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Reality is that we're never going to copy one of these. Supporting this was becoming a nightmare because nothing even causes it to compile most of the time. Lots of subtle errors built up that wouldn't have been caught by any "normal" testing. Also, make the move assignment actually work rather than the bogus swap implementation that would just infloop if used. As part of that, factor out the graph pointer updates into a helper to share between move construction and move assignment. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206583 91177308-0d34-0410-b5e6-96231b3b80d8
423 lines
15 KiB
C++
423 lines
15 KiB
C++
//===- LazyCallGraph.h - Analysis of a Module's call graph ------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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/// \file
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///
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/// Implements a lazy call graph analysis and related passes for the new pass
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/// manager.
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///
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/// NB: This is *not* a traditional call graph! It is a graph which models both
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/// the current calls and potential calls. As a consequence there are many
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/// edges in this call graph that do not correspond to a 'call' or 'invoke'
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/// instruction.
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///
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/// The primary use cases of this graph analysis is to facilitate iterating
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/// across the functions of a module in ways that ensure all callees are
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/// visited prior to a caller (given any SCC constraints), or vice versa. As
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/// such is it particularly well suited to organizing CGSCC optimizations such
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/// as inlining, outlining, argument promotion, etc. That is its primary use
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/// case and motivates the design. It may not be appropriate for other
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/// purposes. The use graph of functions or some other conservative analysis of
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/// call instructions may be interesting for optimizations and subsequent
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/// analyses which don't work in the context of an overly specified
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/// potential-call-edge graph.
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///
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/// To understand the specific rules and nature of this call graph analysis,
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/// see the documentation of the \c LazyCallGraph below.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_LAZY_CALL_GRAPH
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#define LLVM_ANALYSIS_LAZY_CALL_GRAPH
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/PointerUnion.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/Allocator.h"
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#include <iterator>
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namespace llvm {
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class ModuleAnalysisManager;
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class PreservedAnalyses;
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class raw_ostream;
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/// \brief A lazily constructed view of the call graph of a module.
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///
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/// With the edges of this graph, the motivating constraint that we are
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/// attempting to maintain is that function-local optimization, CGSCC-local
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/// optimizations, and optimizations transforming a pair of functions connected
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/// by an edge in the graph, do not invalidate a bottom-up traversal of the SCC
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/// DAG. That is, no optimizations will delete, remove, or add an edge such
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/// that functions already visited in a bottom-up order of the SCC DAG are no
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/// longer valid to have visited, or such that functions not yet visited in
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/// a bottom-up order of the SCC DAG are not required to have already been
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/// visited.
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///
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/// Within this constraint, the desire is to minimize the merge points of the
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/// SCC DAG. The greater the fanout of the SCC DAG and the fewer merge points
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/// in the SCC DAG, the more independence there is in optimizing within it.
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/// There is a strong desire to enable parallelization of optimizations over
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/// the call graph, and both limited fanout and merge points will (artificially
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/// in some cases) limit the scaling of such an effort.
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///
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/// To this end, graph represents both direct and any potential resolution to
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/// an indirect call edge. Another way to think about it is that it represents
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/// both the direct call edges and any direct call edges that might be formed
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/// through static optimizations. Specifically, it considers taking the address
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/// of a function to be an edge in the call graph because this might be
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/// forwarded to become a direct call by some subsequent function-local
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/// optimization. The result is that the graph closely follows the use-def
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/// edges for functions. Walking "up" the graph can be done by looking at all
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/// of the uses of a function.
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///
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/// The roots of the call graph are the external functions and functions
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/// escaped into global variables. Those functions can be called from outside
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/// of the module or via unknowable means in the IR -- we may not be able to
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/// form even a potential call edge from a function body which may dynamically
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/// load the function and call it.
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///
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/// This analysis still requires updates to remain valid after optimizations
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/// which could potentially change the set of potential callees. The
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/// constraints it operates under only make the traversal order remain valid.
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///
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/// The entire analysis must be re-computed if full interprocedural
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/// optimizations run at any point. For example, globalopt completely
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/// invalidates the information in this analysis.
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///
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/// FIXME: This class is named LazyCallGraph in a lame attempt to distinguish
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/// it from the existing CallGraph. At some point, it is expected that this
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/// will be the only call graph and it will be renamed accordingly.
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class LazyCallGraph {
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public:
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class Node;
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class SCC;
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typedef SmallVector<PointerUnion<Function *, Node *>, 4> NodeVectorT;
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typedef SmallVectorImpl<PointerUnion<Function *, Node *>> NodeVectorImplT;
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/// \brief A lazy iterator used for both the entry nodes and child nodes.
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///
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/// When this iterator is dereferenced, if not yet available, a function will
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/// be scanned for "calls" or uses of functions and its child information
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/// will be constructed. All of these results are accumulated and cached in
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/// the graph.
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class iterator : public std::iterator<std::bidirectional_iterator_tag, Node *,
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ptrdiff_t, Node *, Node *> {
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friend class LazyCallGraph;
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friend class LazyCallGraph::Node;
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typedef std::iterator<std::bidirectional_iterator_tag, Node *, ptrdiff_t,
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Node *, Node *> BaseT;
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/// \brief Nonce type to select the constructor for the end iterator.
