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();
// Iterate over the block-expr bindings.
for (Environment::iterator I = Env.begin(), E = Env.end();
I != E; ++I) {
const Stmt *BlkExpr = I.getKey();
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);
}
return NewEnv;
}
// 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;
}