///
//===----------------------------------------------------------------------===//
-#ifndef LLVM_ANALYSIS_LAZY_CALL_GRAPH
-#define LLVM_ANALYSIS_LAZY_CALL_GRAPH
+#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 <iterator>
namespace llvm {
-class ModuleAnalysisManager;
class PreservedAnalyses;
class raw_ostream;
class LazyCallGraph {
public:
class Node;
+ class SCC;
typedef SmallVector<PointerUnion<Function *, Node *>, 4> NodeVectorT;
typedef SmallVectorImpl<PointerUnion<Function *, Node *>> NodeVectorImplT;
/// 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 iterator : public std::iterator<std::bidirectional_iterator_tag, Node *,
- ptrdiff_t, Node *, Node *> {
+ class iterator
+ : public iterator_adaptor_base<iterator, NodeVectorImplT::iterator,
+ std::forward_iterator_tag, Node> {
friend class LazyCallGraph;
friend class LazyCallGraph::Node;
- typedef std::iterator<std::bidirectional_iterator_tag, Node *, ptrdiff_t,
- Node *, Node *> BaseT;
- /// \brief Nonce type to select the constructor for the end iterator.
- struct IsAtEndT {};
+ LazyCallGraph *G;
+ NodeVectorImplT::iterator E;
- LazyCallGraph &G;
- NodeVectorImplT::iterator NI;
-
- // Build the begin iterator for a node.
- explicit iterator(LazyCallGraph &G, NodeVectorImplT &Nodes)
- : G(G), NI(Nodes.begin()) {}
-
- // Build the end iterator for a node. This is selected purely by overload.
- iterator(LazyCallGraph &G, NodeVectorImplT &Nodes, IsAtEndT /*Nonce*/)
- : G(G), NI(Nodes.end()) {}
+ // Build the iterator for a specific position in a node list.
+ iterator(LazyCallGraph &G, NodeVectorImplT::iterator NI,
+ NodeVectorImplT::iterator E)
+ : iterator_adaptor_base(NI), G(&G), E(E) {
+ while (I != E && I->isNull())
+ ++I;
+ }
public:
- iterator(const iterator &Arg) : G(Arg.G), NI(Arg.NI) {}
+ iterator() {}
- iterator &operator=(iterator Arg) {
- std::swap(Arg, *this);
+ using iterator_adaptor_base::operator++;
+ iterator &operator++() {
+ do {
+ ++I;
+ } while (I != E && I->isNull());
return *this;
}
- bool operator==(const iterator &Arg) { return NI == Arg.NI; }
- bool operator!=(const iterator &Arg) { return !operator==(Arg); }
-
reference operator*() const {
- if (NI->is<Node *>())
- return NI->get<Node *>();
+ if (I->is<Node *>())
+ return *I->get<Node *>();
- Function *F = NI->get<Function *>();
- Node *ChildN = G.get(*F);
- *NI = ChildN;
+ Function *F = I->get<Function *>();
+ Node &ChildN = G->get(*F);
+ *I = &ChildN;
return ChildN;
}
- pointer operator->() const { return operator*(); }
+ };
- iterator &operator++() {
- ++NI;
- return *this;
+ /// \brief 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.
+ int DFSNumber;
+ int LowLink;
+
+ mutable NodeVectorT Callees;
+ DenseMap<Function *, size_t> CalleeIndexMap;
+
+ /// \brief Basic constructor implements the scanning of F into Callees and
+ /// CalleeIndexMap.
+ Node(LazyCallGraph &G, Function &F);
+
+ /// \brief Internal helper to insert a callee.
+ void insertEdgeInternal(Function &Callee);
+
+ /// \brief Internal helper to insert a callee.
+ void insertEdgeInternal(Node &CalleeN);
+
+ /// \brief Internal helper to remove a callee from this node.
+ void removeEdgeInternal(Function &Callee);
+
+ public:
+ typedef LazyCallGraph::iterator iterator;
+
+ Function &getFunction() const {
+ return F;
}
- iterator operator++(int) {
- iterator prev = *this;
- ++*this;
- return prev;
+
+ iterator begin() const {
+ return iterator(*G, Callees.begin(), Callees.end());
}
+ iterator end() const { return iterator(*G, Callees.end(), Callees.end()); }
- iterator &operator--() {
- --NI;
- return *this;
+ /// Equality is defined as address equality.
+ bool operator==(const Node &N) const { return this == &N; }
+ bool operator!=(const Node &N) const { return !operator==(N); }
+ };
+
+ /// \brief An SCC of the call graph.