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struct IsAtEndT {};
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LazyCallGraph *G;
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NodeVectorImplT::iterator NI;
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// Build the begin iterator for a node.
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explicit iterator(LazyCallGraph &G, NodeVectorImplT &Nodes)
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: G(&G), NI(Nodes.begin()) {}
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// Build the end iterator for a node. This is selected purely by overload.
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iterator(LazyCallGraph &G, NodeVectorImplT &Nodes, IsAtEndT /*Nonce*/)
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: G(&G), NI(Nodes.end()) {}
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public:
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bool operator==(const iterator &Arg) { return NI == Arg.NI; }
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bool operator!=(const iterator &Arg) { return !operator==(Arg); }
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reference operator*() const {
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if (NI->is<Node *>())
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return NI->get<Node *>();
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Function *F = NI->get<Function *>();
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Node *ChildN = G->get(*F);
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*NI = ChildN;
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return ChildN;
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}
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pointer operator->() const { return operator*(); }
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iterator &operator++() {
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++NI;
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return *this;
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}
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iterator operator++(int) {
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iterator prev = *this;
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++*this;
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return prev;
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}
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iterator &operator--() {
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--NI;
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return *this;
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}
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iterator operator--(int) {
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iterator next = *this;
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--*this;
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return next;
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}
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};
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/// \brief A node in the call graph.
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///
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/// This represents a single node. It's primary roles are to cache the list of
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/// callees, de-duplicate and provide fast testing of whether a function is
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/// a callee, and facilitate iteration of child nodes in the graph.
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class Node {
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friend class LazyCallGraph;
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friend class LazyCallGraph::SCC;
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LazyCallGraph *G;
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Function &F;
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// We provide for the DFS numbering and Tarjan walk lowlink numbers to be
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// stored directly within the node.
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int DFSNumber;
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int LowLink;
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mutable NodeVectorT Callees;
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SmallPtrSet<Function *, 4> CalleeSet;
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/// \brief Basic constructor implements the scanning of F into Callees and
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/// CalleeSet.
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Node(LazyCallGraph &G, Function &F);
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public:
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typedef LazyCallGraph::iterator iterator;
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Function &getFunction() const {
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return F;
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};
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iterator begin() const { return iterator(*G, Callees); }
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iterator end() const { return iterator(*G, Callees, iterator::IsAtEndT()); }
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/// Equality is defined as address equality.
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bool operator==(const Node &N) const { return this == &N; }
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bool operator!=(const Node &N) const { return !operator==(N); }
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};
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/// \brief An SCC of the call graph.
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///
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/// This represents a Strongly Connected Component of the call graph as
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/// a collection of call graph nodes. While the order of nodes in the SCC is
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/// stable, it is not any particular order.
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class SCC {
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friend class LazyCallGraph;
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friend class LazyCallGraph::Node;
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SmallSetVector<SCC *, 1> ParentSCCs;
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SmallVector<Node *, 1> Nodes;
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SmallPtrSet<Function *, 1> NodeSet;
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SCC() {}
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public:
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typedef SmallVectorImpl<Node *>::const_iterator iterator;
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iterator begin() const { return Nodes.begin(); }
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iterator end() const { return Nodes.end(); }
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};
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/// \brief A post-order depth-first SCC iterator over the call graph.
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///
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/// This iterator triggers the Tarjan DFS-based formation of the SCC DAG for
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/// the call graph, walking it lazily in depth-first post-order. That is, it
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/// always visits SCCs for a callee prior to visiting the SCC for a caller
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/// (when they are in different SCCs).
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class postorder_scc_iterator
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: public std::iterator<std::forward_iterator_tag, SCC *, ptrdiff_t, SCC *,
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SCC *> {
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friend class LazyCallGraph;
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friend class LazyCallGraph::Node;
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typedef std::iterator<std::forward_iterator_tag, SCC *, ptrdiff_t,
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SCC *, SCC *> BaseT;
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/// \brief Nonce type to select the constructor for the end iterator.
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struct IsAtEndT {};
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LazyCallGraph *G;
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SCC *C;
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// Build the begin iterator for a node.
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postorder_scc_iterator(LazyCallGraph &G) : G(&G) {
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C = G.getNextSCCInPostOrder();
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}
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// Build the end iterator for a node. This is selected purely by overload.
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postorder_scc_iterator(LazyCallGraph &G, IsAtEndT /*Nonce*/)
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: G(&G), C(nullptr) {}
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public:
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bool operator==(const postorder_scc_iterator &Arg) {
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return G == Arg.G && C == Arg.C;
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}
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bool operator!=(const postorder_scc_iterator &Arg) {
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return !operator==(Arg);
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}
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reference operator*() const { return C; }
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pointer operator->() const { return operator*(); }
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postorder_scc_iterator &operator++() {
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C = G->getNextSCCInPostOrder();
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return *this;
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}
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postorder_scc_iterator operator++(int) {
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postorder_scc_iterator prev = *this;
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++*this;
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return prev;
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}
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};
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/// \brief Construct a graph for the given module.
