forked from OSchip/llvm-project
1430 lines
54 KiB
C++
1430 lines
54 KiB
C++
//===---- MachineOutliner.cpp - Outline instructions -----------*- 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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///
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/// \file
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/// Replaces repeated sequences of instructions with function calls.
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///
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/// This works by placing every instruction from every basic block in a
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/// suffix tree, and repeatedly querying that tree for repeated sequences of
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/// instructions. If a sequence of instructions appears often, then it ought
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/// to be beneficial to pull out into a function.
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///
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/// This was originally presented at the 2016 LLVM Developers' Meeting in the
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/// talk "Reducing Code Size Using Outlining". For a high-level overview of
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/// how this pass works, the talk is available on YouTube at
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///
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/// https://www.youtube.com/watch?v=yorld-WSOeU
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///
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/// The slides for the talk are available at
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///
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/// http://www.llvm.org/devmtg/2016-11/Slides/Paquette-Outliner.pdf
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///
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/// The talk provides an overview of how the outliner finds candidates and
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/// ultimately outlines them. It describes how the main data structure for this
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/// pass, the suffix tree, is queried and purged for candidates. It also gives
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/// a simplified suffix tree construction algorithm for suffix trees based off
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/// of the algorithm actually used here, Ukkonen's algorithm.
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///
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/// For the original RFC for this pass, please see
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///
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/// http://lists.llvm.org/pipermail/llvm-dev/2016-August/104170.html
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///
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/// For more information on the suffix tree data structure, please see
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/// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Target/TargetSubtargetInfo.h"
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#include <functional>
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#include <map>
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#include <sstream>
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#include <tuple>
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#include <vector>
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#define DEBUG_TYPE "machine-outliner"
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using namespace llvm;
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STATISTIC(NumOutlined, "Number of candidates outlined");
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STATISTIC(FunctionsCreated, "Number of functions created");
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namespace {
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/// Represents an undefined index in the suffix tree.
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const size_t EmptyIdx = -1;
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/// A node in a suffix tree which represents a substring or suffix.
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///
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/// Each node has either no children or at least two children, with the root
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/// being a exception in the empty tree.
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///
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/// Children are represented as a map between unsigned integers and nodes. If
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/// a node N has a child M on unsigned integer k, then the mapping represented
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/// by N is a proper prefix of the mapping represented by M. Note that this,
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/// although similar to a trie is somewhat different: each node stores a full
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/// substring of the full mapping rather than a single character state.
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///
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/// Each internal node contains a pointer to the internal node representing
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/// the same string, but with the first character chopped off. This is stored
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/// in \p Link. Each leaf node stores the start index of its respective
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/// suffix in \p SuffixIdx.
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struct SuffixTreeNode {
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/// The children of this node.
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///
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/// A child existing on an unsigned integer implies that from the mapping
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/// represented by the current node, there is a way to reach another
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/// mapping by tacking that character on the end of the current string.
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DenseMap<unsigned, SuffixTreeNode *> Children;
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/// A flag set to false if the node has been pruned from the tree.
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bool IsInTree = true;
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/// The start index of this node's substring in the main string.
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size_t StartIdx = EmptyIdx;
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/// The end index of this node's substring in the main string.
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///
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/// Every leaf node must have its \p EndIdx incremented at the end of every
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/// step in the construction algorithm. To avoid having to update O(N)
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/// nodes individually at the end of every step, the end index is stored
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/// as a pointer.
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size_t *EndIdx = nullptr;
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/// For leaves, the start index of the suffix represented by this node.
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///
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/// For all other nodes, this is ignored.
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size_t SuffixIdx = EmptyIdx;
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/// \brief For internal nodes, a pointer to the internal node representing
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/// the same sequence with the first character chopped off.
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///
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/// This has two major purposes in the suffix tree. The first is as a
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/// shortcut in Ukkonen's construction algorithm. One of the things that
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/// Ukkonen's algorithm does to achieve linear-time construction is
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/// keep track of which node the next insert should be at. This makes each
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/// insert O(1), and there are a total of O(N) inserts. The suffix link
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/// helps with inserting children of internal nodes.
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///
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/// Say we add a child to an internal node with associated mapping S. The
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/// next insertion must be at the node representing S - its first character.
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/// This is given by the way that we iteratively build the tree in Ukkonen's
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/// algorithm. The main idea is to look at the suffixes of each prefix in the
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/// string, starting with the longest suffix of the prefix, and ending with
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/// the shortest. Therefore, if we keep pointers between such nodes, we can
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/// move to the next insertion point in O(1) time. If we don't, then we'd
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/// have to query from the root, which takes O(N) time. This would make the
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/// construction algorithm O(N^2) rather than O(N).
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///
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/// The suffix link is also used during the tree pruning process to let us
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/// quickly throw out a bunch of potential overlaps. Say we have a sequence
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/// S we want to outline. Then each of its suffixes contribute to at least
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/// one overlapping case. Therefore, we can follow the suffix links
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/// starting at the node associated with S to the root and "delete" those
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/// nodes, save for the root. For each candidate, this removes
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/// O(|candidate|) overlaps from the search space. We don't actually
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/// completely invalidate these nodes though; doing that is far too
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/// aggressive. Consider the following pathological string:
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///
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/// 1 2 3 1 2 3 2 3 2 3 2 3 2 3 2 3 2 3
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///
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/// If we, for the sake of example, outlined 1 2 3, then we would throw
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/// out all instances of 2 3. This isn't desirable. To get around this,
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/// when we visit a link node, we decrement its occurrence count by the
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/// number of sequences we outlined in the current step. In the pathological
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/// example, the 2 3 node would have an occurrence count of 8, while the
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/// 1 2 3 node would have an occurrence count of 2. Thus, the 2 3 node
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/// would survive to the next round allowing us to outline the extra
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/// instances of 2 3.
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SuffixTreeNode *Link = nullptr;
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/// The parent of this node. Every node except for the root has a parent.
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SuffixTreeNode *Parent = nullptr;
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/// The number of times this node's string appears in the tree.
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///
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/// This is equal to the number of leaf children of the string. It represents
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/// the number of suffixes that the node's string is a prefix of.
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size_t OccurrenceCount = 0;
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/// Returns true if this node is a leaf.
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bool isLeaf() const { return SuffixIdx != EmptyIdx; }
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/// Returns true if this node is the root of its owning \p SuffixTree.
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bool isRoot() const { return StartIdx == EmptyIdx; }
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/// Return the number of elements in the substring associated with this node.
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size_t size() const {
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// Is it the root? If so, it's the empty string so return 0.
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if (isRoot())
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return 0;
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assert(*EndIdx != EmptyIdx && "EndIdx is undefined!");
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// Size = the number of elements in the string.
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// For example, [0 1 2 3] has length 4, not 3. 3-0 = 3, so we have 3-0+1.
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return *EndIdx - StartIdx + 1;
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}
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SuffixTreeNode(size_t StartIdx, size_t *EndIdx, SuffixTreeNode *Link,
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SuffixTreeNode *Parent)
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: StartIdx(StartIdx), EndIdx(EndIdx), Link(Link), Parent(Parent) {}
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SuffixTreeNode() {}
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};
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/// A data structure for fast substring queries.
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///
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/// Suffix trees represent the suffixes of their input strings in their leaves.
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/// A suffix tree is a type of compressed trie structure where each node
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/// represents an entire substring rather than a single character. Each leaf
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/// of the tree is a suffix.
