//
// 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.
+// but this pass will warn about it anyway. This is the main reason why most
+// of these checks live here instead of in the Verifier pass.
//
// Optimization passes may make conditions that this pass checks for more or
// less obvious. If an optimization pass appears to be introducing a warning,
void visitFunction(Function &F);
void visitCallSite(CallSite CS);
- void visitMemoryReference(Instruction &I, Value *Ptr, unsigned Align,
+ void visitMemoryReference(Instruction &I, Value *Ptr,
+ unsigned Size, unsigned Align,
const Type *Ty, unsigned Flags);
void visitCallInst(CallInst &I);
void visitUnreachableInst(UnreachableInst &I);
Value *findValue(Value *V, bool OffsetOk) const;
+ Value *findValueImpl(Value *V, bool OffsetOk,
+ SmallPtrSet<Value *, 4> &Visited) const;
public:
Module *Mod;
raw_string_ostream MessagesStr;
static char ID; // Pass identification, replacement for typeid
- Lint() : FunctionPass(&ID), MessagesStr(Messages) {}
+ Lint() : FunctionPass(ID), MessagesStr(Messages) {}
virtual bool runOnFunction(Function &F);
}
char Lint::ID = 0;
-static RegisterPass<Lint>
-X("lint", "Statically lint-checks LLVM IR", false, true);
+INITIALIZE_PASS(Lint, "lint", "Statically lint-checks LLVM IR", false, true);
// Assert - We know that cond should be true, if not print an error message.
#define Assert(C, M) \
// fairly common mistake to neglect to name a function.
Assert1(F.hasName() || F.hasLocalLinkage(),
"Unusual: Unnamed function with non-local linkage", &F);
+
+ // TODO: Check for irreducible control flow.
}
void Lint::visitCallSite(CallSite CS) {
Instruction &I = *CS.getInstruction();
Value *Callee = CS.getCalledValue();
- visitMemoryReference(I, Callee, 0, 0, MemRef::Callee);
+ visitMemoryReference(I, Callee, ~0u, 0, 0, MemRef::Callee);
if (Function *F = dyn_cast<Function>(findValue(Callee, /*OffsetOk=*/false))) {
Assert1(CS.getCallingConv() == F->getCallingConv(),
FT->getNumParams() == NumActualArgs,
"Undefined behavior: Call argument count mismatches callee "
"argument count", &I);
-
- // TODO: Check argument types (in case the callee was casted)
-
- // TODO: Check ABI-significant attributes.
-
- // TODO: Check noalias attribute.
- // TODO: Check sret attribute.
+ Assert1(FT->getReturnType() == I.getType(),
+ "Undefined behavior: Call return type mismatches "
+ "callee return type", &I);
+
+ // Check argument types (in case the callee was casted) and attributes.
+ // TODO: Verify that caller and callee attributes are compatible.
+ Function::arg_iterator PI = F->arg_begin(), PE = F->arg_end();
+ CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ for (; AI != AE; ++AI) {
+ Value *Actual = *AI;
+ if (PI != PE) {
+ Argument *Formal = PI++;
+ Assert1(Formal->getType() == Actual->getType(),
+ "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.
+ if (Formal->hasNoAliasAttr() && Actual->getType()->isPointerTy())
+ for (CallSite::arg_iterator BI = CS.arg_begin(); BI != AE; ++BI) {
+ Assert1(AI == BI || AA->alias(*AI, *BI) != AliasAnalysis::MustAlias,
+ "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 =
+ cast<PointerType>(Formal->getType())->getElementType();
+ visitMemoryReference(I, Actual, AA->getTypeStoreSize(Ty),
+ TD ? TD->getABITypeAlignment(Ty) : 0,
+ Ty, MemRef::Read | MemRef::Write);
+ }
+ }
+ }
}
if (CS.isCall() && cast<CallInst>(CS.getInstruction())->isTailCall())
case Intrinsic::memcpy: {
MemCpyInst *MCI = cast<MemCpyInst>(&I);
- visitMemoryReference(I, MCI->getSource(), MCI->getAlignment(), 0,
+ // TODO: If the size is known, use it.
