//
// Function: getAllCallees()
//
// Description:
// Given a DSCallSite, add to the list the functions that can be called by
// the call site *if* it is resolvable. Uses 'applyCallsiteFilter' to
// only add the functions that are valid targets of this callsite.
//
void BUDataStructures::
getAllCallees(const DSCallSite &CS, FuncSet &Callees) {
//
// FIXME: Should we check for the Unknown flag on indirect call sites?
//
// Direct calls to functions that have bodies are always resolvable.
// Indirect function calls that are for a complete call site (the analysis
// knows everything about the call site) and do not target external functions
// are also resolvable.
//
if (CS.isDirectCall()) {
if (!CS.getCalleeFunc()->isDeclaration())
Callees.insert(CS.getCalleeFunc());
} else if (CS.getCalleeNode()->isCompleteNode()) {
// Get all callees.
if (!CS.getCalleeNode()->isExternFuncNode()) {
// Get all the callees for this callsite
FuncSet TempCallees;
CS.getCalleeNode()->addFullFunctionSet(TempCallees);
// Filter out the ones that are invalid targets with respect
// to this particular callsite.
applyCallsiteFilter(CS, TempCallees);
// Insert the remaining callees (legal ones, if we're filtering)
// into the master 'Callees' list
Callees.insert(TempCallees.begin(), TempCallees.end());
}
}
}
void DSCallGraph::buildRoots() {
FuncSet knownCallees;
FuncSet knownCallers;
for (SimpleCalleesTy::iterator ii = SimpleCallees.begin(),
ee = SimpleCallees.end(); ii != ee; ++ii) {
knownCallees.insert(ii->second.begin(), ii->second.end());
knownCallers.insert(ii->first);
}
knownRoots.clear();
std::set_difference(knownCallers.begin(), knownCallers.end(),
knownCallees.begin(), knownCallees.end(),
std::inserter(knownRoots, knownRoots.begin()));
}
/**
* @brief Tries to find functions that can be called by indirect call.
*
* @par Preconditions
* - @a callInst is a call that calls some function indirectly.
*
* @param[in] call We try to find functions for this indirect call.
* @param[in] funcsToCheck We are finding functions that can be indirectly called
* only in this functions.
*
* @return Found functions that can be called indirectly.
*/
FuncSet IndirectlyCalledFuncsAnalysis::getFuncsForIndirectCall(
const CallInst &call,
const FuncVec &funcsToCheck)
{
assert(isIndirectCall(call) && "Expected an indirect call.");
FuncSet result;
Type *callReturnType = call.getType();
for (Function *func : funcsToCheck)
{
if (func->getReturnType() != callReturnType)
{
continue;
}
if (!func->isVarArg())
{
if (!hasEqArgsAndParams(call, *func))
{
continue;
}
}
result.insert(func);
}
return result;
}
/**
* @brief Visits the given node in the call graph.
*
* @param[in] calledFunc The given node.
* @param[in,out] calledFuncInfo Information about @a calledFunc.
*
* Corresponds to the strongconnect(v) function from
* http://en.wikipedia.org/wiki/Tarjan%27s_strongly_connected_components_algorithm
*/
void CallInfoObtainer::SCCComputer::visit(ShPtr<CG::CalledFuncs> calledFunc,
CalledFuncInfo &calledFuncInfo) {
// Set the depth index for calledFunc to the smallest unused index.
calledFuncInfo.index = calledFuncInfo.lowlink = index;
index++;
// Push calledFunc onto the stack.
stack.push(calledFunc);
calledFuncInfo.onStack = true;
// Consider the successors of calledFunc.
for (const auto &callee : calledFunc->callees) {
ShPtr<CG::CalledFuncs> succ(cg->getCalledFuncs(callee));
CalledFuncInfo &succInfo(calledFuncInfoMap[succ]);
if (succInfo.index < 0) { // '< 0' means 'undefined'
// The successor has not yet been visited; recurse on it.
visit(succ, succInfo);
calledFuncInfo.lowlink = std::min(calledFuncInfo.lowlink,
succInfo.lowlink);
} else if (succInfo.onStack) {
// The successor is on the stack and hence in the current SCC.
calledFuncInfo.lowlink = std::min(calledFuncInfo.lowlink,
succInfo.index);
}
}
// If calledFunc is a root node, pop the stack and generate an SCC.
if (calledFuncInfo.lowlink == calledFuncInfo.index) {
// Generate a new SCC.
FuncSet scc;
ShPtr<CG::CalledFuncs> poppedCalledFunc;
do {
poppedCalledFunc = stack.top();
stack.pop();
calledFuncInfoMap[cg->getCalledFuncs(
poppedCalledFunc->caller)].onStack = false;
scc.insert(poppedCalledFunc->caller);
} while (calledFunc != poppedCalledFunc);
// Store the generated SCC. However, if the SCC contains just a single
// function, do this only if it calls itself (see the description of
// computeSCCs()).
if (scc.size() != 1 || hasItem(calledFunc->callees, calledFunc->caller)) {
sccs.insert(scc);
}
}
}
/**
* @brief Finds a next SCC and its represent and returns them.
*
* @param[in] sccs All SCCs in the call graph.
* @param[in] computedFuncs Functions that already have been included in
* FuncInfoCompOrder::order.
* @param[in] remainingFuncs Functions that haven't been included in
* FuncInfoCompOrder::order.
*
* @par Preconditions
* - @a remainingFuncs is non-empty
* - @a remainingFuncs doesn't contain a function which calls just functions
* from @a computedFuncs.
*/
CallInfoObtainer::SCCWithRepresent CallInfoObtainer::findNextSCC(const FuncSetSet &sccs,
const FuncSet &computedFuncs, const FuncSet &remainingFuncs) const {
PRECONDITION(!remainingFuncs.empty(), "it should not be empty");
//
// We try to locate an SCC whose members call just the functions in
// the SCC or in computedFuncs. Then, if the found SCC contains a function
// from remainingFuncs, return the function.
//
// For every SCC...
for (const auto &scc : sccs) {
bool sccFound = true;
ShPtr<Function> funcFromRemainingFuncs;
// For every function in the SCC...
for (const auto &func : scc) {
// Check whether the function calls just the functions in the SCC
// or in computedFuncs.
ShPtr<CG::CalledFuncs> calledFuncs(cg->getCalledFuncs(func));
FuncSet mayCall(setUnion(scc, computedFuncs));
if (!setDifference(calledFuncs->callees, mayCall).empty()) {
sccFound = false;
} else {
// Have we encountered a function from remainingFuncs?
if (hasItem(remainingFuncs, func)) {
funcFromRemainingFuncs = func;
}
}
}
if (sccFound && funcFromRemainingFuncs) {
return SCCWithRepresent(scc, funcFromRemainingFuncs);
}
}
// TODO Can this happen?
printWarningMessage("[SCCComputer] No viable SCC has been found.");
FuncSet scc;
ShPtr<Function> func(*(remainingFuncs.begin()));
scc.insert(func);
return SCCWithRepresent(scc, func);
}