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///
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/// This sets up the graph and computes all of the entry points of the graph.
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/// No function definitions are scanned until their nodes in the graph are
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/// requested during traversal.
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LazyCallGraph(Module &M);
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LazyCallGraph(LazyCallGraph &&G);
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LazyCallGraph &operator=(LazyCallGraph &&RHS);
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iterator begin() { return iterator(*this, EntryNodes); }
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iterator end() { return iterator(*this, EntryNodes, iterator::IsAtEndT()); }
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postorder_scc_iterator postorder_scc_begin() {
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return postorder_scc_iterator(*this);
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}
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postorder_scc_iterator postorder_scc_end() {
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return postorder_scc_iterator(*this, postorder_scc_iterator::IsAtEndT());
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}
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iterator_range<postorder_scc_iterator> postorder_sccs() {
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return iterator_range<postorder_scc_iterator>(postorder_scc_begin(),
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postorder_scc_end());
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}
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/// \brief Lookup a function in the graph which has already been scanned and
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/// added.
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Node *lookup(const Function &F) const { return NodeMap.lookup(&F); }
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/// \brief Get a graph node for a given function, scanning it to populate the
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/// graph data as necessary.
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Node *get(Function &F) {
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Node *&N = NodeMap[&F];
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if (N)
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return N;
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return insertInto(F, N);
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}
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private:
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/// \brief Allocator that holds all the call graph nodes.
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SpecificBumpPtrAllocator<Node> BPA;
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/// \brief Maps function->node for fast lookup.
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DenseMap<const Function *, Node *> NodeMap;
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/// \brief The entry nodes to the graph.
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///
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/// These nodes are reachable through "external" means. Put another way, they
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/// escape at the module scope.
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NodeVectorT EntryNodes;
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/// \brief Set of the entry nodes to the graph.
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SmallPtrSet<Function *, 4> EntryNodeSet;
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/// \brief Allocator that holds all the call graph SCCs.
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SpecificBumpPtrAllocator<SCC> SCCBPA;
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/// \brief Maps Function -> SCC for fast lookup.
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DenseMap<const Function *, SCC *> SCCMap;
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/// \brief The leaf SCCs of the graph.
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///
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/// These are all of the SCCs which have no children.
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SmallVector<SCC *, 4> LeafSCCs;
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/// \brief Stack of nodes not-yet-processed into SCCs.
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SmallVector<std::pair<Node *, iterator>, 4> DFSStack;
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/// \brief Set of entry nodes not-yet-processed into SCCs.
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SmallSetVector<Function *, 4> SCCEntryNodes;
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/// \brief Counter for the next DFS number to assign.
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int NextDFSNumber;
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/// \brief Helper to insert a new function, with an already looked-up entry in
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/// the NodeMap.
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Node *insertInto(Function &F, Node *&MappedN);
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/// \brief Helper to update pointers back to the graph object during moves.
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void updateGraphPtrs();
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/// \brief Retrieve the next node in the post-order SCC walk of the call graph.
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SCC *getNextSCCInPostOrder();
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};
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// Provide GraphTraits specializations for call graphs.
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template <> struct GraphTraits<LazyCallGraph::Node *> {
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typedef LazyCallGraph::Node NodeType;
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typedef LazyCallGraph::iterator ChildIteratorType;
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static NodeType *getEntryNode(NodeType *N) { return N; }
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static ChildIteratorType child_begin(NodeType *N) { return N->begin(); }
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static ChildIteratorType child_end(NodeType *N) { return N->end(); }
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};
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template <> struct GraphTraits<LazyCallGraph *> {
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typedef LazyCallGraph::Node NodeType;
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typedef LazyCallGraph::iterator ChildIteratorType;
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static NodeType *getEntryNode(NodeType *N) { return N; }
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static ChildIteratorType child_begin(NodeType *N) { return N->begin(); }
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static ChildIteratorType child_end(NodeType *N) { return N->end(); }
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};
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/// \brief An analysis pass which computes the call graph for a module.
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class LazyCallGraphAnalysis {
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public:
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/// \brief Inform generic clients of the result type.
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typedef LazyCallGraph Result;
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static void *ID() { return (void *)&PassID; }
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/// \brief Compute the \c LazyCallGraph for a the module \c M.
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///
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/// This just builds the set of entry points to the call graph. The rest is
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/// built lazily as it is walked.
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LazyCallGraph run(Module *M) { return LazyCallGraph(*M); }
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private:
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static char PassID;
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};
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/// \brief A pass which prints the call graph to a \c raw_ostream.
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///
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/// This is primarily useful for testing the analysis.
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class LazyCallGraphPrinterPass {
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raw_ostream &OS;
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public:
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explicit LazyCallGraphPrinterPass(raw_ostream &OS);
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PreservedAnalyses run(Module *M, ModuleAnalysisManager *AM);
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static StringRef name() { return "LazyCallGraphPrinterPass"; }
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};
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}
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#endif
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