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///
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/// A suffix tree can be seen as a type of state machine where each state is a
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/// substring of the full string. The tree is structured so that, for a string
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/// of length N, there are exactly N leaves in the tree. This structure allows
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/// us to quickly find repeated substrings of the input string.
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///
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/// In this implementation, a "string" is a vector of unsigned integers.
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/// These integers may result from hashing some data type. A suffix tree can
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/// contain 1 or many strings, which can then be queried as one large string.
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///
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/// The suffix tree is implemented using Ukkonen's algorithm for linear-time
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/// suffix tree construction. Ukkonen's algorithm is explained in more detail
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/// in the paper by Esko Ukkonen "On-line construction of suffix trees. The
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/// paper is available at
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///
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/// https://www.cs.helsinki.fi/u/ukkonen/SuffixT1withFigs.pdf
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class SuffixTree {
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private:
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/// Each element is an integer representing an instruction in the module.
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ArrayRef<unsigned> Str;
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/// Maintains each node in the tree.
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SpecificBumpPtrAllocator<SuffixTreeNode> NodeAllocator;
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/// The root of the suffix tree.
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///
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/// The root represents the empty string. It is maintained by the
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/// \p NodeAllocator like every other node in the tree.
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SuffixTreeNode *Root = nullptr;
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/// Stores each leaf in the tree for better pruning.
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std::vector<SuffixTreeNode *> LeafVector;
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/// Maintains the end indices of the internal nodes in the tree.
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///
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/// Each internal node is guaranteed to never have its end index change
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/// during the construction algorithm; however, leaves must be updated at
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/// every step. Therefore, we need to store leaf end indices by reference
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/// to avoid updating O(N) leaves at every step of construction. Thus,
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/// every internal node must be allocated its own end index.
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BumpPtrAllocator InternalEndIdxAllocator;
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/// The end index of each leaf in the tree.
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size_t LeafEndIdx = -1;
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/// \brief Helper struct which keeps track of the next insertion point in
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/// Ukkonen's algorithm.
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struct ActiveState {
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/// The next node to insert at.
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SuffixTreeNode *Node;
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/// The index of the first character in the substring currently being added.
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size_t Idx = EmptyIdx;
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/// The length of the substring we have to add at the current step.
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size_t Len = 0;
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};
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/// \brief The point the next insertion will take place at in the
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/// construction algorithm.
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ActiveState Active;
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/// Allocate a leaf node and add it to the tree.
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///
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/// \param Parent The parent of this node.
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/// \param StartIdx The start index of this node's associated string.
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/// \param Edge The label on the edge leaving \p Parent to this node.
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///
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/// \returns A pointer to the allocated leaf node.
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SuffixTreeNode *insertLeaf(SuffixTreeNode &Parent, size_t StartIdx,
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unsigned Edge) {
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assert(StartIdx <= LeafEndIdx && "String can't start after it ends!");
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SuffixTreeNode *N = new (NodeAllocator.Allocate()) SuffixTreeNode(StartIdx,
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&LeafEndIdx,
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nullptr,
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&Parent);
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Parent.Children[Edge] = N;
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return N;
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}
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/// Allocate an internal node and add it to the tree.
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///
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/// \param Parent The parent of this node. Only null when allocating the root.
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/// \param StartIdx The start index of this node's associated string.
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/// \param EndIdx The end index of this node's associated string.
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/// \param Edge The label on the edge leaving \p Parent to this node.
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///
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/// \returns A pointer to the allocated internal node.
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SuffixTreeNode *insertInternalNode(SuffixTreeNode *Parent, size_t StartIdx,
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size_t EndIdx, unsigned Edge) {
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assert(StartIdx <= EndIdx && "String can't start after it ends!");
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assert(!(!Parent && StartIdx != EmptyIdx) &&
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"Non-root internal nodes must have parents!");
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size_t *E = new (InternalEndIdxAllocator) size_t(EndIdx);
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SuffixTreeNode *N = new (NodeAllocator.Allocate()) SuffixTreeNode(StartIdx,
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E,
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Root,
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Parent);
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if (Parent)
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Parent->Children[Edge] = N;
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return N;
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}
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/// \brief Set the suffix indices of the leaves to the start indices of their
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/// respective suffixes. Also stores each leaf in \p LeafVector at its
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/// respective suffix index.
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///
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/// \param[in] CurrNode The node currently being visited.
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/// \param CurrIdx The current index of the string being visited.
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void setSuffixIndices(SuffixTreeNode &CurrNode, size_t CurrIdx) {
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bool IsLeaf = CurrNode.Children.size() == 0 && !CurrNode.isRoot();
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// Traverse the tree depth-first.
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for (auto &ChildPair : CurrNode.Children) {
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assert(ChildPair.second && "Node had a null child!");
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setSuffixIndices(*ChildPair.second,
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CurrIdx + ChildPair.second->size());
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}
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// Is this node a leaf?
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if (IsLeaf) {
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// If yes, give it a suffix index and bump its parent's occurrence count.
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CurrNode.SuffixIdx = Str.size() - CurrIdx;
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assert(CurrNode.Parent && "CurrNode had no parent!");
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CurrNode.Parent->OccurrenceCount++;
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// Store the leaf in the leaf vector for pruning later.
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LeafVector[CurrNode.SuffixIdx] = &CurrNode;
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}
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}
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/// \brief Construct the suffix tree for the prefix of the input ending at
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/// \p EndIdx.
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///
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/// Used to construct the full suffix tree iteratively. At the end of each
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/// step, the constructed suffix tree is either a valid suffix tree, or a
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/// suffix tree with implicit suffixes. At the end of the final step, the
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/// suffix tree is a valid tree.
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///
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/// \param EndIdx The end index of the current prefix in the main string.
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/// \param SuffixesToAdd The number of suffixes that must be added
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/// to complete the suffix tree at the current phase.
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///
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/// \returns The number of suffixes that have not been added at the end of
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/// this step.
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unsigned extend(size_t EndIdx, size_t SuffixesToAdd) {
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SuffixTreeNode *NeedsLink = nullptr;
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while (SuffixesToAdd > 0) {
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// Are we waiting to add anything other than just the last character?
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if (Active.Len == 0) {
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// If not, then say the active index is the end index.
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Active.Idx = EndIdx;
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}
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assert(Active.Idx <= EndIdx && "Start index can't be after end index!");
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// The first character in the current substring we're looking at.
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unsigned FirstChar = Str[Active.Idx];
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// Have we inserted anything starting with FirstChar at the current node?
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if (Active.Node->Children.count(FirstChar) == 0) {
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// If not, then we can just insert a leaf and move too the next step.
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insertLeaf(*Active.Node, EndIdx, FirstChar);
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// The active node is an internal node, and we visited it, so it must
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// need a link if it doesn't have one.
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if (NeedsLink) {
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NeedsLink->Link = Active.Node;
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NeedsLink = nullptr;
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}
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} else {
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// There's a match with FirstChar, so look for the point in the tree to
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// insert a new node.
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SuffixTreeNode *NextNode = Active.Node->Children[FirstChar];
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size_t SubstringLen = NextNode->size();
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// Is the current suffix we're trying to insert longer than the size of
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// the child we want to move to?
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if (Active.Len >= SubstringLen) {
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// If yes, then consume the characters we've seen and move to the next
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// node.
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Active.Idx += SubstringLen;
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Active.Len -= SubstringLen;
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Active.Node = NextNode;
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continue;
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}
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// Otherwise, the suffix we're trying to insert must be contained in the
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// next node we want to move to.
