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//===- CallGraph.h - Build a Module's call graph ----------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file provides interfaces used to build and manipulate a call graph,
/// which is a very useful tool for interprocedural optimization.
///
/// Every function in a module is represented as a node in the call graph. The
/// callgraph node keeps track of which functions are called by the function
/// corresponding to the node.
///
/// A call graph may contain nodes where the function that they correspond to
/// is null. These 'external' nodes are used to represent control flow that is
/// not represented (or analyzable) in the module. In particular, this
/// analysis builds one external node such that:
/// 1. All functions in the module without internal linkage will have edges
/// from this external node, indicating that they could be called by
/// functions outside of the module.
/// 2. All functions whose address is used for something more than a direct
/// call, for example being stored into a memory location will also have
/// an edge from this external node. Since they may be called by an
/// unknown caller later, they must be tracked as such.
///
/// There is a second external node added for calls that leave this module.
/// Functions have a call edge to the external node iff:
/// 1. The function is external, reflecting the fact that they could call
/// anything without internal linkage or that has its address taken.
/// 2. The function contains an indirect function call.
///
/// As an extension in the future, there may be multiple nodes with a null
/// function. These will be used when we can prove (through pointer analysis)
/// that an indirect call site can call only a specific set of functions.
///
/// Because of these properties, the CallGraph captures a conservative superset
/// of all of the caller-callee relationships, which is useful for
/// transformations.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_CALLGRAPH_H
#define LLVM_ANALYSIS_CALLGRAPH_H
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
#include <cassert>
#include <map>
#include <memory>
#include <utility>
#include <vector>
namespace llvm {
template <class GraphType> struct GraphTraits;
class CallGraphNode;
class Function;
class Module;
class raw_ostream;
/// The basic data container for the call graph of a \c Module of IR.
///
/// This class exposes both the interface to the call graph for a module of IR.
///
/// The core call graph itself can also be updated to reflect changes to the IR.
class CallGraph {
Module &M;
using FunctionMapTy =
std::map<const Function *, std::unique_ptr<CallGraphNode>>;
/// A map from \c Function* to \c CallGraphNode*.
FunctionMapTy FunctionMap;
/// This node has edges to all external functions and those internal
/// functions that have their address taken.
CallGraphNode *ExternalCallingNode;
/// This node has edges to it from all functions making indirect calls
/// or calling an external function.
std::unique_ptr<CallGraphNode> CallsExternalNode;
public:
explicit CallGraph(Module &M);
CallGraph(CallGraph &&Arg);
~CallGraph();
void print(raw_ostream &OS) const;
void dump() const;
using iterator = FunctionMapTy::iterator;
using const_iterator = FunctionMapTy::const_iterator;
/// Returns the module the call graph corresponds to.
Module &getModule() const { return M; }
bool invalidate(Module &, const PreservedAnalyses &PA,
ModuleAnalysisManager::Invalidator &);
inline iterator begin() { return FunctionMap.begin(); }
inline iterator end() { return FunctionMap.end(); }
inline const_iterator begin() const { return FunctionMap.begin(); }
inline const_iterator end() const { return FunctionMap.end(); }
/// Returns the call graph node for the provided function.
inline const CallGraphNode *operator[](const Function *F) const {
const_iterator I = FunctionMap.find(F);
assert(I != FunctionMap.end() && "Function not in callgraph!");
return I->second.get();
}
/// Returns the call graph node for the provided function.
inline CallGraphNode *operator[](const Function *F) {
const_iterator I = FunctionMap.find(F);
assert(I != FunctionMap.end() && "Function not in callgraph!");
return I->second.get();
}
/// Returns the \c CallGraphNode which is used to represent
/// undetermined calls into the callgraph.
CallGraphNode *getExternalCallingNode() const { return ExternalCallingNode; }
CallGraphNode *getCallsExternalNode() const {
return CallsExternalNode.get();
}
/// Old node has been deleted, and New is to be used in its place, update the
/// ExternalCallingNode.
void ReplaceExternalCallEdge(CallGraphNode *Old, CallGraphNode *New);
//===---------------------------------------------------------------------
// Functions to keep a call graph up to date with a function that has been
// modified.
//
/// Unlink the function from this module, returning it.
