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//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
///
/// Implements a lazy call graph analysis and related passes for the new pass
/// manager.
///
/// NB: This is *not* a traditional call graph! It is a graph which models both
/// the current calls and potential calls. As a consequence there are many
/// edges in this call graph that do not correspond to a 'call' or 'invoke'
/// instruction.
///
/// The primary use cases of this graph analysis is to facilitate iterating
/// across the functions of a module in ways that ensure all callees are
/// visited prior to a caller (given any SCC constraints), or vice versa. As
/// such is it particularly well suited to organizing CGSCC optimizations such
/// as inlining, outlining, argument promotion, etc. That is its primary use
/// case and motivates the design. It may not be appropriate for other
/// purposes. The use graph of functions or some other conservative analysis of
/// call instructions may be interesting for optimizations and subsequent
/// analyses which don't work in the context of an overly specified
/// potential-call-edge graph.
///
/// To understand the specific rules and nature of this call graph analysis,
/// see the documentation of the \c LazyCallGraph below.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LAZYCALLGRAPH_H
#define LLVM_ANALYSIS_LAZYCALLGRAPH_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/raw_ostream.h"
#include <iterator>
#include <utility>
namespace llvm {
class PreservedAnalyses;
class raw_ostream;
/// A lazily constructed view of the call graph of a module.
///
/// With the edges of this graph, the motivating constraint that we are
/// attempting to maintain is that function-local optimization, CGSCC-local
/// optimizations, and optimizations transforming a pair of functions connected
/// by an edge in the graph, do not invalidate a bottom-up traversal of the SCC
/// DAG. That is, no optimizations will delete, remove, or add an edge such
/// that functions already visited in a bottom-up order of the SCC DAG are no
/// longer valid to have visited, or such that functions not yet visited in
/// a bottom-up order of the SCC DAG are not required to have already been
/// visited.
///
/// Within this constraint, the desire is to minimize the merge points of the
/// SCC DAG. The greater the fanout of the SCC DAG and the fewer merge points
/// in the SCC DAG, the more independence there is in optimizing within it.
/// There is a strong desire to enable parallelization of optimizations over
/// the call graph, and both limited fanout and merge points will (artificially
/// in some cases) limit the scaling of such an effort.
///
/// To this end, graph represents both direct and any potential resolution to
/// an indirect call edge. Another way to think about it is that it represents
/// both the direct call edges and any direct call edges that might be formed
/// through static optimizations. Specifically, it considers taking the address
/// of a function to be an edge in the call graph because this might be
/// forwarded to become a direct call by some subsequent function-local
/// optimization. The result is that the graph closely follows the use-def
/// edges for functions. Walking "up" the graph can be done by looking at all
/// of the uses of a function.
///
/// The roots of the call graph are the external functions and functions
/// escaped into global variables. Those functions can be called from outside
/// of the module or via unknowable means in the IR -- we may not be able to
/// form even a potential call edge from a function body which may dynamically
/// load the function and call it.
///
/// This analysis still requires updates to remain valid after optimizations
/// which could potentially change the set of potential callees. The
/// constraints it operates under only make the traversal order remain valid.
///
/// The entire analysis must be re-computed if full interprocedural
/// optimizations run at any point. For example, globalopt completely
/// invalidates the information in this analysis.
///
/// FIXME: This class is named LazyCallGraph in a lame attempt to distinguish
/// it from the existing CallGraph. At some point, it is expected that this
/// will be the only call graph and it will be renamed accordingly.
class LazyCallGraph {
public:
class Node;
class SCC;
class RefSCC;
class edge_iterator;
class call_edge_iterator;
/// A class used to represent edges in the call graph.
///
/// The lazy call graph models both *call* edges and *reference* edges. Call
/// edges are much what you would expect, and exist when there is a 'call' or
/// 'invoke' instruction of some function. Reference edges are also tracked
/// along side these, and exist whenever any instruction (transitively
/// through its operands) references a function. All call edges are
/// inherently reference edges, and so the reference graph forms a superset
/// of the formal call graph.
///
/// Furthermore, edges also may point to raw \c Function objects when those
/// functions have not been scanned and incorporated into the graph (yet).
/// This is one of the primary ways in which the graph can be lazy. When
/// functions are scanned and fully incorporated into the graph, all of the
/// edges referencing them are updated to point to the graph \c Node objects
/// instead of to the raw \c Function objects. This class even provides
/// methods to trigger this scan on-demand by attempting to get the target
/// node of the graph and providing a reference back to the graph in order to
/// lazily build it if necessary.