+ visitMemoryReference(I, MCI->getDest(), ~0u, MCI->getAlignment(), 0,
MemRef::Write);
- visitMemoryReference(I, MCI->getDest(), MCI->getAlignment(), 0,
+ visitMemoryReference(I, MCI->getSource(), ~0u, MCI->getAlignment(), 0,
MemRef::Read);
// Check that the memcpy arguments don't overlap. The AliasAnalysis API
}
case Intrinsic::memmove: {
MemMoveInst *MMI = cast<MemMoveInst>(&I);
- visitMemoryReference(I, MMI->getSource(), MMI->getAlignment(), 0,
+ // TODO: If the size is known, use it.
+ visitMemoryReference(I, MMI->getDest(), ~0u, MMI->getAlignment(), 0,
MemRef::Write);
- visitMemoryReference(I, MMI->getDest(), MMI->getAlignment(), 0,
+ visitMemoryReference(I, MMI->getSource(), ~0u, MMI->getAlignment(), 0,
MemRef::Read);
break;
}
case Intrinsic::memset: {
MemSetInst *MSI = cast<MemSetInst>(&I);
- visitMemoryReference(I, MSI->getDest(), MSI->getAlignment(), 0,
+ // TODO: If the size is known, use it.
+ visitMemoryReference(I, MSI->getDest(), ~0u, MSI->getAlignment(), 0,
MemRef::Write);
break;
}
"Undefined behavior: va_start called in a non-varargs function",
&I);
- visitMemoryReference(I, CS.getArgument(0), 0, 0,
+ visitMemoryReference(I, CS.getArgument(0), ~0u, 0, 0,
MemRef::Read | MemRef::Write);
break;
case Intrinsic::vacopy:
- visitMemoryReference(I, CS.getArgument(0), 0, 0, MemRef::Write);
- visitMemoryReference(I, CS.getArgument(1), 0, 0, MemRef::Read);
+ visitMemoryReference(I, CS.getArgument(0), ~0u, 0, 0, MemRef::Write);
+ visitMemoryReference(I, CS.getArgument(1), ~0u, 0, 0, MemRef::Read);
break;
case Intrinsic::vaend:
- visitMemoryReference(I, CS.getArgument(0), 0, 0,
+ visitMemoryReference(I, CS.getArgument(0), ~0u, 0, 0,
MemRef::Read | MemRef::Write);
break;
// Stackrestore doesn't read or write memory, but it sets the
// 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), 0, 0,
+ visitMemoryReference(I, CS.getArgument(0), ~0u, 0, 0,
MemRef::Read | MemRef::Write);
break;
}
}
}
-// TODO: Add a length argument and check that the reference is in bounds
+// TODO: Check that the reference is in bounds.
+// TODO: Check readnone/readonly function attributes.
void Lint::visitMemoryReference(Instruction &I,
- Value *Ptr, unsigned Align, const Type *Ty,
- unsigned Flags) {
+ Value *Ptr, unsigned Size, unsigned Align,
+ const Type *Ty, unsigned Flags) {
+ // If no memory is being referenced, it doesn't matter if the pointer
+ // is valid.
+ if (Size == 0)
+ return;
+
Value *UnderlyingObject = findValue(Ptr, /*OffsetOk=*/true);
Assert1(!isa<ConstantPointerNull>(UnderlyingObject),
"Undefined behavior: Null pointer dereference", &I);
Assert1(!isa<UndefValue>(UnderlyingObject),
"Undefined behavior: Undef pointer dereference", &I);
+ Assert1(!isa<ConstantInt>(UnderlyingObject) ||
+ !cast<ConstantInt>(UnderlyingObject)->isAllOnesValue(),
+ "Unusual: All-ones pointer dereference", &I);
+ Assert1(!isa<ConstantInt>(UnderlyingObject) ||
+ !cast<ConstantInt>(UnderlyingObject)->isOne(),
+ "Unusual: Address one pointer dereference", &I);
if (Flags & MemRef::Write) {
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(UnderlyingObject))
}
void Lint::visitLoadInst(LoadInst &I) {
- visitMemoryReference(I, I.getPointerOperand(), I.getAlignment(), I.getType(),
- MemRef::Read);
+ visitMemoryReference(I, I.getPointerOperand(),
+ AA->getTypeStoreSize(I.getType()), I.getAlignment(),
+ I.getType(), MemRef::Read);
}
void Lint::visitStoreInst(StoreInst &I) {
- visitMemoryReference(I, I.getPointerOperand(), I.getAlignment(),
- I.getOperand(0)->getType(), MemRef::Write);
+ visitMemoryReference(I, I.getPointerOperand(),
+ AA->getTypeStoreSize(I.getOperand(0)->getType()),
+ I.getAlignment(),
+ I.getOperand(0)->getType(), MemRef::Write);
}
void Lint::visitXor(BinaryOperator &I) {
// This isn't undefined behavior, it's just an obvious pessimization.