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unsigned LastChar = Str[EndIdx];
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// Is the string we're trying to insert a substring of the next node?
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if (Str[NextNode->StartIdx + Active.Len] == LastChar) {
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// If yes, then we're done for this step. Remember our insertion point
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// and move to the next end index. At this point, we have an implicit
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// suffix tree.
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if (NeedsLink && !Active.Node->isRoot()) {
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NeedsLink->Link = Active.Node;
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NeedsLink = nullptr;
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}
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Active.Len++;
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break;
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}
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// The string we're trying to insert isn't a substring of the next node,
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// but matches up to a point. Split the node.
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//
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// For example, say we ended our search at a node n and we're trying to
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// insert ABD. Then we'll create a new node s for AB, reduce n to just
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// representing C, and insert a new leaf node l to represent d. This
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// allows us to ensure that if n was a leaf, it remains a leaf.
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//
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// | ABC ---split---> | AB
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// n s
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// C / \ D
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// n l
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// The node s from the diagram
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SuffixTreeNode *SplitNode =
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insertInternalNode(Active.Node,
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NextNode->StartIdx,
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NextNode->StartIdx + Active.Len - 1,
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FirstChar);
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// Insert the new node representing the new substring into the tree as
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// a child of the split node. This is the node l from the diagram.
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insertLeaf(*SplitNode, EndIdx, LastChar);
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// Make the old node a child of the split node and update its start
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// index. This is the node n from the diagram.
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NextNode->StartIdx += Active.Len;
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NextNode->Parent = SplitNode;
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SplitNode->Children[Str[NextNode->StartIdx]] = NextNode;
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// SplitNode is an internal node, update the suffix link.
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if (NeedsLink)
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NeedsLink->Link = SplitNode;
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NeedsLink = SplitNode;
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}
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// We've added something new to the tree, so there's one less suffix to
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// add.
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SuffixesToAdd--;
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if (Active.Node->isRoot()) {
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if (Active.Len > 0) {
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Active.Len--;
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Active.Idx = EndIdx - SuffixesToAdd + 1;
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}
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} else {
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// Start the next phase at the next smallest suffix.
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Active.Node = Active.Node->Link;
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}
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}
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return SuffixesToAdd;
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}
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/// \brief Return the start index and length of a string which maximizes a
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/// benefit function by traversing the tree depth-first.
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///
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/// Helper function for \p bestRepeatedSubstring.
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///
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/// \param CurrNode The node currently being visited.
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/// \param CurrLen Length of the current string.
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/// \param[out] BestLen Length of the most beneficial substring.
|
|
/// \param[out] MaxBenefit Benefit of the most beneficial substring.
|
|
/// \param[out] BestStartIdx Start index of the most beneficial substring.
|
|
/// \param BenefitFn The function the query should return a maximum string
|
|
/// for.
|
|
void findBest(SuffixTreeNode &CurrNode, size_t CurrLen, size_t &BestLen,
|
|
size_t &MaxBenefit, size_t &BestStartIdx,
|
|
const std::function<unsigned(SuffixTreeNode &, size_t CurrLen)>
|
|
&BenefitFn) {
|
|
|
|
if (!CurrNode.IsInTree)
|
|
return;
|
|
|
|
// Can we traverse further down the tree?
|
|
if (!CurrNode.isLeaf()) {
|
|
// If yes, continue the traversal.
|
|
for (auto &ChildPair : CurrNode.Children) {
|
|
if (ChildPair.second && ChildPair.second->IsInTree)
|
|
findBest(*ChildPair.second, CurrLen + ChildPair.second->size(),
|
|
BestLen, MaxBenefit, BestStartIdx, BenefitFn);
|
|
}
|
|
} else {
|
|
// We hit a leaf.
|
|
size_t StringLen = CurrLen - CurrNode.size();
|
|
unsigned Benefit = BenefitFn(CurrNode, StringLen);
|
|
|
|
// Did we do better than in the last step?
|
|
if (Benefit <= MaxBenefit)
|
|
return;
|
|
|
|
// We did better, so update the best string.
|
|
MaxBenefit = Benefit;
|
|
BestStartIdx = CurrNode.SuffixIdx;
|
|
BestLen = StringLen;
|
|
}
|
|
}
|
|
|
|
public:
|
|
|
|
unsigned operator[](const size_t i) const {
|
|
return Str[i];
|
|
}
|
|
|
|
/// \brief Return a substring of the tree with maximum benefit if such a
|
|
/// substring exists.
|
|
///
|
|
/// Clears the input vector and fills it with a maximum substring or empty.
|
|
///
|
|
/// \param[in,out] Best The most beneficial substring in the tree. Empty
|
|
/// if it does not exist.
|
|
/// \param BenefitFn The function the query should return a maximum string
|
|
/// for.
|
|
void bestRepeatedSubstring(std::vector<unsigned> &Best,
|
|
const std::function<unsigned(SuffixTreeNode &, size_t CurrLen)>
|
|
&BenefitFn) {
|
|
Best.clear();
|
|
size_t Length = 0; // Becomes the length of the best substring.
|
|
size_t Benefit = 0; // Becomes the benefit of the best substring.
|
|
size_t StartIdx = 0; // Becomes the start index of the best substring.
|
|
findBest(*Root, 0, Length, Benefit, StartIdx, BenefitFn);
|
|
|
|
for (size_t Idx = 0; Idx < Length; Idx++)
|
|
Best.push_back(Str[Idx + StartIdx]);
|
|
}
|
|
|
|
/// Perform a depth-first search for \p QueryString on the suffix tree.
|
|
///
|
|
/// \param QueryString The string to search for.
|
|
/// \param CurrIdx The current index in \p QueryString that is being matched
|
|
/// against.
|
|
/// \param CurrNode The suffix tree node being searched in.
|
|
///
|
|
/// \returns A \p SuffixTreeNode that \p QueryString appears in if such a
|
|
/// node exists, and \p nullptr otherwise.
|
|
SuffixTreeNode *findString(const std::vector<unsigned> &QueryString,
|
|
size_t &CurrIdx, SuffixTreeNode *CurrNode) {
|
|
|
|
// The search ended at a nonexistent or pruned node. Quit.
|
|
if (!CurrNode || !CurrNode->IsInTree)
|
|
return nullptr;
|
|
|
|
unsigned Edge = QueryString[CurrIdx]; // The edge we want to move on.
|
|
SuffixTreeNode *NextNode = CurrNode->Children[Edge]; // Next node in query.
|
|
|
|
if (CurrNode->isRoot()) {
|
|
// If we're at the root we have to check if there's a child, and move to
|
|
// that child. Don't consume the character since \p Root represents the
|
|
// empty string.
|
|
if (NextNode && NextNode->IsInTree)
|
|
return findString(QueryString, CurrIdx, NextNode);
|
|
return nullptr;
|
|
}
|
|
|
|
size_t StrIdx = CurrNode->StartIdx;
|
|
size_t MaxIdx = QueryString.size();
|
|
bool ContinueSearching = false;
|
|
|
|
// Match as far as possible into the string. If there's a mismatch, quit.
|
|
for (; CurrIdx < MaxIdx; CurrIdx++, StrIdx++) {
|
|
Edge = QueryString[CurrIdx];
|
|
|
|
// We matched perfectly, but still have a remainder to search.
|
|
if (StrIdx > *(CurrNode->EndIdx)) {
|
|
ContinueSearching = true;
|
|
break;
|
|
}
|
|
|
|
if (Edge != Str[StrIdx])
|
|
return nullptr;
|
|
}
|
|
|
|
NextNode = CurrNode->Children[Edge];
|
|
|
|
// Move to the node which matches what we're looking for and continue
|
|
// searching.
