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+//===-- Lint.cpp - Check for common errors in LLVM IR ---------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass statically checks for common and easily-identified constructs
+// which produce undefined or likely unintended behavior in LLVM IR.
+//
+// It is not a guarantee of correctness, in two ways. First, it isn't
+// comprehensive. There are checks which could be done statically which are
+// not yet implemented. Some of these are indicated by TODO comments, but
+// 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
+// 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,
+// 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/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"
+#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"
+using namespace llvm;
+
+namespace {
+ namespace MemRef {
+ static unsigned Read = 1;
+ static unsigned Write = 2;
+ static unsigned Callee = 4;
+ static unsigned Branchee = 8;
+ }
+
+ class Lint : public FunctionPass, public InstVisitor<Lint> {
+ friend class InstVisitor<Lint>;
+
+ void visitFunction(Function &F);
+
+ void visitCallSite(CallSite CS);
+ void visitMemoryReference(Instruction &I, Value *Ptr,
+ unsigned Size, unsigned Align,
+ const Type *Ty, unsigned Flags);
+
+ void visitCallInst(CallInst &I);
+ void visitInvokeInst(InvokeInst &I);
+ void visitReturnInst(ReturnInst &I);
+ void visitLoadInst(LoadInst &I);
+ void visitStoreInst(StoreInst &I);
+ void visitXor(BinaryOperator &I);
+ void visitSub(BinaryOperator &I);
+ void visitLShr(BinaryOperator &I);
+ void visitAShr(BinaryOperator &I);
+ void visitShl(BinaryOperator &I);
+ void visitSDiv(BinaryOperator &I);
+ void visitUDiv(BinaryOperator &I);
+ void visitSRem(BinaryOperator &I);
+ void visitURem(BinaryOperator &I);
+ void visitAllocaInst(AllocaInst &I);
+ void visitVAArgInst(VAArgInst &I);
+ void visitIndirectBrInst(IndirectBrInst &I);
+ void visitExtractElementInst(ExtractElementInst &I);
+ 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;
+ raw_string_ostream MessagesStr;
+
+ static char ID; // Pass identification, replacement for typeid
+ Lint() : FunctionPass(ID), MessagesStr(Messages) {}
+
+ virtual bool runOnFunction(Function &F);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ AU.addRequired<AliasAnalysis>();
+ AU.addRequired<DominatorTree>();
+ }
+ virtual void print(raw_ostream &O, const Module *M) const {}
+
+ void WriteValue(const Value *V) {
+ if (!V) return;
+ if (isa<Instruction>(V)) {
+ MessagesStr << *V << '\n';
+ } else {
+ WriteAsOperand(MessagesStr, V, true, Mod);
+ MessagesStr << '\n';
+ }
+ }
+
+ void WriteType(const Type *T) {
+ if (!T) return;
+ MessagesStr << ' ';
+ WriteTypeSymbolic(MessagesStr, T, Mod);
+ }
+
+ // CheckFailed - A check failed, so print out the condition and the message
+ // 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) {
+ MessagesStr << Message.str() << "\n";
+ WriteValue(V1);
+ WriteValue(V2);
+ WriteValue(V3);
+ WriteValue(V4);
+ }
+
+ void CheckFailed(const Twine &Message, const Value *V1,
+ const Type *T2, const Value *V3 = 0) {
+ MessagesStr << Message.str() << "\n";
+ WriteValue(V1);
+ WriteType(T2);
+ WriteValue(V3);
+ }
+
+ void CheckFailed(const Twine &Message, const Type *T1,
+ const Type *T2 = 0, const Type *T3 = 0) {
+ MessagesStr << Message.str() << "\n";
+ WriteType(T1);
+ WriteType(T2);
+ WriteType(T3);
+ }
+ };
+}
+
+char Lint::ID = 0;
+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) \
+ do { if (!(C)) { CheckFailed(M); return; } } while (0)
+#define Assert1(C, M, V1) \
+ do { if (!(C)) { CheckFailed(M, V1); return; } } while (0)
+#define Assert2(C, M, V1, V2) \
+ do { if (!(C)) { CheckFailed(M, V1, V2); return; } } while (0)
+#define Assert3(C, M, V1, V2, V3) \
+ do { if (!(C)) { CheckFailed(M, V1, V2, V3); return; } } while (0)
+#define Assert4(C, M, V1, V2, V3, V4) \
+ do { if (!(C)) { CheckFailed(M, V1, V2, V3, V4); return; } } while (0)
+
+// Lint::run - This is the main Analysis entry point for a
+// function.