///
/// Because this removes the function from the module, the call graph node is
/// destroyed. This is only valid if the function does not call any other
/// functions (ie, there are no edges in it's CGN). The easiest way to do
/// this is to dropAllReferences before calling this.
Function *removeFunctionFromModule(CallGraphNode *CGN);
/// Similar to operator[], but this will insert a new CallGraphNode for
/// \c F if one does not already exist.
CallGraphNode *getOrInsertFunction(const Function *F);
/// Populate \p CGN based on the calls inside the associated function.
void populateCallGraphNode(CallGraphNode *CGN);
/// Add a function to the call graph, and link the node to all of the
/// functions that it calls.
void addToCallGraph(Function *F);
};
/// A node in the call graph for a module.
///
/// Typically represents a function in the call graph. There are also special
/// "null" nodes used to represent theoretical entries in the call graph.
class CallGraphNode {
public:
/// A pair of the calling instruction (a call or invoke)
/// and the call graph node being called.
/// Call graph node may have two types of call records which represent an edge
/// in the call graph - reference or a call edge. Reference edges are not
/// associated with any call instruction and are created with the first field
/// set to `None`, while real call edges have instruction address in this
/// field. Therefore, all real call edges are expected to have a value in the
/// first field and it is not supposed to be `nullptr`.
/// Reference edges, for example, are used for connecting broker function
/// caller to the callback function for callback call sites.
using CallRecord = std::pair<std::optional<WeakTrackingVH>, CallGraphNode *>;
public:
using CalledFunctionsVector = std::vector<CallRecord>;
/// Creates a node for the specified function.
inline CallGraphNode(CallGraph *CG, Function *F) : CG(CG), F(F) {}
CallGraphNode(const CallGraphNode &) = delete;
CallGraphNode &operator=(const CallGraphNode &) = delete;
~CallGraphNode() {
assert(NumReferences == 0 && "Node deleted while references remain");
}
using iterator = std::vector<CallRecord>::iterator;
using const_iterator = std::vector<CallRecord>::const_iterator;
/// Returns the function that this call graph node represents.
Function *getFunction() const { return F; }
inline iterator begin() { return CalledFunctions.begin(); }
inline iterator end() { return CalledFunctions.end(); }
inline const_iterator begin() const { return CalledFunctions.begin(); }
inline const_iterator end() const { return CalledFunctions.end(); }
inline bool empty() const { return CalledFunctions.empty(); }
inline unsigned size() const { return (unsigned)CalledFunctions.size(); }
/// Returns the number of other CallGraphNodes in this CallGraph that
/// reference this node in their callee list.
unsigned getNumReferences() const { return NumReferences; }
/// Returns the i'th called function.
CallGraphNode *operator[](unsigned i) const {
assert(i < CalledFunctions.size() && "Invalid index");
return CalledFunctions[i].second;
}
/// Print out this call graph node.
void dump() const;
void print(raw_ostream &OS) const;
//===---------------------------------------------------------------------
// Methods to keep a call graph up to date with a function that has been
// modified
//
/// Removes all edges from this CallGraphNode to any functions it
/// calls.
void removeAllCalledFunctions() {
while (!CalledFunctions.empty()) {
CalledFunctions.back().second->DropRef();
CalledFunctions.pop_back();
}
}
/// Moves all the callee information from N to this node.
void stealCalledFunctionsFrom(CallGraphNode *N) {
assert(CalledFunctions.empty() &&
"Cannot steal callsite information if I already have some");
std::swap(CalledFunctions, N->CalledFunctions);
}
/// Adds a function to the list of functions called by this one.
void addCalledFunction(CallBase *Call, CallGraphNode *M) {
CalledFunctions.emplace_back(Call ? std::optional<WeakTrackingVH>(Call)
: std::optional<WeakTrackingVH>(),
M);
M->AddRef();
}
void removeCallEdge(iterator I) {
I->second->DropRef();
*I = CalledFunctions.back();
CalledFunctions.pop_back();
}
/// Removes the edge in the node for the specified call site.
///
/// Note that this method takes linear time, so it should be used sparingly.
void removeCallEdgeFor(CallBase &Call);
/// Removes all call edges from this node to the specified callee
/// function.
///
/// This takes more time to execute than removeCallEdgeTo, so it should not
/// be used unless necessary.
void removeAnyCallEdgeTo(CallGraphNode *Callee);
/// Removes one edge associated with a null callsite from this node to
/// the specified callee function.
void removeOneAbstractEdgeTo(CallGraphNode *Callee);
/// Replaces the edge in the node for the specified call site with a
/// new one.
