// those aren't comprehensive either. Second, many conditions cannot be
// checked statically. This pass does no dynamic instrumentation, so it
// can't check for all possible problems.
-//
+//
// Another limitation is that it assumes all code will be executed. A store
// through a null pointer in a basic block which is never reached is harmless,
// but this pass will warn about it anyway. This is the main reason why most
// less obvious. If an optimization pass appears to be introducing a warning,
// it may be that the optimization pass is merely exposing an existing
// condition in the code.
-//
+//
// This code may be run before instcombine. In many cases, instcombine checks
// for the same kinds of things and turns instructions with undefined behavior
// into unreachable (or equivalent). Because of this, this pass makes some
// effort to look through bitcasts and so on.
-//
+//
//===----------------------------------------------------------------------===//
-#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Lint.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/AssumptionTracker.h"
#include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/Analysis/Lint.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/Loads.h"
+#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/Assembly/Writer.h"
-#include "llvm/Target/TargetData.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/PassManager.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Function.h"
-#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
-#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/Target/TargetLibraryInfo.h"
using namespace llvm;
namespace {
void visitCallSite(CallSite CS);
void visitMemoryReference(Instruction &I, Value *Ptr,
uint64_t Size, unsigned Align,
- const Type *Ty, unsigned Flags);
+ Type *Ty, unsigned Flags);
void visitCallInst(CallInst &I);
void visitInvokeInst(InvokeInst &I);
Value *findValue(Value *V, bool OffsetOk) const;
Value *findValueImpl(Value *V, bool OffsetOk,
- SmallPtrSet<Value *, 4> &Visited) const;
+ SmallPtrSetImpl<Value *> &Visited) const;
public:
Module *Mod;
AliasAnalysis *AA;
+ AssumptionTracker *AT;
DominatorTree *DT;
- TargetData *TD;
+ const DataLayout *DL;
+ TargetLibraryInfo *TLI;
std::string Messages;
raw_string_ostream MessagesStr;
initializeLintPass(*PassRegistry::getPassRegistry());
}
- virtual bool runOnFunction(Function &F);
+ bool runOnFunction(Function &F) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
AU.addRequired<AliasAnalysis>();
- AU.addRequired<DominatorTree>();
+ AU.addRequired<AssumptionTracker>();
+ AU.addRequired<TargetLibraryInfo>();
+ AU.addRequired<DominatorTreeWrapperPass>();
}
- virtual void print(raw_ostream &O, const Module *M) const {}
+ void print(raw_ostream &O, const Module *M) const override {}
void WriteValue(const Value *V) {
if (!V) return;
if (isa<Instruction>(V)) {
MessagesStr << *V << '\n';
} else {
- WriteAsOperand(MessagesStr, V, true, Mod);
+ V->printAsOperand(MessagesStr, true, Mod);
MessagesStr << '\n';
}
}
// that failed. This provides a nice place to put a breakpoint if you want
// to see why something is not correct.
void CheckFailed(const Twine &Message,
- const Value *V1 = 0, const Value *V2 = 0,
- const Value *V3 = 0, const Value *V4 = 0) {
+ const Value *V1 = nullptr, const Value *V2 = nullptr,
+ const Value *V3 = nullptr, const Value *V4 = nullptr) {
MessagesStr << Message.str() << "\n";
WriteValue(V1);
WriteValue(V2);
char Lint::ID = 0;
INITIALIZE_PASS_BEGIN(Lint, "lint", "Statically lint-checks LLVM IR",
false, true)
-INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(AssumptionTracker)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(Lint, "lint", "Statically lint-checks LLVM IR",
false, true)
bool Lint::runOnFunction(Function &F) {
Mod = F.getParent();
AA = &getAnalysis<AliasAnalysis>();
- DT = &getAnalysis<DominatorTree>();
- TD = getAnalysisIfAvailable<TargetData>();
+ AT = &getAnalysis<AssumptionTracker>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : nullptr;
+ TLI = &getAnalysis<TargetLibraryInfo>();
visit(F);
dbgs() << MessagesStr.str();
Messages.clear();
Value *Callee = CS.getCalledValue();
visitMemoryReference(I, Callee, AliasAnalysis::UnknownSize,
- 0, 0, MemRef::Callee);
+ 0, nullptr, MemRef::Callee);
if (Function *F = dyn_cast<Function>(findValue(Callee, /*OffsetOk=*/false))) {
Assert1(CS.getCallingConv() == F->getCallingConv(),
"Undefined behavior: Caller and callee calling convention differ",
&I);
- const FunctionType *FT = F->getFunctionType();
- unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
+ FunctionType *FT = F->getFunctionType();
+ unsigned NumActualArgs = CS.arg_size();
Assert1(FT->isVarArg() ?
