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// SimpleSValuator.cpp - A basic SValuator ------------------------*- C++ -*--//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines SimpleSValuator, a basic implementation of SValuator.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/PathSensitive/SValuator.h"
#include "clang/Analysis/PathSensitive/GRState.h"
using namespace clang;
namespace {
class SimpleSValuator : public SValuator {
protected:
virtual SVal EvalCastNL(NonLoc val, QualType castTy);
virtual SVal EvalCastL(Loc val, QualType castTy);
public:
SimpleSValuator(ValueManager &valMgr) : SValuator(valMgr) {}
virtual ~SimpleSValuator() {}
virtual SVal EvalMinus(NonLoc val);
virtual SVal EvalComplement(NonLoc val);
virtual SVal EvalBinOpNN(const GRState *state, BinaryOperator::Opcode op,
NonLoc lhs, NonLoc rhs, QualType resultTy);
virtual SVal EvalBinOpLL(BinaryOperator::Opcode op, Loc lhs, Loc rhs,
QualType resultTy);
virtual SVal EvalBinOpLN(const GRState *state, BinaryOperator::Opcode op,
Loc lhs, NonLoc rhs, QualType resultTy);
};
} // end anonymous namespace
SValuator *clang::CreateSimpleSValuator(ValueManager &valMgr) {
return new SimpleSValuator(valMgr);
}
//===----------------------------------------------------------------------===//
// Transfer function for Casts.
//===----------------------------------------------------------------------===//
SVal SimpleSValuator::EvalCastNL(NonLoc val, QualType castTy) {
bool isLocType = Loc::IsLocType(castTy);
if (nonloc::LocAsInteger *LI = dyn_cast<nonloc::LocAsInteger>(&val)) {
if (isLocType)
return LI->getLoc();
ASTContext &Ctx = ValMgr.getContext();
// FIXME: Support promotions/truncations.
if (Ctx.getTypeSize(castTy) == Ctx.getTypeSize(Ctx.VoidPtrTy))
return val;
return UnknownVal();
}
if (const SymExpr *se = val.getAsSymbolicExpression()) {
ASTContext &Ctx = ValMgr.getContext();
QualType T = Ctx.getCanonicalType(se->getType(Ctx));
if (T == Ctx.getCanonicalType(castTy))
return val;
// FIXME: Remove this hack when we support symbolic truncation/extension.
// HACK: If both castTy and T are integers, ignore the cast. This is
// not a permanent solution. Eventually we want to precisely handle
// extension/truncation of symbolic integers. This prevents us from losing
// precision when we assign 'x = y' and 'y' is symbolic and x and y are
// different integer types.
if (T->isIntegerType() && castTy->isIntegerType())
return val;
return UnknownVal();
}
if (!isa<nonloc::ConcreteInt>(val))
return UnknownVal();
// Only handle casts from integers to integers.
if (!isLocType && !castTy->isIntegerType())
return UnknownVal();
llvm::APSInt i = cast<nonloc::ConcreteInt>(val).getValue();
i.setIsUnsigned(castTy->isUnsignedIntegerType() || Loc::IsLocType(castTy));
i.extOrTrunc(ValMgr.getContext().getTypeSize(castTy));
if (isLocType)
return ValMgr.makeIntLocVal(i);
else
return ValMgr.makeIntVal(i);
}
SVal SimpleSValuator::EvalCastL(Loc val, QualType castTy) {
// Casts from pointers -> pointers, just return the lval.
//
// Casts from pointers -> references, just return the lval. These
// can be introduced by the frontend for corner cases, e.g
// casting from va_list* to __builtin_va_list&.
