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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/Checker/PathSensitive/GRState.h"
#include "clang/Analysis/Analyses/LiveVariables.h"
#include "llvm/ADT/ImmutableMap.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::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));
}
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
// 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, const Stmt *S,
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();
// Not a block-level expression?
if (!C.isBlkExpr(BlkExpr))
continue;
const SVal &X = I.getData();
if (SymReaper.isLive(S, 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 the super region of the RX as live.
// e.g.: int x; char *y = (char*) &x; if (*y) ...
// 'y' => element region. 'x' is its super region.
// We only add one level super region for now.
// FIXME: maybe multiple level of super regions should be added.
if (const SubRegion *SR = dyn_cast<SubRegion>(R))
DRoots.push_back(SR->getSuperRegion());
}
// 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;
}
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