#include "llvm/Analysis/LazyCallGraph.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "lcg"
static void findCallees(
SmallVectorImpl<Constant *> &Worklist, SmallPtrSetImpl<Constant *> &Visited,
SmallVectorImpl<PointerUnion<Function *, LazyCallGraph::Node *>> &Callees,
DenseMap<Function *, size_t> &CalleeIndexMap) {
while (!Worklist.empty()) {
Constant *C = Worklist.pop_back_val();
if (Function *F = dyn_cast<Function>(C)) {
if (!F->isDeclaration() &&
CalleeIndexMap.insert(std::make_pair(F, Callees.size())).second) {
DEBUG(dbgs() << " Added callable function: " << F->getName()
<< "\n");
Callees.push_back(F);
}
continue;
}
for (Value *Op : C->operand_values())
if (Visited.insert(cast<Constant>(Op)))
Worklist.push_back(cast<Constant>(Op));
}
}
LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F)
: G(&G), F(F), DFSNumber(0), LowLink(0) {
DEBUG(dbgs() << " Adding functions called by '" << F.getName()
<< "' to the graph.\n");
SmallVector<Constant *, 16> Worklist;
SmallPtrSet<Constant *, 16> Visited;
for (BasicBlock &BB : F)
for (Instruction &I : BB)
for (Value *Op : I.operand_values())
if (Constant *C = dyn_cast<Constant>(Op))
if (Visited.insert(C))
Worklist.push_back(C);
findCallees(Worklist, Visited, Callees, CalleeIndexMap);
}
void LazyCallGraph::Node::insertEdgeInternal(Function &Callee) {
if (Node *N = G->lookup(Callee))
return insertEdgeInternal(*N);
CalleeIndexMap.insert(std::make_pair(&Callee, Callees.size()));
Callees.push_back(&Callee);
}
void LazyCallGraph::Node::insertEdgeInternal(Node &CalleeN) {
CalleeIndexMap.insert(std::make_pair(&CalleeN.getFunction(), Callees.size()));
Callees.push_back(&CalleeN);
}
void LazyCallGraph::Node::removeEdgeInternal(Function &Callee) {
auto IndexMapI = CalleeIndexMap.find(&Callee);
assert(IndexMapI != CalleeIndexMap.end() &&
"Callee not in the callee set for this caller?");
Callees[IndexMapI->second] = nullptr;
CalleeIndexMap.erase(IndexMapI);
}
LazyCallGraph::LazyCallGraph(Module &M) : NextDFSNumber(0) {
DEBUG(dbgs() << "Building CG for module: " << M.getModuleIdentifier()
<< "\n");
for (Function &F : M)
if (!F.isDeclaration() && !F.hasLocalLinkage())
if (EntryIndexMap.insert(std::make_pair(&F, EntryNodes.size())).second) {
DEBUG(dbgs() << " Adding '" << F.getName()
<< "' to entry set of the graph.\n");
EntryNodes.push_back(&F);
}
SmallVector<Constant *, 16> Worklist;
SmallPtrSet<Constant *, 16> Visited;
for (GlobalVariable &GV : M.globals())
if (GV.hasInitializer())
if (Visited.insert(GV.getInitializer()))
Worklist.push_back(GV.getInitializer());
DEBUG(dbgs() << " Adding functions referenced by global initializers to the "
"entry set.\n");
findCallees(Worklist, Visited, EntryNodes, EntryIndexMap);
for (auto &Entry : EntryNodes) {
assert(!Entry.isNull() &&
"We can't have removed edges before we finish the constructor!");
if (Function *F = Entry.dyn_cast<Function *>())
SCCEntryNodes.push_back(F);
else
SCCEntryNodes.push_back(&Entry.get<Node *>()->getFunction());
}
}
LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
: BPA(std::move(G.BPA)), NodeMap(std::move(G.NodeMap)),
EntryNodes(std::move(G.EntryNodes)),
EntryIndexMap(std::move(G.EntryIndexMap)), SCCBPA(std::move(G.SCCBPA)),