///
/// All of these forms of edges are fundamentally represented as outgoing
/// edges. The edges are stored in the source node and point at the target
/// node. This allows the edge structure itself to be a very compact data
/// structure: essentially a tagged pointer.
class Edge {
public:
/// The kind of edge in the graph.
enum Kind : bool { Ref = false, Call = true };
Edge();
explicit Edge(Function &F, Kind K);
explicit Edge(Node &N, Kind K);
/// Test whether the edge is null.
///
/// This happens when an edge has been deleted. We leave the edge objects
/// around but clear them.
operator bool() const;
/// Test whether the edge represents a direct call to a function.
///
/// This requires that the edge is not null.
bool isCall() const;
/// Get the function referenced by this edge.
///
/// This requires that the edge is not null, but will succeed whether we
/// have built a graph node for the function yet or not.
Function &getFunction() const;
/// Get the call graph node referenced by this edge if one exists.
///
/// This requires that the edge is not null. If we have built a graph node
/// for the function this edge points to, this will return that node,
/// otherwise it will return null.
Node *getNode() const;
/// Get the call graph node for this edge, building it if necessary.
///
/// This requires that the edge is not null. If we have not yet built
/// a graph node for the function this edge points to, this will first ask
/// the graph to build that node, inserting it into all the relevant
/// structures.
Node &getNode(LazyCallGraph &G);
private:
friend class LazyCallGraph::Node;
PointerIntPair<PointerUnion<Function *, Node *>, 1, Kind> Value;
void setKind(Kind K) { Value.setInt(K); }
};
typedef SmallVector<Edge, 4> EdgeVectorT;
typedef SmallVectorImpl<Edge> EdgeVectorImplT;
/// A node in the call graph.
///
/// This represents a single node. It's primary roles are to cache the list of
/// callees, de-duplicate and provide fast testing of whether a function is
/// a callee, and facilitate iteration of child nodes in the graph.
class Node {
friend class LazyCallGraph;
friend class LazyCallGraph::SCC;
LazyCallGraph *G;
Function &F;
// We provide for the DFS numbering and Tarjan walk lowlink numbers to be
// stored directly within the node. These are both '-1' when nodes are part
// of an SCC (or RefSCC), or '0' when not yet reached in a DFS walk.
int DFSNumber;
int LowLink;
mutable EdgeVectorT Edges;
DenseMap<Function *, int> EdgeIndexMap;
/// Basic constructor implements the scanning of F into Edges and
/// EdgeIndexMap.
Node(LazyCallGraph &G, Function &F);
/// Internal helper to insert an edge to a function.
void insertEdgeInternal(Function &ChildF, Edge::Kind EK);
/// Internal helper to insert an edge to a node.
void insertEdgeInternal(Node &ChildN, Edge::Kind EK);
/// Internal helper to change an edge kind.
void setEdgeKind(Function &ChildF, Edge::Kind EK);
/// Internal helper to remove the edge to the given function.
void removeEdgeInternal(Function &ChildF);
/// Print the name of this node's function.
friend raw_ostream &operator<<(raw_ostream &OS, const Node &N) {
return OS << N.F.getName();
}
/// Dump the name of this node's function to stderr.
void dump() const;
public:
LazyCallGraph &getGraph() const { return *G; }
Function &getFunction() const { return F; }
edge_iterator begin() const {
return edge_iterator(Edges.begin(), Edges.end());
}
edge_iterator end() const { return edge_iterator(Edges.end(), Edges.end()); }
const Edge &operator[](int i) const { return Edges[i]; }
const Edge &operator[](Function &F) const {
assert(EdgeIndexMap.find(&F) != EdgeIndexMap.end() && "No such edge!");
return Edges[EdgeIndexMap.find(&F)->second];
}
const Edge &operator[](Node &N) const { return (*this)[N.getFunction()]; }
call_edge_iterator call_begin() const {
return call_edge_iterator(Edges.begin(), Edges.end());
}
call_edge_iterator call_end() const {
return call_edge_iterator(Edges.end(), Edges.end());
}
iterator_range<call_edge_iterator> calls() const {
return make_range(call_begin(), call_end());
}
/// Equality is defined as address equality.
bool operator==(const Node &N) const { return this == &N; }
bool operator!=(const Node &N) const { return !operator==(N); }
};
/// A lazy iterator used for both the entry nodes and child nodes.
