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-rw-r--r--lib/Analysis/Lint.cpp239
1 files changed, 199 insertions, 40 deletions
diff --git a/lib/Analysis/Lint.cpp b/lib/Analysis/Lint.cpp
index a031cbc..9f1b30d 100644
--- a/lib/Analysis/Lint.cpp
+++ b/lib/Analysis/Lint.cpp
@@ -19,7 +19,8 @@
//
// 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,
@@ -35,7 +36,11 @@
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/Lint.h"
+#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Target/TargetData.h"
@@ -64,7 +69,8 @@ namespace {
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);
@@ -88,9 +94,14 @@ namespace {
void visitInsertElementInst(InsertElementInst &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;
AliasAnalysis *AA;
+ DominatorTree *DT;
TargetData *TD;
std::string Messages;
@@ -104,6 +115,7 @@ namespace {
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<AliasAnalysis>();
+ AU.addRequired<DominatorTree>();
}
virtual void print(raw_ostream &O, const Module *M) const {}
@@ -176,6 +188,7 @@ X("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>();
visit(F);
dbgs() << MessagesStr.str();
@@ -188,15 +201,17 @@ void Lint::visitFunction(Function &F) {
// 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>(Callee->stripPointerCasts())) {
+ if (Function *F = dyn_cast<Function>(findValue(Callee, /*OffsetOk=*/false))) {
Assert1(CS.getCallingConv() == F->getCallingConv(),
"Undefined behavior: Caller and callee calling convention differ",
&I);
@@ -209,23 +224,53 @@ void Lint::visitCallSite(CallSite CS) {
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, ~0u, *BI, ~0u) != 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())
for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
AI != AE; ++AI) {
- Value *Obj = (*AI)->getUnderlyingObject();
- Assert1(!isa<AllocaInst>(Obj) && !isa<VAArgInst>(Obj),
+ Value *Obj = findValue(*AI, /*OffsetOk=*/true);
+ Assert1(!isa<AllocaInst>(Obj),
"Undefined behavior: Call with \"tail\" keyword references "
- "alloca or va_arg", &I);
+ "alloca", &I);
}
@@ -237,9 +282,10 @@ void Lint::visitCallSite(CallSite CS) {
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
@@ -247,7 +293,8 @@ void Lint::visitCallSite(CallSite CS) {
// overlap is not distinguished from the case where nothing is known.
unsigned Size = 0;
if (const ConstantInt *Len =
- dyn_cast<ConstantInt>(MCI->getLength()->stripPointerCasts()))
+ dyn_cast<ConstantInt>(findValue(MCI->getLength(),
+ /*OffsetOk=*/false)))
if (Len->getValue().isIntN(32))
Size = Len->getValue().getZExtValue();
Assert1(AA->alias(MCI->getSource(), Size, MCI->getDest(), Size) !=
@@ -257,15 +304,17 @@ void Lint::visitCallSite(CallSite CS) {
}
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;
}
@@ -275,15 +324,15 @@ void Lint::visitCallSite(CallSite CS) {
"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;
@@ -291,7 +340,7 @@ void Lint::visitCallSite(CallSite CS) {
// 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;
}
@@ -310,17 +359,35 @@ void Lint::visitReturnInst(ReturnInst &I) {
Assert1(!F->doesNotReturn(),
"Unusual: Return statement in function with noreturn attribute",
&I);
+
+ if (Value *V = I.getReturnValue()) {
+ Value *Obj = findValue(V, /*OffsetOk=*/true);
+ Assert1(!isa<AllocaInst>(Obj),
+ "Unusual: Returning alloca value", &I);
+ }
}
-// 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 *UnderlyingObject = Ptr->getUnderlyingObject();
+ 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))
@@ -361,13 +428,16 @@ void Lint::visitMemoryReference(Instruction &I,
}
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) {
@@ -384,21 +454,21 @@ void Lint::visitSub(BinaryOperator &I) {
void Lint::visitLShr(BinaryOperator &I) {
if (ConstantInt *CI =
- dyn_cast<ConstantInt>(I.getOperand(1)->stripPointerCasts()))
+ dyn_cast<ConstantInt>(findValue(I.getOperand(1), /*OffsetOk=*/false)))
Assert1(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
"Undefined result: Shift count out of range", &I);
}
void Lint::visitAShr(BinaryOperator &I) {
if (ConstantInt *CI =
- dyn_cast<ConstantInt>(I.getOperand(1)->stripPointerCasts()))
+ dyn_cast<ConstantInt>(findValue(I.getOperand(1), /*OffsetOk=*/false)))
Assert1(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
"Undefined result: Shift count out of range", &I);
}
void Lint::visitShl(BinaryOperator &I) {
if (ConstantInt *CI =
- dyn_cast<ConstantInt>(I.getOperand(1)->stripPointerCasts()))
+ dyn_cast<ConstantInt>(findValue(I.getOperand(1), /*OffsetOk=*/false)))
Assert1(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
"Undefined result: Shift count out of range", &I);
}
@@ -439,27 +509,31 @@ void Lint::visitAllocaInst(AllocaInst &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);
}
void Lint::visitExtractElementInst(ExtractElementInst &I) {
if (ConstantInt *CI =
- dyn_cast<ConstantInt>(I.getIndexOperand()->stripPointerCasts()))
+ dyn_cast<ConstantInt>(findValue(I.getIndexOperand(),
+ /*OffsetOk=*/false)))
Assert1(CI->getValue().ult(I.getVectorOperandType()->getNumElements()),
"Undefined result: extractelement index out of range", &I);
}
void Lint::visitInsertElementInst(InsertElementInst &I) {
if (ConstantInt *CI =
- dyn_cast<ConstantInt>(I.getOperand(2)->stripPointerCasts()))
+ dyn_cast<ConstantInt>(findValue(I.getOperand(2),
+ /*OffsetOk=*/false)))
Assert1(CI->getValue().ult(I.getType()->getNumElements()),
"Undefined result: insertelement index out of range", &I);
}
@@ -472,6 +546,91 @@ void Lint::visitUnreachableInst(UnreachableInst &I) {
"side effects", &I);
}
+/// findValue - Look through bitcasts and simple memory reference patterns
+/// to identify an equivalent, but more informative, value. If OffsetOk
+/// is true, look through getelementptrs with non-zero offsets too.
+///
+/// Most analysis passes don't require this logic, because instcombine
+/// 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 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 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 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 findValueImpl(W, OffsetOk, Visited);
+ } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
+ if (Value *W = ConstantFoldConstantExpression(CE, TD))
+ if (W != V)
+ return findValueImpl(W, OffsetOk, Visited);
+ }
+
+ return V;
+}
+
//===----------------------------------------------------------------------===//
// Implement the public interfaces to this file...
//===----------------------------------------------------------------------===//
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