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MachineDominators.h
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1 //==- llvm/CodeGen/MachineDominators.h - Machine Dom Calculation -*- C++ -*-==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines classes mirroring those in llvm/Analysis/Dominators.h,
10 // but for target-specific code rather than target-independent IR.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CODEGEN_MACHINEDOMINATORS_H
15 #define LLVM_CODEGEN_MACHINEDOMINATORS_H
16 
17 #include "llvm/ADT/SmallSet.h"
18 #include "llvm/ADT/SmallVector.h"
24 #include <cassert>
25 #include <memory>
26 #include <vector>
27 
28 namespace llvm {
29 
30 template <>
32  MachineBasicBlock *MBB) {
33  this->Roots.push_back(MBB);
34 }
35 
36 extern template class DomTreeNodeBase<MachineBasicBlock>;
37 extern template class DominatorTreeBase<MachineBasicBlock, false>; // DomTree
38 extern template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTree
39 
41 
42 //===-------------------------------------
43 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
44 /// compute a normal dominator tree.
45 ///
48 
49  /// Helper structure used to hold all the basic blocks
50  /// involved in the split of a critical edge.
51  struct CriticalEdge {
52  MachineBasicBlock *FromBB;
53  MachineBasicBlock *ToBB;
54  MachineBasicBlock *NewBB;
55  };
56 
57  /// Pile up all the critical edges to be split.
58  /// The splitting of a critical edge is local and thus, it is possible
59  /// to apply several of those changes at the same time.
60  mutable SmallVector<CriticalEdge, 32> CriticalEdgesToSplit;
61 
62  /// Remember all the basic blocks that are inserted during
63  /// edge splitting.
64  /// Invariant: NewBBs == all the basic blocks contained in the NewBB
65  /// field of all the elements of CriticalEdgesToSplit.
66  /// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs
67  /// such as BB == elt.NewBB.
68  mutable SmallSet<MachineBasicBlock *, 32> NewBBs;
69 
70  /// The DominatorTreeBase that is used to compute a normal dominator tree.
71  std::unique_ptr<DomTreeT> DT;
72 
73  /// Apply all the recorded critical edges to the DT.
74  /// This updates the underlying DT information in a way that uses
75  /// the fast query path of DT as much as possible.
76  ///
77  /// \post CriticalEdgesToSplit.empty().
78  void applySplitCriticalEdges() const;
79 
80 public:
81  static char ID; // Pass ID, replacement for typeid
82 
85  calculate(MF);
86  }
87 
89  if (!DT) DT.reset(new DomTreeT());
90  applySplitCriticalEdges();
91  return *DT;
92  }
93 
94  void getAnalysisUsage(AnalysisUsage &AU) const override;
95 
96  /// getRoots - Return the root blocks of the current CFG. This may include
97  /// multiple blocks if we are computing post dominators. For forward
98  /// dominators, this will always be a single block (the entry node).
99  ///
101  applySplitCriticalEdges();
102  return DT->getRoots();
103  }
104 
106  applySplitCriticalEdges();
107  return DT->getRoot();
108  }
109 
111  applySplitCriticalEdges();
112  return DT->getRootNode();
113  }
114 
115  bool runOnMachineFunction(MachineFunction &F) override;
116 
117  void calculate(MachineFunction &F);
118 
120  const MachineDomTreeNode *B) const {
121  applySplitCriticalEdges();
122  return DT->dominates(A, B);
123  }
124 
125  bool dominates(const MachineBasicBlock *A, const MachineBasicBlock *B) const {
126  applySplitCriticalEdges();
127  return DT->dominates(A, B);
128  }
129 
130  // dominates - Return true if A dominates B. This performs the
131  // special checks necessary if A and B are in the same basic block.
132  bool dominates(const MachineInstr *A, const MachineInstr *B) const {
133  applySplitCriticalEdges();
134  const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent();
135  if (BBA != BBB) return DT->dominates(BBA, BBB);
136 
137  // Loop through the basic block until we find A or B.
139  for (; &*I != A && &*I != B; ++I)
140  /*empty*/ ;
141 
142  return &*I == A;
143  }
144 
146  const MachineDomTreeNode *B) const {
147  applySplitCriticalEdges();
148  return DT->properlyDominates(A, B);
149  }
150 
152  const MachineBasicBlock *B) const {
153  applySplitCriticalEdges();
154  return DT->properlyDominates(A, B);
155  }
156 
157  /// findNearestCommonDominator - Find nearest common dominator basic block
158  /// for basic block A and B. If there is no such block then return NULL.
160  MachineBasicBlock *B) {
161  applySplitCriticalEdges();
162  return DT->findNearestCommonDominator(A, B);
163  }
164 
166  applySplitCriticalEdges();
167  return DT->getNode(BB);
168  }
169 
170  /// getNode - return the (Post)DominatorTree node for the specified basic
171  /// block. This is the same as using operator[] on this class.
172  ///
174  applySplitCriticalEdges();
175  return DT->getNode(BB);
176  }
177 
178  /// addNewBlock - Add a new node to the dominator tree information. This
179  /// creates a new node as a child of DomBB dominator node,linking it into
180  /// the children list of the immediate dominator.
182  MachineBasicBlock *DomBB) {
183  applySplitCriticalEdges();
184  return DT->addNewBlock(BB, DomBB);
185  }
186 
187  /// changeImmediateDominator - This method is used to update the dominator
188  /// tree information when a node's immediate dominator changes.