+ ///
+ /// This represents a Strongly Connected Component of the call graph as
+ /// a collection of call graph nodes. While the order of nodes in the SCC is
+ /// stable, it is not any particular order.
+ class SCC {
+ friend class LazyCallGraph;
+ friend class LazyCallGraph::Node;
+
+ LazyCallGraph *G;
+ SmallPtrSet<SCC *, 1> ParentSCCs;
+ SmallVector<Node *, 1> Nodes;
+
+ SCC(LazyCallGraph &G) : G(&G) {}
+
+ void insert(Node &N);
+
+ void
+ internalDFS(SmallVectorImpl<std::pair<Node *, Node::iterator>> &DFSStack,
+ SmallVectorImpl<Node *> &PendingSCCStack, Node *N,
+ SmallVectorImpl<SCC *> &ResultSCCs);
+
+ public:
+ typedef SmallVectorImpl<Node *>::const_iterator iterator;
+ typedef pointee_iterator<SmallPtrSet<SCC *, 1>::const_iterator> parent_iterator;
+
+ iterator begin() const { return Nodes.begin(); }
+ iterator end() const { return Nodes.end(); }
+
+ parent_iterator parent_begin() const { return ParentSCCs.begin(); }
+ parent_iterator parent_end() const { return ParentSCCs.end(); }
+
+ iterator_range<parent_iterator> parents() const {
+ return iterator_range<parent_iterator>(parent_begin(), parent_end());
+ }
+
+ /// \brief Test if this SCC is a parent of \a C.
+ bool isParentOf(const SCC &C) const { return C.isChildOf(*this); }
+
+ /// \brief Test if this SCC is an ancestor of \a C.
+ bool isAncestorOf(const SCC &C) const { return C.isDescendantOf(*this); }
+
+ /// \brief Test if this SCC is a child of \a C.
+ bool isChildOf(const SCC &C) const {
+ return ParentSCCs.count(const_cast<SCC *>(&C));
+ }
+
+ /// \brief Test if this SCC is a descendant of \a C.
+ bool isDescendantOf(const SCC &C) const;
+
+ /// \brief Short name useful for debugging or logging.
+ ///
+ /// We use the name of the first function in the SCC to name the SCC for
+ /// the purposes of debugging and logging.
+ StringRef getName() const { return (*begin())->getFunction().getName(); }
+
+ ///@{
+ /// \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.
+
+ /// \brief Insert an edge from one node in this SCC to another in this SCC.
+ ///
+ /// By the definition of an SCC, this does not change the nature or make-up
+ /// of any SCCs.
+ void insertIntraSCCEdge(Node &CallerN, Node &CalleeN);
+
+ /// \brief Insert an edge whose tail is in this SCC and head is in some
+ /// child SCC.
+ ///
+ /// There must be an existing path from the caller to the callee. This
+ /// operation is inexpensive and does not change the set of SCCs in the
+ /// graph.
+ void insertOutgoingEdge(Node &CallerN, Node &CalleeN);
+
+ /// \brief Insert an edge whose tail is in a descendant SCC and head is in
+ /// this SCC.
+ ///
+ /// There must be an existing path from the callee to the caller in this
+ /// case. NB! This is has the potential to be a very expensive function. It
+ /// inherently forms a cycle in the prior SCC DAG and we have to merge SCCs
+ /// to resolve that cycle. But finding all of the SCCs which participate in
+ /// the cycle can in the worst case require traversing every SCC in the
+ /// graph. Every attempt is made to avoid that, but passes must still
+ /// exercise caution calling this routine repeatedly.
+ ///
+ /// 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<SCC *, 1> insertIncomingEdge(Node &CallerN, Node &CalleeN);
+
+ /// \brief Remove an edge whose source is in this SCC and target is *not*.
+ ///
+ /// This removes an inter-SCC edge. All inter-SCC edges originating from
+ /// this SCC have been fully explored by any in-flight DFS SCC formation,
+ /// so this is always safe to call once you have the source SCC.
+ ///
+ /// This operation does not change the set of SCCs or the members of the
+ /// SCCs 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 removeInterSCCEdge(Node &CallerN, Node &CalleeN);
+
+ /// \brief Remove an edge which is entirely within this SCC.
+ ///
+ /// Both the \a Caller and the \a Callee must be within this SCC. Removing
+ /// such an edge make break cycles that form this SCC and thus this
+ /// operation may change the SCC graph significantly. In particular, this
+ /// operation will re-form new SCCs based on the remaining connectivity of
+ /// the graph. The following invariants are guaranteed to hold after
+ /// calling this method:
+ ///
+ /// 1) This SCC is still an SCC in the graph.