///
/// When this iterator is dereferenced, if not yet available, a function will
/// be scanned for "calls" or uses of functions and its child information
/// will be constructed. All of these results are accumulated and cached in
/// the graph.
class edge_iterator
: public iterator_adaptor_base<edge_iterator, EdgeVectorImplT::iterator,
std::forward_iterator_tag> {
friend class LazyCallGraph;
friend class LazyCallGraph::Node;
EdgeVectorImplT::iterator E;
// Build the iterator for a specific position in the edge list.
edge_iterator(EdgeVectorImplT::iterator BaseI,
EdgeVectorImplT::iterator E)
: iterator_adaptor_base(BaseI), E(E) {
while (I != E && !*I)
++I;
}
public:
edge_iterator() {}
using iterator_adaptor_base::operator++;
edge_iterator &operator++() {
do {
++I;
} while (I != E && !*I);
return *this;
}
};
/// A lazy iterator over specifically call edges.
///
/// This has the same iteration properties as the \c edge_iterator, but
/// restricts itself to edges which represent actual calls.
class call_edge_iterator
: public iterator_adaptor_base<call_edge_iterator,
EdgeVectorImplT::iterator,
std::forward_iterator_tag> {
friend class LazyCallGraph;
friend class LazyCallGraph::Node;
EdgeVectorImplT::iterator E;
/// Advance the iterator to the next valid, call edge.
void advanceToNextEdge() {
while (I != E && (!*I || !I->isCall()))
++I;
}
// Build the iterator for a specific position in the edge list.
call_edge_iterator(EdgeVectorImplT::iterator BaseI,
EdgeVectorImplT::iterator E)
: iterator_adaptor_base(BaseI), E(E) {
advanceToNextEdge();
}
public:
call_edge_iterator() {}
using iterator_adaptor_base::operator++;
call_edge_iterator &operator++() {
++I;
advanceToNextEdge();
return *this;
}
};
/// An SCC of the call graph.
///
/// This represents a Strongly Connected Component of the direct call graph
/// -- ignoring indirect calls and function references. It stores this as
/// a collection of call graph nodes. While the order of nodes in the SCC is
/// stable, it is not any particular order.
///
/// The SCCs are nested within a \c RefSCC, see below for details about that
/// outer structure. SCCs do not support mutation of the call graph, that
/// must be done through the containing \c RefSCC in order to fully reason
/// about the ordering and connections of the graph.
class SCC {
friend class LazyCallGraph;
friend class LazyCallGraph::Node;
RefSCC *OuterRefSCC;
SmallVector<Node *, 1> Nodes;
template <typename NodeRangeT>
SCC(RefSCC &OuterRefSCC, NodeRangeT &&Nodes)
: OuterRefSCC(&OuterRefSCC), Nodes(std::forward<NodeRangeT>(Nodes)) {}
void clear() {
OuterRefSCC = nullptr;
Nodes.clear();
}
/// Print a short descrtiption useful for debugging or logging.
///
/// We print the function names in the SCC wrapped in '()'s and skipping
/// the middle functions if there are a large number.
//
// Note: this is defined inline to dodge issues with GCC's interpretation
// of enclosing namespaces for friend function declarations.
friend raw_ostream &operator<<(raw_ostream &OS, const SCC &C) {
OS << '(';
int i = 0;
for (LazyCallGraph::Node &N : C) {
if (i > 0)
OS << ", ";
// Elide the inner elements if there are too many.
if (i > 8) {
OS << "..., " << *C.Nodes.back();
break;
}
OS << N;
++i;
}
OS << ')';
return OS;
}
/// Dump a short description of this SCC to stderr.
void dump() const;
#ifndef NDEBUG
/// Verify invariants about the SCC.
///
/// This will attempt to validate all of the basic invariants within an
/// SCC, but not that it is a strongly connected componet per-se. Primarily
/// useful while building and updating the graph to check that basic
/// properties are in place rather than having inexplicable crashes later.
void verify();
#endif
public:
typedef pointee_iterator<SmallVectorImpl<Node *>::const_iterator> iterator;
iterator begin() const { return Nodes.begin(); }
iterator end() const { return Nodes.end(); }
int size() const { return Nodes.size(); }
RefSCC &getOuterRefSCC() const { return *OuterRefSCC; }
/// Provide a short name by printing this SCC to a std::string.