SCCMap(std::move(G.SCCMap)), LeafSCCs(std::move(G.LeafSCCs)),
DFSStack(std::move(G.DFSStack)),
SCCEntryNodes(std::move(G.SCCEntryNodes)),
NextDFSNumber(G.NextDFSNumber) {
updateGraphPtrs();
}
LazyCallGraph &LazyCallGraph::operator=(LazyCallGraph &&G) {
BPA = std::move(G.BPA);
NodeMap = std::move(G.NodeMap);
EntryNodes = std::move(G.EntryNodes);
EntryIndexMap = std::move(G.EntryIndexMap);
SCCBPA = std::move(G.SCCBPA);
SCCMap = std::move(G.SCCMap);
LeafSCCs = std::move(G.LeafSCCs);
DFSStack = std::move(G.DFSStack);
SCCEntryNodes = std::move(G.SCCEntryNodes);
NextDFSNumber = G.NextDFSNumber;
updateGraphPtrs();
return *this;
}
void LazyCallGraph::SCC::insert(Node &N) {
N.DFSNumber = N.LowLink = -1;
Nodes.push_back(&N);
G->SCCMap[&N] = this;
}
bool LazyCallGraph::SCC::isDescendantOf(const SCC &C) const {
SmallVector<const SCC *, 4> AncestorWorklist;
AncestorWorklist.push_back(this);
do {
const SCC *AncestorC = AncestorWorklist.pop_back_val();
if (AncestorC->isChildOf(C))
return true;
for (const SCC *ParentC : AncestorC->ParentSCCs)
AncestorWorklist.push_back(ParentC);
} while (!AncestorWorklist.empty());
return false;
}
void LazyCallGraph::SCC::insertIntraSCCEdge(Node &CallerN, Node &CalleeN) {
CallerN.insertEdgeInternal(CalleeN);
assert(G->SCCMap.lookup(&CallerN) == this && "Caller must be in this SCC.");
assert(G->SCCMap.lookup(&CalleeN) == this && "Callee must be in this SCC.");
}
void LazyCallGraph::SCC::insertOutgoingEdge(Node &CallerN, Node &CalleeN) {
CallerN.insertEdgeInternal(CalleeN);
assert(G->SCCMap.lookup(&CallerN) == this && "Caller must be in this SCC.");
SCC &CalleeC = *G->SCCMap.lookup(&CalleeN);
assert(&CalleeC != this && "Callee must not be in this SCC.");
assert(CalleeC.isDescendantOf(*this) &&
"Callee must be a descendant of the Caller.");
CalleeC.ParentSCCs.insert(this);
}
SmallVector<LazyCallGraph::SCC *, 1>
LazyCallGraph::SCC::insertIncomingEdge(Node &CallerN, Node &CalleeN) {
CallerN.insertEdgeInternal(CalleeN);
assert(G->SCCMap.lookup(&CalleeN) == this && "Callee must be in this SCC.");
SCC &CallerC = *G->SCCMap.lookup(&CallerN);
assert(&CallerC != this && "Caller must not be in this SCC.");
assert(CallerC.isDescendantOf(*this) &&
"Caller must be a descendant of the Callee.");
SmallPtrSet<SCC *, 8> ConnectedSCCs;
ConnectedSCCs.insert(this);
ConnectedSCCs.insert(&CallerC);
SmallVector<std::pair<SCC *, SCC::parent_iterator>, 8> DFSSCCs;
SmallPtrSet<SCC *, 8> VisitedSCCs;
int ConnectedDepth = -1;
SCC *C = this;
parent_iterator I = parent_begin(), E = parent_end();
for (;;) {
while (I != E) {
SCC &ParentSCC = *I++;
if (ConnectedSCCs.count(&ParentSCC)) {
ConnectedDepth = std::max<int>(ConnectedDepth, DFSSCCs.size());
continue;
}
if (VisitedSCCs.count(&ParentSCC))
continue;
DFSSCCs.push_back(std::make_pair(C, I));
C = &ParentSCC;
I = ParentSCC.parent_begin();
E = ParentSCC.parent_end();
}
if ((int)DFSSCCs.size() == ConnectedDepth) {
--ConnectedDepth; ConnectedSCCs.insert(C);
} else {
assert(ConnectedDepth < (int)DFSSCCs.size() &&
"Cannot have a connected depth greater than the DFS depth!");
VisitedSCCs.insert(C);
}
if (DFSSCCs.empty())
break;
