bool InsertRootInitializers(Function &F,
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AllocaInst **Roots, unsigned Count);
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public:
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static char ID;
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LowerIntrinsics();
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const char *getPassName() const;
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void getAnalysisUsage(AnalysisUsage &AU) const;
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bool doInitialization(Module &M);
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bool runOnFunction(Function &F);
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};
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/// MachineCodeAnalysis - This is a target-independent pass over the machine
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/// function representation to identify safe points for the garbage collector
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/// in the machine code. It inserts labels at safe points and populates a
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/// GCMetadata record for each function.
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class VISIBILITY_HIDDEN MachineCodeAnalysis : public MachineFunctionPass {
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const TargetMachine *TM;
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GCFunctionInfo *FI;
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MachineModuleInfo *MMI;
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const TargetInstrInfo *TII;
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void FindSafePoints(MachineFunction &MF);
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void VisitCallPoint(MachineBasicBlock::iterator MI);
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unsigned InsertLabel(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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DebugLoc DL) const;
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void FindStackOffsets(MachineFunction &MF);
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public:
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static char ID;
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MachineCodeAnalysis();
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const char *getPassName() const;
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void getAnalysisUsage(AnalysisUsage &AU) const;
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bool runOnMachineFunction(MachineFunction &MF);
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};
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}
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// -----------------------------------------------------------------------------
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GCStrategy::GCStrategy() :
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NeededSafePoints(0),
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CustomReadBarriers(false),
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CustomWriteBarriers(false),
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CustomRoots(false),
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InitRoots(true),
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UsesMetadata(false)
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{}
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GCStrategy::~GCStrategy() {
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for (iterator I = begin(), E = end(); I != E; ++I)
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delete *I;
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Functions.clear();
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}
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bool GCStrategy::initializeCustomLowering(Module &M) { return false; }
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bool GCStrategy::performCustomLowering(Function &F) {
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errs() << "gc " << getName() << " must override performCustomLowering.\n";
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llvm_unreachable(0);
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return 0;
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}
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GCFunctionInfo *GCStrategy::insertFunctionInfo(const Function &F) {
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GCFunctionInfo *FI = new GCFunctionInfo(F, *this);
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Functions.push_back(FI);
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return FI;
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}
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// -----------------------------------------------------------------------------
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FunctionPass *llvm::createGCLoweringPass() {
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return new LowerIntrinsics();
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}
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char LowerIntrinsics::ID = 0;
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LowerIntrinsics::LowerIntrinsics()
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: FunctionPass(&ID) {}
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const char *LowerIntrinsics::getPassName() const {
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return "Lower Garbage Collection Instructions";
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}
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void LowerIntrinsics::getAnalysisUsage(AnalysisUsage &AU) const {
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FunctionPass::getAnalysisUsage(AU);
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AU.addRequired<GCModuleInfo>();
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}
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/// doInitialization - If this module uses the GC intrinsics, find them now.
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bool LowerIntrinsics::doInitialization(Module &M) {
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// FIXME: This is rather antisocial in the context of a JIT since it performs
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// work against the entire module. But this cannot be done at
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// runFunction time (initializeCustomLowering likely needs to change
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// the module).
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GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
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assert(MI && "LowerIntrinsics didn't require GCModuleInfo!?");
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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if (!I->isDeclaration() && I->hasGC())
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MI->getFunctionInfo(*I); // Instantiate the GC strategy.
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bool MadeChange = false;
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for (GCModuleInfo::iterator I = MI->begin(), E = MI->end(); I != E; ++I)
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if (NeedsCustomLoweringPass(**I))
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if ((*I)->initializeCustomLowering(M))
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MadeChange = true;
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return MadeChange;
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}
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bool LowerIntrinsics::InsertRootInitializers(Function &F, AllocaInst **Roots,
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unsigned Count) {
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// Scroll past alloca instructions.
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BasicBlock::iterator IP = F.getEntryBlock().begin();
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while (isa<AllocaInst>(IP)) ++IP;
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// Search for initializers in the initial BB.
