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llvm-project/clang/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp

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// SimpleSValBuilder.cpp - A basic SValBuilder -----------------------*- 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 SimpleSValBuilder, a basic implementation of SValBuilder.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/APSIntType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SubEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SValVisitor.h"
using namespace clang;
using namespace ento;
namespace {
class SimpleSValBuilder : public SValBuilder {
protected:
SVal dispatchCast(SVal val, QualType castTy) override;
SVal evalCastFromNonLoc(NonLoc val, QualType castTy) override;
SVal evalCastFromLoc(Loc val, QualType castTy) override;
public:
SimpleSValBuilder(llvm::BumpPtrAllocator &alloc, ASTContext &context,
ProgramStateManager &stateMgr)
: SValBuilder(alloc, context, stateMgr) {}
~SimpleSValBuilder() override {}
SVal evalMinus(NonLoc val) override;
SVal evalComplement(NonLoc val) override;
SVal evalBinOpNN(ProgramStateRef state, BinaryOperator::Opcode op,
NonLoc lhs, NonLoc rhs, QualType resultTy) override;
SVal evalBinOpLL(ProgramStateRef state, BinaryOperator::Opcode op,
Loc lhs, Loc rhs, QualType resultTy) override;
SVal evalBinOpLN(ProgramStateRef state, BinaryOperator::Opcode op,
Loc lhs, NonLoc rhs, QualType resultTy) override;
/// getKnownValue - evaluates a given SVal. If the SVal has only one possible
/// (integer) value, that value is returned. Otherwise, returns NULL.
const llvm::APSInt *getKnownValue(ProgramStateRef state, SVal V) override;
/// Recursively descends into symbolic expressions and replaces symbols
/// with their known values (in the sense of the getKnownValue() method).
SVal simplifySVal(ProgramStateRef State, SVal V) override;
SVal MakeSymIntVal(const SymExpr *LHS, BinaryOperator::Opcode op,
const llvm::APSInt &RHS, QualType resultTy);
};
} // end anonymous namespace
SValBuilder *ento::createSimpleSValBuilder(llvm::BumpPtrAllocator &alloc,
ASTContext &context,
ProgramStateManager &stateMgr) {
return new SimpleSValBuilder(alloc, context, stateMgr);
}
//===----------------------------------------------------------------------===//
// Transfer function for Casts.
//===----------------------------------------------------------------------===//
SVal SimpleSValBuilder::dispatchCast(SVal Val, QualType CastTy) {
assert(Val.getAs<Loc>() || Val.getAs<NonLoc>());
return Val.getAs<Loc>() ? evalCastFromLoc(Val.castAs<Loc>(), CastTy)
: evalCastFromNonLoc(Val.castAs<NonLoc>(), CastTy);
}
SVal SimpleSValBuilder::evalCastFromNonLoc(NonLoc val, QualType castTy) {
bool isLocType = Loc::isLocType(castTy);
if (val.getAs<nonloc::PointerToMember>())
return val;
if (Optional<nonloc::LocAsInteger> LI = val.getAs<nonloc::LocAsInteger>()) {
if (isLocType)
return LI->getLoc();
// FIXME: Correctly support promotions/truncations.
unsigned castSize = Context.getIntWidth(castTy);
if (castSize == LI->getNumBits())
return val;
return makeLocAsInteger(LI->getLoc(), castSize);
}
if (const SymExpr *se = val.getAsSymbolicExpression()) {
QualType T = Context.getCanonicalType(se->getType());
// If types are the same or both are integers, ignore the cast.
// 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 (haveSameType(T, castTy))
return val;
if (!isLocType)
return makeNonLoc(se, T, castTy);
return UnknownVal();
}
// If value is a non-integer constant, produce unknown.
if (!val.getAs<nonloc::ConcreteInt>())
return UnknownVal();
// Handle casts to a boolean type.
if (castTy->isBooleanType()) {
bool b = val.castAs<nonloc::ConcreteInt>().getValue().getBoolValue();
return makeTruthVal(b, castTy);
}
// Only handle casts from integers to integers - if val is an integer constant
// being cast to a non-integer type, produce unknown.
if (!isLocType && !castTy->isIntegralOrEnumerationType())
return UnknownVal();
llvm::APSInt i = val.castAs<nonloc::ConcreteInt>().getValue();
BasicVals.getAPSIntType(castTy).apply(i);
if (isLocType)
return makeIntLocVal(i);
else
return makeIntVal(i);
}
SVal SimpleSValBuilder::evalCastFromLoc(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();
// Casting a Loc to a bool will almost always be true,
// unless this is a weak function or a symbolic region.
if (castTy->isBooleanType()) {
switch (val.getSubKind()) {
case loc::MemRegionValKind: {
const MemRegion *R = val.castAs<loc::MemRegionVal>().getRegion();
if (const FunctionCodeRegion *FTR = dyn_cast<FunctionCodeRegion>(R))
if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl()))
if (FD->isWeak())
// FIXME: Currently we are using an extent symbol here,
// because there are no generic region address metadata
// symbols to use, only content metadata.
return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR));
if (const SymbolicRegion *SymR = R->getSymbolicBase())
return makeNonLoc(SymR->getSymbol(), BO_NE,
BasicVals.getZeroWithPtrWidth(), castTy);
// FALL-THROUGH
LLVM_FALLTHROUGH;
}
case loc::GotoLabelKind:
// Labels and non-symbolic memory regions are always true.
return makeTruthVal(true, castTy);
}
}
if (castTy->isIntegralOrEnumerationType()) {
unsigned BitWidth = Context.getIntWidth(castTy);
if (!val.getAs<loc::ConcreteInt>())
return makeLocAsInteger(val, BitWidth);
llvm::APSInt i = val.castAs<loc::ConcreteInt>().getValue();
BasicVals.getAPSIntType(castTy).apply(i);
return makeIntVal(i);
}
// All other cases: return 'UnknownVal'. This includes casting pointers
// to floats, which is probably badness it itself, but this is a good
// intermediate solution until we do something better.
return UnknownVal();
}
//===----------------------------------------------------------------------===//
// Transfer function for unary operators.