std::tie(C, I) = DFSSCCs.pop_back_val();
E = C->parent_end();
}
unsigned NewNodeBeginIdx = Nodes.size();
for (SCC *C : ConnectedSCCs) {
if (C == this)
continue;
for (SCC *ParentC : C->ParentSCCs)
if (!ConnectedSCCs.count(ParentC))
ParentSCCs.insert(ParentC);
C->ParentSCCs.clear();
for (Node *N : *C) {
for (Node &ChildN : *N) {
SCC &ChildC = *G->SCCMap.lookup(&ChildN);
if (&ChildC != C)
ChildC.ParentSCCs.erase(C);
}
G->SCCMap[N] = this;
Nodes.push_back(N);
}
C->Nodes.clear();
}
for (auto I = Nodes.begin() + NewNodeBeginIdx, E = Nodes.end(); I != E; ++I)
for (Node &ChildN : **I) {
SCC &ChildC = *G->SCCMap.lookup(&ChildN);
if (&ChildC != this)
ChildC.ParentSCCs.insert(this);
}
return SmallVector<SCC *, 1>(ConnectedSCCs.begin(), ConnectedSCCs.end());
}
void LazyCallGraph::SCC::removeInterSCCEdge(Node &CallerN, Node &CalleeN) {
CallerN.removeEdgeInternal(CalleeN.getFunction());
assert(G->SCCMap.lookup(&CallerN) == this &&
"The caller must be a member of this SCC.");
SCC &CalleeC = *G->SCCMap.lookup(&CalleeN);
assert(&CalleeC != this &&
"This API only supports the rmoval of inter-SCC edges.");
assert(std::find(G->LeafSCCs.begin(), G->LeafSCCs.end(), this) ==
G->LeafSCCs.end() &&
"Cannot have a leaf SCC caller with a different SCC callee.");
bool HasOtherCallToCalleeC = false;
bool HasOtherCallOutsideSCC = false;
for (Node *N : *this) {
for (Node &OtherCalleeN : *N) {
SCC &OtherCalleeC = *G->SCCMap.lookup(&OtherCalleeN);
if (&OtherCalleeC == &CalleeC) {
HasOtherCallToCalleeC = true;
break;
}
if (&OtherCalleeC != this)
HasOtherCallOutsideSCC = true;
}
if (HasOtherCallToCalleeC)
break;
}
if (!HasOtherCallToCalleeC) {
bool Removed = CalleeC.ParentSCCs.erase(this);
(void)Removed;
assert(Removed &&
"Did not find the caller SCC in the callee SCC's parent list!");
if (CalleeC.ParentSCCs.empty())
DEBUG(dbgs() << "LCG: Update removing " << CallerN.getFunction().getName()
<< " -> " << CalleeN.getFunction().getName()
<< " edge orphaned the callee's SCC!\n");
}
if (!HasOtherCallOutsideSCC)
G->LeafSCCs.push_back(this);
}
void LazyCallGraph::SCC::internalDFS(
SmallVectorImpl<std::pair<Node *, Node::iterator>> &DFSStack,
SmallVectorImpl<Node *> &PendingSCCStack, Node *N,
SmallVectorImpl<SCC *> &ResultSCCs) {
Node::iterator I = N->begin();
N->LowLink = N->DFSNumber = 1;
int NextDFSNumber = 2;
for (;;) {
assert(N->DFSNumber != 0 && "We should always assign a DFS number "
"before processing a node.");
Node::iterator E = N->end();
while (I != E) {
Node &ChildN = *I;
if (SCC *ChildSCC = G->SCCMap.lookup(&ChildN)) {
if (ChildSCC == this) {
insert(*N);
while (!PendingSCCStack.empty())
insert(*PendingSCCStack.pop_back_val());
while (!DFSStack.empty())
insert(*DFSStack.pop_back_val().first);
return;
}
ChildSCC->ParentSCCs.erase(this);
++I;
continue;
}
if (ChildN.DFSNumber == 0) {
DFSStack.push_back(std::make_pair(N, I));
ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
N = &ChildN;
I = ChildN.begin();
E = ChildN.end();
continue;
}
assert(ChildN.LowLink != 0 &&
"Low-link must not be zero with a non-zero DFS number.");
if (ChildN.LowLink >= 0 && ChildN.LowLink < N->LowLink)
N->LowLink = ChildN.LowLink;
++I;
}
if (N->LowLink == N->DFSNumber) {