FT->getNumParams() <= NumActualArgs :
"Undefined behavior: Call argument type mismatches "
"callee parameter type", &I);
- // Check that noalias arguments don't alias other arguments. The
- // AliasAnalysis API isn't expressive enough for what we really want
- // to do. Known partial overlap is not distinguished from the case
- // where nothing is known.
+ // Check that noalias arguments don't alias other arguments. This is
+ // not fully precise because we don't know the sizes of the dereferenced
+ // memory regions.
if (Formal->hasNoAliasAttr() && Actual->getType()->isPointerTy())
for (CallSite::arg_iterator BI = CS.arg_begin(); BI != AE; ++BI)
- Assert1(AI == BI ||
- !(*BI)->getType()->isPointerTy() ||
- AA->alias(*AI, *BI) != AliasAnalysis::MustAlias,
- "Unusual: noalias argument aliases another argument", &I);
+ if (AI != BI && (*BI)->getType()->isPointerTy()) {
+ AliasAnalysis::AliasResult Result = AA->alias(*AI, *BI);
+ Assert1(Result != AliasAnalysis::MustAlias &&
+ Result != AliasAnalysis::PartialAlias,
+ "Unusual: noalias argument aliases another argument", &I);
+ }
// Check that an sret argument points to valid memory.
if (Formal->hasStructRetAttr() && Actual->getType()->isPointerTy()) {
- const Type *Ty =
+ Type *Ty =
cast<PointerType>(Formal->getType())->getElementType();
visitMemoryReference(I, Actual, AA->getTypeStoreSize(Ty),
- TD ? TD->getABITypeAlignment(Ty) : 0,
+ DL ? DL->getABITypeAlignment(Ty) : 0,
Ty, MemRef::Read | MemRef::Write);
}
}
MemCpyInst *MCI = cast<MemCpyInst>(&I);
// TODO: If the size is known, use it.
visitMemoryReference(I, MCI->getDest(), AliasAnalysis::UnknownSize,
- MCI->getAlignment(), 0,
+ MCI->getAlignment(), nullptr,
MemRef::Write);
visitMemoryReference(I, MCI->getSource(), AliasAnalysis::UnknownSize,
- MCI->getAlignment(), 0,
+ MCI->getAlignment(), nullptr,
MemRef::Read);
// Check that the memcpy arguments don't overlap. The AliasAnalysis API
MemMoveInst *MMI = cast<MemMoveInst>(&I);
// TODO: If the size is known, use it.
visitMemoryReference(I, MMI->getDest(), AliasAnalysis::UnknownSize,
- MMI->getAlignment(), 0,
+ MMI->getAlignment(), nullptr,
MemRef::Write);
visitMemoryReference(I, MMI->getSource(), AliasAnalysis::UnknownSize,
- MMI->getAlignment(), 0,
+ MMI->getAlignment(), nullptr,
MemRef::Read);
break;
}
MemSetInst *MSI = cast<MemSetInst>(&I);
// TODO: If the size is known, use it.