///
/// Note that this method takes linear time, so it should be used sparingly.
void replaceCallEdge(CallBase &Call, CallBase &NewCall,
CallGraphNode *NewNode);
private:
friend class CallGraph;
CallGraph *CG;
Function *F;
std::vector<CallRecord> CalledFunctions;
/// The number of times that this CallGraphNode occurs in the
/// CalledFunctions array of this or other CallGraphNodes.
unsigned NumReferences = 0;
void DropRef() { --NumReferences; }
void AddRef() { ++NumReferences; }
/// A special function that should only be used by the CallGraph class.
void allReferencesDropped() { NumReferences = 0; }
};
/// An analysis pass to compute the \c CallGraph for a \c Module.
///
/// This class implements the concept of an analysis pass used by the \c
/// ModuleAnalysisManager to run an analysis over a module and cache the
/// resulting data.
class CallGraphAnalysis : public AnalysisInfoMixin<CallGraphAnalysis> {
friend AnalysisInfoMixin<CallGraphAnalysis>;
static AnalysisKey Key;
public:
/// A formulaic type to inform clients of the result type.
using Result = CallGraph;
/// Compute the \c CallGraph for the module \c M.
///
/// The real work here is done in the \c CallGraph constructor.
CallGraph run(Module &M, ModuleAnalysisManager &) { return CallGraph(M); }
};
/// Printer pass for the \c CallGraphAnalysis results.
class CallGraphPrinterPass : public PassInfoMixin<CallGraphPrinterPass> {
raw_ostream &OS;
public:
explicit CallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
static bool isRequired() { return true; }
};
/// Printer pass for the summarized \c CallGraphAnalysis results.
class CallGraphSCCsPrinterPass
: public PassInfoMixin<CallGraphSCCsPrinterPass> {
raw_ostream &OS;
public:
explicit CallGraphSCCsPrinterPass(raw_ostream &OS) : OS(OS) {}
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
static bool isRequired() { return true; }
};
/// The \c ModulePass which wraps up a \c CallGraph and the logic to
/// build it.
///
/// This class exposes both the interface to the call graph container and the
/// module pass which runs over a module of IR and produces the call graph. The
/// call graph interface is entirelly a wrapper around a \c CallGraph object
/// which is stored internally for each module.
class CallGraphWrapperPass : public ModulePass {
std::unique_ptr<CallGraph> G;
public:
static char ID; // Class identification, replacement for typeinfo
CallGraphWrapperPass();
~CallGraphWrapperPass() override;
/// The internal \c CallGraph around which the rest of this interface
/// is wrapped.
const CallGraph &getCallGraph() const { return *G; }
CallGraph &getCallGraph() { return *G; }
using iterator = CallGraph::iterator;
using const_iterator = CallGraph::const_iterator;
/// Returns the module the call graph corresponds to.
Module &getModule() const { return G->getModule(); }
inline iterator begin() { return G->begin(); }
inline iterator end() { return G->end(); }
inline const_iterator begin() const { return G->begin(); }
inline const_iterator end() const { return G->end(); }
/// Returns the call graph node for the provided function.
inline const CallGraphNode *operator[](const Function *F) const {
return (*G)[F];
}
/// Returns the call graph node for the provided function.
inline CallGraphNode *operator[](const Function *F) { return (*G)[F]; }
/// Returns the \c CallGraphNode which is used to represent
/// undetermined calls into the callgraph.
CallGraphNode *getExternalCallingNode() const {
return G->getExternalCallingNode();
}
CallGraphNode *getCallsExternalNode() const {
return G->getCallsExternalNode();
}
//===---------------------------------------------------------------------
// Functions to keep a call graph up to date with a function that has been
// modified.
//
/// Unlink the function from this module, returning it.
///
/// Because this removes the function from the module, the call graph node is
/// destroyed. This is only valid if the function does not call any other
/// functions (ie, there are no edges in it's CGN). The easiest way to do
/// this is to dropAllReferences before calling this.
Function *removeFunctionFromModule(CallGraphNode *CGN) {
return G->removeFunctionFromModule(CGN);
}
/// Similar to operator[], but this will insert a new CallGraphNode for
/// \c F if one does not already exist.
