1 //===- LazyCallGraph.cpp - Analysis of a Module's call graph --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/Analysis/LazyCallGraph.h"
11 #include "llvm/ADT/SCCIterator.h"
12 #include "llvm/IR/CallSite.h"
13 #include "llvm/IR/InstVisitor.h"
14 #include "llvm/IR/Instructions.h"
15 #include "llvm/IR/PassManager.h"
16 #include "llvm/Support/raw_ostream.h"
20 static void findCallees(
21 SmallVectorImpl<Constant *> &Worklist, SmallPtrSetImpl<Constant *> &Visited,
22 SmallVectorImpl<PointerUnion<Function *, LazyCallGraph::Node *>> &Callees,
23 SmallPtrSetImpl<Function *> &CalleeSet) {
24 while (!Worklist.empty()) {
25 Constant *C = Worklist.pop_back_val();
27 if (Function *F = dyn_cast<Function>(C)) {
28 // Note that we consider *any* function with a definition to be a viable
29 // edge. Even if the function's definition is subject to replacement by
30 // some other module (say, a weak definition) there may still be
31 // optimizations which essentially speculate based on the definition and
32 // a way to check that the specific definition is in fact the one being
33 // used. For example, this could be done by moving the weak definition to
34 // a strong (internal) definition and making the weak definition be an
35 // alias. Then a test of the address of the weak function against the new
36 // strong definition's address would be an effective way to determine the
37 // safety of optimizing a direct call edge.
38 if (!F->isDeclaration() && CalleeSet.insert(F))
43 for (Value *Op : C->operand_values())
44 if (Visited.insert(cast<Constant>(Op)))
45 Worklist.push_back(cast<Constant>(Op));
49 LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F) : G(&G), F(F) {
50 SmallVector<Constant *, 16> Worklist;
51 SmallPtrSet<Constant *, 16> Visited;
52 // Find all the potential callees in this function. First walk the
53 // instructions and add every operand which is a constant to the worklist.
54 for (BasicBlock &BB : F)
55 for (Instruction &I : BB)
56 for (Value *Op : I.operand_values())
57 if (Constant *C = dyn_cast<Constant>(Op))
58 if (Visited.insert(C))
59 Worklist.push_back(C);
61 // We've collected all the constant (and thus potentially function or
62 // function containing) operands to all of the instructions in the function.
63 // Process them (recursively) collecting every function found.
64 findCallees(Worklist, Visited, Callees, CalleeSet);
67 LazyCallGraph::Node::Node(LazyCallGraph &G, const Node &OtherN)
68 : G(&G), F(OtherN.F), CalleeSet(OtherN.CalleeSet) {
69 // Loop over the other node's callees, adding the Function*s to our list
70 // directly, and recursing to add the Node*s.
71 Callees.reserve(OtherN.Callees.size());
72 for (const auto &OtherCallee : OtherN.Callees)
73 if (Function *Callee = OtherCallee.dyn_cast<Function *>())
74 Callees.push_back(Callee);
76 Callees.push_back(G.copyInto(*OtherCallee.get<Node *>()));
79 LazyCallGraph::LazyCallGraph(Module &M) {
81 if (!F.isDeclaration() && !F.hasLocalLinkage())
82 if (EntryNodeSet.insert(&F))
83 EntryNodes.push_back(&F);
85 // Now add entry nodes for functions reachable via initializers to globals.
86 SmallVector<Constant *, 16> Worklist;
87 SmallPtrSet<Constant *, 16> Visited;
88 for (GlobalVariable &GV : M.globals())
89 if (GV.hasInitializer())
90 if (Visited.insert(GV.getInitializer()))
91 Worklist.push_back(GV.getInitializer());
93 findCallees(Worklist, Visited, EntryNodes, EntryNodeSet);
96 LazyCallGraph::LazyCallGraph(const LazyCallGraph &G)
97 : EntryNodeSet(G.EntryNodeSet) {
98 EntryNodes.reserve(G.EntryNodes.size());
99 for (const auto &EntryNode : G.EntryNodes)
100 if (Function *Callee = EntryNode.dyn_cast<Function *>())
101 EntryNodes.push_back(Callee);
103 EntryNodes.push_back(copyInto(*EntryNode.get<Node *>()));
106 LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
107 : BPA(std::move(G.BPA)), EntryNodes(std::move(G.EntryNodes)),
108 EntryNodeSet(std::move(G.EntryNodeSet)) {
109 // Process all nodes updating the graph pointers.
110 SmallVector<Node *, 16> Worklist;
111 for (auto &Entry : EntryNodes)
112 if (Node *EntryN = Entry.dyn_cast<Node *>())
113 Worklist.push_back(EntryN);
115 while (!Worklist.empty()) {
116 Node *N = Worklist.pop_back_val();
118 for (auto &Callee : N->Callees)
119 if (Node *CalleeN = Callee.dyn_cast<Node *>())
120 Worklist.push_back(CalleeN);
124 LazyCallGraph::Node *LazyCallGraph::insertInto(Function &F, Node *&MappedN) {
125 return new (MappedN = BPA.Allocate()) Node(*this, F);
128 LazyCallGraph::Node *LazyCallGraph::copyInto(const Node &OtherN) {
129 Node *&N = NodeMap[&OtherN.F];
133 return new (N = BPA.Allocate()) Node(*this, OtherN);
136 char LazyCallGraphAnalysis::PassID;
138 LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}
140 static void printNodes(raw_ostream &OS, LazyCallGraph::Node &N,
141 SmallPtrSetImpl<LazyCallGraph::Node *> &Printed) {
142 // Recurse depth first through the nodes.
143 for (LazyCallGraph::Node *ChildN : N)
144 if (Printed.insert(ChildN))
145 printNodes(OS, *ChildN, Printed);
147 OS << " Call edges in function: " << N.getFunction().getName() << "\n";
148 for (LazyCallGraph::iterator I = N.begin(), E = N.end(); I != E; ++I)
149 OS << " -> " << I->getFunction().getName() << "\n";
154 PreservedAnalyses LazyCallGraphPrinterPass::run(Module *M,
155 ModuleAnalysisManager *AM) {
156 LazyCallGraph &G = AM->getResult<LazyCallGraphAnalysis>(M);
158 OS << "Printing the call graph for module: " << M->getModuleIdentifier()
161 SmallPtrSet<LazyCallGraph::Node *, 16> Printed;
162 for (LazyCallGraph::Node *N : G)
163 if (Printed.insert(N))
164 printNodes(OS, *N, Printed);
166 return PreservedAnalyses::all();