//===----------------------------------------------------------------------===//
SVal SimpleSValBuilder::evalMinus(NonLoc val) {
switch (val.getSubKind()) {
case nonloc::ConcreteIntKind:
return val.castAs<nonloc::ConcreteInt>().evalMinus(*this);
default:
return UnknownVal();
}
}
SVal SimpleSValBuilder::evalComplement(NonLoc X) {
switch (X.getSubKind()) {
case nonloc::ConcreteIntKind:
return X.castAs<nonloc::ConcreteInt>().evalComplement(*this);
default:
return UnknownVal();
}
}
//===----------------------------------------------------------------------===//
// Transfer function for binary operators.
//===----------------------------------------------------------------------===//
SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
BinaryOperator::Opcode op,
const llvm::APSInt &RHS,
QualType resultTy) {
bool isIdempotent = false;
// Check for a few special cases with known reductions first.
switch (op) {
default:
// We can't reduce this case; just treat it normally.
break;
case BO_Mul:
// a*0 and a*1
if (RHS == 0)
return makeIntVal(0, resultTy);
else if (RHS == 1)
isIdempotent = true;
break;
case BO_Div:
// a/0 and a/1
if (RHS == 0)
// This is also handled elsewhere.
return UndefinedVal();
else if (RHS == 1)
isIdempotent = true;
break;
case BO_Rem:
// a%0 and a%1
if (RHS == 0)
// This is also handled elsewhere.
return UndefinedVal();
else if (RHS == 1)
return makeIntVal(0, resultTy);
break;
case BO_Add:
case BO_Sub:
case BO_Shl:
case BO_Shr:
case BO_Xor:
// a+0, a-0, a<<0, a>>0, a^0
if (RHS == 0)
isIdempotent = true;
break;
case BO_And:
// a&0 and a&(~0)
if (RHS == 0)
return makeIntVal(0, resultTy);
else if (RHS.isAllOnesValue())
isIdempotent = true;
break;
case BO_Or:
// a|0 and a|(~0)
if (RHS == 0)
isIdempotent = true;
else if (RHS.isAllOnesValue()) {
const llvm::APSInt &Result = BasicVals.Convert(resultTy, RHS);
return nonloc::ConcreteInt(Result);
}
break;
}
// Idempotent ops (like a*1) can still change the type of an expression.
// Wrap the LHS up in a NonLoc again and let evalCastFromNonLoc do the
// dirty work.
if (isIdempotent)
return evalCastFromNonLoc(nonloc::SymbolVal(LHS), resultTy);
// If we reach this point, the expression cannot be simplified.
// Make a SymbolVal for the entire expression, after converting the RHS.
const llvm::APSInt *ConvertedRHS = &RHS;
if (BinaryOperator::isComparisonOp(op)) {
// We're looking for a type big enough to compare the symbolic value
// with the given constant.
// FIXME: This is an approximation of Sema::UsualArithmeticConversions.
ASTContext &Ctx = getContext();
QualType SymbolType = LHS->getType();
uint64_t ValWidth = RHS.getBitWidth();
uint64_t TypeWidth = Ctx.getTypeSize(SymbolType);
if (ValWidth < TypeWidth) {
// If the value is too small, extend it.
ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
} else if (ValWidth == TypeWidth) {
// If the value is signed but the symbol is unsigned, do the comparison
// in unsigned space. [C99 6.3.1.8]
// (For the opposite case, the value is already unsigned.)
if (RHS.isSigned() && !SymbolType->isSignedIntegerOrEnumerationType())
ConvertedRHS = &BasicVals.Convert(SymbolType, RHS);
}
} else
ConvertedRHS = &BasicVals.Convert(resultTy, RHS);
return makeNonLoc(LHS, op, *ConvertedRHS, resultTy);
}
// See if Sym is known to be a relation Rel with Bound.
static bool isInRelation(BinaryOperator::Opcode Rel, SymbolRef Sym,
llvm::APSInt Bound, ProgramStateRef State) {
SValBuilder &SVB = State->getStateManager().getSValBuilder();
SVal Result =
SVB.evalBinOpNN(State, Rel, nonloc::SymbolVal(Sym),
nonloc::ConcreteInt(Bound), SVB.getConditionType());
if (auto DV = Result.getAs<DefinedSVal>()) {
return !State->assume(*DV, false);
}
return false;
}
// See if Sym is known to be within [min/4, max/4], where min and max
// are the bounds of the symbol's integral type. With such symbols,
// some manipulations can be performed without the risk of overflow.
// assume() doesn't cause infinite recursion because we should be dealing
// with simpler symbols on every recursive call.
static bool isWithinConstantOverflowBounds(SymbolRef Sym,
ProgramStateRef State) {
SValBuilder &SVB = State->getStateManager().getSValBuilder();
BasicValueFactory &BV = SVB.getBasicValueFactory();
QualType T = Sym->getType();
assert(T->isSignedIntegerOrEnumerationType() &&
"This only works with signed integers!");
APSIntType AT = BV.getAPSIntType(T);
llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;
return isInRelation(BO_LE, Sym, Max, State) &&
isInRelation(BO_GE, Sym, Min, State);
}
// Same for the concrete integers: see if I is within [min/4, max/4].
static bool isWithinConstantOverflowBounds(llvm::APSInt I) {
APSIntType AT(I);
assert(!AT.isUnsigned() &&
"This only works with signed integers!");
llvm::APSInt Max = AT.getMaxValue() / AT.getValue(4), Min = -Max;
return (I <= Max) && (I >= -Max);
}
static std::pair<SymbolRef, llvm::APSInt>
decomposeSymbol(SymbolRef Sym, BasicValueFactory &BV) {
if (const auto *SymInt = dyn_cast<SymIntExpr>(Sym))
if (BinaryOperator::isAdditiveOp(SymInt->getOpcode()))
return std::make_pair(SymInt->getLHS(),
(SymInt->getOpcode() == BO_Add) ?