|
|
if (ContinueSearching)
|
|
return findString(QueryString, CurrIdx, NextNode);
|
|
|
|
// We matched perfectly so we're done.
|
|
return CurrNode;
|
|
}
|
|
|
|
/// \brief Remove a node from a tree and all nodes representing proper
|
|
/// suffixes of that node's string.
|
|
///
|
|
/// This is used in the outlining algorithm to reduce the number of
|
|
/// overlapping candidates
|
|
///
|
|
/// \param N The suffix tree node to start pruning from.
|
|
/// \param Len The length of the string to be pruned.
|
|
///
|
|
/// \returns True if this candidate didn't overlap with a previously chosen
|
|
/// candidate.
|
|
bool prune(SuffixTreeNode *N, size_t Len) {
|
|
|
|
bool NoOverlap = true;
|
|
std::vector<unsigned> IndicesToPrune;
|
|
|
|
// Look at each of N's children.
|
|
for (auto &ChildPair : N->Children) {
|
|
SuffixTreeNode *M = ChildPair.second;
|
|
|
|
// Is this a leaf child?
|
|
if (M && M->IsInTree && M->isLeaf()) {
|
|
// Save each leaf child's suffix indices and remove them from the tree.
|
|
IndicesToPrune.push_back(M->SuffixIdx);
|
|
M->IsInTree = false;
|
|
}
|
|
}
|
|
|
|
// Remove each suffix we have to prune from the tree. Each of these will be
|
|
// I + some offset for I in IndicesToPrune and some offset < Len.
|
|
unsigned Offset = 1;
|
|
for (unsigned CurrentSuffix = 1; CurrentSuffix < Len; CurrentSuffix++) {
|
|
for (unsigned I : IndicesToPrune) {
|
|
|
|
unsigned PruneIdx = I + Offset;
|
|
|
|
// Is this index actually in the string?
|
|
if (PruneIdx < LeafVector.size()) {
|
|
// If yes, we have to try and prune it.
|
|
// Was the current leaf already pruned by another candidate?
|
|
if (LeafVector[PruneIdx]->IsInTree) {
|
|
// If not, prune it.
|
|
LeafVector[PruneIdx]->IsInTree = false;
|
|
} else {
|
|
// If yes, signify that we've found an overlap, but keep pruning.
|
|
NoOverlap = false;
|
|
}
|
|
|
|
// Update the parent of the current leaf's occurrence count.
|
|
SuffixTreeNode *Parent = LeafVector[PruneIdx]->Parent;
|
|
|
|
// Is the parent still in the tree?
|
|
if (Parent->OccurrenceCount > 0) {
|
|
Parent->OccurrenceCount--;
|
|
Parent->IsInTree = (Parent->OccurrenceCount > 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Move to the next character in the string.
|
|
Offset++;
|
|
}
|
|
|
|
// We know we can never outline anything which starts one index back from
|
|
// the indices we want to outline. This is because our minimum outlining
|
|
// length is always 2.
|
|
for (unsigned I : IndicesToPrune) {
|
|
if (I > 0) {
|
|
|
|
unsigned PruneIdx = I-1;
|
|
SuffixTreeNode *Parent = LeafVector[PruneIdx]->Parent;
|
|
|
|
// Was the leaf one index back from I already pruned?
|
|
if (LeafVector[PruneIdx]->IsInTree) {
|
|
// If not, prune it.
|
|
LeafVector[PruneIdx]->IsInTree = false;
|
|
} else {
|
|
// If yes, signify that we've found an overlap, but keep pruning.
|
|
NoOverlap = false;
|
|
}
|
|
|
|
// Update the parent of the current leaf's occurrence count.
|
|
if (Parent->OccurrenceCount > 0) {
|
|
Parent->OccurrenceCount--;
|
|
Parent->IsInTree = (Parent->OccurrenceCount > 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Finally, remove N from the tree and set its occurrence count to 0.
|
|
N->IsInTree = false;
|
|
N->OccurrenceCount = 0;
|
|
|
|
return NoOverlap;
|
|
}
|
|
|
|
/// \brief Find each occurrence of of a string in \p QueryString and prune
|
|
/// their nodes.
|
|
///
|
|
/// \param QueryString The string to search for.
|
|
/// \param[out] Occurrences The start indices of each occurrence.
|
|
///
|
|
/// \returns Whether or not the occurrence overlaps with a previous candidate.
|
|
bool findOccurrencesAndPrune(const std::vector<unsigned> &QueryString,
|
|
std::vector<size_t> &Occurrences) {
|
|
size_t Dummy = 0;
|
|
SuffixTreeNode *N = findString(QueryString, Dummy, Root);
|
|
|
|
if (!N || !N->IsInTree)
|
|
return false;
|
|
|
|
// If this is an internal node, occurrences are the number of leaf children
|
|
// of the node.
|
|
for (auto &ChildPair : N->Children) {
|
|
SuffixTreeNode *M = ChildPair.second;
|
|
|
|
// Is it a leaf? If so, we have an occurrence.
|
|
if (M && M->IsInTree && M->isLeaf())
|
|
Occurrences.push_back(M->SuffixIdx);
|
|
}
|
|
|
|
// If we're in a leaf, then this node is the only occurrence.
|
|
if (N->isLeaf())
|
|
Occurrences.push_back(N->SuffixIdx);
|
|
|
|
return prune(N, QueryString.size());
|
|
}
|
|
|
|
/// Construct a suffix tree from a sequence of unsigned integers.
|
|
///
|
|
/// \param Str The string to construct the suffix tree for.
|
|
SuffixTree(const std::vector<unsigned> &Str) : Str(Str) {
|
|
Root = insertInternalNode(nullptr, EmptyIdx, EmptyIdx, 0);
|
|
Root->IsInTree = true;
|
|
Active.Node = Root;
|
|
LeafVector = std::vector<SuffixTreeNode*>(Str.size());
|
|
|
|
// Keep track of the number of suffixes we have to add of the current
|
|
// prefix.
|
|
size_t SuffixesToAdd = 0;
|
|
Active.Node = Root;
|
|
|
|
// Construct the suffix tree iteratively on each prefix of the string.
|
|
// PfxEndIdx is the end index of the current prefix.
|
|
// End is one past the last element in the string.
|
|
for (size_t PfxEndIdx = 0, End = Str.size(); PfxEndIdx < End; PfxEndIdx++) {
|
|
SuffixesToAdd++;
|
|
LeafEndIdx = PfxEndIdx; // Extend each of the leaves.
|
|
SuffixesToAdd = extend(PfxEndIdx, SuffixesToAdd);
|
|
}
|
|
|
|
// Set the suffix indices of each leaf.
|
|
assert(Root && "Root node can't be nullptr!");
|
|
setSuffixIndices(*Root, 0);
|
|
}
|
|
};
|
|
|
|
/// \brief An individual sequence of instructions to be replaced with a call to
|
|
/// an outlined function.
|
|
struct Candidate {
|
|
|
|
/// Set to false if the candidate overlapped with another candidate.
|
|
bool InCandidateList = true;
|
|
|
|
/// The start index of this \p Candidate.
|
|
size_t StartIdx;
|
|
|
|
/// The number of instructions in this \p Candidate.
|
|
size_t Len;
|
|
|
|
/// The index of this \p Candidate's \p OutlinedFunction in the list of
|
|
/// \p OutlinedFunctions.
