1//=- llvm/CodeGen/MachineDominators.h - Machine Dom Calculation --*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines classes mirroring those in llvm/Analysis/Dominators.h,
11// but for target-specific code rather than target-independent IR.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CODEGEN_MACHINEDOMINATORS_H
16#define LLVM_CODEGEN_MACHINEDOMINATORS_H
17
18#include "llvm/ADT/SmallSet.h"
19#include "llvm/CodeGen/MachineBasicBlock.h"
20#include "llvm/CodeGen/MachineFunction.h"
21#include "llvm/CodeGen/MachineFunctionPass.h"
22#include "llvm/Support/GenericDomTree.h"
23#include "llvm/Support/GenericDomTreeConstruction.h"
24
25namespace llvm {
26
27template<>
28inline void DominatorTreeBase<MachineBasicBlock>::addRoot(MachineBasicBlock* MBB) {
29  this->Roots.push_back(MBB);
30}
31
32EXTERN_TEMPLATE_INSTANTIATION(class DomTreeNodeBase<MachineBasicBlock>);
33EXTERN_TEMPLATE_INSTANTIATION(class DominatorTreeBase<MachineBasicBlock>);
34
35typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
36
37//===-------------------------------------
38/// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
39/// compute a normal dominator tree.
40///
41class MachineDominatorTree : public MachineFunctionPass {
42  /// \brief Helper structure used to hold all the basic blocks
43  /// involved in the split of a critical edge.
44  struct CriticalEdge {
45    MachineBasicBlock *FromBB;
46    MachineBasicBlock *ToBB;
47    MachineBasicBlock *NewBB;
48  };
49
50  /// \brief Pile up all the critical edges to be split.
51  /// The splitting of a critical edge is local and thus, it is possible
52  /// to apply several of those changes at the same time.
53  mutable SmallVector<CriticalEdge, 32> CriticalEdgesToSplit;
54  /// \brief Remember all the basic blocks that are inserted during
55  /// edge splitting.
56  /// Invariant: NewBBs == all the basic blocks contained in the NewBB
57  /// field of all the elements of CriticalEdgesToSplit.
58  /// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs
59  /// such as BB == elt.NewBB.
60  mutable SmallSet<MachineBasicBlock *, 32> NewBBs;
61
62  /// \brief Apply all the recorded critical edges to the DT.
63  /// This updates the underlying DT information in a way that uses
64  /// the fast query path of DT as much as possible.
65  ///
66  /// \post CriticalEdgesToSplit.empty().
67  void applySplitCriticalEdges() const;
68
69public:
70  static char ID; // Pass ID, replacement for typeid
71  DominatorTreeBase<MachineBasicBlock>* DT;
72
73  MachineDominatorTree();
74
75  ~MachineDominatorTree() override;
76
77  DominatorTreeBase<MachineBasicBlock> &getBase() {
78    applySplitCriticalEdges();
79    return *DT;
80  }
81
82  void getAnalysisUsage(AnalysisUsage &AU) const override;
83
84  /// getRoots -  Return the root blocks of the current CFG.  This may include
85  /// multiple blocks if we are computing post dominators.  For forward
86  /// dominators, this will always be a single block (the entry node).
87  ///
88  inline const std::vector<MachineBasicBlock*> &getRoots() const {
89    applySplitCriticalEdges();
90    return DT->getRoots();
91  }
92
93  inline MachineBasicBlock *getRoot() const {
94    applySplitCriticalEdges();
95    return DT->getRoot();
96  }
97
98  inline MachineDomTreeNode *getRootNode() const {
99    applySplitCriticalEdges();
100    return DT->getRootNode();
101  }
102
103  bool runOnMachineFunction(MachineFunction &F) override;
104
105  inline bool dominates(const MachineDomTreeNode* A,
106                        const MachineDomTreeNode* B) const {
107    applySplitCriticalEdges();
108    return DT->dominates(A, B);
109  }
110
111  inline bool dominates(const MachineBasicBlock* A,
112                        const MachineBasicBlock* B) const {
113    applySplitCriticalEdges();
114    return DT->dominates(A, B);
115  }
116
117  // dominates - Return true if A dominates B. This performs the
118  // special checks necessary if A and B are in the same basic block.
119  bool dominates(const MachineInstr *A, const MachineInstr *B) const {
120    applySplitCriticalEdges();
121    const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent();
122    if (BBA != BBB) return DT->dominates(BBA, BBB);
123
124    // Loop through the basic block until we find A or B.
125    MachineBasicBlock::const_iterator I = BBA->begin();
126    for (; &*I != A && &*I != B; ++I)
127      /*empty*/ ;
128
129    //if(!DT.IsPostDominators) {
130      // A dominates B if it is found first in the basic block.
131      return &*I == A;
132    //} else {
133    //  // A post-dominates B if B is found first in the basic block.