(SymInt->getRHS()) :
(-SymInt->getRHS()));
// Fail to decompose: "reduce" the problem to the "$x + 0" case.
return std::make_pair(Sym, BV.getValue(0, Sym->getType()));
}
// Simplify "(LSym + LInt) Op (RSym + RInt)" assuming all values are of the
// same signed integral type and no overflows occur (which should be checked
// by the caller).
static NonLoc doRearrangeUnchecked(ProgramStateRef State,
BinaryOperator::Opcode Op,
SymbolRef LSym, llvm::APSInt LInt,
SymbolRef RSym, llvm::APSInt RInt) {
SValBuilder &SVB = State->getStateManager().getSValBuilder();
BasicValueFactory &BV = SVB.getBasicValueFactory();
SymbolManager &SymMgr = SVB.getSymbolManager();
QualType SymTy = LSym->getType();
assert(SymTy == RSym->getType() &&
"Symbols are not of the same type!");
assert(APSIntType(LInt) == BV.getAPSIntType(SymTy) &&
"Integers are not of the same type as symbols!");
assert(APSIntType(RInt) == BV.getAPSIntType(SymTy) &&
"Integers are not of the same type as symbols!");
QualType ResultTy;
if (BinaryOperator::isComparisonOp(Op))
ResultTy = SVB.getConditionType();
else if (BinaryOperator::isAdditiveOp(Op))
ResultTy = SymTy;
else
llvm_unreachable("Operation not suitable for unchecked rearrangement!");
// FIXME: Can we use assume() without getting into an infinite recursion?
if (LSym == RSym)
return SVB.evalBinOpNN(State, Op, nonloc::ConcreteInt(LInt),
nonloc::ConcreteInt(RInt), ResultTy)
.castAs<NonLoc>();
SymbolRef ResultSym = nullptr;
BinaryOperator::Opcode ResultOp;
llvm::APSInt ResultInt;
if (BinaryOperator::isComparisonOp(Op)) {
// Prefer comparing to a non-negative number.
// FIXME: Maybe it'd be better to have consistency in
// "$x - $y" vs. "$y - $x" because those are solver's keys.
if (LInt > RInt) {
ResultSym = SymMgr.getSymSymExpr(RSym, BO_Sub, LSym, SymTy);
ResultOp = BinaryOperator::reverseComparisonOp(Op);
ResultInt = LInt - RInt; // Opposite order!
} else {
ResultSym = SymMgr.getSymSymExpr(LSym, BO_Sub, RSym, SymTy);
ResultOp = Op;
ResultInt = RInt - LInt; // Opposite order!
}
} else {
ResultSym = SymMgr.getSymSymExpr(LSym, Op, RSym, SymTy);
ResultInt = (Op == BO_Add) ? (LInt + RInt) : (LInt - RInt);
ResultOp = BO_Add;
// Bring back the cosmetic difference.
if (ResultInt < 0) {
ResultInt = -ResultInt;
ResultOp = BO_Sub;
} else if (ResultInt == 0) {
// Shortcut: Simplify "$x + 0" to "$x".
return nonloc::SymbolVal(ResultSym);
}
}
const llvm::APSInt &PersistentResultInt = BV.getValue(ResultInt);
return nonloc::SymbolVal(
SymMgr.getSymIntExpr(ResultSym, ResultOp, PersistentResultInt, ResultTy));
}
// Rearrange if symbol type matches the result type and if the operator is a
// comparison operator, both symbol and constant must be within constant
// overflow bounds.
static bool shouldRearrange(ProgramStateRef State, BinaryOperator::Opcode Op,
SymbolRef Sym, llvm::APSInt Int, QualType Ty) {
return Sym->getType() == Ty &&
(!BinaryOperator::isComparisonOp(Op) ||
(isWithinConstantOverflowBounds(Sym, State) &&
isWithinConstantOverflowBounds(Int)));
}
static Optional<NonLoc> tryRearrange(ProgramStateRef State,
BinaryOperator::Opcode Op, NonLoc Lhs,
NonLoc Rhs, QualType ResultTy) {
ProgramStateManager &StateMgr = State->getStateManager();
SValBuilder &SVB = StateMgr.getSValBuilder();
// We expect everything to be of the same type - this type.
QualType SingleTy;
auto &Opts =
StateMgr.getOwningEngine()->getAnalysisManager().getAnalyzerOptions();
// FIXME: After putting complexity threshold to the symbols we can always
// rearrange additive operations but rearrange comparisons only if
// option is set.
if(!Opts.shouldAggressivelySimplifyBinaryOperation())
return None;
SymbolRef LSym = Lhs.getAsSymbol();
if (!LSym)
return None;
if (BinaryOperator::isComparisonOp(Op)) {
SingleTy = LSym->getType();
if (ResultTy != SVB.getConditionType())
return None;
// Initialize SingleTy later with a symbol's type.
} else if (BinaryOperator::isAdditiveOp(Op)) {
SingleTy = ResultTy;
if (LSym->getType() != SingleTy)
return None;
// Substracting unsigned integers is a nightmare.
if (!SingleTy->isSignedIntegerOrEnumerationType())
return None;
} else {
// Don't rearrange other operations.
return None;
}
assert(!SingleTy.isNull() && "We should have figured out the type by now!");
SymbolRef RSym = Rhs.getAsSymbol();
if (!RSym || RSym->getType() != SingleTy)
return None;
BasicValueFactory &BV = State->getBasicVals();
llvm::APSInt LInt, RInt;
std::tie(LSym, LInt) = decomposeSymbol(LSym, BV);
std::tie(RSym, RInt) = decomposeSymbol(RSym, BV);
if (!shouldRearrange(State, Op, LSym, LInt, SingleTy) ||
!shouldRearrange(State, Op, RSym, RInt, SingleTy))
return None;
// We know that no overflows can occur anymore.
