304 lines
11 KiB
C++
304 lines
11 KiB
C++
//===- Dominators.h - Dominator Info Calculation ----------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the DominatorTree class, which provides fast and efficient
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// dominance queries.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_IR_DOMINATORS_H
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#define LLVM_IR_DOMINATORS_H
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#include "llvm/ADT/DenseMapInfo.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/GraphTraits.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/GenericDomTree.h"
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#include <utility>
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namespace llvm {
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class Function;
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class Instruction;
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class Module;
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class raw_ostream;
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extern template class DomTreeNodeBase<BasicBlock>;
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extern template class DominatorTreeBase<BasicBlock, false>; // DomTree
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extern template class DominatorTreeBase<BasicBlock, true>; // PostDomTree
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extern template class cfg::Update<BasicBlock *>;
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namespace DomTreeBuilder {
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using BBDomTree = DomTreeBase<BasicBlock>;
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using BBPostDomTree = PostDomTreeBase<BasicBlock>;
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using BBUpdates = ArrayRef<llvm::cfg::Update<BasicBlock *>>;
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using BBDomTreeGraphDiff = GraphDiff<BasicBlock *, false>;
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using BBPostDomTreeGraphDiff = GraphDiff<BasicBlock *, true>;
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extern template void Calculate<BBDomTree>(BBDomTree &DT);
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extern template void CalculateWithUpdates<BBDomTree>(BBDomTree &DT,
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BBUpdates U);
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extern template void Calculate<BBPostDomTree>(BBPostDomTree &DT);
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extern template void InsertEdge<BBDomTree>(BBDomTree &DT, BasicBlock *From,
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BasicBlock *To);
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extern template void InsertEdge<BBPostDomTree>(BBPostDomTree &DT,
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BasicBlock *From,
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BasicBlock *To);
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extern template void DeleteEdge<BBDomTree>(BBDomTree &DT, BasicBlock *From,
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BasicBlock *To);
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extern template void DeleteEdge<BBPostDomTree>(BBPostDomTree &DT,
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BasicBlock *From,
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BasicBlock *To);
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extern template void ApplyUpdates<BBDomTree>(BBDomTree &DT,
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BBDomTreeGraphDiff &,
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BBDomTreeGraphDiff *);
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extern template void ApplyUpdates<BBPostDomTree>(BBPostDomTree &DT,
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BBPostDomTreeGraphDiff &,
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BBPostDomTreeGraphDiff *);
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extern template bool Verify<BBDomTree>(const BBDomTree &DT,
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BBDomTree::VerificationLevel VL);
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extern template bool Verify<BBPostDomTree>(const BBPostDomTree &DT,
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BBPostDomTree::VerificationLevel VL);
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} // namespace DomTreeBuilder
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using DomTreeNode = DomTreeNodeBase<BasicBlock>;
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class BasicBlockEdge {
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const BasicBlock *Start;
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const BasicBlock *End;
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public:
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BasicBlockEdge(const BasicBlock *Start_, const BasicBlock *End_) :
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Start(Start_), End(End_) {}
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BasicBlockEdge(const std::pair<BasicBlock *, BasicBlock *> &Pair)
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: Start(Pair.first), End(Pair.second) {}
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BasicBlockEdge(const std::pair<const BasicBlock *, const BasicBlock *> &Pair)
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: Start(Pair.first), End(Pair.second) {}
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const BasicBlock *getStart() const {
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return Start;
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}
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const BasicBlock *getEnd() const {
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return End;
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}
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/// Check if this is the only edge between Start and End.
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bool isSingleEdge() const;
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};
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template <> struct DenseMapInfo<BasicBlockEdge> {
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using BBInfo = DenseMapInfo<const BasicBlock *>;
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static unsigned getHashValue(const BasicBlockEdge *V);
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static inline BasicBlockEdge getEmptyKey() {
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return BasicBlockEdge(BBInfo::getEmptyKey(), BBInfo::getEmptyKey());
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}
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static inline BasicBlockEdge getTombstoneKey() {
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return BasicBlockEdge(BBInfo::getTombstoneKey(), BBInfo::getTombstoneKey());
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}
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static unsigned getHashValue(const BasicBlockEdge &Edge) {
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return hash_combine(BBInfo::getHashValue(Edge.getStart()),
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BBInfo::getHashValue(Edge.getEnd()));
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}
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static bool isEqual(const BasicBlockEdge &LHS, const BasicBlockEdge &RHS) {
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return BBInfo::isEqual(LHS.getStart(), RHS.getStart()) &&
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BBInfo::isEqual(LHS.getEnd(), RHS.getEnd());
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}
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};
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/// Concrete subclass of DominatorTreeBase that is used to compute a
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/// normal dominator tree.
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///
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/// Definition: A block is said to be forward statically reachable if there is
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/// a path from the entry of the function to the block. A statically reachable
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/// block may become statically unreachable during optimization.
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///
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/// A forward unreachable block may appear in the dominator tree, or it may
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/// not. If it does, dominance queries will return results as if all reachable
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/// blocks dominate it. When asking for a Node corresponding to a potentially
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/// unreachable block, calling code must handle the case where the block was
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/// unreachable and the result of getNode() is nullptr.
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///
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/// Generally, a block known to be unreachable when the dominator tree is
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/// constructed will not be in the tree. One which becomes unreachable after
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/// the dominator tree is initially constructed may still exist in the tree,
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/// even if the tree is properly updated. Calling code should not rely on the
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/// preceding statements; this is stated only to assist human understanding.