///
/// This copes with the fact that we don't have a name per-se for an SCC
/// while still making the use of this in debugging and logging useful.
std::string getName() const {
std::string Name;
raw_string_ostream OS(Name);
OS << *this;
OS.flush();
return Name;
}
};
/// A RefSCC of the call graph.
///
/// This models a Strongly Connected Component of function reference edges in
/// the call graph. As opposed to actual SCCs, these can be used to scope
/// subgraphs of the module which are independent from other subgraphs of the
/// module because they do not reference it in any way. This is also the unit
/// where we do mutation of the graph in order to restrict mutations to those
/// which don't violate this independence.
///
/// A RefSCC contains a DAG of actual SCCs. All the nodes within the RefSCC
/// are necessarily within some actual SCC that nests within it. Since
/// a direct call *is* a reference, there will always be at least one RefSCC
/// around any SCC.
class RefSCC {
friend class LazyCallGraph;
friend class LazyCallGraph::Node;
LazyCallGraph *G;
SmallPtrSet<RefSCC *, 1> Parents;
/// A postorder list of the inner SCCs.
SmallVector<SCC *, 4> SCCs;
/// A map from SCC to index in the postorder list.
SmallDenseMap<SCC *, int, 4> SCCIndices;
/// Fast-path constructor. RefSCCs should instead be constructed by calling
/// formRefSCCFast on the graph itself.
RefSCC(LazyCallGraph &G);
/// Print a short description useful for debugging or logging.
///
/// We print the SCCs wrapped in '[]'s and skipping the middle SCCs if
/// there are a large number.
//
// Note: this is defined inline to dodge issues with GCC's interpretation
// of enclosing namespaces for friend function declarations.
friend raw_ostream &operator<<(raw_ostream &OS, const RefSCC &RC) {
OS << '[';
int i = 0;
for (LazyCallGraph::SCC &C : RC) {
if (i > 0)
OS << ", ";
// Elide the inner elements if there are too many.
if (i > 4) {
OS << "..., " << *RC.SCCs.back();
break;
}
OS << C;
++i;
}
OS << ']';
return OS;
}
/// Dump a short description of this RefSCC to stderr.
void dump() const;
#ifndef NDEBUG
/// Verify invariants about the RefSCC and all its SCCs.
///
/// This will attempt to validate all of the invariants *within* the
/// RefSCC, but not that it is a strongly connected component of the larger
/// graph. This makes it useful even when partially through an update.
///
/// Invariants checked:
/// - SCCs and their indices match.
/// - The SCCs list is in fact in post-order.
void verify();
#endif
public:
typedef pointee_iterator<SmallVectorImpl<SCC *>::const_iterator> iterator;
typedef iterator_range<iterator> range;
typedef pointee_iterator<SmallPtrSetImpl<RefSCC *>::const_iterator>
parent_iterator;
iterator begin() const { return SCCs.begin(); }
iterator end() const { return SCCs.end(); }
ssize_t size() const { return SCCs.size(); }
SCC &operator[](int Idx) { return *SCCs[Idx]; }
iterator find(SCC &C) const {
return SCCs.begin() + SCCIndices.find(&C)->second;
}
parent_iterator parent_begin() const { return Parents.begin(); }
parent_iterator parent_end() const { return Parents.end(); }
iterator_range<parent_iterator> parents() const {
return make_range(parent_begin(), parent_end());
}
/// Test if this SCC is a parent of \a C.
bool isParentOf(const RefSCC &C) const { return C.isChildOf(*this); }
/// Test if this RefSCC is an ancestor of \a C.
bool isAncestorOf(const RefSCC &C) const { return C.isDescendantOf(*this); }
/// Test if this RefSCC is a child of \a C.
bool isChildOf(const RefSCC &C) const {
return Parents.count(const_cast<RefSCC *>(&C));
}
/// Test if this RefSCC is a descendant of \a C.
bool isDescendantOf(const RefSCC &C) const;
/// Provide a short name by printing this SCC to a std::string.
///
/// This copes with the fact that we don't have a name per-se for an SCC
/// while still making the use of this in debugging and logging useful.
std::string getName() const {
std::string Name;
raw_string_ostream OS(Name);
OS << *this;
OS.flush();
return Name;
}
///@{
/// \name Mutation API
///
/// These methods provide the core API for updating the call graph in the
/// presence of a (potentially still in-flight) DFS-found SCCs.