return doRearrangeUnchecked(State, Op, LSym, LInt, RSym, RInt);
}
SVal SimpleSValBuilder::evalBinOpNN(ProgramStateRef state,
BinaryOperator::Opcode op,
NonLoc lhs, NonLoc rhs,
QualType resultTy) {
NonLoc InputLHS = lhs;
NonLoc InputRHS = rhs;
// Handle trivial case where left-side and right-side are the same.
if (lhs == rhs)
switch (op) {
default:
break;
case BO_EQ:
case BO_LE:
case BO_GE:
return makeTruthVal(true, resultTy);
case BO_LT:
case BO_GT:
case BO_NE:
return makeTruthVal(false, resultTy);
case BO_Xor:
case BO_Sub:
if (resultTy->isIntegralOrEnumerationType())
return makeIntVal(0, resultTy);
return evalCastFromNonLoc(makeIntVal(0, /*Unsigned=*/false), resultTy);
case BO_Or:
case BO_And:
return evalCastFromNonLoc(lhs, resultTy);
}
while (1) {
switch (lhs.getSubKind()) {
default:
return makeSymExprValNN(state, op, lhs, rhs, resultTy);
case nonloc::PointerToMemberKind: {
assert(rhs.getSubKind() == nonloc::PointerToMemberKind &&
"Both SVals should have pointer-to-member-type");
auto LPTM = lhs.castAs<nonloc::PointerToMember>(),
RPTM = rhs.castAs<nonloc::PointerToMember>();
auto LPTMD = LPTM.getPTMData(), RPTMD = RPTM.getPTMData();
switch (op) {
case BO_EQ:
return makeTruthVal(LPTMD == RPTMD, resultTy);
case BO_NE:
return makeTruthVal(LPTMD != RPTMD, resultTy);
default:
return UnknownVal();
}
}
case nonloc::LocAsIntegerKind: {
Loc lhsL = lhs.castAs<nonloc::LocAsInteger>().getLoc();
switch (rhs.getSubKind()) {
case nonloc::LocAsIntegerKind:
// FIXME: at the moment the implementation
// of modeling "pointers as integers" is not complete.
if (!BinaryOperator::isComparisonOp(op))
return UnknownVal();
return evalBinOpLL(state, op, lhsL,
rhs.castAs<nonloc::LocAsInteger>().getLoc(),
resultTy);
case nonloc::ConcreteIntKind: {
// FIXME: at the moment the implementation
// of modeling "pointers as integers" is not complete.
if (!BinaryOperator::isComparisonOp(op))
return UnknownVal();
// Transform the integer into a location and compare.
// FIXME: This only makes sense for comparisons. If we want to, say,
// add 1 to a LocAsInteger, we'd better unpack the Loc and add to it,
// then pack it back into a LocAsInteger.
llvm::APSInt i = rhs.castAs<nonloc::ConcreteInt>().getValue();
BasicVals.getAPSIntType(Context.VoidPtrTy).apply(i);
return evalBinOpLL(state, op, lhsL, makeLoc(i), resultTy);
}
default:
switch (op) {
case BO_EQ:
return makeTruthVal(false, resultTy);
case BO_NE:
return makeTruthVal(true, resultTy);
default:
// This case also handles pointer arithmetic.
return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
}
}
}
case nonloc::ConcreteIntKind: {
llvm::APSInt LHSValue = lhs.castAs<nonloc::ConcreteInt>().getValue();
// If we're dealing with two known constants, just perform the operation.
if (const llvm::APSInt *KnownRHSValue = getKnownValue(state, rhs)) {
llvm::APSInt RHSValue = *KnownRHSValue;
if (BinaryOperator::isComparisonOp(op)) {
// We're looking for a type big enough to compare the two values.
// FIXME: This is not correct. char + short will result in a promotion
// to int. Unfortunately we have lost types by this point.
APSIntType CompareType = std::max(APSIntType(LHSValue),
APSIntType(RHSValue));
CompareType.apply(LHSValue);
CompareType.apply(RHSValue);
} else if (!BinaryOperator::isShiftOp(op)) {
APSIntType IntType = BasicVals.getAPSIntType(resultTy);
IntType.apply(LHSValue);
IntType.apply(RHSValue);
}
const llvm::APSInt *Result =
BasicVals.evalAPSInt(op, LHSValue, RHSValue);
if (!Result)
return UndefinedVal();
return nonloc::ConcreteInt(*Result);
}
// 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).
// While we're at it, catch some special cases for non-commutative ops.
switch (op) {
case BO_LT:
case BO_GT:
case BO_LE:
case BO_GE:
op = BinaryOperator::reverseComparisonOp(op);
// FALL-THROUGH
case BO_EQ:
case BO_NE:
case BO_Add:
case BO_Mul:
case BO_And:
case BO_Xor:
case BO_Or:
std::swap(lhs, rhs);
continue;
case BO_Shr:
// (~0)>>a
if (LHSValue.isAllOnesValue() && LHSValue.isSigned())
return evalCastFromNonLoc(lhs, resultTy);
// FALL-THROUGH
case BO_Shl:
// 0<<a and 0>>a
if (LHSValue == 0)
return evalCastFromNonLoc(lhs, resultTy);
return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
default:
return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
}
}
case nonloc::SymbolValKind: {
// We only handle LHS as simple symbols or SymIntExprs.
SymbolRef Sym = lhs.castAs<nonloc::SymbolVal>().getSymbol();
// LHS is a symbolic expression.
if (const SymIntExpr *symIntExpr = dyn_cast<SymIntExpr>(Sym)) {
// Is this a logical not? (!x is represented as x == 0.)
if (op == BO_EQ && rhs.isZeroConstant()) {
// We know how to negate certain expressions. Simplify them here.
BinaryOperator::Opcode opc = symIntExpr->getOpcode();
switch (opc) {
default:
// We don't know how to negate this operation.