ResultSCCs.push_back(G->formSCC(N, PendingSCCStack));
if (DFSStack.empty())
return;
} else {
PendingSCCStack.push_back(N);
assert(!DFSStack.empty() && "We shouldn't have an empty stack!");
}
N = DFSStack.back().first;
I = DFSStack.back().second;
DFSStack.pop_back();
}
}
SmallVector<LazyCallGraph::SCC *, 1>
LazyCallGraph::SCC::removeIntraSCCEdge(Node &CallerN,
Node &CalleeN) {
CallerN.removeEdgeInternal(CalleeN.getFunction());
SmallVector<SCC *, 1> ResultSCCs;
if (&CallerN == &CalleeN)
return ResultSCCs;
SmallVector<Node *, 1> Worklist;
Worklist.swap(Nodes);
for (Node *N : Worklist) {
N->DFSNumber = 0;
N->LowLink = 0;
G->SCCMap.erase(N);
}
assert(Worklist.size() > 1 && "We have to have at least two nodes to have an "
"edge between them that is within the SCC.");
insert(CalleeN);
SmallVector<std::pair<Node *, Node::iterator>, 4> DFSStack;
SmallVector<Node *, 4> PendingSCCStack;
do {
Node *N = Worklist.pop_back_val();
if (N->DFSNumber == 0)
internalDFS(DFSStack, PendingSCCStack, N, ResultSCCs);
assert(DFSStack.empty() && "Didn't flush the entire DFS stack!");
assert(PendingSCCStack.empty() && "Didn't flush all pending SCC nodes!");
} while (!Worklist.empty());
bool IsLeafSCC = true;
for (Node *N : Nodes) {
for (Node &ChildN : *N) {
SCC &ChildSCC = *G->SCCMap.lookup(&ChildN);
if (&ChildSCC == this)
continue;
ChildSCC.ParentSCCs.insert(this);
IsLeafSCC = false;
}
}
#ifndef NDEBUG
if (!ResultSCCs.empty())
assert(!IsLeafSCC && "This SCC cannot be a leaf as we have split out new "
"SCCs by removing this edge.");
if (!std::any_of(G->LeafSCCs.begin(), G->LeafSCCs.end(),
[&](SCC *C) { return C == this; }))
assert(!IsLeafSCC && "This SCC cannot be a leaf as it already had child "
"SCCs before we removed this edge.");
#endif
if (!IsLeafSCC && !ResultSCCs.empty())
G->LeafSCCs.erase(std::remove(G->LeafSCCs.begin(), G->LeafSCCs.end(), this),
G->LeafSCCs.end());
return ResultSCCs;
}
void LazyCallGraph::insertEdge(Node &CallerN, Function &Callee) {
assert(SCCMap.empty() && DFSStack.empty() &&
"This method cannot be called after SCCs have been formed!");
return CallerN.insertEdgeInternal(Callee);
}
void LazyCallGraph::removeEdge(Node &CallerN, Function &Callee) {
assert(SCCMap.empty() && DFSStack.empty() &&
"This method cannot be called after SCCs have been formed!");
return CallerN.removeEdgeInternal(Callee);
}
LazyCallGraph::Node &LazyCallGraph::insertInto(Function &F, Node *&MappedN) {
return *new (MappedN = BPA.Allocate()) Node(*this, F);
}
void LazyCallGraph::updateGraphPtrs() {
{
SmallVector<Node *, 16> Worklist;
for (auto &Entry : EntryNodes)
if (Node *EntryN = Entry.dyn_cast<Node *>())
Worklist.push_back(EntryN);
while (!Worklist.empty()) {
Node *N = Worklist.pop_back_val();
N->G = this;
for (auto &Callee : N->Callees)
if (!Callee.isNull())
if (Node *CalleeN = Callee.dyn_cast<Node *>())
Worklist.push_back(CalleeN);
}
}
{
SmallVector<SCC *, 16> Worklist(LeafSCCs.begin(), LeafSCCs.end());
while (!Worklist.empty()) {
SCC *C = Worklist.pop_back_val();
C->G = this;
Worklist.insert(Worklist.end(), C->ParentSCCs.begin(),
C->ParentSCCs.end());
}
}
}
LazyCallGraph::SCC *LazyCallGraph::formSCC(Node *RootN,