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SmallPtrSet<AllocaInst*,16> InitedRoots;
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for (; !CouldBecomeSafePoint(IP); ++IP)
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if (StoreInst *SI = dyn_cast<StoreInst>(IP))
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if (AllocaInst *AI =
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dyn_cast<AllocaInst>(SI->getOperand(1)->stripPointerCasts()))
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InitedRoots.insert(AI);
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// Add root initializers.
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bool MadeChange = false;
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for (AllocaInst **I = Roots, **E = Roots + Count; I != E; ++I)
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if (!InitedRoots.count(*I)) {
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new StoreInst(ConstantPointerNull::get(cast<PointerType>(
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cast<PointerType>((*I)->getType())->getElementType())),
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*I, IP);
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MadeChange = true;
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}
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return MadeChange;
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}
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bool LowerIntrinsics::NeedsDefaultLoweringPass(const GCStrategy &C) {
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// Default lowering is necessary only if read or write barriers have a default
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// action. The default for roots is no action.
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return !C.customWriteBarrier()
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|| !C.customReadBarrier()
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|| C.initializeRoots();
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}
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bool LowerIntrinsics::NeedsCustomLoweringPass(const GCStrategy &C) {
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// Custom lowering is only necessary if enabled for some action.
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return C.customWriteBarrier()
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|| C.customReadBarrier()
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|| C.customRoots();
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}
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/// CouldBecomeSafePoint - Predicate to conservatively determine whether the
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/// instruction could introduce a safe point.
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bool LowerIntrinsics::CouldBecomeSafePoint(Instruction *I) {
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// The natural definition of instructions which could introduce safe points
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// are:
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//
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// - call, invoke (AfterCall, BeforeCall)
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// - phis (Loops)
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// - invoke, ret, unwind (Exit)
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//
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// However, instructions as seemingly inoccuous as arithmetic can become
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// libcalls upon lowering (e.g., div i64 on a 32-bit platform), so instead
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// it is necessary to take a conservative approach.
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if (isa<AllocaInst>(I) || isa<GetElementPtrInst>(I) ||
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isa<StoreInst>(I) || isa<LoadInst>(I))
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return false;
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// llvm.gcroot is safe because it doesn't do anything at runtime.
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if (CallInst *CI = dyn_cast<CallInst>(I))
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if (Function *F = CI->getCalledFunction())
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if (unsigned IID = F->getIntrinsicID())
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if (IID == Intrinsic::gcroot)
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return false;
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return true;
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}
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/// runOnFunction - Replace gcread/gcwrite intrinsics with loads and stores.
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/// Leave gcroot intrinsics; the code generator needs to see those.
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bool LowerIntrinsics::runOnFunction(Function &F) {
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// Quick exit for functions that do not use GC.
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if (!F.hasGC())
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return false;
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GCFunctionInfo &FI = getAnalysis<GCModuleInfo>().getFunctionInfo(F);
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GCStrategy &S = FI.getStrategy();
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bool MadeChange = false;
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if (NeedsDefaultLoweringPass(S))
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MadeChange |= PerformDefaultLowering(F, S);
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if (NeedsCustomLoweringPass(S))
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MadeChange |= S.performCustomLowering(F);
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return MadeChange;
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}
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bool LowerIntrinsics::PerformDefaultLowering(Function &F, GCStrategy &S) {
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bool LowerWr = !S.customWriteBarrier();
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bool LowerRd = !S.customReadBarrier();
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bool InitRoots = S.initializeRoots();
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SmallVector<AllocaInst*,32> Roots;
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bool MadeChange = false;
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for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
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for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) {
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if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++)) {
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Function *F = CI->getCalledFunction();
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switch (F->getIntrinsicID()) {
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case Intrinsic::gcwrite:
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if (LowerWr) {
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// Replace a write barrier with a simple store.
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Value *St = new StoreInst(CI->getOperand(1), CI->getOperand(3), CI);
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CI->replaceAllUsesWith(St);
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CI->eraseFromParent();
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}
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break;
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case Intrinsic::gcread:
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if (LowerRd) {
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// Replace a read barrier with a simple load.