// Just handle it as if it were a normal comparison to 0.
break;
case BO_LAnd:
case BO_LOr:
llvm_unreachable("Logical operators handled by branching logic.");
case BO_Assign:
case BO_MulAssign:
case BO_DivAssign:
case BO_RemAssign:
case BO_AddAssign:
case BO_SubAssign:
case BO_ShlAssign:
case BO_ShrAssign:
case BO_AndAssign:
case BO_XorAssign:
case BO_OrAssign:
case BO_Comma:
llvm_unreachable("'=' and ',' operators handled by ExprEngine.");
case BO_PtrMemD:
case BO_PtrMemI:
llvm_unreachable("Pointer arithmetic not handled here.");
case BO_LT:
case BO_GT:
case BO_LE:
case BO_GE:
case BO_EQ:
case BO_NE:
assert(resultTy->isBooleanType() ||
resultTy == getConditionType());
assert(symIntExpr->getType()->isBooleanType() ||
getContext().hasSameUnqualifiedType(symIntExpr->getType(),
getConditionType()));
// Negate the comparison and make a value.
opc = BinaryOperator::negateComparisonOp(opc);
return makeNonLoc(symIntExpr->getLHS(), opc,
symIntExpr->getRHS(), resultTy);
}
}
// For now, only handle expressions whose RHS is a constant.
if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs)) {
// If both the LHS and the current expression are additive,
// fold their constants and try again.
if (BinaryOperator::isAdditiveOp(op)) {
BinaryOperator::Opcode lop = symIntExpr->getOpcode();
if (BinaryOperator::isAdditiveOp(lop)) {
// Convert the two constants to a common type, then combine them.
// resultTy may not be the best type to convert to, but it's
// probably the best choice in expressions with mixed type
// (such as x+1U+2LL). The rules for implicit conversions should
// choose a reasonable type to preserve the expression, and will
// at least match how the value is going to be used.
APSIntType IntType = BasicVals.getAPSIntType(resultTy);
const llvm::APSInt &first = IntType.convert(symIntExpr->getRHS());
const llvm::APSInt &second = IntType.convert(*RHSValue);
const llvm::APSInt *newRHS;
if (lop == op)
newRHS = BasicVals.evalAPSInt(BO_Add, first, second);
else
newRHS = BasicVals.evalAPSInt(BO_Sub, first, second);
assert(newRHS && "Invalid operation despite common type!");
rhs = nonloc::ConcreteInt(*newRHS);
lhs = nonloc::SymbolVal(symIntExpr->getLHS());
op = lop;
continue;
}
}
// Otherwise, make a SymIntExpr out of the expression.
return MakeSymIntVal(symIntExpr, op, *RHSValue, resultTy);
}
}
// Does the symbolic expression simplify to a constant?
// If so, "fold" the constant by setting 'lhs' to a ConcreteInt
// and try again.
SVal simplifiedLhs = simplifySVal(state, lhs);
if (simplifiedLhs != lhs)
if (auto simplifiedLhsAsNonLoc = simplifiedLhs.getAs<NonLoc>()) {
lhs = *simplifiedLhsAsNonLoc;
continue;
}
// Is the RHS a constant?
if (const llvm::APSInt *RHSValue = getKnownValue(state, rhs))
return MakeSymIntVal(Sym, op, *RHSValue, resultTy);
if (Optional<NonLoc> V = tryRearrange(state, op, lhs, rhs, resultTy))
return *V;
// Give up -- this is not a symbolic expression we can handle.
return makeSymExprValNN(state, op, InputLHS, InputRHS, resultTy);
}
}
}
}
static SVal evalBinOpFieldRegionFieldRegion(const FieldRegion *LeftFR,
const FieldRegion *RightFR,
BinaryOperator::Opcode op,
QualType resultTy,
SimpleSValBuilder &SVB) {
// Only comparisons are meaningful here!
if (!BinaryOperator::isComparisonOp(op))
return UnknownVal();
// Next, see if the two FRs have the same super-region.
// FIXME: This doesn't handle casts yet, and simply stripping the casts
// doesn't help.
if (LeftFR->getSuperRegion() != RightFR->getSuperRegion())
return UnknownVal();
const FieldDecl *LeftFD = LeftFR->getDecl();
const FieldDecl *RightFD = RightFR->getDecl();
const RecordDecl *RD = LeftFD->getParent();
// Make sure the two FRs are from the same kind of record. Just in case!
// FIXME: This is probably where inheritance would be a problem.
if (RD != RightFD->getParent())
return UnknownVal();
// We know for sure that the two fields are not the same, since that
// would have given us the same SVal.
if (op == BO_EQ)
return SVB.makeTruthVal(false, resultTy);
if (op == BO_NE)
return SVB.makeTruthVal(true, resultTy);
// Iterate through the fields and see which one comes first.
// [C99 6.7.2.1.13] "Within a structure object, the non-bit-field
// members and the units in which bit-fields reside have addresses that
// increase in the order in which they are declared."
bool leftFirst = (op == BO_LT || op == BO_LE);
for (const auto *I : RD->fields()) {
if (I == LeftFD)
return SVB.makeTruthVal(leftFirst, resultTy);
if (I == RightFD)
return SVB.makeTruthVal(!leftFirst, resultTy);
}
llvm_unreachable("Fields not found in parent record's definition");
}
// FIXME: all this logic will change if/when we have MemRegion::getLocation().
SVal SimpleSValBuilder::evalBinOpLL(ProgramStateRef state,
BinaryOperator::Opcode op,
Loc lhs, Loc rhs,
QualType resultTy) {
// Only comparisons and subtractions are valid operations on two pointers.
// See [C99 6.5.5 through 6.5.14] or [C++0x 5.6 through 5.15].