+ /// 2) This SCC will be the parent of any new SCCs. Thus, this SCC is
+ /// preserved as the root of any new SCC directed graph formed.
+ /// 3) No SCC other than this SCC has its member set changed (this is
+ /// inherent in the definition of removing such an edge).
+ /// 4) All of the parent links of the SCC graph will be updated to reflect
+ /// the new SCC structure.
+ /// 5) All SCCs formed out of this SCC, excluding this SCC, will be
+ /// returned in a vector.
+ /// 6) The order of the SCCs in the vector will be a valid postorder
+ /// traversal of the new SCCs.
+ ///
+ /// These invariants are very important to ensure that we can build
+ /// optimization pipeliens on top of the CGSCC pass manager which
+ /// intelligently update the SCC graph without invalidating other parts of
+ /// the SCC graph.
+ ///
+ /// The runtime complexity of this method is, in the worst case, O(V+E)
+ /// where V is the number of nodes in this SCC and E is the number of edges
+ /// leaving the nodes in this SCC. Note that E includes both edges within
+ /// this SCC and edges from this SCC to child SCCs. 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.
+ SmallVector<SCC *, 1> removeIntraSCCEdge(Node &CallerN, Node &CalleeN);
+
+ ///@}
+ };
+
+ /// \brief 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_scc_iterator
+ : public iterator_facade_base<postorder_scc_iterator,
+ std::forward_iterator_tag, SCC> {
+ friend class LazyCallGraph;
+ friend class LazyCallGraph::Node;
+
+ /// \brief Nonce type to select the constructor for the end iterator.
+ struct IsAtEndT {};
+
+ LazyCallGraph *G;
+ SCC *C;
+
+ // Build the begin iterator for a node.
+ postorder_scc_iterator(LazyCallGraph &G) : G(&G) {
+ C = G.getNextSCCInPostOrder();
}
- iterator operator--(int) {
- iterator next = *this;
- --*this;
- return next;
+
+ // Build the end iterator for a node. This is selected purely by overload.
+ postorder_scc_iterator(LazyCallGraph &G, IsAtEndT /*Nonce*/)
+ : G(&G), C(nullptr) {}
+
+ public:
+ bool operator==(const postorder_scc_iterator &Arg) const {
+ return G == Arg.G && C == Arg.C;
+ }
+
+ reference operator*() const { return *C; }
+
+ using iterator_facade_base::operator++;
+ postorder_scc_iterator &operator++() {
+ C = G->getNextSCCInPostOrder();
+ return *this;
}
};
/// requested during traversal.
LazyCallGraph(Module &M);
- /// \brief Copy constructor.
- ///
- /// This does a deep copy of the graph. It does no verification that the
- /// graph remains valid for the module. It is also relatively expensive.
- LazyCallGraph(const LazyCallGraph &G);
-
- /// \brief Move constructor.
- ///
- /// This is a deep move. It leaves G in an undefined but destroyable state.
- /// Any other operation on G is likely to fail.
LazyCallGraph(LazyCallGraph &&G);
+ LazyCallGraph &operator=(LazyCallGraph &&RHS);
- iterator begin() { return iterator(*this, EntryNodes); }
- iterator end() { return iterator(*this, EntryNodes, iterator::IsAtEndT()); }
+ iterator begin() {
+ return iterator(*this, EntryNodes.begin(), EntryNodes.end());
+ }
+ iterator end() { return iterator(*this, EntryNodes.end(), EntryNodes.end()); }
+
+ postorder_scc_iterator postorder_scc_begin() {
+ return postorder_scc_iterator(*this);
+ }
+ postorder_scc_iterator postorder_scc_end() {
+ return postorder_scc_iterator(*this, postorder_scc_iterator::IsAtEndT());
+ }
+
+ iterator_range<postorder_scc_iterator> postorder_sccs() {
+ return iterator_range<postorder_scc_iterator>(postorder_scc_begin(),
+ postorder_scc_end());
+ }
/// \brief Lookup a function in the graph which has already been scanned and
/// added.
Node *lookup(const Function &F) const { return NodeMap.lookup(&F); }
+ /// \brief 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); }
+
/// \brief Get a graph node for a given function, scanning it to populate the
/// graph data as necessary.
- Node *get(Function &F) {
+ Node &get(Function &F) {
Node *&N = NodeMap[&F];
if (N)
- return N;
+ return *N;
return insertInto(F, N);
}
-private:
- Module &M;
+ ///@{
+ /// \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.
+
+ /// \brief Update the call graph after inserting a new edge.
+ void insertEdge(Node &Caller, Function &Callee);
+
+ /// \brief Update the call graph after inserting a new edge.