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class DominatorTree : public DominatorTreeBase<BasicBlock, false> {
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public:
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using Base = DominatorTreeBase<BasicBlock, false>;
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DominatorTree() = default;
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explicit DominatorTree(Function &F) { recalculate(F); }
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explicit DominatorTree(DominatorTree &DT, DomTreeBuilder::BBUpdates U) {
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recalculate(*DT.Parent, U);
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}
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/// Handle invalidation explicitly.
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bool invalidate(Function &F, const PreservedAnalyses &PA,
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FunctionAnalysisManager::Invalidator &);
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// Ensure base-class overloads are visible.
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using Base::dominates;
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/// Return true if value Def dominates use U, in the sense that Def is
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/// available at U, and could be substituted as the used value without
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/// violating the SSA dominance requirement.
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///
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/// In particular, it is worth noting that:
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/// * Non-instruction Defs dominate everything.
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/// * Def does not dominate a use in Def itself (outside of degenerate cases
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/// like unreachable code or trivial phi cycles).
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/// * Invoke/callbr Defs only dominate uses in their default destination.
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bool dominates(const Value *Def, const Use &U) const;
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/// Return true if value Def dominates all possible uses inside instruction
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/// User. Same comments as for the Use-based API apply.
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bool dominates(const Value *Def, const Instruction *User) const;
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// Does not accept Value to avoid ambiguity with dominance checks between
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// two basic blocks.
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bool dominates(const Instruction *Def, const BasicBlock *BB) const;
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/// Return true if an edge dominates a use.
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///
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/// If BBE is not a unique edge between start and end of the edge, it can
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/// never dominate the use.
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bool dominates(const BasicBlockEdge &BBE, const Use &U) const;
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bool dominates(const BasicBlockEdge &BBE, const BasicBlock *BB) const;
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/// Returns true if edge \p BBE1 dominates edge \p BBE2.
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bool dominates(const BasicBlockEdge &BBE1, const BasicBlockEdge &BBE2) const;
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// Ensure base class overloads are visible.
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using Base::isReachableFromEntry;
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/// Provide an overload for a Use.
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bool isReachableFromEntry(const Use &U) const;
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// Pop up a GraphViz/gv window with the Dominator Tree rendered using `dot`.
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void viewGraph(const Twine &Name, const Twine &Title);
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void viewGraph();
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};
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//===-------------------------------------
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// DominatorTree GraphTraits specializations so the DominatorTree can be
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// iterable by generic graph iterators.
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template <class Node, class ChildIterator> struct DomTreeGraphTraitsBase {
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using NodeRef = Node *;
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using ChildIteratorType = ChildIterator;
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using nodes_iterator = df_iterator<Node *, df_iterator_default_set<Node*>>;
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static NodeRef getEntryNode(NodeRef N) { return N; }
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static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
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static ChildIteratorType child_end(NodeRef N) { return N->end(); }
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static nodes_iterator nodes_begin(NodeRef N) {
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return df_begin(getEntryNode(N));
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}
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static nodes_iterator nodes_end(NodeRef N) { return df_end(getEntryNode(N)); }
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};
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template <>
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struct GraphTraits<DomTreeNode *>
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: public DomTreeGraphTraitsBase<DomTreeNode, DomTreeNode::const_iterator> {
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};
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template <>
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struct GraphTraits<const DomTreeNode *>
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: public DomTreeGraphTraitsBase<const DomTreeNode,
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DomTreeNode::const_iterator> {};
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template <> struct GraphTraits<DominatorTree*>
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: public GraphTraits<DomTreeNode*> {
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static NodeRef getEntryNode(DominatorTree *DT) { return DT->getRootNode(); }
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static nodes_iterator nodes_begin(DominatorTree *N) {
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return df_begin(getEntryNode(N));
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}
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static nodes_iterator nodes_end(DominatorTree *N) {
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return df_end(getEntryNode(N));
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}
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};
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/// Analysis pass which computes a \c DominatorTree.
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class DominatorTreeAnalysis : public AnalysisInfoMixin<DominatorTreeAnalysis> {
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friend AnalysisInfoMixin<DominatorTreeAnalysis>;
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static AnalysisKey Key;
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public:
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/// Provide the result typedef for this analysis pass.
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using Result = DominatorTree;
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/// Run the analysis pass over a function and produce a dominator tree.
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DominatorTree run(Function &F, FunctionAnalysisManager &);
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};
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/// Printer pass for the \c DominatorTree.
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class DominatorTreePrinterPass
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: public PassInfoMixin<DominatorTreePrinterPass> {
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raw_ostream &OS;
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public:
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explicit DominatorTreePrinterPass(raw_ostream &OS);
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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};
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/// Verifier pass for the \c DominatorTree.
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struct DominatorTreeVerifierPass : PassInfoMixin<DominatorTreeVerifierPass> {
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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};
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/// Legacy analysis pass which computes a \c DominatorTree.
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class DominatorTreeWrapperPass : public FunctionPass {
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DominatorTree DT;
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public:
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static char ID;
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DominatorTreeWrapperPass();
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DominatorTree &getDomTree() { return DT; }
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const DominatorTree &getDomTree() const { return DT; }
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bool runOnFunction(Function &F) override;
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void verifyAnalysis() const override;
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesAll();
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}
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void releaseMemory() override { DT.reset(); }
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void print(raw_ostream &OS, const Module *M = nullptr) const override;
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};
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} // end namespace llvm
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#endif // LLVM_IR_DOMINATORS_H
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