// However, if a pointer is casted to an integer, evalBinOpNN may end up
// calling this function with another operation (PR7527). We don't attempt to
// model this for now, but it could be useful, particularly when the
// "location" is actually an integer value that's been passed through a void*.
if (!(BinaryOperator::isComparisonOp(op) || op == BO_Sub))
return UnknownVal();
// Special cases for when both sides are identical.
if (lhs == rhs) {
switch (op) {
default:
llvm_unreachable("Unimplemented operation for two identical values");
case BO_Sub:
return makeZeroVal(resultTy);
case BO_EQ:
case BO_LE:
case BO_GE:
return makeTruthVal(true, resultTy);
case BO_NE:
case BO_LT:
case BO_GT:
return makeTruthVal(false, resultTy);
}
}
switch (lhs.getSubKind()) {
default:
llvm_unreachable("Ordering not implemented for this Loc.");
case loc::GotoLabelKind:
// The only thing we know about labels is that they're non-null.
if (rhs.isZeroConstant()) {
switch (op) {
default:
break;
case BO_Sub:
return evalCastFromLoc(lhs, resultTy);
case BO_EQ:
case BO_LE:
case BO_LT:
return makeTruthVal(false, resultTy);
case BO_NE:
case BO_GT:
case BO_GE:
return makeTruthVal(true, resultTy);
}
}
// There may be two labels for the same location, and a function region may
// have the same address as a label at the start of the function (depending
// on the ABI).
// FIXME: we can probably do a comparison against other MemRegions, though.
// FIXME: is there a way to tell if two labels refer to the same location?
return UnknownVal();
case loc::ConcreteIntKind: {
// If one of the operands is a symbol and the other is a constant,
// build an expression for use by the constraint manager.
if (SymbolRef rSym = rhs.getAsLocSymbol()) {
// We can only build expressions with symbols on the left,
// so we need a reversible operator.
if (!BinaryOperator::isComparisonOp(op) || op == BO_Cmp)
return UnknownVal();
const llvm::APSInt &lVal = lhs.castAs<loc::ConcreteInt>().getValue();
op = BinaryOperator::reverseComparisonOp(op);
return makeNonLoc(rSym, op, lVal, resultTy);
}
// If both operands are constants, just perform the operation.
if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
SVal ResultVal =
lhs.castAs<loc::ConcreteInt>().evalBinOp(BasicVals, op, *rInt);
if (Optional<NonLoc> Result = ResultVal.getAs<NonLoc>())
return evalCastFromNonLoc(*Result, resultTy);
assert(!ResultVal.getAs<Loc>() && "Loc-Loc ops should not produce Locs");
return UnknownVal();
}
// Special case comparisons against NULL.
// This must come after the test if the RHS is a symbol, which is used to
// build constraints. The address of any non-symbolic region is guaranteed
// to be non-NULL, as is any label.
assert(rhs.getAs<loc::MemRegionVal>() || rhs.getAs<loc::GotoLabel>());
if (lhs.isZeroConstant()) {
switch (op) {
default:
break;
case BO_EQ:
case BO_GT:
case BO_GE:
return makeTruthVal(false, resultTy);
case BO_NE:
case BO_LT:
case BO_LE:
return makeTruthVal(true, resultTy);
}
}
// Comparing an arbitrary integer to a region or label address is
// completely unknowable.
return UnknownVal();
}
case loc::MemRegionValKind: {
if (Optional<loc::ConcreteInt> rInt = rhs.getAs<loc::ConcreteInt>()) {
// If one of the operands is a symbol and the other is a constant,
// build an expression for use by the constraint manager.
if (SymbolRef lSym = lhs.getAsLocSymbol(true)) {
if (BinaryOperator::isComparisonOp(op))
return MakeSymIntVal(lSym, op, rInt->getValue(), resultTy);
return UnknownVal();
}
// Special case comparisons to NULL.
// This must come after the test if the LHS is a symbol, which is used to
// build constraints. The address of any non-symbolic region is guaranteed
// to be non-NULL.
if (rInt->isZeroConstant()) {
if (op == BO_Sub)
return evalCastFromLoc(lhs, resultTy);
if (BinaryOperator::isComparisonOp(op)) {
QualType boolType = getContext().BoolTy;
NonLoc l = evalCastFromLoc(lhs, boolType).castAs<NonLoc>();
NonLoc r = makeTruthVal(false, boolType).castAs<NonLoc>();
return evalBinOpNN(state, op, l, r, resultTy);
}
}
// Comparing a region to an arbitrary integer is completely unknowable.
return UnknownVal();
}
// Get both values as regions, if possible.
const MemRegion *LeftMR = lhs.getAsRegion();
assert(LeftMR && "MemRegionValKind SVal doesn't have a region!");
const MemRegion *RightMR = rhs.getAsRegion();
if (!RightMR)
// The RHS is probably a label, which in theory could address a region.
// FIXME: we can probably make a more useful statement about non-code
// regions, though.
return UnknownVal();
const MemRegion *LeftBase = LeftMR->getBaseRegion();
const MemRegion *RightBase = RightMR->getBaseRegion();
const MemSpaceRegion *LeftMS = LeftBase->getMemorySpace();
const MemSpaceRegion *RightMS = RightBase->getMemorySpace();
const MemSpaceRegion *UnknownMS = MemMgr.getUnknownRegion();
// If the two regions are from different known memory spaces they cannot be
// equal. Also, assume that no symbolic region (whose memory space is
// unknown) is on the stack.
if (LeftMS != RightMS &&
((LeftMS != UnknownMS && RightMS != UnknownMS) ||
(isa<StackSpaceRegion>(LeftMS) || isa<StackSpaceRegion>(RightMS)))) {
switch (op) {
default:
return UnknownVal();
case BO_EQ:
return makeTruthVal(false, resultTy);
case BO_NE:
return makeTruthVal(true, resultTy);
}
}
// If both values wrap regions, see if they're from different base regions.
// Note, heap base symbolic regions are assumed to not alias with
// each other; for example, we assume that malloc returns different address
// on each invocation.