///
/// Note that these methods sometimes have complex runtimes, so be careful
/// how you call them.
/// Make an existing internal ref edge into a call edge.
///
/// This may form a larger cycle and thus collapse SCCs into TargetN's SCC.
/// If that happens, the deleted SCC pointers are returned. These SCCs are
/// not in a valid state any longer but the pointers will remain valid
/// until destruction of the parent graph instance for the purpose of
/// clearing cached information.
///
/// After this operation, both SourceN's SCC and TargetN's SCC may move
/// position within this RefSCC's postorder list. Any SCCs merged are
/// merged into the TargetN's SCC in order to preserve reachability analyses
/// which took place on that SCC.
SmallVector<SCC *, 1> switchInternalEdgeToCall(Node &SourceN,
Node &TargetN);
/// Make an existing internal call edge into a ref edge.
///
/// If SourceN and TargetN are part of a single SCC, it may be split up due
/// to breaking a cycle in the call edges that formed it. If that happens,
/// then this routine will insert new SCCs into the postorder list *before*
/// the SCC of TargetN (previously the SCC of both). This preserves
/// postorder as the TargetN can reach all of the other nodes by definition
/// of previously being in a single SCC formed by the cycle from SourceN to
/// TargetN. The newly added nodes are added *immediately* and contiguously
/// prior to the TargetN SCC and so they may be iterated starting from
/// there.
void switchInternalEdgeToRef(Node &SourceN, Node &TargetN);
/// Make an existing outgoing ref edge into a call edge.
///
/// Note that this is trivial as there are no cyclic impacts and there
/// remains a reference edge.
void switchOutgoingEdgeToCall(Node &SourceN, Node &TargetN);
/// Make an existing outgoing call edge into a ref edge.
///
/// This is trivial as there are no cyclic impacts and there remains
/// a reference edge.
void switchOutgoingEdgeToRef(Node &SourceN, Node &TargetN);
/// Insert a ref edge from one node in this RefSCC to another in this
/// RefSCC.
///
/// This is always a trivial operation as it doesn't change any part of the
/// graph structure besides connecting the two nodes.
///
/// Note that we don't support directly inserting internal *call* edges
/// because that could change the graph structure and requires returning
/// information about what became invalid. As a consequence, the pattern
/// should be to first insert the necessary ref edge, and then to switch it
/// to a call edge if needed and handle any invalidation that results. See
/// the \c switchInternalEdgeToCall routine for details.
void insertInternalRefEdge(Node &SourceN, Node &TargetN);
/// Insert an edge whose parent is in this RefSCC and child is in some
/// child RefSCC.
///
/// There must be an existing path from the \p SourceN to the \p TargetN.
/// This operation is inexpensive and does not change the set of SCCs and
/// RefSCCs in the graph.
void insertOutgoingEdge(Node &SourceN, Node &TargetN, Edge::Kind EK);
/// Insert an edge whose source is in a descendant RefSCC and target is in
/// this RefSCC.
///
/// There must be an existing path from the target to the source in this
/// case.
///
/// NB! This is has the potential to be a very expensive function. It
/// inherently forms a cycle in the prior RefSCC DAG and we have to merge
/// RefSCCs to resolve that cycle. But finding all of the RefSCCs which
/// participate in the cycle can in the worst case require traversing every
/// RefSCC in the graph. Every attempt is made to avoid that, but passes
/// must still exercise caution calling this routine repeatedly.
///
/// Also note that this can only insert ref edges. In order to insert
/// a call edge, first insert a ref edge and then switch it to a call edge.
/// These are intentionally kept as separate interfaces because each step
/// of the operation invalidates a different set of data structures.
///
/// This returns all the RefSCCs which were merged into the this RefSCC
/// (the target's). This allows callers to invalidate any cached
/// information.
///
/// FIXME: We could possibly optimize this quite a bit for cases where the
/// caller and callee are very nearby in the graph. See comments in the
/// implementation for details, but that use case might impact users.
SmallVector<RefSCC *, 1> insertIncomingRefEdge(Node &SourceN,
Node &TargetN);
/// Remove an edge whose source is in this RefSCC and target is *not*.
///
/// This removes an inter-RefSCC edge. All inter-RefSCC edges originating
/// from this SCC have been fully explored by any in-flight DFS graph
/// formation, so this is always safe to call once you have the source
/// RefSCC.