CallGraphNode *getOrInsertFunction(const Function *F) {
return G->getOrInsertFunction(F);
}
//===---------------------------------------------------------------------
// Implementation of the ModulePass interface needed here.
//
void getAnalysisUsage(AnalysisUsage &AU) const override;
bool runOnModule(Module &M) override;
void releaseMemory() override;
void print(raw_ostream &o, const Module *) const override;
void dump() const;
};
//===----------------------------------------------------------------------===//
// GraphTraits specializations for call graphs so that they can be treated as
// graphs by the generic graph algorithms.
//
// Provide graph traits for traversing call graphs using standard graph
// traversals.
template <> struct GraphTraits<CallGraphNode *> {
using NodeRef = CallGraphNode *;
using CGNPairTy = CallGraphNode::CallRecord;
static NodeRef getEntryNode(CallGraphNode *CGN) { return CGN; }
static CallGraphNode *CGNGetValue(CGNPairTy P) { return P.second; }
using ChildIteratorType =
mapped_iterator<CallGraphNode::iterator, decltype(&CGNGetValue)>;
static ChildIteratorType child_begin(NodeRef N) {
return ChildIteratorType(N->begin(), &CGNGetValue);
}
static ChildIteratorType child_end(NodeRef N) {
return ChildIteratorType(N->end(), &CGNGetValue);
}
};
template <> struct GraphTraits<const CallGraphNode *> {
using NodeRef = const CallGraphNode *;
using CGNPairTy = CallGraphNode::CallRecord;
using EdgeRef = const CallGraphNode::CallRecord &;
static NodeRef getEntryNode(const CallGraphNode *CGN) { return CGN; }
static const CallGraphNode *CGNGetValue(CGNPairTy P) { return P.second; }
using ChildIteratorType =
mapped_iterator<CallGraphNode::const_iterator, decltype(&CGNGetValue)>;
using ChildEdgeIteratorType = CallGraphNode::const_iterator;
static ChildIteratorType child_begin(NodeRef N) {
return ChildIteratorType(N->begin(), &CGNGetValue);
}
static ChildIteratorType child_end(NodeRef N) {
return ChildIteratorType(N->end(), &CGNGetValue);
}
static ChildEdgeIteratorType child_edge_begin(NodeRef N) {
return N->begin();
}
static ChildEdgeIteratorType child_edge_end(NodeRef N) { return N->end(); }
static NodeRef edge_dest(EdgeRef E) { return E.second; }
};
template <>
struct GraphTraits<CallGraph *> : public GraphTraits<CallGraphNode *> {
using PairTy =
std::pair<const Function *const, std::unique_ptr<CallGraphNode>>;
static NodeRef getEntryNode(CallGraph *CGN) {
return CGN->getExternalCallingNode(); // Start at the external node!
}
static CallGraphNode *CGGetValuePtr(const PairTy &P) {
return P.second.get();
}
// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
using nodes_iterator =
mapped_iterator<CallGraph::iterator, decltype(&CGGetValuePtr)>;
static nodes_iterator nodes_begin(CallGraph *CG) {
return nodes_iterator(CG->begin(), &CGGetValuePtr);
}
static nodes_iterator nodes_end(CallGraph *CG) {
return nodes_iterator(CG->end(), &CGGetValuePtr);
}
};
template <>
struct GraphTraits<const CallGraph *> : public GraphTraits<
const CallGraphNode *> {
using PairTy =
std::pair<const Function *const, std::unique_ptr<CallGraphNode>>;
static NodeRef getEntryNode(const CallGraph *CGN) {
return CGN->getExternalCallingNode(); // Start at the external node!
}
static const CallGraphNode *CGGetValuePtr(const PairTy &P) {
return P.second.get();
}
// nodes_iterator/begin/end - Allow iteration over all nodes in the graph
using nodes_iterator =
mapped_iterator<CallGraph::const_iterator, decltype(&CGGetValuePtr)>;
static nodes_iterator nodes_begin(const CallGraph *CG) {
return nodes_iterator(CG->begin(), &CGGetValuePtr);
}
static nodes_iterator nodes_end(const CallGraph *CG) {
return nodes_iterator(CG->end(), &CGGetValuePtr);
}
};
} // end namespace llvm
#endif // LLVM_ANALYSIS_CALLGRAPH_H
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