// FIXME: ObjC object pointers always reside on the heap, but currently
// we treat their memory space as unknown, because symbolic pointers
// to ObjC objects may alias. There should be a way to construct
// possibly-aliasing heap-based regions. For instance, MacOSXApiChecker
// guesses memory space for ObjC object pointers manually instead of
// relying on us.
if (LeftBase != RightBase &&
((!isa<SymbolicRegion>(LeftBase) && !isa<SymbolicRegion>(RightBase)) ||
(isa<HeapSpaceRegion>(LeftMS) || isa<HeapSpaceRegion>(RightMS))) ){
switch (op) {
default:
return UnknownVal();
case BO_EQ:
return makeTruthVal(false, resultTy);
case BO_NE:
return makeTruthVal(true, resultTy);
}
}
// Handle special cases for when both regions are element regions.
const ElementRegion *RightER = dyn_cast<ElementRegion>(RightMR);
const ElementRegion *LeftER = dyn_cast<ElementRegion>(LeftMR);
if (RightER && LeftER) {
// Next, see if the two ERs have the same super-region and matching types.
// FIXME: This should do something useful even if the types don't match,
// though if both indexes are constant the RegionRawOffset path will
// give the correct answer.
if (LeftER->getSuperRegion() == RightER->getSuperRegion() &&
LeftER->getElementType() == RightER->getElementType()) {
// Get the left index and cast it to the correct type.
// If the index is unknown or undefined, bail out here.
SVal LeftIndexVal = LeftER->getIndex();
Optional<NonLoc> LeftIndex = LeftIndexVal.getAs<NonLoc>();
if (!LeftIndex)
return UnknownVal();
LeftIndexVal = evalCastFromNonLoc(*LeftIndex, ArrayIndexTy);
LeftIndex = LeftIndexVal.getAs<NonLoc>();
if (!LeftIndex)
return UnknownVal();
// Do the same for the right index.
SVal RightIndexVal = RightER->getIndex();
Optional<NonLoc> RightIndex = RightIndexVal.getAs<NonLoc>();
if (!RightIndex)
return UnknownVal();
RightIndexVal = evalCastFromNonLoc(*RightIndex, ArrayIndexTy);
RightIndex = RightIndexVal.getAs<NonLoc>();
if (!RightIndex)
return UnknownVal();
// Actually perform the operation.
// evalBinOpNN expects the two indexes to already be the right type.
return evalBinOpNN(state, op, *LeftIndex, *RightIndex, resultTy);
}
}
// Special handling of the FieldRegions, even with symbolic offsets.
const FieldRegion *RightFR = dyn_cast<FieldRegion>(RightMR);
const FieldRegion *LeftFR = dyn_cast<FieldRegion>(LeftMR);
if (RightFR && LeftFR) {
SVal R = evalBinOpFieldRegionFieldRegion(LeftFR, RightFR, op, resultTy,
*this);
if (!R.isUnknown())
return R;
}
// Compare the regions using the raw offsets.
RegionOffset LeftOffset = LeftMR->getAsOffset();
RegionOffset RightOffset = RightMR->getAsOffset();
if (LeftOffset.getRegion() != nullptr &&
LeftOffset.getRegion() == RightOffset.getRegion() &&
!LeftOffset.hasSymbolicOffset() && !RightOffset.hasSymbolicOffset()) {
int64_t left = LeftOffset.getOffset();
int64_t right = RightOffset.getOffset();
switch (op) {
default:
return UnknownVal();
case BO_LT:
return makeTruthVal(left < right, resultTy);
case BO_GT:
return makeTruthVal(left > right, resultTy);
case BO_LE:
return makeTruthVal(left <= right, resultTy);
case BO_GE:
return makeTruthVal(left >= right, resultTy);
case BO_EQ:
return makeTruthVal(left == right, resultTy);
case BO_NE:
return makeTruthVal(left != right, resultTy);
}
}
// At this point we're not going to get a good answer, but we can try
// conjuring an expression instead.
SymbolRef LHSSym = lhs.getAsLocSymbol();
SymbolRef RHSSym = rhs.getAsLocSymbol();
if (LHSSym && RHSSym)
return makeNonLoc(LHSSym, op, RHSSym, resultTy);
// If we get here, we have no way of comparing the regions.
return UnknownVal();
}
}
}
SVal SimpleSValBuilder::evalBinOpLN(ProgramStateRef state,
BinaryOperator::Opcode op,
Loc lhs, NonLoc rhs, QualType resultTy) {
if (op >= BO_PtrMemD && op <= BO_PtrMemI) {
if (auto PTMSV = rhs.getAs<nonloc::PointerToMember>()) {
if (PTMSV->isNullMemberPointer())
return UndefinedVal();
if (const FieldDecl *FD = PTMSV->getDeclAs<FieldDecl>()) {
SVal Result = lhs;
for (const auto &I : *PTMSV)
Result = StateMgr.getStoreManager().evalDerivedToBase(
Result, I->getType(),I->isVirtual());
return state->getLValue(FD, Result);
}
}
return rhs;
}
assert(!BinaryOperator::isComparisonOp(op) &&
"arguments to comparison ops must be of the same type");
// Special case: rhs is a zero constant.
if (rhs.isZeroConstant())
return lhs;
// Perserve the null pointer so that it can be found by the DerefChecker.
if (lhs.isZeroConstant())
return lhs;
// We are dealing with pointer arithmetic.
// Handle pointer arithmetic on constant values.
if (Optional<nonloc::ConcreteInt> rhsInt = rhs.getAs<nonloc::ConcreteInt>()) {
if (Optional<loc::ConcreteInt> lhsInt = lhs.getAs<loc::ConcreteInt>()) {
const llvm::APSInt &leftI = lhsInt->getValue();
assert(leftI.isUnsigned());
llvm::APSInt rightI(rhsInt->getValue(), /* isUnsigned */ true);
// Convert the bitwidth of rightI. This should deal with overflow
// since we are dealing with concrete values.
rightI = rightI.extOrTrunc(leftI.getBitWidth());
// Offset the increment by the pointer size.
llvm::APSInt Multiplicand(rightI.getBitWidth(), /* isUnsigned */ true);
QualType pointeeType = resultTy->getPointeeType();
Multiplicand = getContext().getTypeSizeInChars(pointeeType).getQuantity();
rightI *= Multiplicand;
// Compute the adjusted pointer.
switch (op) {
case BO_Add:
rightI = leftI + rightI;
break;
case BO_Sub:
rightI = leftI - rightI;
break;
default:
llvm_unreachable("Invalid pointer arithmetic operation");
}
return loc::ConcreteInt(getBasicValueFactory().getValue(rightI));
}
}
// Handle cases where 'lhs' is a region.
if (const MemRegion *region = lhs.getAsRegion()) {
rhs = convertToArrayIndex(rhs).castAs<NonLoc>();
SVal index = UnknownVal();
const SubRegion *superR = nullptr;
// We need to know the type of the pointer in order to add an integer to it.