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Value *Ld = new LoadInst(CI->getOperand(2), "", CI);
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Ld->takeName(CI);
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CI->replaceAllUsesWith(Ld);
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CI->eraseFromParent();
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}
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break;
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case Intrinsic::gcroot:
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if (InitRoots) {
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// Initialize the GC root, but do not delete the intrinsic. The
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// backend needs the intrinsic to flag the stack slot.
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Roots.push_back(cast<AllocaInst>(
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CI->getOperand(1)->stripPointerCasts()));
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}
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break;
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default:
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continue;
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}
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MadeChange = true;
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}
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}
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}
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if (Roots.size())
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MadeChange |= InsertRootInitializers(F, Roots.begin(), Roots.size());
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return MadeChange;
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}
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// -----------------------------------------------------------------------------
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FunctionPass *llvm::createGCMachineCodeAnalysisPass() {
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return new MachineCodeAnalysis();
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}
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char MachineCodeAnalysis::ID = 0;
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MachineCodeAnalysis::MachineCodeAnalysis()
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: MachineFunctionPass(&ID) {}
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const char *MachineCodeAnalysis::getPassName() const {
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return "Analyze Machine Code For Garbage Collection";
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}
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void MachineCodeAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
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MachineFunctionPass::getAnalysisUsage(AU);
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AU.setPreservesAll();
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AU.addRequired<MachineModuleInfo>();
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AU.addRequired<GCModuleInfo>();
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}
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unsigned MachineCodeAnalysis::InsertLabel(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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DebugLoc DL) const {
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unsigned Label = MMI->NextLabelID();
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BuildMI(MBB, MI, DL,
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TII->get(TargetInstrInfo::GC_LABEL)).addImm(Label);
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return Label;
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}
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void MachineCodeAnalysis::VisitCallPoint(MachineBasicBlock::iterator CI) {
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// Find the return address (next instruction), too, so as to bracket the call
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// instruction.
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MachineBasicBlock::iterator RAI = CI;
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++RAI;
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if (FI->getStrategy().needsSafePoint(GC::PreCall))
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FI->addSafePoint(GC::PreCall, InsertLabel(*CI->getParent(), CI,
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CI->getDebugLoc()));
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if (FI->getStrategy().needsSafePoint(GC::PostCall))
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FI->addSafePoint(GC::PostCall, InsertLabel(*CI->getParent(), RAI,
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CI->getDebugLoc()));
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}
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void MachineCodeAnalysis::FindSafePoints(MachineFunction &MF) {
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for (MachineFunction::iterator BBI = MF.begin(),
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BBE = MF.end(); BBI != BBE; ++BBI)
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for (MachineBasicBlock::iterator MI = BBI->begin(),
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ME = BBI->end(); MI != ME; ++MI)
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if (MI->getDesc().isCall())
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VisitCallPoint(MI);
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}
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void MachineCodeAnalysis::FindStackOffsets(MachineFunction &MF) {
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const TargetRegisterInfo *TRI = TM->getRegisterInfo();
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assert(TRI && "TargetRegisterInfo not available!");
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for (GCFunctionInfo::roots_iterator RI = FI->roots_begin(),
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RE = FI->roots_end(); RI != RE; ++RI)
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RI->StackOffset = TRI->getFrameIndexOffset(MF, RI->Num);
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}
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bool MachineCodeAnalysis::runOnMachineFunction(MachineFunction &MF) {
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// Quick exit for functions that do not use GC.
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if (!MF.getFunction()->hasGC())
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return false;
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FI = &getAnalysis<GCModuleInfo>().getFunctionInfo(*MF.getFunction());
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if (!FI->getStrategy().needsSafePoints())
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return false;
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TM = &MF.getTarget();
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MMI = &getAnalysis<MachineModuleInfo>();
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TII = TM->getInstrInfo();
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// Find the size of the stack frame.
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FI->setFrameSize(MF.getFrameInfo()->getStackSize());
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// Find all safe points.
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FindSafePoints(MF);
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// Find the stack offsets for all roots.
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FindStackOffsets(MF);
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return false;
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}
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