///
/// This operation does not change the cyclic structure of the graph and so
/// is very inexpensive. It may change the connectivity graph of the SCCs
/// though, so be careful calling this while iterating over them.
void removeOutgoingEdge(Node &SourceN, Node &TargetN);
/// Remove a ref edge which is entirely within this RefSCC.
///
/// Both the \a SourceN and the \a TargetN must be within this RefSCC.
/// Removing such an edge may break cycles that form this RefSCC and thus
/// this operation may change the RefSCC graph significantly. In
/// particular, this operation will re-form new RefSCCs based on the
/// remaining connectivity of the graph. The following invariants are
/// guaranteed to hold after calling this method:
///
/// 1) This RefSCC is still a RefSCC in the graph.
/// 2) This RefSCC will be the parent of any new RefSCCs. Thus, this RefSCC
/// is preserved as the root of any new RefSCC DAG formed.
/// 3) No RefSCC other than this RefSCC has its member set changed (this is
/// inherent in the definition of removing such an edge).
/// 4) All of the parent links of the RefSCC graph will be updated to
/// reflect the new RefSCC structure.
/// 5) All RefSCCs formed out of this RefSCC, excluding this RefSCC, will
/// be returned in post-order.
/// 6) The order of the RefSCCs in the vector will be a valid postorder
/// traversal of the new RefSCCs.
///
/// These invariants are very important to ensure that we can build
/// optimization pipelines on top of the CGSCC pass manager which
/// intelligently update the RefSCC graph without invalidating other parts
/// of the RefSCC graph.
///
/// Note that we provide no routine to remove a *call* edge. Instead, you
/// must first switch it to a ref edge using \c switchInternalEdgeToRef.
/// This split API is intentional as each of these two steps can invalidate
/// a different aspect of the graph structure and needs to have the
/// invalidation handled independently.
///
/// The runtime complexity of this method is, in the worst case, O(V+E)
/// where V is the number of nodes in this RefSCC and E is the number of
/// edges leaving the nodes in this RefSCC. Note that E includes both edges
/// within this RefSCC and edges from this RefSCC to child RefSCCs. Some
/// effort has been made to minimize the overhead of common cases such as
/// self-edges and edge removals which result in a spanning tree with no
/// more cycles. There are also detailed comments within the implementation
/// on techniques which could substantially improve this routine's
/// efficiency.
SmallVector<RefSCC *, 1> removeInternalRefEdge(Node &SourceN,
Node &TargetN);
///@}
};
/// A post-order depth-first SCC iterator over the call graph.
///
/// This iterator triggers the Tarjan DFS-based formation of the SCC DAG for
/// the call graph, walking it lazily in depth-first post-order. That is, it
/// always visits SCCs for a callee prior to visiting the SCC for a caller
/// (when they are in different SCCs).
class postorder_ref_scc_iterator
: public iterator_facade_base<postorder_ref_scc_iterator,
std::forward_iterator_tag, RefSCC> {
friend class LazyCallGraph;
friend class LazyCallGraph::Node;
/// Nonce type to select the constructor for the end iterator.
struct IsAtEndT {};
LazyCallGraph *G;
RefSCC *C;
// Build the begin iterator for a node.
postorder_ref_scc_iterator(LazyCallGraph &G) : G(&G) {
C = G.getNextRefSCCInPostOrder();
}
// Build the end iterator for a node. This is selected purely by overload.
postorder_ref_scc_iterator(LazyCallGraph &G, IsAtEndT /*Nonce*/)
: G(&G), C(nullptr) {}
public:
bool operator==(const postorder_ref_scc_iterator &Arg) const {
return G == Arg.G && C == Arg.C;
}
reference operator*() const { return *C; }
using iterator_facade_base::operator++;
postorder_ref_scc_iterator &operator++() {
C = G->getNextRefSCCInPostOrder();
return *this;
}
};
/// Construct a graph for the given module.
///
/// This sets up the graph and computes all of the entry points of the graph.
/// No function definitions are scanned until their nodes in the graph are
/// requested during traversal.