//
if (Loc::IsLocType(castTy) || castTy->isReferenceType())
return val;
// FIXME: Handle transparent unions where a value can be "transparently"
// lifted into a union type.
if (castTy->isUnionType())
return UnknownVal();
assert(castTy->isIntegerType());
unsigned BitWidth = ValMgr.getContext().getTypeSize(castTy);
if (!isa<loc::ConcreteInt>(val))
return ValMgr.makeLocAsInteger(val, BitWidth);
llvm::APSInt i = cast<loc::ConcreteInt>(val).getValue();
i.setIsUnsigned(castTy->isUnsignedIntegerType() || Loc::IsLocType(castTy));
i.extOrTrunc(BitWidth);
return ValMgr.makeIntVal(i);
}
//===----------------------------------------------------------------------===//
// Transfer function for unary operators.
//===----------------------------------------------------------------------===//
SVal SimpleSValuator::EvalMinus(NonLoc val) {
switch (val.getSubKind()) {
case nonloc::ConcreteIntKind:
return cast<nonloc::ConcreteInt>(val).evalMinus(ValMgr);
default:
return UnknownVal();
}
}
SVal SimpleSValuator::EvalComplement(NonLoc X) {
switch (X.getSubKind()) {
case nonloc::ConcreteIntKind:
return cast<nonloc::ConcreteInt>(X).evalComplement(ValMgr);
default:
return UnknownVal();
}
}
//===----------------------------------------------------------------------===//
// Transfer function for binary operators.
//===----------------------------------------------------------------------===//
static BinaryOperator::Opcode NegateComparison(BinaryOperator::Opcode op) {
switch (op) {
default:
assert(false && "Invalid opcode.");
case BinaryOperator::LT: return BinaryOperator::GE;
case BinaryOperator::GT: return BinaryOperator::LE;
case BinaryOperator::LE: return BinaryOperator::GT;
case BinaryOperator::GE: return BinaryOperator::LT;
case BinaryOperator::EQ: return BinaryOperator::NE;
case BinaryOperator::NE: return BinaryOperator::EQ;
}
}
// Equality operators for Locs.
// FIXME: All this logic will be revamped when we have MemRegion::getLocation()
// implemented.
static SVal EvalEquality(ValueManager &ValMgr, Loc lhs, Loc rhs, bool isEqual,
QualType resultTy) {
switch (lhs.getSubKind()) {
default:
assert(false && "EQ/NE not implemented for this Loc.");
return UnknownVal();
case loc::ConcreteIntKind: {
if (SymbolRef rSym = rhs.getAsSymbol())
return ValMgr.makeNonLoc(rSym,
isEqual ? BinaryOperator::EQ
: BinaryOperator::NE,
cast<loc::ConcreteInt>(lhs).getValue(),
resultTy);
break;
}
case loc::MemRegionKind: {
if (SymbolRef lSym = lhs.getAsLocSymbol()) {
if (isa<loc::ConcreteInt>(rhs)) {
return ValMgr.makeNonLoc(lSym,
isEqual ? BinaryOperator::EQ
: BinaryOperator::NE,
cast<loc::ConcreteInt>(rhs).getValue(),
resultTy);
}
}
break;
}
case loc::GotoLabelKind:
break;
}
return ValMgr.makeTruthVal(isEqual ? lhs == rhs : lhs != rhs, resultTy);
}
SVal SimpleSValuator::EvalBinOpNN(const GRState *state,
BinaryOperator::Opcode op,
NonLoc lhs, NonLoc rhs,
QualType resultTy) {
// Handle trivial case where left-side and right-side are the same.
if (lhs == rhs)
switch (op) {
default:
break;
case BinaryOperator::EQ:
case BinaryOperator::LE:
case BinaryOperator::GE:
return ValMgr.makeTruthVal(true, resultTy);
case BinaryOperator::LT:
case BinaryOperator::GT:
case BinaryOperator::NE:
return ValMgr.makeTruthVal(false, resultTy);
}
while (1) {
switch (lhs.getSubKind()) {
default:
return UnknownVal();
case nonloc::LocAsIntegerKind: {
Loc lhsL = cast<nonloc::LocAsInteger>(lhs).getLoc();
switch (rhs.getSubKind()) {
case nonloc::LocAsIntegerKind:
return EvalBinOpLL(op, lhsL, cast<nonloc::LocAsInteger>(rhs).getLoc(),
resultTy);
case nonloc::ConcreteIntKind: {
// Transform the integer into a location and compare.