Assert1(&I.getParent()->getParent()->getEntryBlock() == I.getParent(),
"Pessimization: Static alloca outside of entry block", &I);
+
+ // TODO: Check for an unusual size (MSB set?)
}
void Lint::visitVAArgInst(VAArgInst &I) {
- visitMemoryReference(I, I.getOperand(0), 0, 0,
+ visitMemoryReference(I, I.getOperand(0), ~0u, 0, 0,
MemRef::Read | MemRef::Write);
}
void Lint::visitIndirectBrInst(IndirectBrInst &I) {
- visitMemoryReference(I, I.getAddress(), 0, 0, MemRef::Branchee);
+ visitMemoryReference(I, I.getAddress(), ~0u, 0, 0, MemRef::Branchee);
+
+ Assert1(I.getNumDestinations() != 0,
+ "Undefined behavior: indirectbr with no destinations", &I);
}
void Lint::visitExtractElementInst(ExtractElementInst &I) {
/// will simplify most of these kinds of things away. But it's a goal of
/// this Lint pass to be useful even on non-optimized IR.
Value *Lint::findValue(Value *V, bool OffsetOk) const {
+ SmallPtrSet<Value *, 4> Visited;
+ return findValueImpl(V, OffsetOk, Visited);
+}
+
+/// findValueImpl - Implementation helper for findValue.
+Value *Lint::findValueImpl(Value *V, bool OffsetOk,
+ SmallPtrSet<Value *, 4> &Visited) const {
+ // Detect self-referential values.
+ if (!Visited.insert(V))
+ return UndefValue::get(V->getType());
+
// TODO: Look through sext or zext cast, when the result is known to
// be interpreted as signed or unsigned, respectively.
+ // 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();
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 (Value *U = FindAvailableLoadedValue(L->getPointerOperand(),
BB, BBI, 6, AA))
- return findValue(U, OffsetOk);
- BB = L->getParent()->getUniquePredecessor();
+ return findValueImpl(U, OffsetOk, Visited);
+ if (BBI != BB->begin()) break;
+ BB = BB->getUniquePredecessor();
if (!BB) break;
BBI = BB->end();
}
+ } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
+ if (Value *W = PN->hasConstantValue(DT))
+ 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())))
- return findValue(CI->getOperand(0), OffsetOk);
- } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
- if (Value *W = PN->hasConstantValue(DT))
- return findValue(W, OffsetOk);
+ 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()))
if (W != V)
- return findValue(W, OffsetOk);
+ return findValueImpl(W, OffsetOk, Visited);
+ } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+ // Same as above, but for ConstantExpr instead of Instruction.
+ if (Instruction::isCast(CE->getOpcode())) {
+ if (CastInst::isNoopCast(Instruction::CastOps(CE->getOpcode()),
+ CE->getOperand(0)->getType(),
+ CE->getType(),
+ TD ? TD->getIntPtrType(V->getContext()) :
+ 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()))
+ 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))
if (W != Inst)
- return findValue(W, OffsetOk);
+ return findValueImpl(W, OffsetOk, Visited);
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (Value *W = ConstantFoldConstantExpression(CE, TD))
if (W != V)
- return findValue(W, OffsetOk);
+ return findValueImpl(W, OffsetOk, Visited);
}
return V;
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