// Depending on the type, different amount of bytes is added.
QualType elementType;
if (const ElementRegion *elemReg = dyn_cast<ElementRegion>(region)) {
assert(op == BO_Add || op == BO_Sub);
index = evalBinOpNN(state, op, elemReg->getIndex(), rhs,
getArrayIndexType());
superR = cast<SubRegion>(elemReg->getSuperRegion());
elementType = elemReg->getElementType();
}
else if (isa<SubRegion>(region)) {
assert(op == BO_Add || op == BO_Sub);
index = (op == BO_Add) ? rhs : evalMinus(rhs);
superR = cast<SubRegion>(region);
// TODO: Is this actually reliable? Maybe improving our MemRegion
// hierarchy to provide typed regions for all non-void pointers would be
// better. For instance, we cannot extend this towards LocAsInteger
// operations, where result type of the expression is integer.
if (resultTy->isAnyPointerType())
elementType = resultTy->getPointeeType();
}
// Represent arithmetic on void pointers as arithmetic on char pointers.
// It is fine when a TypedValueRegion of char value type represents
// a void pointer. Note that arithmetic on void pointers is a GCC extension.
if (elementType->isVoidType())
elementType = getContext().CharTy;
if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
superR, getContext()));
}
}
return UnknownVal();
}
const llvm::APSInt *SimpleSValBuilder::getKnownValue(ProgramStateRef state,
SVal V) {
if (V.isUnknownOrUndef())
return nullptr;
if (Optional<loc::ConcreteInt> X = V.getAs<loc::ConcreteInt>())
return &X->getValue();
if (Optional<nonloc::ConcreteInt> X = V.getAs<nonloc::ConcreteInt>())
return &X->getValue();
if (SymbolRef Sym = V.getAsSymbol())
return state->getConstraintManager().getSymVal(state, Sym);
// FIXME: Add support for SymExprs.
return nullptr;
}
SVal SimpleSValBuilder::simplifySVal(ProgramStateRef State, SVal V) {
// For now, this function tries to constant-fold symbols inside a
// nonloc::SymbolVal, and does nothing else. More simplifications should
// be possible, such as constant-folding an index in an ElementRegion.
class Simplifier : public FullSValVisitor<Simplifier, SVal> {
ProgramStateRef State;
SValBuilder &SVB;
// Cache results for the lifetime of the Simplifier. Results change every
// time new constraints are added to the program state, which is the whole
// point of simplifying, and for that very reason it's pointless to maintain
// the same cache for the duration of the whole analysis.
llvm::DenseMap<SymbolRef, SVal> Cached;
static bool isUnchanged(SymbolRef Sym, SVal Val) {
return Sym == Val.getAsSymbol();
}
public:
Simplifier(ProgramStateRef State)
: State(State), SVB(State->getStateManager().getSValBuilder()) {}
SVal VisitSymbolData(const SymbolData *S) {
if (const llvm::APSInt *I =
SVB.getKnownValue(State, SVB.makeSymbolVal(S)))
return Loc::isLocType(S->getType()) ? (SVal)SVB.makeIntLocVal(*I)
: (SVal)SVB.makeIntVal(*I);
return SVB.makeSymbolVal(S);
}
// TODO: Support SymbolCast. Support IntSymExpr when/if we actually
// start producing them.
SVal VisitSymIntExpr(const SymIntExpr *S) {
auto I = Cached.find(S);
if (I != Cached.end())
return I->second;
SVal LHS = Visit(S->getLHS());
if (isUnchanged(S->getLHS(), LHS)) {
SVal V = SVB.makeSymbolVal(S);
Cached[S] = V;
return V;
}
SVal RHS;
// By looking at the APSInt in the right-hand side of S, we cannot
// figure out if it should be treated as a Loc or as a NonLoc.
// So make our guess by recalling that we cannot multiply pointers
// or compare a pointer to an integer.
if (Loc::isLocType(S->getLHS()->getType()) &&
BinaryOperator::isComparisonOp(S->getOpcode())) {
// The usual conversion of $sym to &SymRegion{$sym}, as they have
// the same meaning for Loc-type symbols, but the latter form
// is preferred in SVal computations for being Loc itself.
if (SymbolRef Sym = LHS.getAsSymbol()) {
assert(Loc::isLocType(Sym->getType()));
LHS = SVB.makeLoc(Sym);
}
RHS = SVB.makeIntLocVal(S->getRHS());
} else {
RHS = SVB.makeIntVal(S->getRHS());
}
SVal V = SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
Cached[S] = V;
return V;
}
SVal VisitSymSymExpr(const SymSymExpr *S) {
auto I = Cached.find(S);
if (I != Cached.end())
return I->second;
SVal LHS = Visit(S->getLHS());
SVal RHS = Visit(S->getRHS());
if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS)) {
SVal V = SVB.makeSymbolVal(S);
Cached[S] = V;
return V;
}
SVal V = SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
Cached[S] = V;
return V;
}
SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }
SVal VisitMemRegion(const MemRegion *R) { return loc::MemRegionVal(R); }
SVal VisitNonLocSymbolVal(nonloc::SymbolVal V) {
// Simplification is much more costly than computing complexity.
// For high complexity, it may be not worth it.
return Visit(V.getSymbol());
}
SVal VisitSVal(SVal V) { return V; }
};
// A crude way of preventing this function from calling itself from evalBinOp.
static bool isReentering = false;
if (isReentering)
return V;
isReentering = true;
SVal SimplifiedV = Simplifier(State).Visit(V);
isReentering = false;
return SimplifiedV;
}
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