+ void insertEdge(Function &Caller, Function &Callee) {
+ return insertEdge(get(Caller), Callee);
+ }
+
+ /// \brief Update the call graph after deleting an edge.
+ void removeEdge(Node &Caller, Function &Callee);
+
+ /// \brief Update the call graph after deleting an edge.
+ void removeEdge(Function &Caller, Function &Callee) {
+ return removeEdge(get(Caller), Callee);
+ }
+
+ ///@}
+private:
/// \brief Allocator that holds all the call graph nodes.
SpecificBumpPtrAllocator<Node> BPA;
/// escape at the module scope.
NodeVectorT EntryNodes;
- /// \brief Set of the entry nodes to the graph.
- SmallPtrSet<Function *, 4> EntryNodeSet;
-
- /// \brief Helper to insert a new function, with an already looked-up entry in
- /// the NodeMap.
- Node *insertInto(Function &F, Node *&MappedN);
+ /// \brief Map of the entry nodes in the graph to their indices in
+ /// \c EntryNodes.
+ DenseMap<Function *, size_t> EntryIndexMap;
- /// \brief Helper to copy a node from another graph into this one.
- Node *copyInto(const Node &OtherN);
+ /// \brief Allocator that holds all the call graph SCCs.
+ SpecificBumpPtrAllocator<SCC> SCCBPA;
- /// \brief Helper to move a node from another graph into this one.
- Node *moveInto(Node &&OtherN);
-};
+ /// \brief Maps Function -> SCC for fast lookup.
+ DenseMap<Node *, SCC *> SCCMap;
-/// \brief 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 LazyCallGraph::Node {
- friend class LazyCallGraph;
+ /// \brief The leaf SCCs of the graph.
+ ///
+ /// These are all of the SCCs which have no children.
+ SmallVector<SCC *, 4> LeafSCCs;
- LazyCallGraph &G;
- Function &F;
- mutable NodeVectorT Callees;
- SmallPtrSet<Function *, 4> CalleeSet;
+ /// \brief Stack of nodes in the DFS walk.
+ SmallVector<std::pair<Node *, iterator>, 4> DFSStack;
- /// \brief Basic constructor implements the scanning of F into Callees and
- /// CalleeSet.
- Node(LazyCallGraph &G, Function &F);
+ /// \brief Set of entry nodes not-yet-processed into SCCs.
+ SmallVector<Function *, 4> SCCEntryNodes;
- /// \brief Constructor used when copying a node from one graph to another.
- Node(LazyCallGraph &G, const Node &OtherN);
+ /// \brief Stack of nodes the DFS has walked but not yet put into a SCC.
+ SmallVector<Node *, 4> PendingSCCStack;
- /// \brief Constructor used when moving a node from one graph to another.
- Node(LazyCallGraph &G, Node &&OtherN);
+ /// \brief Counter for the next DFS number to assign.
+ int NextDFSNumber;
-public:
- typedef LazyCallGraph::iterator iterator;
+ /// \brief Helper to insert a new function, with an already looked-up entry in
+ /// the NodeMap.
+ Node &insertInto(Function &F, Node *&MappedN);
- Function &getFunction() const {
- return F;
- };
+ /// \brief Helper to update pointers back to the graph object during moves.
+ void updateGraphPtrs();
- iterator begin() const { return iterator(G, Callees); }
- iterator end() const { return iterator(G, Callees, iterator::IsAtEndT()); }
+ /// \brief Helper to form a new SCC out of the top of a DFSStack-like
+ /// structure.
+ SCC *formSCC(Node *RootN, SmallVectorImpl<Node *> &NodeStack);
- /// Equality is defined as address equality.
- bool operator==(const Node &N) const { return this == &N; }
- bool operator!=(const Node &N) const { return !operator==(N); }
+ /// \brief Retrieve the next node in the post-order SCC walk of the call graph.
+ SCC *getNextSCCInPostOrder();
};
// Provide GraphTraits specializations for call graphs.
static void *ID() { return (void *)&PassID; }
- /// \brief Compute the \c LazyCallGraph for a the module \c M.
+ static StringRef name() { return "Lazy CallGraph Analysis"; }
+
+ /// \brief 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) { return LazyCallGraph(*M); }
+ LazyCallGraph run(Module &M) { return LazyCallGraph(M); }
private:
static char PassID;
public:
explicit LazyCallGraphPrinterPass(raw_ostream &OS);
- PreservedAnalyses run(Module *M, ModuleAnalysisManager *AM);
+ PreservedAnalyses run(Module &M, ModuleAnalysisManager *AM);
static StringRef name() { return "LazyCallGraphPrinterPass"; }
};
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