134    //  return &*I == B;
135    //}
136  }
137
138  inline bool properlyDominates(const MachineDomTreeNode* A,
139                                const MachineDomTreeNode* B) const {
140    applySplitCriticalEdges();
141    return DT->properlyDominates(A, B);
142  }
143
144  inline bool properlyDominates(const MachineBasicBlock* A,
145                                const MachineBasicBlock* B) const {
146    applySplitCriticalEdges();
147    return DT->properlyDominates(A, B);
148  }
149
150  /// findNearestCommonDominator - Find nearest common dominator basic block
151  /// for basic block A and B. If there is no such block then return NULL.
152  inline MachineBasicBlock *findNearestCommonDominator(MachineBasicBlock *A,
153                                                       MachineBasicBlock *B) {
154    applySplitCriticalEdges();
155    return DT->findNearestCommonDominator(A, B);
156  }
157
158  inline MachineDomTreeNode *operator[](MachineBasicBlock *BB) const {
159    applySplitCriticalEdges();
160    return DT->getNode(BB);
161  }
162
163  /// getNode - return the (Post)DominatorTree node for the specified basic
164  /// block.  This is the same as using operator[] on this class.
165  ///
166  inline MachineDomTreeNode *getNode(MachineBasicBlock *BB) const {
167    applySplitCriticalEdges();
168    return DT->getNode(BB);
169  }
170
171  /// addNewBlock - Add a new node to the dominator tree information.  This
172  /// creates a new node as a child of DomBB dominator node,linking it into
173  /// the children list of the immediate dominator.
174  inline MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB,
175                                         MachineBasicBlock *DomBB) {
176    applySplitCriticalEdges();
177    return DT->addNewBlock(BB, DomBB);
178  }
179
180  /// changeImmediateDominator - This method is used to update the dominator
181  /// tree information when a node's immediate dominator changes.
182  ///
183  inline void changeImmediateDominator(MachineBasicBlock *N,
184                                       MachineBasicBlock* NewIDom) {
185    applySplitCriticalEdges();
186    DT->changeImmediateDominator(N, NewIDom);
187  }
188
189  inline void changeImmediateDominator(MachineDomTreeNode *N,
190                                       MachineDomTreeNode* NewIDom) {
191    applySplitCriticalEdges();
192    DT->changeImmediateDominator(N, NewIDom);
193  }
194
195  /// eraseNode - Removes a node from  the dominator tree. Block must not
196  /// dominate any other blocks. Removes node from its immediate dominator's
197  /// children list. Deletes dominator node associated with basic block BB.
198  inline void eraseNode(MachineBasicBlock *BB) {
199    applySplitCriticalEdges();
200    DT->eraseNode(BB);
201  }
202
203  /// splitBlock - BB is split and now it has one successor. Update dominator
204  /// tree to reflect this change.
205  inline void splitBlock(MachineBasicBlock* NewBB) {
206    applySplitCriticalEdges();
207    DT->splitBlock(NewBB);
208  }
209
210  /// isReachableFromEntry - Return true if A is dominated by the entry
211  /// block of the function containing it.
212  bool isReachableFromEntry(const MachineBasicBlock *A) {
213    applySplitCriticalEdges();
214    return DT->isReachableFromEntry(A);
215  }
216
217  void releaseMemory() override;
218
219  void print(raw_ostream &OS, const Module*) const override;
220
221  /// \brief Record that the critical edge (FromBB, ToBB) has been
222  /// split with NewBB.
223  /// This is best to use this method instead of directly update the
224  /// underlying information, because this helps mitigating the
225  /// number of time the DT information is invalidated.
226  ///
227  /// \note Do not use this method with regular edges.
228  ///
229  /// \note To benefit from the compile time improvement incurred by this
230  /// method, the users of this method have to limit the queries to the DT
231  /// interface between two edges splitting. In other words, they have to
232  /// pack the splitting of critical edges as much as possible.
233  void recordSplitCriticalEdge(MachineBasicBlock *FromBB,
234                              MachineBasicBlock *ToBB,
235                              MachineBasicBlock *NewBB) {
236    bool Inserted = NewBBs.insert(NewBB).second;
237    (void)Inserted;
238    assert(Inserted &&
239           "A basic block inserted via edge splitting cannot appear twice");
240    CriticalEdgesToSplit.push_back({FromBB, ToBB, NewBB});
241  }
242};
243
244//===-------------------------------------
245/// DominatorTree GraphTraits specialization so the DominatorTree can be
246/// iterable by generic graph iterators.
247///
248
249template<class T> struct GraphTraits;
250
251template <> struct GraphTraits<MachineDomTreeNode *> {
252  typedef MachineDomTreeNode NodeType;
253  typedef NodeType::iterator  ChildIteratorType;
254
255  static NodeType *getEntryNode(NodeType *N) {
256    return N;
257  }
258  static inline ChildIteratorType child_begin(NodeType* N) {
259    return N->begin();
260  }
261  static inline ChildIteratorType child_end(NodeType* N) {
262    return N->end();
263  }
264};
265
266template <> struct GraphTraits<MachineDominatorTree*>
267  : public GraphTraits<MachineDomTreeNode *> {
268  static NodeType *getEntryNode(MachineDominatorTree *DT) {
269    return DT->getRootNode();
270  }
271};
272
273}
274
275#endif
276