LazyCallGraph(Module &M);
LazyCallGraph(LazyCallGraph &&G);
LazyCallGraph &operator=(LazyCallGraph &&RHS);
edge_iterator begin() {
return edge_iterator(EntryEdges.begin(), EntryEdges.end());
}
edge_iterator end() {
return edge_iterator(EntryEdges.end(), EntryEdges.end());
}
postorder_ref_scc_iterator postorder_ref_scc_begin() {
return postorder_ref_scc_iterator(*this);
}
postorder_ref_scc_iterator postorder_ref_scc_end() {
return postorder_ref_scc_iterator(*this,
postorder_ref_scc_iterator::IsAtEndT());
}
iterator_range<postorder_ref_scc_iterator> postorder_ref_sccs() {
return make_range(postorder_ref_scc_begin(), postorder_ref_scc_end());
}
/// Lookup a function in the graph which has already been scanned and added.
Node *lookup(const Function &F) const { return NodeMap.lookup(&F); }
/// Lookup a function's SCC in the graph.
///
/// \returns null if the function hasn't been assigned an SCC via the SCC
/// iterator walk.
SCC *lookupSCC(Node &N) const { return SCCMap.lookup(&N); }
/// Lookup a function's RefSCC in the graph.
///
/// \returns null if the function hasn't been assigned a RefSCC via the
/// RefSCC iterator walk.
RefSCC *lookupRefSCC(Node &N) const {
if (SCC *C = lookupSCC(N))
return &C->getOuterRefSCC();
return nullptr;
}
/// Get a graph node for a given function, scanning it to populate the graph
/// data as necessary.
Node &get(Function &F) {
Node *&N = NodeMap[&F];
if (N)
return *N;
return insertInto(F, N);
}
///@{
/// \name Pre-SCC Mutation API
///
/// These methods are only valid to call prior to forming any SCCs for this
/// call graph. They can be used to update the core node-graph during
/// a node-based inorder traversal that precedes any SCC-based traversal.
///
/// Once you begin manipulating a call graph's SCCs, you must perform all
/// mutation of the graph via the SCC methods.
/// Update the call graph after inserting a new edge.
void insertEdge(Node &Caller, Function &Callee, Edge::Kind EK);
/// Update the call graph after inserting a new edge.
void insertEdge(Function &Caller, Function &Callee, Edge::Kind EK) {
return insertEdge(get(Caller), Callee, EK);
}
/// Update the call graph after deleting an edge.
void removeEdge(Node &Caller, Function &Callee);
/// Update the call graph after deleting an edge.
void removeEdge(Function &Caller, Function &Callee) {
return removeEdge(get(Caller), Callee);
}
///@}
private:
typedef SmallVectorImpl<Node *>::reverse_iterator node_stack_iterator;
typedef iterator_range<node_stack_iterator> node_stack_range;
/// Allocator that holds all the call graph nodes.
SpecificBumpPtrAllocator<Node> BPA;
/// Maps function->node for fast lookup.
DenseMap<const Function *, Node *> NodeMap;
/// The entry nodes to the graph.
///
/// These nodes are reachable through "external" means. Put another way, they
/// escape at the module scope.
EdgeVectorT EntryEdges;
/// Map of the entry nodes in the graph to their indices in \c EntryEdges.
DenseMap<Function *, int> EntryIndexMap;
/// Allocator that holds all the call graph SCCs.
SpecificBumpPtrAllocator<SCC> SCCBPA;
/// Maps Function -> SCC for fast lookup.
DenseMap<Node *, SCC *> SCCMap;
/// Allocator that holds all the call graph RefSCCs.
SpecificBumpPtrAllocator<RefSCC> RefSCCBPA;
/// The leaf RefSCCs of the graph.
///
/// These are all of the RefSCCs which have no children.
SmallVector<RefSCC *, 4> LeafRefSCCs;
/// Stack of nodes in the DFS walk.
SmallVector<std::pair<Node *, edge_iterator>, 4> DFSStack;
/// Set of entry nodes not-yet-processed into RefSCCs.
SmallVector<Function *, 4> RefSCCEntryNodes;
/// Stack of nodes the DFS has walked but not yet put into a SCC.
SmallVector<Node *, 4> PendingRefSCCStack;
/// Counter for the next DFS number to assign.
int NextDFSNumber;
/// Helper to insert a new function, with an already looked-up entry in
/// the NodeMap.
Node &insertInto(Function &F, Node *&MappedN);
/// Helper to update pointers back to the graph object during moves.
void updateGraphPtrs();
/// Allocates an SCC and constructs it using the graph allocator.
///
/// The arguments are forwarded to the constructor.
template <typename... Ts> SCC *createSCC(Ts &&... Args) {
return new (SCCBPA.Allocate()) SCC(std::forward<Ts>(Args)...);
}
/// Allocates a RefSCC and constructs it using the graph allocator.