|
|
size_t FunctionIdx;
|
|
|
|
Candidate(size_t StartIdx, size_t Len, size_t FunctionIdx)
|
|
: StartIdx(StartIdx), Len(Len), FunctionIdx(FunctionIdx) {}
|
|
|
|
Candidate() {}
|
|
|
|
/// \brief Used to ensure that \p Candidates are outlined in an order that
|
|
/// preserves the start and end indices of other \p Candidates.
|
|
bool operator<(const Candidate &RHS) const { return StartIdx > RHS.StartIdx; }
|
|
};
|
|
|
|
/// \brief The information necessary to create an outlined function for some
|
|
/// class of candidate.
|
|
struct OutlinedFunction {
|
|
|
|
/// The actual outlined function created.
|
|
/// This is initialized after we go through and create the actual function.
|
|
MachineFunction *MF = nullptr;
|
|
|
|
/// A number assigned to this function which appears at the end of its name.
|
|
size_t Name;
|
|
|
|
/// The number of times that this function has appeared.
|
|
size_t OccurrenceCount = 0;
|
|
|
|
/// \brief The sequence of integers corresponding to the instructions in this
|
|
/// function.
|
|
std::vector<unsigned> Sequence;
|
|
|
|
/// The number of instructions this function would save.
|
|
unsigned Benefit = 0;
|
|
|
|
bool IsTailCall = false;
|
|
|
|
OutlinedFunction(size_t Name, size_t OccurrenceCount,
|
|
const std::vector<unsigned> &Sequence,
|
|
unsigned Benefit, bool IsTailCall)
|
|
: Name(Name), OccurrenceCount(OccurrenceCount), Sequence(Sequence),
|
|
Benefit(Benefit), IsTailCall(IsTailCall)
|
|
{}
|
|
};
|
|
|
|
/// \brief Maps \p MachineInstrs to unsigned integers and stores the mappings.
|
|
struct InstructionMapper {
|
|
|
|
/// \brief The next available integer to assign to a \p MachineInstr that
|
|
/// cannot be outlined.
|
|
///
|
|
/// Set to -3 for compatability with \p DenseMapInfo<unsigned>.
|
|
unsigned IllegalInstrNumber = -3;
|
|
|
|
/// \brief The next available integer to assign to a \p MachineInstr that can
|
|
/// be outlined.
|
|
unsigned LegalInstrNumber = 0;
|
|
|
|
/// Correspondence from \p MachineInstrs to unsigned integers.
|
|
DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>
|
|
InstructionIntegerMap;
|
|
|
|
/// Corresponcence from unsigned integers to \p MachineInstrs.
|
|
/// Inverse of \p InstructionIntegerMap.
|
|
DenseMap<unsigned, MachineInstr *> IntegerInstructionMap;
|
|
|
|
/// The vector of unsigned integers that the module is mapped to.
|
|
std::vector<unsigned> UnsignedVec;
|
|
|
|
/// \brief Stores the location of the instruction associated with the integer
|
|
/// at index i in \p UnsignedVec for each index i.
|
|
std::vector<MachineBasicBlock::iterator> InstrList;
|
|
|
|
/// \brief Maps \p *It to a legal integer.
|
|
///
|
|
/// Updates \p InstrList, \p UnsignedVec, \p InstructionIntegerMap,
|
|
/// \p IntegerInstructionMap, and \p LegalInstrNumber.
|
|
///
|
|
/// \returns The integer that \p *It was mapped to.
|
|
unsigned mapToLegalUnsigned(MachineBasicBlock::iterator &It) {
|
|
|
|
// Get the integer for this instruction or give it the current
|
|
// LegalInstrNumber.
|
|
InstrList.push_back(It);
|
|
MachineInstr &MI = *It;
|
|
bool WasInserted;
|
|
DenseMap<MachineInstr *, unsigned, MachineInstrExpressionTrait>::iterator
|
|
ResultIt;
|
|
std::tie(ResultIt, WasInserted) =
|
|
InstructionIntegerMap.insert(std::make_pair(&MI, LegalInstrNumber));
|
|
unsigned MINumber = ResultIt->second;
|
|
|
|
// There was an insertion.
|
|
if (WasInserted) {
|
|
LegalInstrNumber++;
|
|
IntegerInstructionMap.insert(std::make_pair(MINumber, &MI));
|
|
}
|
|
|
|
UnsignedVec.push_back(MINumber);
|
|
|
|
// Make sure we don't overflow or use any integers reserved by the DenseMap.
|
|
if (LegalInstrNumber >= IllegalInstrNumber)
|
|
report_fatal_error("Instruction mapping overflow!");
|
|
|
|
assert(LegalInstrNumber != DenseMapInfo<unsigned>::getEmptyKey()
|
|
&& "Tried to assign DenseMap tombstone or empty key to instruction.");
|
|
assert(LegalInstrNumber != DenseMapInfo<unsigned>::getTombstoneKey()
|
|
&& "Tried to assign DenseMap tombstone or empty key to instruction.");
|
|
|
|
return MINumber;
|
|
}
|
|
|
|
/// Maps \p *It to an illegal integer.
|
|
///
|
|
/// Updates \p InstrList, \p UnsignedVec, and \p IllegalInstrNumber.
|
|
///
|
|
/// \returns The integer that \p *It was mapped to.
|
|
unsigned mapToIllegalUnsigned(MachineBasicBlock::iterator &It) {
|
|
unsigned MINumber = IllegalInstrNumber;
|
|
|
|
InstrList.push_back(It);
|
|
UnsignedVec.push_back(IllegalInstrNumber);
|
|
IllegalInstrNumber--;
|
|
|
|
assert(LegalInstrNumber < IllegalInstrNumber &&
|
|
"Instruction mapping overflow!");
|
|
|
|
assert(IllegalInstrNumber !=
|
|
DenseMapInfo<unsigned>::getEmptyKey() &&
|
|
"IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
|
|
|
|
assert(IllegalInstrNumber !=
|
|
DenseMapInfo<unsigned>::getTombstoneKey() &&
|
|
"IllegalInstrNumber cannot be DenseMap tombstone or empty key!");
|
|
|
|
return MINumber;
|
|
}
|
|
|
|
/// \brief Transforms a \p MachineBasicBlock into a \p vector of \p unsigneds
|
|
/// and appends it to \p UnsignedVec and \p InstrList.
|
|
///
|
|
/// Two instructions are assigned the same integer if they are identical.
|
|
/// If an instruction is deemed unsafe to outline, then it will be assigned an
|
|
/// unique integer. The resulting mapping is placed into a suffix tree and
|
|
/// queried for candidates.
|
|
///
|
|
/// \param MBB The \p MachineBasicBlock to be translated into integers.
|
|
/// \param TRI \p TargetRegisterInfo for the module.
|
|
/// \param TII \p TargetInstrInfo for the module.
|
|
void convertToUnsignedVec(MachineBasicBlock &MBB,
|
|
const TargetRegisterInfo &TRI,
|
|
const TargetInstrInfo &TII) {
|
|
for (MachineBasicBlock::iterator It = MBB.begin(), Et = MBB.end(); It != Et;
|
|
It++) {
|
|
|
|
// Keep track of where this instruction is in the module.