SmallVectorImpl<Node *> &NodeStack) {
SCC *NewSCC = new (SCCBPA.Allocate()) SCC(*this);
while (!NodeStack.empty() && NodeStack.back()->DFSNumber > RootN->DFSNumber) {
assert(NodeStack.back()->LowLink >= RootN->LowLink &&
"We cannot have a low link in an SCC lower than its root on the "
"stack!");
NewSCC->insert(*NodeStack.pop_back_val());
}
NewSCC->insert(*RootN);
bool IsLeafSCC = true;
for (Node *SCCN : NewSCC->Nodes)
for (Node &SCCChildN : *SCCN) {
SCC &ChildSCC = *SCCMap.lookup(&SCCChildN);
if (&ChildSCC == NewSCC)
continue;
ChildSCC.ParentSCCs.insert(NewSCC);
IsLeafSCC = false;
}
if (IsLeafSCC)
LeafSCCs.push_back(NewSCC);
return NewSCC;
}
LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
Node *N;
Node::iterator I;
if (!DFSStack.empty()) {
N = DFSStack.back().first;
I = DFSStack.back().second;
DFSStack.pop_back();
} else {
do {
if (SCCEntryNodes.empty())
return nullptr;
N = &get(*SCCEntryNodes.pop_back_val());
} while (N->DFSNumber != 0);
I = N->begin();
N->LowLink = N->DFSNumber = 1;
NextDFSNumber = 2;
}
for (;;) {
assert(N->DFSNumber != 0 && "We should always assign a DFS number "
"before placing a node onto the stack.");
Node::iterator E = N->end();
while (I != E) {
Node &ChildN = *I;
if (ChildN.DFSNumber == 0) {
DFSStack.push_back(std::make_pair(N, N->begin()));
assert(!SCCMap.count(&ChildN) &&
"Found a node with 0 DFS number but already in an SCC!");
ChildN.LowLink = ChildN.DFSNumber = NextDFSNumber++;
N = &ChildN;
I = ChildN.begin();
E = ChildN.end();
continue;
}
assert(ChildN.LowLink != 0 &&
"Low-link must not be zero with a non-zero DFS number.");
if (ChildN.LowLink >= 0 && ChildN.LowLink < N->LowLink)
N->LowLink = ChildN.LowLink;
++I;
}
if (N->LowLink == N->DFSNumber)
return formSCC(N, PendingSCCStack);
PendingSCCStack.push_back(N);
assert(!DFSStack.empty() && "We never found a viable root!");
N = DFSStack.back().first;
I = DFSStack.back().second;
DFSStack.pop_back();
}
}
char LazyCallGraphAnalysis::PassID;
LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}
static void printNodes(raw_ostream &OS, LazyCallGraph::Node &N,
SmallPtrSetImpl<LazyCallGraph::Node *> &Printed) {
for (LazyCallGraph::Node &ChildN : N)
if (Printed.insert(&ChildN))
printNodes(OS, ChildN, Printed);
OS << " Call edges in function: " << N.getFunction().getName() << "\n";
for (LazyCallGraph::iterator I = N.begin(), E = N.end(); I != E; ++I)
OS << " -> " << I->getFunction().getName() << "\n";
OS << "\n";
}
static void printSCC(raw_ostream &OS, LazyCallGraph::SCC &SCC) {
ptrdiff_t SCCSize = std::distance(SCC.begin(), SCC.end());
OS << " SCC with " << SCCSize << " functions:\n";
for (LazyCallGraph::Node *N : SCC)
OS << " " << N->getFunction().getName() << "\n";
OS << "\n";
}
PreservedAnalyses LazyCallGraphPrinterPass::run(Module *M,
ModuleAnalysisManager *AM) {
LazyCallGraph &G = AM->getResult<LazyCallGraphAnalysis>(M);
OS << "Printing the call graph for module: " << M->getModuleIdentifier()
<< "\n\n";
SmallPtrSet<LazyCallGraph::Node *, 16> Printed;
for (LazyCallGraph::Node &N : G)
if (Printed.insert(&N))
printNodes(OS, N, Printed);
for (LazyCallGraph::SCC &SCC : G.postorder_sccs())
printSCC(OS, SCC);
return PreservedAnalyses::all();
}