ASTContext& Ctx = ValMgr.getContext();
llvm::APSInt i = cast<nonloc::ConcreteInt>(rhs).getValue();
i.setIsUnsigned(true);
i.extOrTrunc(Ctx.getTypeSize(Ctx.VoidPtrTy));
return EvalBinOpLL(op, lhsL, ValMgr.makeLoc(i), resultTy);
}
default:
switch (op) {
case BinaryOperator::EQ:
return ValMgr.makeTruthVal(false, resultTy);
case BinaryOperator::NE:
return ValMgr.makeTruthVal(true, resultTy);
default:
// This case also handles pointer arithmetic.
return UnknownVal();
}
}
}
case nonloc::SymExprValKind: {
// Logical not?
if (!(op == BinaryOperator::EQ && rhs.isZeroConstant()))
return UnknownVal();
const SymExpr *symExpr =
cast<nonloc::SymExprVal>(lhs).getSymbolicExpression();
// Only handle ($sym op constant) for now.
if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(symExpr)) {
BinaryOperator::Opcode opc = symIntExpr->getOpcode();
switch (opc) {
case BinaryOperator::LAnd:
case BinaryOperator::LOr:
assert(false && "Logical operators handled by branching logic.");
return UnknownVal();
case BinaryOperator::Assign:
case BinaryOperator::MulAssign:
case BinaryOperator::DivAssign:
case BinaryOperator::RemAssign:
case BinaryOperator::AddAssign:
case BinaryOperator::SubAssign:
case BinaryOperator::ShlAssign:
case BinaryOperator::ShrAssign:
case BinaryOperator::AndAssign:
case BinaryOperator::XorAssign:
case BinaryOperator::OrAssign:
case BinaryOperator::Comma:
assert(false && "'=' and ',' operators handled by GRExprEngine.");
return UnknownVal();
case BinaryOperator::PtrMemD:
case BinaryOperator::PtrMemI:
assert(false && "Pointer arithmetic not handled here.");
return UnknownVal();
case BinaryOperator::Mul:
case BinaryOperator::Div:
case BinaryOperator::Rem:
case BinaryOperator::Add:
case BinaryOperator::Sub:
case BinaryOperator::Shl:
case BinaryOperator::Shr:
case BinaryOperator::And:
case BinaryOperator::Xor:
case BinaryOperator::Or:
// Not handled yet.
return UnknownVal();
case BinaryOperator::LT:
case BinaryOperator::GT:
case BinaryOperator::LE:
case BinaryOperator::GE:
case BinaryOperator::EQ:
case BinaryOperator::NE:
opc = NegateComparison(opc);
assert(symIntExpr->getType(ValMgr.getContext()) == resultTy);
return ValMgr.makeNonLoc(symIntExpr->getLHS(), opc,
symIntExpr->getRHS(), resultTy);
}
}
}
case nonloc::ConcreteIntKind: {
if (isa<nonloc::ConcreteInt>(rhs)) {
const nonloc::ConcreteInt& lhsInt = cast<nonloc::ConcreteInt>(lhs);
return lhsInt.evalBinOp(ValMgr, op, cast<nonloc::ConcreteInt>(rhs));
}
else {
// Swap the left and right sides and flip the operator if doing so
// allows us to better reason about the expression (this is a form
// of expression canonicalization).