+//
+bool Lint::runOnFunction(Function &F) {
+ Mod = F.getParent();
+ AA = &getAnalysis<AliasAnalysis>();
+ DT = &getAnalysis<DominatorTree>();
+ TD = getAnalysisIfAvailable<TargetData>();
+ visit(F);
+ dbgs() << MessagesStr.str();
+ Messages.clear();
+ return false;
+}
+
+void Lint::visitFunction(Function &F) {
+ // This isn't undefined behavior, it's just a little unusual, and it's a
+ // 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, ~0u, 0, 0, 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());
+
+ Assert1(FT->isVarArg() ?
+ FT->getNumParams() <= NumActualArgs :
+ FT->getNumParams() == NumActualArgs,
+ "Undefined behavior: Call argument count mismatches callee "
+ "argument count", &I);
+
+ 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())
+ for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
+ AI != AE; ++AI) {
+ Value *Obj = findValue(*AI, /*OffsetOk=*/true);
+ Assert1(!isa<AllocaInst>(Obj),
+ "Undefined behavior: Call with \"tail\" keyword references "
+ "alloca", &I);
+ }
+
+
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I))
+ switch (II->getIntrinsicID()) {
+ default: break;
+
+ // TODO: Check more intrinsics
+
+ case Intrinsic::memcpy: {
+ MemCpyInst *MCI = cast<MemCpyInst>(&I);
+ // TODO: If the size is known, use it.
+ visitMemoryReference(I, MCI->getDest(), ~0u, MCI->getAlignment(), 0,
+ MemRef::Write);
+ visitMemoryReference(I, MCI->getSource(), ~0u, MCI->getAlignment(), 0,
+ MemRef::Read);
+
+ // Check that the memcpy arguments don't overlap. 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.
+ unsigned Size = 0;
+ if (const ConstantInt *Len =
+ 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) !=
+ AliasAnalysis::MustAlias,
+ "Undefined behavior: memcpy source and destination overlap", &I);
+ break;
+ }
+ case Intrinsic::memmove: {
+ MemMoveInst *MMI = cast<MemMoveInst>(&I);
+ // TODO: If the size is known, use it.
+ visitMemoryReference(I, MMI->getDest(), ~0u, MMI->getAlignment(), 0,
+ MemRef::Write);
+ visitMemoryReference(I, MMI->getSource(), ~0u, MMI->getAlignment(), 0,
+ MemRef::Read);
+ break;
+ }
+ case Intrinsic::memset: {
+ MemSetInst *MSI = cast<MemSetInst>(&I);
+ // TODO: If the size is known, use it.
+ visitMemoryReference(I, MSI->getDest(), ~0u, MSI->getAlignment(), 0,
+ MemRef::Write);
+ break;
+ }
+
+ case Intrinsic::vastart:
+ Assert1(I.getParent()->getParent()->isVarArg(),
+ "Undefined behavior: va_start called in a non-varargs function",
+ &I);
+
+ visitMemoryReference(I, CS.getArgument(0), ~0u, 0, 0,
+ MemRef::Read | MemRef::Write);
+ break;
+ case Intrinsic::vacopy:
+ 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), ~0u, 0, 0,
+ MemRef::Read | MemRef::Write);
+ break;
+
+ case Intrinsic::stackrestore:
+ // 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), ~0u, 0, 0,
+ MemRef::Read | MemRef::Write);
+ break;
+ }
+}
+
+void Lint::visitCallInst(CallInst &I) {
+ return visitCallSite(&I);
+}
+
+void Lint::visitInvokeInst(InvokeInst &I) {
+ return visitCallSite(&I);
+}
+
+void Lint::visitReturnInst(ReturnInst &I) {
+ Function *F = I.getParent()->getParent();
+ 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: Check that the reference is in bounds.
+// TODO: Check readnone/readonly function attributes.
