DependencyAnalysis.cpp [plain text]
#include "ObjCARC.h"
#include "DependencyAnalysis.h"
#include "ProvenanceAnalysis.h"
#include "llvm/IR/CFG.h"
using namespace llvm;
using namespace llvm::objcarc;
#define DEBUG_TYPE "objc-arc-dependency"
bool llvm::objcarc::CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
ProvenanceAnalysis &PA,
ARCInstKind Class) {
switch (Class) {
case ARCInstKind::Autorelease:
case ARCInstKind::AutoreleaseRV:
case ARCInstKind::IntrinsicUser:
case ARCInstKind::User:
return false;
default: break;
}
ImmutableCallSite CS = static_cast<const Value *>(Inst);
assert(CS && "Only calls can alter reference counts!");
AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
if (AliasAnalysis::onlyReadsMemory(MRB))
return false;
if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
const DataLayout &DL = Inst->getModule()->getDataLayout();
for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
I != E; ++I) {
const Value *Op = *I;
if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) &&
PA.related(Ptr, Op, DL))
return true;
}
return false;
}
return true;
}
bool llvm::objcarc::CanDecrementRefCount(const Instruction *Inst,
const Value *Ptr,
ProvenanceAnalysis &PA,
ARCInstKind Class) {
if (!CanDecrementRefCount(Class))
return false;
return CanAlterRefCount(Inst, Ptr, PA, Class);
}
bool llvm::objcarc::CanUse(const Instruction *Inst, const Value *Ptr,
ProvenanceAnalysis &PA, ARCInstKind Class) {
if (Class == ARCInstKind::Call)
return false;
const DataLayout &DL = Inst->getModule()->getDataLayout();
if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
if (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
return false;
} else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
OE = CS.arg_end(); OI != OE; ++OI) {
const Value *Op = *OI;
if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) &&
PA.related(Ptr, Op, DL))
return true;
}
return false;
} else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand(), DL);
return IsPotentialRetainableObjPtr(Op, *PA.getAA()) &&
PA.related(Op, Ptr, DL);
}
for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
OI != OE; ++OI) {
const Value *Op = *OI;
if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op, DL))
return true;
}
return false;
}
bool
llvm::objcarc::Depends(DependenceKind Flavor, Instruction *Inst,
const Value *Arg, ProvenanceAnalysis &PA) {
if (Inst == Arg)
return true;
switch (Flavor) {
case NeedsPositiveRetainCount: {
ARCInstKind Class = GetARCInstKind(Inst);
switch (Class) {
case ARCInstKind::AutoreleasepoolPop:
case ARCInstKind::AutoreleasepoolPush:
case ARCInstKind::None:
return false;
default:
return CanUse(Inst, Arg, PA, Class);
}
}
case AutoreleasePoolBoundary: {
ARCInstKind Class = GetARCInstKind(Inst);
switch (Class) {
case ARCInstKind::AutoreleasepoolPop:
case ARCInstKind::AutoreleasepoolPush:
return true;
default:
return false;
}
}
case CanChangeRetainCount: {
ARCInstKind Class = GetARCInstKind(Inst);
switch (Class) {
case ARCInstKind::AutoreleasepoolPop:
return true;
case ARCInstKind::AutoreleasepoolPush:
case ARCInstKind::None:
return false;
default:
return CanAlterRefCount(Inst, Arg, PA, Class);
}
}
case RetainAutoreleaseDep:
switch (GetBasicARCInstKind(Inst)) {
case ARCInstKind::AutoreleasepoolPop:
case ARCInstKind::AutoreleasepoolPush:
return true;
case ARCInstKind::Retain:
case ARCInstKind::RetainRV:
return GetArgRCIdentityRoot(Inst) == Arg;
default:
return false;
}
case RetainAutoreleaseRVDep: {
ARCInstKind Class = GetBasicARCInstKind(Inst);
switch (Class) {
case ARCInstKind::Retain:
case ARCInstKind::RetainRV:
return GetArgRCIdentityRoot(Inst) == Arg;
default:
return CanInterruptRV(Class);
}
}
case RetainRVDep:
return CanInterruptRV(GetBasicARCInstKind(Inst));
}
llvm_unreachable("Invalid dependence flavor");
}
void
llvm::objcarc::FindDependencies(DependenceKind Flavor,
const Value *Arg,
BasicBlock *StartBB, Instruction *StartInst,
SmallPtrSetImpl<Instruction *> &DependingInsts,
SmallPtrSetImpl<const BasicBlock *> &Visited,
ProvenanceAnalysis &PA) {
BasicBlock::iterator StartPos = StartInst;
SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
Worklist.push_back(std::make_pair(StartBB, StartPos));
do {
std::pair<BasicBlock *, BasicBlock::iterator> Pair =
Worklist.pop_back_val();
BasicBlock *LocalStartBB = Pair.first;
BasicBlock::iterator LocalStartPos = Pair.second;
BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
for (;;) {
if (LocalStartPos == StartBBBegin) {
pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
if (PI == PE)
DependingInsts.insert(nullptr);
else
do {
BasicBlock *PredBB = *PI;
if (Visited.insert(PredBB).second)
Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
} while (++PI != PE);
break;
}
Instruction *Inst = --LocalStartPos;
if (Depends(Flavor, Inst, Arg, PA)) {
DependingInsts.insert(Inst);
break;
}
}
} while (!Worklist.empty());
for (const BasicBlock *BB : Visited) {
if (BB == StartBB)
continue;
const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
const BasicBlock *Succ = *SI;
if (Succ != StartBB && !Visited.count(Succ)) {
DependingInsts.insert(reinterpret_cast<Instruction *>(-1));
return;
}
}
}
}