visitMemoryReference(I, MSI->getDest(), AliasAnalysis::UnknownSize,
- MSI->getAlignment(), 0,
+ MSI->getAlignment(), nullptr,
MemRef::Write);
break;
}
&I);
visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
- 0, 0, MemRef::Read | MemRef::Write);
+ 0, nullptr, MemRef::Read | MemRef::Write);
break;
case Intrinsic::vacopy:
visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
- 0, 0, MemRef::Write);
+ 0, nullptr, MemRef::Write);
visitMemoryReference(I, CS.getArgument(1), AliasAnalysis::UnknownSize,
- 0, 0, MemRef::Read);
+ 0, nullptr, MemRef::Read);
break;
case Intrinsic::vaend:
visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
- 0, 0, MemRef::Read | MemRef::Write);
+ 0, nullptr, MemRef::Read | MemRef::Write);
break;
case Intrinsic::stackrestore:
// stack pointer, which the compiler may read from or write to
// at any time, so check it for both readability and writeability.
visitMemoryReference(I, CS.getArgument(0), AliasAnalysis::UnknownSize,
- 0, 0, MemRef::Read | MemRef::Write);
+ 0, nullptr, MemRef::Read | MemRef::Write);
break;
}
}
// TODO: Check readnone/readonly function attributes.
void Lint::visitMemoryReference(Instruction &I,
Value *Ptr, uint64_t Size, unsigned Align,
- const Type *Ty, unsigned Flags) {
+ Type *Ty, unsigned Flags) {
// If no memory is being referenced, it doesn't matter if the pointer
// is valid.
if (Size == 0)
"Undefined behavior: Branch to non-blockaddress", &I);
}
- if (TD) {
- if (Align == 0 && Ty) Align = TD->getABITypeAlignment(Ty);
-
- if (Align != 0) {
- unsigned BitWidth = TD->getTypeSizeInBits(Ptr->getType());
- APInt Mask = APInt::getAllOnesValue(BitWidth),
- KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
- ComputeMaskedBits(Ptr, Mask, KnownZero, KnownOne, TD);
- Assert1(!(KnownOne & APInt::getLowBitsSet(BitWidth, Log2_32(Align))),
- "Undefined behavior: Memory reference address is misaligned", &I);
+ // Check for buffer overflows and misalignment.
+ // Only handles memory references that read/write something simple like an
+ // alloca instruction or a global variable.
+ int64_t Offset = 0;
+ if (Value *Base = GetPointerBaseWithConstantOffset(Ptr, Offset, DL)) {
+ // OK, so the access is to a constant offset from Ptr. Check that Ptr is
+ // something we can handle and if so extract the size of this base object
+ // along with its alignment.
+ uint64_t BaseSize = AliasAnalysis::UnknownSize;
+ unsigned BaseAlign = 0;
+
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(Base)) {
+ Type *ATy = AI->getAllocatedType();
+ if (DL && !AI->isArrayAllocation() && ATy->isSized())
+ BaseSize = DL->getTypeAllocSize(ATy);
+ BaseAlign = AI->getAlignment();
+ if (DL && BaseAlign == 0 && ATy->isSized())
+ BaseAlign = DL->getABITypeAlignment(ATy);
+ } else if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Base)) {
+ // If the global may be defined differently in another compilation unit
+ // then don't warn about funky memory accesses.
+ if (GV->hasDefinitiveInitializer()) {
+ Type *GTy = GV->getType()->getElementType();
+ if (DL && GTy->isSized())
+ BaseSize = DL->getTypeAllocSize(GTy);
+ BaseAlign = GV->getAlignment();
+ if (DL && BaseAlign == 0 && GTy->isSized())
+ BaseAlign = DL->getABITypeAlignment(GTy);
+ }
}
+
+ // Accesses from before the start or after the end of the object are not
+ // defined.
+ Assert1(Size == AliasAnalysis::UnknownSize ||
+ BaseSize == AliasAnalysis::UnknownSize ||
+ (Offset >= 0 && Offset + Size <= BaseSize),
+ "Undefined behavior: Buffer overflow", &I);
+
+ // Accesses that say that the memory is more aligned than it is are not
+ // defined.