|
|
switch(TII.getOutliningType(*It)) {
|
|
case TargetInstrInfo::MachineOutlinerInstrType::Illegal:
|
|
mapToIllegalUnsigned(It);
|
|
break;
|
|
|
|
case TargetInstrInfo::MachineOutlinerInstrType::Legal:
|
|
mapToLegalUnsigned(It);
|
|
break;
|
|
|
|
case TargetInstrInfo::MachineOutlinerInstrType::Invisible:
|
|
break;
|
|
}
|
|
}
|
|
|
|
// After we're done every insertion, uniquely terminate this part of the
|
|
// "string". This makes sure we won't match across basic block or function
|
|
// boundaries since the "end" is encoded uniquely and thus appears in no
|
|
// repeated substring.
|
|
InstrList.push_back(MBB.end());
|
|
UnsignedVec.push_back(IllegalInstrNumber);
|
|
IllegalInstrNumber--;
|
|
}
|
|
|
|
InstructionMapper() {
|
|
// Make sure that the implementation of DenseMapInfo<unsigned> hasn't
|
|
// changed.
|
|
assert(DenseMapInfo<unsigned>::getEmptyKey() == (unsigned)-1 &&
|
|
"DenseMapInfo<unsigned>'s empty key isn't -1!");
|
|
assert(DenseMapInfo<unsigned>::getTombstoneKey() == (unsigned)-2 &&
|
|
"DenseMapInfo<unsigned>'s tombstone key isn't -2!");
|
|
}
|
|
};
|
|
|
|
/// \brief An interprocedural pass which finds repeated sequences of
|
|
/// instructions and replaces them with calls to functions.
|
|
///
|
|
/// Each instruction is mapped to an unsigned integer and placed in a string.
|
|
/// The resulting mapping is then placed in a \p SuffixTree. The \p SuffixTree
|
|
/// is then repeatedly queried for repeated sequences of instructions. Each
|
|
/// non-overlapping repeated sequence is then placed in its own
|
|
/// \p MachineFunction and each instance is then replaced with a call to that
|
|
/// function.
|
|
struct MachineOutliner : public ModulePass {
|
|
|
|
static char ID;
|
|
|
|
StringRef getPassName() const override { return "Machine Outliner"; }
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.addRequired<MachineModuleInfo>();
|
|
AU.addPreserved<MachineModuleInfo>();
|
|
AU.setPreservesAll();
|
|
ModulePass::getAnalysisUsage(AU);
|
|
}
|
|
|
|
MachineOutliner() : ModulePass(ID) {
|
|
initializeMachineOutlinerPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
/// \brief Replace the sequences of instructions represented by the
|
|
/// \p Candidates in \p CandidateList with calls to \p MachineFunctions
|
|
/// described in \p FunctionList.
|
|
///
|
|
/// \param M The module we are outlining from.
|
|
/// \param CandidateList A list of candidates to be outlined.
|
|
/// \param FunctionList A list of functions to be inserted into the module.
|
|
/// \param Mapper Contains the instruction mappings for the module.
|
|
bool outline(Module &M, const ArrayRef<Candidate> &CandidateList,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
InstructionMapper &Mapper);
|
|
|
|
/// Creates a function for \p OF and inserts it into the module.
|
|
MachineFunction *createOutlinedFunction(Module &M, const OutlinedFunction &OF,
|
|
InstructionMapper &Mapper);
|
|
|
|
/// Find potential outlining candidates and store them in \p CandidateList.
|
|
///
|
|
/// For each type of potential candidate, also build an \p OutlinedFunction
|
|
/// struct containing the information to build the function for that
|
|
/// candidate.
|
|
///
|
|
/// \param[out] CandidateList Filled with outlining candidates for the module.
|
|
/// \param[out] FunctionList Filled with functions corresponding to each type
|
|
/// of \p Candidate.
|
|
/// \param ST The suffix tree for the module.
|
|
/// \param TII TargetInstrInfo for the module.
|
|
///
|
|
/// \returns The length of the longest candidate found. 0 if there are none.
|
|
unsigned buildCandidateList(std::vector<Candidate> &CandidateList,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
SuffixTree &ST,
|
|
InstructionMapper &Mapper,
|
|
const TargetInstrInfo &TII);
|
|
|
|
/// \brief Remove any overlapping candidates that weren't handled by the
|
|
/// suffix tree's pruning method.
|
|
///
|
|
/// Pruning from the suffix tree doesn't necessarily remove all overlaps.
|
|
/// If a short candidate is chosen for outlining, then a longer candidate
|
|
/// which has that short candidate as a suffix is chosen, the tree's pruning
|
|
/// method will not find it. Thus, we need to prune before outlining as well.
|
|
///
|
|
/// \param[in,out] CandidateList A list of outlining candidates.
|
|
/// \param[in,out] FunctionList A list of functions to be outlined.
|
|
/// \param MaxCandidateLen The length of the longest candidate.
|
|
/// \param TII TargetInstrInfo for the module.
|
|
void pruneOverlaps(std::vector<Candidate> &CandidateList,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
unsigned MaxCandidateLen,
|
|
const TargetInstrInfo &TII);
|
|
|
|
/// Construct a suffix tree on the instructions in \p M and outline repeated
|
|
/// strings from that tree.
|
|
bool runOnModule(Module &M) override;
|
|
};
|
|
|
|
} // Anonymous namespace.
|
|
|
|
char MachineOutliner::ID = 0;
|
|
|
|
namespace llvm {
|
|
ModulePass *createMachineOutlinerPass() { return new MachineOutliner(); }
|
|
}
|
|
|
|
INITIALIZE_PASS(MachineOutliner, "machine-outliner",
|
|
"Machine Function Outliner", false, false)
|
|
|
|
void MachineOutliner::pruneOverlaps(std::vector<Candidate> &CandidateList,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
unsigned MaxCandidateLen,
|
|
const TargetInstrInfo &TII) {
|
|
|
|
// Check for overlaps in the range. This is O(n^2) worst case, but we can
|
|
// alleviate that somewhat by bounding our search space using the start
|
|
// index of our first candidate and the maximum distance an overlapping
|
|
// candidate could have from the first candidate.
|
|
for (auto It = CandidateList.begin(), Et = CandidateList.end(); It != Et;
|
|
It++) {
|
|
Candidate &C1 = *It;
|
|
OutlinedFunction &F1 = FunctionList[C1.FunctionIdx];
|
|
|
|
// If we removed this candidate, skip it.
|
|
if (!C1.InCandidateList)
|
|
continue;
|
|
|
|
// If the candidate's function isn't good to outline anymore, then
|
|
// remove the candidate and skip it.
|
|
if (F1.OccurrenceCount < 2 || F1.Benefit < 1) {
|
|
C1.InCandidateList = false;
|
|
continue;
|
|
}
|
|
|
|
// The minimum start index of any candidate that could overlap with this
|
|
// one.
|
|
unsigned FarthestPossibleIdx = 0;
|
|
|
|
// Either the index is 0, or it's at most MaxCandidateLen indices away.
|
|
if (C1.StartIdx > MaxCandidateLen)
|
|
FarthestPossibleIdx = C1.StartIdx - MaxCandidateLen;
|
|
|
|
// Compare against the other candidates in the list.
|
|
// This is at most MaxCandidateLen/2 other candidates.
|
|
// This is because each candidate has to be at least 2 indices away.
|
|
// = O(n * MaxCandidateLen/2) comparisons
|
|
//
|
|
// On average, the maximum length of a candidate is quite small; a fraction
|
|
// of the total module length in terms of instructions. If the maximum
|
|
// candidate length is large, then there are fewer possible candidates to
|
|
// compare against in the first place.
