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//== Environment.cpp - Map from Stmt* to Locations/Values -------*- C++ -*--==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defined the Environment and EnvironmentManager classes.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/AnalysisContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Checker/PathSensitive/GRState.h"
using namespace clang;
SVal Environment::GetSVal(const Stmt *E, ValueManager& ValMgr) const {
for (;;) {
switch (E->getStmtClass()) {
case Stmt::AddrLabelExprClass:
return ValMgr.makeLoc(cast<AddrLabelExpr>(E));
// ParenExprs are no-ops.
case Stmt::ParenExprClass:
E = cast<ParenExpr>(E)->getSubExpr();
continue;
case Stmt::CharacterLiteralClass: {
const CharacterLiteral* C = cast<CharacterLiteral>(E);
return ValMgr.makeIntVal(C->getValue(), C->getType());
}
case Stmt::CXXBoolLiteralExprClass: {
const SVal *X = ExprBindings.lookup(E);
if (X)
return *X;
else
return ValMgr.makeIntVal(cast<CXXBoolLiteralExpr>(E));
}
case Stmt::IntegerLiteralClass: {
// In C++, this expression may have been bound to a temporary object.
SVal const *X = ExprBindings.lookup(E);
if (X)
return *X;
else
return ValMgr.makeIntVal(cast<IntegerLiteral>(E));
}
// Casts where the source and target type are the same
// are no-ops. We blast through these to get the descendant
// subexpression that has a value.
case Stmt::ImplicitCastExprClass:
case Stmt::CStyleCastExprClass: {
const CastExpr* C = cast<CastExpr>(E);
QualType CT = C->getType();
if (CT->isVoidType())
return UnknownVal();
break;
}
// Handle all other Stmt* using a lookup.
default:
break;
};
break;
}
return LookupExpr(E);
}
Environment EnvironmentManager::bindExpr(Environment Env, const Stmt *S,
SVal V, bool Invalidate) {
assert(S);
if (V.isUnknown()) {
if (Invalidate)
return Environment(F.remove(Env.ExprBindings, S));
else
return Env;
}
return Environment(F.add(Env.ExprBindings, S, V));
}
static inline const Stmt *MakeLocation(const Stmt *S) {
return (const Stmt*) (((uintptr_t) S) | 0x1);
}
Environment EnvironmentManager::bindExprAndLocation(Environment Env,
const Stmt *S,
SVal location, SVal V) {
return Environment(F.add(F.add(Env.ExprBindings, MakeLocation(S), location),
S, V));
}
namespace {
class MarkLiveCallback : public SymbolVisitor {
SymbolReaper &SymReaper;
public:
MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
bool VisitSymbol(SymbolRef sym) { SymReaper.markLive(sym); return true; }
};
} // end anonymous namespace
static bool isBlockExprInCallers(const Stmt *E, const LocationContext *LC) {
const LocationContext *ParentLC = LC->getParent();
while (ParentLC) {
CFG &C = *ParentLC->getCFG();
if (C.isBlkExpr(E))
return true;
ParentLC = ParentLC->getParent();
}
return false;
}
// In addition to mapping from Stmt * - > SVals in the Environment, we also
// maintain a mapping from Stmt * -> SVals (locations) that were used during
// a load and store.
static inline bool IsLocation(const Stmt *S) {
return (bool) (((uintptr_t) S) & 0x1);
}
// RemoveDeadBindings:
// - Remove subexpression bindings.
// - Remove dead block expression bindings.
// - Keep live block expression bindings:
// - Mark their reachable symbols live in SymbolReaper,
// see ScanReachableSymbols.
// - Mark the region in DRoots if the binding is a loc::MemRegionVal.
Environment
EnvironmentManager::RemoveDeadBindings(Environment Env,
SymbolReaper &SymReaper,
const GRState *ST,
llvm::SmallVectorImpl<const MemRegion*> &DRoots) {
CFG &C = *SymReaper.getLocationContext()->getCFG();
// We construct a new Environment object entirely, as this is cheaper than
// individually removing all the subexpression bindings (which will greatly
// outnumber block-level expression bindings).
Environment NewEnv = getInitialEnvironment();
llvm::SmallVector<std::pair<const Stmt*, SVal>, 10> deferredLocations;
// Iterate over the block-expr bindings.
for (Environment::iterator I = Env.begin(), E = Env.end();
I != E; ++I) {
const Stmt *BlkExpr = I.getKey();
// For recorded locations (used when evaluating loads and stores), we
// consider them live only when their associated normal expression is
// also live.
// NOTE: This assumes that loads/stores that evaluated to UnknownVal
// still have an entry in the map.
if (IsLocation(BlkExpr)) {
deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
continue;
}
const SVal &X = I.getData();
// Block-level expressions in callers are assumed always live.
if (isBlockExprInCallers(BlkExpr, SymReaper.getLocationContext())) {
NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, BlkExpr, X);
if (isa<loc::MemRegionVal>(X)) {
const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
DRoots.push_back(R);
}
// Mark all symbols in the block expr's value live.
MarkLiveCallback cb(SymReaper);
ST->scanReachableSymbols(X, cb);
continue;
}
// Not a block-level expression?
if (!C.isBlkExpr(BlkExpr))
continue;
if (SymReaper.isLive(BlkExpr)) {
// Copy the binding to the new map.
NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, BlkExpr, X);
// If the block expr's value is a memory region, then mark that region.
if (isa<loc::MemRegionVal>(X)) {
const MemRegion* R = cast<loc::MemRegionVal>(X).getRegion();
DRoots.push_back(R);
}
// Mark all symbols in the block expr's value live.
MarkLiveCallback cb(SymReaper);
ST->scanReachableSymbols(X, cb);
continue;
}
// Otherwise the expression is dead with a couple exceptions.
// Do not misclean LogicalExpr or ConditionalOperator. It is dead at the
// beginning of itself, but we need its UndefinedVal to determine its
// SVal.
if (X.isUndef() && cast<UndefinedVal>(X).getData())
NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, BlkExpr, X);
}
// Go through he deferred locations and add them to the new environment if
// the correspond Stmt* is in the map as well.
for (llvm::SmallVectorImpl<std::pair<const Stmt*, SVal> >::iterator
I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
const Stmt *S = (Stmt*) (((uintptr_t) I->first) & (uintptr_t) ~0x1);
if (NewEnv.ExprBindings.lookup(S))
NewEnv.ExprBindings = F.add(NewEnv.ExprBindings, I->first, I->second);
}
return NewEnv;
}