+ if (DL && Align == 0 && Ty && Ty->isSized())
+ Align = DL->getABITypeAlignment(Ty);
+ Assert1(!BaseAlign || Align <= MinAlign(BaseAlign, Offset),
+ "Undefined behavior: Memory reference address is misaligned", &I);
}
}
"Undefined result: Shift count out of range", &I);
}
-static bool isZero(Value *V, TargetData *TD) {
+static bool isZero(Value *V, const DataLayout *DL, DominatorTree *DT,
+ AssumptionTracker *AT) {
// Assume undef could be zero.
- if (isa<UndefValue>(V)) return true;
+ if (isa<UndefValue>(V))
+ return true;
+
+ VectorType *VecTy = dyn_cast<VectorType>(V->getType());
+ if (!VecTy) {
+ unsigned BitWidth = V->getType()->getIntegerBitWidth();
+ APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+ computeKnownBits(V, KnownZero, KnownOne, DL,
+ 0, AT, dyn_cast<Instruction>(V), DT);
+ return KnownZero.isAllOnesValue();
+ }
+
+ // Per-component check doesn't work with zeroinitializer
+ Constant *C = dyn_cast<Constant>(V);
+ if (!C)
+ return false;
+
+ if (C->isZeroValue())
+ return true;
+
+ // For a vector, KnownZero will only be true if all values are zero, so check
+ // this per component
+ unsigned BitWidth = VecTy->getElementType()->getIntegerBitWidth();
+ for (unsigned I = 0, N = VecTy->getNumElements(); I != N; ++I) {
+ Constant *Elem = C->getAggregateElement(I);
+ if (isa<UndefValue>(Elem))
+ return true;
+
+ APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+ computeKnownBits(Elem, KnownZero, KnownOne, DL);
+ if (KnownZero.isAllOnesValue())
+ return true;
+ }
- unsigned BitWidth = cast<IntegerType>(V->getType())->getBitWidth();
- APInt Mask = APInt::getAllOnesValue(BitWidth),
- KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
- ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD);
- return KnownZero.isAllOnesValue();
+ return false;
}
void Lint::visitSDiv(BinaryOperator &I) {
- Assert1(!isZero(I.getOperand(1), TD),
+ Assert1(!isZero(I.getOperand(1), DL, DT, AT),
"Undefined behavior: Division by zero", &I);
}
void Lint::visitUDiv(BinaryOperator &I) {
- Assert1(!isZero(I.getOperand(1), TD),
+ Assert1(!isZero(I.getOperand(1), DL, DT, AT),
"Undefined behavior: Division by zero", &I);
}
void Lint::visitSRem(BinaryOperator &I) {
- Assert1(!isZero(I.getOperand(1), TD),
+ Assert1(!isZero(I.getOperand(1), DL, DT, AT),
"Undefined behavior: Division by zero", &I);
}
void Lint::visitURem(BinaryOperator &I) {
- Assert1(!isZero(I.getOperand(1), TD),
+ Assert1(!isZero(I.getOperand(1), DL, DT, AT),
"Undefined behavior: Division by zero", &I);
}
}
void Lint::visitVAArgInst(VAArgInst &I) {
- visitMemoryReference(I, I.getOperand(0), AliasAnalysis::UnknownSize, 0, 0,
- MemRef::Read | MemRef::Write);
+ visitMemoryReference(I, I.getOperand(0), AliasAnalysis::UnknownSize, 0,
+ nullptr, MemRef::Read | MemRef::Write);
}
void Lint::visitIndirectBrInst(IndirectBrInst &I) {
- visitMemoryReference(I, I.getAddress(), AliasAnalysis::UnknownSize, 0, 0,
- MemRef::Branchee);
+ visitMemoryReference(I, I.getAddress(), AliasAnalysis::UnknownSize, 0,
+ nullptr, MemRef::Branchee);
Assert1(I.getNumDestinations() != 0,
"Undefined behavior: indirectbr with no destinations", &I);
void Lint::visitUnreachableInst(UnreachableInst &I) {
// This isn't undefined behavior, it's merely suspicious.
