#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
using namespace llvm;
static AtomicOrdering strongerOrdering(AtomicOrdering X, AtomicOrdering Y) {
if (X == Acquire && Y == Release)
return AcquireRelease;
if (Y == Acquire && X == Release)
return AcquireRelease;
return (AtomicOrdering)std::max(X, Y);
}
bool llvm::isSafeToDestroyConstant(const Constant *C) {
if (isa<GlobalValue>(C))
return false;
if (isa<ConstantInt>(C) || isa<ConstantFP>(C))
return false;
for (const User *U : C->users())
if (const Constant *CU = dyn_cast<Constant>(U)) {
if (!isSafeToDestroyConstant(CU))
return false;
} else
return false;
return true;
}
static bool analyzeGlobalAux(const Value *V, GlobalStatus &GS,
SmallPtrSetImpl<const PHINode *> &PhiUsers) {
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
if (GV->isExternallyInitialized())
GS.StoredType = GlobalStatus::StoredOnce;
for (const Use &U : V->uses()) {
const User *UR = U.getUser();
if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(UR)) {
GS.HasNonInstructionUser = true;
if (!isa<PointerType>(CE->getType()))
return true;
if (analyzeGlobalAux(CE, GS, PhiUsers))
return true;
} else if (const Instruction *I = dyn_cast<Instruction>(UR)) {
if (!GS.HasMultipleAccessingFunctions) {
const Function *F = I->getParent()->getParent();
if (!GS.AccessingFunction)
GS.AccessingFunction = F;
else if (GS.AccessingFunction != F)
GS.HasMultipleAccessingFunctions = true;
}
if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
GS.IsLoaded = true;
if (LI->isVolatile())
return true;
GS.Ordering = strongerOrdering(GS.Ordering, LI->getOrdering());
} else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (SI->getOperand(0) == V)
return true;
if (SI->isVolatile())
return true;
GS.Ordering = strongerOrdering(GS.Ordering, SI->getOrdering());
if (GS.StoredType != GlobalStatus::Stored) {
if (const GlobalVariable *GV =
dyn_cast<GlobalVariable>(SI->getOperand(1))) {
Value *StoredVal = SI->getOperand(0);
if (Constant *C = dyn_cast<Constant>(StoredVal)) {
if (C->isThreadDependent()) {
return true;
}
}
if (StoredVal == GV->getInitializer()) {
if (GS.StoredType < GlobalStatus::InitializerStored)
GS.StoredType = GlobalStatus::InitializerStored;
} else if (isa<LoadInst>(StoredVal) &&
cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
if (GS.StoredType < GlobalStatus::InitializerStored)
GS.StoredType = GlobalStatus::InitializerStored;
} else if (GS.StoredType < GlobalStatus::StoredOnce) {
GS.StoredType = GlobalStatus::StoredOnce;
GS.StoredOnceValue = StoredVal;
} else if (GS.StoredType == GlobalStatus::StoredOnce &&
GS.StoredOnceValue == StoredVal) {
} else {
GS.StoredType = GlobalStatus::Stored;
}
} else {
GS.StoredType = GlobalStatus::Stored;
}
}
} else if (isa<BitCastInst>(I)) {
if (analyzeGlobalAux(I, GS, PhiUsers))
return true;
} else if (isa<GetElementPtrInst>(I)) {
if (analyzeGlobalAux(I, GS, PhiUsers))
return true;
} else if (isa<SelectInst>(I)) {
if (analyzeGlobalAux(I, GS, PhiUsers))
return true;
} else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
if (PhiUsers.insert(PN).second) if (analyzeGlobalAux(I, GS, PhiUsers))
return true;
} else if (isa<CmpInst>(I)) {
GS.IsCompared = true;
} else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
if (MTI->isVolatile())
return true;
if (MTI->getArgOperand(0) == V)
GS.StoredType = GlobalStatus::Stored;
if (MTI->getArgOperand(1) == V)
GS.IsLoaded = true;
} else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
if (MSI->isVolatile())
return true;
GS.StoredType = GlobalStatus::Stored;
} else if (auto C = ImmutableCallSite(I)) {
if (!C.isCallee(&U))
return true;
GS.IsLoaded = true;
} else {
return true; }
} else if (const Constant *C = dyn_cast<Constant>(UR)) {
GS.HasNonInstructionUser = true;
if (!isSafeToDestroyConstant(C))
return true;
} else {
GS.HasNonInstructionUser = true;
return true;
}
}
return false;
}
bool GlobalStatus::analyzeGlobal(const Value *V, GlobalStatus &GS) {
SmallPtrSet<const PHINode *, 16> PhiUsers;
return analyzeGlobalAux(V, GS, PhiUsers);
}
GlobalStatus::GlobalStatus()
: IsCompared(false), IsLoaded(false), StoredType(NotStored),
StoredOnceValue(nullptr), AccessingFunction(nullptr),
HasMultipleAccessingFunctions(false), HasNonInstructionUser(false),
Ordering(NotAtomic) {}