|
|
for (auto Sit = It + 1; Sit != Et; Sit++) {
|
|
Candidate &C2 = *Sit;
|
|
OutlinedFunction &F2 = FunctionList[C2.FunctionIdx];
|
|
|
|
// Is this candidate too far away to overlap?
|
|
// NOTE: This will be true in
|
|
// O(max(FarthestPossibleIdx/2, #Candidates remaining)) steps
|
|
// for every candidate.
|
|
if (C2.StartIdx < FarthestPossibleIdx)
|
|
break;
|
|
|
|
// Did we already remove this candidate in a previous step?
|
|
if (!C2.InCandidateList)
|
|
continue;
|
|
|
|
// Is the function beneficial to outline?
|
|
if (F2.OccurrenceCount < 2 || F2.Benefit < 1) {
|
|
// If not, remove this candidate and move to the next one.
|
|
C2.InCandidateList = false;
|
|
continue;
|
|
}
|
|
|
|
size_t C2End = C2.StartIdx + C2.Len - 1;
|
|
|
|
// Do C1 and C2 overlap?
|
|
//
|
|
// Not overlapping:
|
|
// High indices... [C1End ... C1Start][C2End ... C2Start] ...Low indices
|
|
//
|
|
// We sorted our candidate list so C2Start <= C1Start. We know that
|
|
// C2End > C2Start since each candidate has length >= 2. Therefore, all we
|
|
// have to check is C2End < C2Start to see if we overlap.
|
|
if (C2End < C1.StartIdx)
|
|
continue;
|
|
|
|
// C2 overlaps with C1. Because we pruned the tree already, the only way
|
|
// this can happen is if C1 is a proper suffix of C2. Thus, we must have
|
|
// found C1 first during our query, so it must have benefit greater or
|
|
// equal to C2. Greedily pick C1 as the candidate to keep and toss out C2.
|
|
DEBUG (
|
|
size_t C1End = C1.StartIdx + C1.Len - 1;
|
|
dbgs() << "- Found an overlap to purge.\n";
|
|
dbgs() << "--- C1 :[" << C1.StartIdx << ", " << C1End << "]\n";
|
|
dbgs() << "--- C2 :[" << C2.StartIdx << ", " << C2End << "]\n";
|
|
);
|
|
|
|
// Update the function's occurrence count and benefit to reflec that C2
|
|
// is being removed.
|
|
F2.OccurrenceCount--;
|
|
F2.Benefit = TII.getOutliningBenefit(F2.Sequence.size(),
|
|
F2.OccurrenceCount,
|
|
F2.IsTailCall
|
|
);
|
|
|
|
// Mark C2 as not in the list.
|
|
C2.InCandidateList = false;
|
|
|
|
DEBUG (
|
|
dbgs() << "- Removed C2. \n";
|
|
dbgs() << "--- Num fns left for C2: " << F2.OccurrenceCount << "\n";
|
|
dbgs() << "--- C2's benefit: " << F2.Benefit << "\n";
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
unsigned
|
|
MachineOutliner::buildCandidateList(std::vector<Candidate> &CandidateList,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
SuffixTree &ST,
|
|
InstructionMapper &Mapper,
|
|
const TargetInstrInfo &TII) {
|
|
|
|
std::vector<unsigned> CandidateSequence; // Current outlining candidate.
|
|
unsigned MaxCandidateLen = 0; // Length of the longest candidate.
|
|
|
|
// Function for maximizing query in the suffix tree.
|
|
// This allows us to define more fine-grained types of things to outline in
|
|
// the target without putting target-specific info in the suffix tree.
|
|
auto BenefitFn = [&TII, &ST, &Mapper](const SuffixTreeNode &Curr,
|
|
size_t StringLen) {
|
|
|
|
// Any leaf whose parent is the root only has one occurrence.
|
|
if (Curr.Parent->isRoot())
|
|
return 0u;
|
|
|
|
// Anything with length < 2 will never be beneficial on any target.
|
|
if (StringLen < 2)
|
|
return 0u;
|
|
|
|
size_t Occurrences = Curr.Parent->OccurrenceCount;
|
|
|
|
// Anything with fewer than 2 occurrences will never be beneficial on any
|
|
// target.
|
|
if (Occurrences < 2)
|
|
return 0u;
|
|
|
|
// Check if the last instruction in the sequence is a return.
|
|
MachineInstr *LastInstr =
|
|
Mapper.IntegerInstructionMap[ST[Curr.SuffixIdx + StringLen - 1]];
|
|
assert(LastInstr && "Last instruction in sequence was unmapped!");
|
|
|
|
// The only way a terminator could be mapped as legal is if it was safe to
|
|
// tail call.
|
|
bool IsTailCall = LastInstr->isTerminator();
|
|
|
|
return TII.getOutliningBenefit(StringLen, Occurrences, IsTailCall);
|
|
};
|
|
|
|
// Repeatedly query the suffix tree for the substring that maximizes
|
|
// BenefitFn. Find the occurrences of that string, prune the tree, and store
|
|
// each occurrence as a candidate.
|
|
for (ST.bestRepeatedSubstring(CandidateSequence, BenefitFn);
|
|
CandidateSequence.size() > 1;
|
|
ST.bestRepeatedSubstring(CandidateSequence, BenefitFn)) {
|
|
|
|
std::vector<size_t> Occurrences;
|
|
|
|
bool GotNonOverlappingCandidate =
|
|
ST.findOccurrencesAndPrune(CandidateSequence, Occurrences);
|
|
|
|
// Is the candidate we found known to overlap with something we already
|
|
// outlined?
|
|
if (!GotNonOverlappingCandidate)
|
|
continue;
|
|
|
|
// Is this candidate the longest so far?
|
|
if (CandidateSequence.size() > MaxCandidateLen)
|
|
MaxCandidateLen = CandidateSequence.size();
|
|
|
|
MachineInstr *LastInstr =
|
|
Mapper.IntegerInstructionMap[CandidateSequence.back()];
|
|
assert(LastInstr && "Last instruction in sequence was unmapped!");
|
|
|
|
// The only way a terminator could be mapped as legal is if it was safe to
|
|
// tail call.
|
|
bool IsTailCall = LastInstr->isTerminator();
|
|
|
|
// Keep track of the benefit of outlining this candidate in its
|
|
// OutlinedFunction.
|
|
unsigned FnBenefit = TII.getOutliningBenefit(CandidateSequence.size(),
|
|
Occurrences.size(),
|
|
IsTailCall
|
|
);
|
|
|
|
assert(FnBenefit > 0 && "Function cannot be unbeneficial!");
|
|
|
|
// Save an OutlinedFunction for this candidate.
|
|
FunctionList.emplace_back(
|
|
FunctionList.size(), // Number of this function.
|
|
Occurrences.size(), // Number of occurrences.
|
|
CandidateSequence, // Sequence to outline.
|
|
FnBenefit, // Instructions saved by outlining this function.
|
|
IsTailCall // Flag set if this function is to be tail called.
|
|
);
|
|
|
|
// Save each of the occurrences of the candidate so we can outline them.
|
|
for (size_t &Occ : Occurrences)
|
|
CandidateList.emplace_back(
|
|
Occ, // Starting idx in that MBB.
|
|
CandidateSequence.size(), // Candidate length.
|
|
FunctionList.size() - 1 // Idx of the corresponding function.
|
|
);
|
|
|
|
FunctionsCreated++;
|
|
}
|
|
|
|
// Sort the candidates in decending order. This will simplify the outlining
|
|
// process when we have to remove the candidates from the mapping by
|
|
// allowing us to cut them out without keeping track of an offset.