///
/// The arguments are forwarded to the constructor.
template <typename... Ts> RefSCC *createRefSCC(Ts &&... Args) {
return new (RefSCCBPA.Allocate()) RefSCC(std::forward<Ts>(Args)...);
}
/// Build the SCCs for a RefSCC out of a list of nodes.
void buildSCCs(RefSCC &RC, node_stack_range Nodes);
/// Connect a RefSCC into the larger graph.
///
/// This walks the edges to connect the RefSCC to its children's parent set,
/// and updates the root leaf list.
void connectRefSCC(RefSCC &RC);
/// Retrieve the next node in the post-order RefSCC walk of the call graph.
RefSCC *getNextRefSCCInPostOrder();
};
inline LazyCallGraph::Edge::Edge() : Value() {}
inline LazyCallGraph::Edge::Edge(Function &F, Kind K) : Value(&F, K) {}
inline LazyCallGraph::Edge::Edge(Node &N, Kind K) : Value(&N, K) {}
inline LazyCallGraph::Edge::operator bool() const {
return !Value.getPointer().isNull();
}
inline bool LazyCallGraph::Edge::isCall() const {
assert(*this && "Queried a null edge!");
return Value.getInt() == Call;
}
inline Function &LazyCallGraph::Edge::getFunction() const {
assert(*this && "Queried a null edge!");
auto P = Value.getPointer();
if (auto *F = P.dyn_cast<Function *>())
return *F;
return P.get<Node *>()->getFunction();
}
inline LazyCallGraph::Node *LazyCallGraph::Edge::getNode() const {
assert(*this && "Queried a null edge!");
auto P = Value.getPointer();
if (auto *N = P.dyn_cast<Node *>())
return N;
return nullptr;
}
inline LazyCallGraph::Node &LazyCallGraph::Edge::getNode(LazyCallGraph &G) {
assert(*this && "Queried a null edge!");
auto P = Value.getPointer();
if (auto *N = P.dyn_cast<Node *>())
return *N;
Node &N = G.get(*P.get<Function *>());
Value.setPointer(&N);
return N;
}
// Provide GraphTraits specializations for call graphs.
template <> struct GraphTraits<LazyCallGraph::Node *> {
typedef LazyCallGraph::Node NodeType;
typedef LazyCallGraph::edge_iterator ChildIteratorType;
static NodeType *getEntryNode(NodeType *N) { return N; }
static ChildIteratorType child_begin(NodeType *N) { return N->begin(); }
static ChildIteratorType child_end(NodeType *N) { return N->end(); }
};
template <> struct GraphTraits<LazyCallGraph *> {
typedef LazyCallGraph::Node NodeType;
typedef LazyCallGraph::edge_iterator ChildIteratorType;
static NodeType *getEntryNode(NodeType *N) { return N; }
static ChildIteratorType child_begin(NodeType *N) { return N->begin(); }
static ChildIteratorType child_end(NodeType *N) { return N->end(); }
};
/// An analysis pass which computes the call graph for a module.
class LazyCallGraphAnalysis : public AnalysisInfoMixin<LazyCallGraphAnalysis> {
friend AnalysisInfoMixin<LazyCallGraphAnalysis>;
static char PassID;
public:
/// Inform generic clients of the result type.
typedef LazyCallGraph Result;
/// Compute the \c LazyCallGraph for the module \c M.
///
/// This just builds the set of entry points to the call graph. The rest is
/// built lazily as it is walked.
LazyCallGraph run(Module &M, ModuleAnalysisManager &) {
return LazyCallGraph(M);
}
};
/// A pass which prints the call graph to a \c raw_ostream.
///
/// This is primarily useful for testing the analysis.
class LazyCallGraphPrinterPass
: public PassInfoMixin<LazyCallGraphPrinterPass> {
raw_ostream &OS;
public:
explicit LazyCallGraphPrinterPass(raw_ostream &OS);
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
};
/// A pass which prints the call graph as a DOT file to a \c raw_ostream.
///
/// This is primarily useful for visualization purposes.
class LazyCallGraphDOTPrinterPass
: public PassInfoMixin<LazyCallGraphDOTPrinterPass> {
raw_ostream &OS;
public:
explicit LazyCallGraphDOTPrinterPass(raw_ostream &OS);
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
};
}
#endif
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