+void Lint::visitMemoryReference(Instruction &I,
+ 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))
+ Assert1(!GV->isConstant(),
+ "Undefined behavior: Write to read-only memory", &I);
+ Assert1(!isa<Function>(UnderlyingObject) &&
+ !isa<BlockAddress>(UnderlyingObject),
+ "Undefined behavior: Write to text section", &I);
+ }
+ if (Flags & MemRef::Read) {
+ Assert1(!isa<Function>(UnderlyingObject),
+ "Unusual: Load from function body", &I);
+ Assert1(!isa<BlockAddress>(UnderlyingObject),
+ "Undefined behavior: Load from block address", &I);
+ }
+ if (Flags & MemRef::Callee) {
+ Assert1(!isa<BlockAddress>(UnderlyingObject),
+ "Undefined behavior: Call to block address", &I);
+ }
+ if (Flags & MemRef::Branchee) {
+ Assert1(!isa<Constant>(UnderlyingObject) ||
+ isa<BlockAddress>(UnderlyingObject),
+ "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);
+ }
+ }
+}
+
+void Lint::visitLoadInst(LoadInst &I) {
+ visitMemoryReference(I, I.getPointerOperand(),
+ AA->getTypeStoreSize(I.getType()), I.getAlignment(),
+ I.getType(), MemRef::Read);
+}
+
+void Lint::visitStoreInst(StoreInst &I) {
+ visitMemoryReference(I, I.getPointerOperand(),
+ AA->getTypeStoreSize(I.getOperand(0)->getType()),
+ I.getAlignment(),
+ I.getOperand(0)->getType(), MemRef::Write);
+}
+
+void Lint::visitXor(BinaryOperator &I) {
+ Assert1(!isa<UndefValue>(I.getOperand(0)) ||
+ !isa<UndefValue>(I.getOperand(1)),
+ "Undefined result: xor(undef, undef)", &I);
+}
+
+void Lint::visitSub(BinaryOperator &I) {
+ Assert1(!isa<UndefValue>(I.getOperand(0)) ||
+ !isa<UndefValue>(I.getOperand(1)),
+ "Undefined result: sub(undef, undef)", &I);
+}
+
+void Lint::visitLShr(BinaryOperator &I) {
+ if (ConstantInt *CI =
+ 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>(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>(findValue(I.getOperand(1), /*OffsetOk=*/false)))
+ Assert1(CI->getValue().ult(cast<IntegerType>(I.getType())->getBitWidth()),
+ "Undefined result: Shift count out of range", &I);
+}
+
+static bool isZero(Value *V, TargetData *TD) {
+ // Assume undef could be zero.
+ if (isa<UndefValue>(V)) 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();
+}
+
+void Lint::visitSDiv(BinaryOperator &I) {
+ Assert1(!isZero(I.getOperand(1), TD),
+ "Undefined behavior: Division by zero", &I);
+}
+
+void Lint::visitUDiv(BinaryOperator &I) {
+ Assert1(!isZero(I.getOperand(1), TD),
+ "Undefined behavior: Division by zero", &I);
+}
+
+void Lint::visitSRem(BinaryOperator &I) {
+ Assert1(!isZero(I.getOperand(1), TD),
+ "Undefined behavior: Division by zero", &I);
+}
+
+void Lint::visitURem(BinaryOperator &I) {
+ Assert1(!isZero(I.getOperand(1), TD),
+ "Undefined behavior: Division by zero", &I);
+}
+
+void Lint::visitAllocaInst(AllocaInst &I) {
+ if (isa<ConstantInt>(I.getArraySize()))
+ // 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), ~0u, 0, 0,
+ MemRef::Read | MemRef::Write);
+}
+
+void Lint::visitIndirectBrInst(IndirectBrInst &I) {
+ 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) {
+ if (ConstantInt *CI =
+ 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>(findValue(I.getOperand(2),
+ /*OffsetOk=*/false)))
+ Assert1(CI->getValue().ult(I.getType()->getNumElements()),
+ "Undefined result: insertelement index out of range", &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(),
+ "Unusual: unreachable immediately preceded by instruction without "
+ "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...
+//===----------------------------------------------------------------------===//
+
+FunctionPass *llvm::createLintPass() {
+ return new Lint();
+}
+
+/// lintFunction - Check a function for errors, printing messages on stderr.
+///
+void llvm::lintFunction(const Function &f) {
+ Function &F = const_cast<Function&>(f);
+ assert(!F.isDeclaration() && "Cannot lint external functions");
+
+ FunctionPassManager FPM(F.getParent());
+ Lint *V = new Lint();
+ FPM.add(V);
+ FPM.run(F);
+}
+
+/// lintModule - Check a module for errors, printing messages on stderr.
+///
+void llvm::lintModule(const Module &M) {
+ PassManager PM;
+ Lint *V = new Lint();
+ PM.add(V);
+ PM.run(const_cast<Module&>(M));
+}
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