|
|
std::stable_sort(CandidateList.begin(), CandidateList.end());
|
|
|
|
return MaxCandidateLen;
|
|
}
|
|
|
|
MachineFunction *
|
|
MachineOutliner::createOutlinedFunction(Module &M, const OutlinedFunction &OF,
|
|
InstructionMapper &Mapper) {
|
|
|
|
// Create the function name. This should be unique. For now, just hash the
|
|
// module name and include it in the function name plus the number of this
|
|
// function.
|
|
std::ostringstream NameStream;
|
|
NameStream << "OUTLINED_FUNCTION" << "_" << OF.Name;
|
|
|
|
// Create the function using an IR-level function.
|
|
LLVMContext &C = M.getContext();
|
|
Function *F = dyn_cast<Function>(
|
|
M.getOrInsertFunction(NameStream.str(), Type::getVoidTy(C), nullptr));
|
|
assert(F && "Function was null!");
|
|
|
|
// NOTE: If this is linkonceodr, then we can take advantage of linker deduping
|
|
// which gives us better results when we outline from linkonceodr functions.
|
|
F->setLinkage(GlobalValue::PrivateLinkage);
|
|
F->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
|
|
|
|
BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
|
|
IRBuilder<> Builder(EntryBB);
|
|
Builder.CreateRetVoid();
|
|
|
|
MachineModuleInfo &MMI = getAnalysis<MachineModuleInfo>();
|
|
MachineFunction &MF = MMI.getMachineFunction(*F);
|
|
MachineBasicBlock &MBB = *MF.CreateMachineBasicBlock();
|
|
const TargetSubtargetInfo &STI = MF.getSubtarget();
|
|
const TargetInstrInfo &TII = *STI.getInstrInfo();
|
|
|
|
// Insert the new function into the module.
|
|
MF.insert(MF.begin(), &MBB);
|
|
|
|
TII.insertOutlinerPrologue(MBB, MF, OF.IsTailCall);
|
|
|
|
// Copy over the instructions for the function using the integer mappings in
|
|
// its sequence.
|
|
for (unsigned Str : OF.Sequence) {
|
|
MachineInstr *NewMI =
|
|
MF.CloneMachineInstr(Mapper.IntegerInstructionMap.find(Str)->second);
|
|
NewMI->dropMemRefs();
|
|
|
|
// Don't keep debug information for outlined instructions.
|
|
// FIXME: This means outlined functions are currently undebuggable.
|
|
NewMI->setDebugLoc(DebugLoc());
|
|
MBB.insert(MBB.end(), NewMI);
|
|
}
|
|
|
|
TII.insertOutlinerEpilogue(MBB, MF, OF.IsTailCall);
|
|
|
|
return &MF;
|
|
}
|
|
|
|
bool MachineOutliner::outline(Module &M,
|
|
const ArrayRef<Candidate> &CandidateList,
|
|
std::vector<OutlinedFunction> &FunctionList,
|
|
InstructionMapper &Mapper) {
|
|
|
|
bool OutlinedSomething = false;
|
|
|
|
// Replace the candidates with calls to their respective outlined functions.
|
|
for (const Candidate &C : CandidateList) {
|
|
|
|
// Was the candidate removed during pruneOverlaps?
|
|
if (!C.InCandidateList)
|
|
continue;
|
|
|
|
// If not, then look at its OutlinedFunction.
|
|
OutlinedFunction &OF = FunctionList[C.FunctionIdx];
|
|
|
|
// Was its OutlinedFunction made unbeneficial during pruneOverlaps?
|
|
if (OF.OccurrenceCount < 2 || OF.Benefit < 1)
|
|
continue;
|
|
|
|
// If not, then outline it.
|
|
assert(C.StartIdx < Mapper.InstrList.size() && "Candidate out of bounds!");
|
|
MachineBasicBlock *MBB = (*Mapper.InstrList[C.StartIdx]).getParent();
|
|
MachineBasicBlock::iterator StartIt = Mapper.InstrList[C.StartIdx];
|
|
unsigned EndIdx = C.StartIdx + C.Len - 1;
|
|
|
|
assert(EndIdx < Mapper.InstrList.size() && "Candidate out of bounds!");
|
|
MachineBasicBlock::iterator EndIt = Mapper.InstrList[EndIdx];
|
|
assert(EndIt != MBB->end() && "EndIt out of bounds!");
|
|
|
|
EndIt++; // Erase needs one past the end index.
|
|
|
|
// Does this candidate have a function yet?
|
|
if (!OF.MF)
|
|
OF.MF = createOutlinedFunction(M, OF, Mapper);
|
|
|
|
MachineFunction *MF = OF.MF;
|
|
const TargetSubtargetInfo &STI = MF->getSubtarget();
|
|
const TargetInstrInfo &TII = *STI.getInstrInfo();
|
|
|
|
// Insert a call to the new function and erase the old sequence.
|
|
TII.insertOutlinedCall(M, *MBB, StartIt, *MF, OF.IsTailCall);
|
|
StartIt = Mapper.InstrList[C.StartIdx];
|
|
MBB->erase(StartIt, EndIt);
|
|
|
|
OutlinedSomething = true;
|
|
|
|
// Statistics.
|
|
NumOutlined++;
|
|
}
|
|
|
|
DEBUG (
|
|
dbgs() << "OutlinedSomething = " << OutlinedSomething << "\n";
|
|
);
|
|
|
|
return OutlinedSomething;
|
|
}
|
|
|
|
bool MachineOutliner::runOnModule(Module &M) {
|
|
|
|
// Is there anything in the module at all?
|
|
if (M.empty())
|
|
return false;
|
|
|
|
MachineModuleInfo &MMI = getAnalysis<MachineModuleInfo>();
|
|
const TargetSubtargetInfo &STI = MMI.getMachineFunction(*M.begin())
|
|
.getSubtarget();
|
|
const TargetRegisterInfo *TRI = STI.getRegisterInfo();
|
|
const TargetInstrInfo *TII = STI.getInstrInfo();
|
|
|
|
InstructionMapper Mapper;
|
|
|
|
// Build instruction mappings for each function in the module.
|
|
for (Function &F : M) {
|
|
MachineFunction &MF = MMI.getMachineFunction(F);
|
|
|
|
// Is the function empty? Safe to outline from?
|
|
if (F.empty() || !TII->isFunctionSafeToOutlineFrom(MF))
|
|
continue;
|
|
|
|
// If it is, look at each MachineBasicBlock in the function.
|
|
for (MachineBasicBlock &MBB : MF) {
|
|
|
|
// Is there anything in MBB?
|
|
if (MBB.empty())
|
|
continue;
|
|
|
|
// If yes, map it.
|
|
Mapper.convertToUnsignedVec(MBB, *TRI, *TII);
|
|
}
|
|
}
|
|
|
|
// Construct a suffix tree, use it to find candidates, and then outline them.
|
|
SuffixTree ST(Mapper.UnsignedVec);
|
|
std::vector<Candidate> CandidateList;
|
|
std::vector<OutlinedFunction> FunctionList;
|
|
|
|
unsigned MaxCandidateLen =
|
|
buildCandidateList(CandidateList, FunctionList, ST, Mapper, *TII);
|
|
|
|
pruneOverlaps(CandidateList, FunctionList, MaxCandidateLen, *TII);
|
|
return outline(M, CandidateList, FunctionList, Mapper);
|
|
}
|