Assert1(&I == I.getParent()->begin() ||
- prior(BasicBlock::iterator(&I))->mayHaveSideEffects(),
+ std::prev(BasicBlock::iterator(&I))->mayHaveSideEffects(),
"Unusual: unreachable immediately preceded by instruction without "
"side effects", &I);
}
/// findValueImpl - Implementation helper for findValue.
Value *Lint::findValueImpl(Value *V, bool OffsetOk,
- SmallPtrSet<Value *, 4> &Visited) const {
+ SmallPtrSetImpl<Value *> &Visited) const {
// Detect self-referential values.
- if (!Visited.insert(V))
+ if (!Visited.insert(V).second)
return UndefValue::get(V->getType());
// TODO: Look through sext or zext cast, when the result is known to
// TODO: Look through eliminable cast pairs.
// TODO: Look through calls with unique return values.
// TODO: Look through vector insert/extract/shuffle.
- V = OffsetOk ? V->getUnderlyingObject() : V->stripPointerCasts();
+ V = OffsetOk ? GetUnderlyingObject(V, DL) : V->stripPointerCasts();
if (LoadInst *L = dyn_cast<LoadInst>(V)) {
BasicBlock::iterator BBI = L;
BasicBlock *BB = L->getParent();
SmallPtrSet<BasicBlock *, 4> VisitedBlocks;
for (;;) {
- if (!VisitedBlocks.insert(BB)) break;
+ if (!VisitedBlocks.insert(BB).second)
+ break;
if (Value *U = FindAvailableLoadedValue(L->getPointerOperand(),
BB, BBI, 6, AA))
return findValueImpl(U, OffsetOk, Visited);
if (W != V)
return findValueImpl(W, OffsetOk, Visited);
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
- if (CI->isNoopCast(TD ? TD->getIntPtrType(V->getContext()) :
- Type::getInt64Ty(V->getContext())))
+ if (CI->isNoopCast(DL))
return findValueImpl(CI->getOperand(0), OffsetOk, Visited);
} else if (ExtractValueInst *Ex = dyn_cast<ExtractValueInst>(V)) {
if (Value *W = FindInsertedValue(Ex->getAggregateOperand(),
- Ex->idx_begin(),
- Ex->idx_end()))
+ Ex->getIndices()))
if (W != V)
return findValueImpl(W, OffsetOk, Visited);
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CastInst::isNoopCast(Instruction::CastOps(CE->getOpcode()),
CE->getOperand(0)->getType(),
CE->getType(),
- TD ? TD->getIntPtrType(V->getContext()) :
+ DL ? DL->getIntPtrType(V->getType()) :
Type::getInt64Ty(V->getContext())))
return findValueImpl(CE->getOperand(0), OffsetOk, Visited);
} else if (CE->getOpcode() == Instruction::ExtractValue) {
- const SmallVector<unsigned, 4> &Indices = CE->getIndices();
- if (Value *W = FindInsertedValue(CE->getOperand(0),
- Indices.begin(),
- Indices.end()))
+ ArrayRef<unsigned> Indices = CE->getIndices();
+ if (Value *W = FindInsertedValue(CE->getOperand(0), Indices))
if (W != V)
return findValueImpl(W, OffsetOk, Visited);
}
// As a last resort, try SimplifyInstruction or constant folding.
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
- if (Value *W = SimplifyInstruction(Inst, TD, DT))
+ if (Value *W = SimplifyInstruction(Inst, DL, TLI, DT, AT))
return findValueImpl(W, OffsetOk, Visited);
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
- if (Value *W = ConstantFoldConstantExpression(CE, TD))
+ if (Value *W = ConstantFoldConstantExpression(CE, DL, TLI))
if (W != V)
return findValueImpl(W, OffsetOk, Visited);
}
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