NonLoc tmp = rhs;
rhs = lhs;
lhs = tmp;
switch (op) {
case BinaryOperator::LT: op = BinaryOperator::GT; continue;
case BinaryOperator::GT: op = BinaryOperator::LT; continue;
case BinaryOperator::LE: op = BinaryOperator::GE; continue;
case BinaryOperator::GE: op = BinaryOperator::LE; continue;
case BinaryOperator::EQ:
case BinaryOperator::NE:
case BinaryOperator::Add:
case BinaryOperator::Mul:
continue;
default:
return UnknownVal();
}
}
}
case nonloc::SymbolValKind: {
nonloc::SymbolVal *slhs = cast<nonloc::SymbolVal>(&lhs);
SymbolRef Sym = slhs->getSymbol();
// Does the symbol simplify to a constant? If so, "fold" the constant
// by setting 'lhs' to a ConcreteInt and try again.
if (Sym->getType(ValMgr.getContext())->isIntegerType())
if (const llvm::APSInt *Constant = state->getSymVal(Sym)) {
// The symbol evaluates to a constant. If necessary, promote the
// folded constant (LHS) to the result type.
BasicValueFactory &BVF = ValMgr.getBasicValueFactory();
const llvm::APSInt &lhs_I = BVF.Convert(resultTy, *Constant);
lhs = nonloc::ConcreteInt(lhs_I);
// Also promote the RHS (if necessary).
// For shifts, it necessary promote the RHS to the result type.
if (BinaryOperator::isShiftOp(op))
continue;
// Other operators: do an implicit conversion. This shouldn't be
// necessary once we support truncation/extension of symbolic values.
if (nonloc::ConcreteInt *rhs_I = dyn_cast<nonloc::ConcreteInt>(&rhs)){
rhs = nonloc::ConcreteInt(BVF.Convert(resultTy, rhs_I->getValue()));
}
continue;
}
if (isa<nonloc::ConcreteInt>(rhs)) {
return ValMgr.makeNonLoc(slhs->getSymbol(), op,
cast<nonloc::ConcreteInt>(rhs).getValue(),
resultTy);
}
return UnknownVal();
}
}
}
}
SVal SimpleSValuator::EvalBinOpLL(BinaryOperator::Opcode op, Loc lhs, Loc rhs,
QualType resultTy) {
switch (op) {
default:
return UnknownVal();
case BinaryOperator::EQ:
case BinaryOperator::NE:
return EvalEquality(ValMgr, lhs, rhs, op == BinaryOperator::EQ, resultTy);
case BinaryOperator::LT:
case BinaryOperator::GT:
// FIXME: Generalize. For now, just handle the trivial case where
// the two locations are identical.
if (lhs == rhs)
return ValMgr.makeTruthVal(false, resultTy);
return UnknownVal();
}
}
SVal SimpleSValuator::EvalBinOpLN(const GRState *state,
BinaryOperator::Opcode op,
Loc lhs, NonLoc rhs, QualType resultTy) {
// Special case: 'rhs' is an integer that has the same width as a pointer and
// we are using the integer location in a comparison. Normally this cannot be
// triggered, but transfer functions like those for OSCommpareAndSwapBarrier32
// can generate comparisons that trigger this code.
// FIXME: Are all locations guaranteed to have pointer width?
if (BinaryOperator::isEqualityOp(op)) {
if (nonloc::ConcreteInt *rhsInt = dyn_cast<nonloc::ConcreteInt>(&rhs)) {
const llvm::APSInt *x = &rhsInt->getValue();
ASTContext &ctx = ValMgr.getContext();
if (ctx.getTypeSize(ctx.VoidPtrTy) == x->getBitWidth()) {
// Convert the signedness of the integer (if necessary).
if (x->isSigned())
x = &ValMgr.getBasicValueFactory().getValue(*x, true);
return EvalBinOpLL(op, lhs, loc::ConcreteInt(*x), resultTy);
}
}
}
// Delegate pointer arithmetic to the StoreManager.
return state->getStateManager().getStoreManager().EvalBinOp(state, op, lhs,
rhs, resultTy);
}