189  ///
191  MachineBasicBlock *NewIDom) {
192  applySplitCriticalEdges();
193  DT->changeImmediateDominator(N, NewIDom);
194  }
195 
197  MachineDomTreeNode *NewIDom) {
198  applySplitCriticalEdges();
199  DT->changeImmediateDominator(N, NewIDom);
200  }
201 
202  /// eraseNode - Removes a node from the dominator tree. Block must not
203  /// dominate any other blocks. Removes node from its immediate dominator's
204  /// children list. Deletes dominator node associated with basic block BB.
206  applySplitCriticalEdges();
207  DT->eraseNode(BB);
208  }
209 
210  /// splitBlock - BB is split and now it has one successor. Update dominator
211  /// tree to reflect this change.
213  applySplitCriticalEdges();
214  DT->splitBlock(NewBB);
215  }
216 
217  /// isReachableFromEntry - Return true if A is dominated by the entry
218  /// block of the function containing it.
220  applySplitCriticalEdges();
221  return DT->isReachableFromEntry(A);
222  }
223 
224  void releaseMemory() override;
225 
226  void verifyAnalysis() const override;
227 
228  void print(raw_ostream &OS, const Module*) const override;
229 
230  /// Record that the critical edge (FromBB, ToBB) has been
231  /// split with NewBB.
232  /// This is best to use this method instead of directly update the
233  /// underlying information, because this helps mitigating the
234  /// number of time the DT information is invalidated.
235  ///
236  /// \note Do not use this method with regular edges.
237  ///
238  /// \note To benefit from the compile time improvement incurred by this
239  /// method, the users of this method have to limit the queries to the DT
240  /// interface between two edges splitting. In other words, they have to
241  /// pack the splitting of critical edges as much as possible.
243  MachineBasicBlock *ToBB,
244  MachineBasicBlock *NewBB) {
245  bool Inserted = NewBBs.insert(NewBB).second;
246  (void)Inserted;
247  assert(Inserted &&
248  "A basic block inserted via edge splitting cannot appear twice");
249  CriticalEdgesToSplit.push_back({FromBB, ToBB, NewBB});
250  }
251 };
252 
253 //===-------------------------------------
254 /// DominatorTree GraphTraits specialization so the DominatorTree can be
255 /// iterable by generic graph iterators.
256 ///
257 
258 template <class Node, class ChildIterator>
260  using NodeRef = Node *;
261  using ChildIteratorType = ChildIterator;
262 
263  static NodeRef getEntryNode(NodeRef N) { return N; }
264  static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
265  static ChildIteratorType child_end(NodeRef N) { return N->end(); }
266 };
267 
268 template <class T> struct GraphTraits;
269 
270 template <>
274 
275 template <>
276 struct GraphTraits<const MachineDomTreeNode *>
279 };
280 
281 template <> struct GraphTraits<MachineDominatorTree*>
284  return DT->getRootNode();
285  }
286 };
287 
288 } // end namespace llvm
289 
290 #endif // LLVM_CODEGEN_MACHINEDOMINATORS_H
MachineBasicBlock * getRoot() const
typename std::vector< DomTreeNodeBase * >::const_iterator const_iterator
MachineDomTreeNode * getNode(MachineBasicBlock *BB) const
getNode - return the (Post)DominatorTree node for the specified basic block.
This class represents lattice values for constants.
Definition: AllocatorList.h:23
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:65
void push_back(const T &Elt)
Definition: SmallVector.h:211
F(f)
void eraseNode(MachineBasicBlock *BB)
eraseNode - Removes a node from the dominator tree.
void splitBlock(MachineBasicBlock *NewBB)
splitBlock - BB is split and now it has one successor.
const SmallVectorImpl< MachineBasicBlock * > & getRoots() const
getRoots - Return the root blocks of the current CFG.
bool dominates(const MachineBasicBlock *A, const MachineBasicBlock *B) const
DomTreeNodeBase< MachineBasicBlock > MachineDomTreeNode
Definition: LiveRangeCalc.h:42
static NodeRef getEntryNode(NodeRef N)
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
MachineDomTreeNode * operator[](MachineBasicBlock *BB) const
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:41
void addRoot(NodeT *BB)
MachineDominatorTree(MachineFunction &MF)
static ChildIteratorType child_end(NodeRef N)
Base class for the actual dominator tree node.
Definition: LiveRangeCalc.h:37
MachineBasicBlock * findNearestCommonDominator(MachineBasicBlock *A, MachineBasicBlock *B)
findNearestCommonDominator - Find nearest common dominator basic block for basic block A and B...
Core dominator tree base class.
Definition: LoopInfo.h:66
void recordSplitCriticalEdge(MachineBasicBlock *FromBB, MachineBasicBlock *ToBB, MachineBasicBlock *NewBB)
Record that the critical edge (FromBB, ToBB) has been split with NewBB.
typename MachineDomTreeNode *::UnknownGraphTypeError NodeRef
Definition: GraphTraits.h:78
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:134
Represent the analysis usage information of a pass.
static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val)
std::pair< NoneType, bool > insert(const T &V)
insert - Insert an element into the set if it isn&#39;t already there.
Definition: SmallSet.h:180
void changeImmediateDominator(MachineDomTreeNode *N, MachineDomTreeNode *NewIDom)
bool properlyDominates(const MachineBasicBlock *A, const MachineBasicBlock *B) const
bool dominates(const MachineInstr *A, const MachineInstr *B) const
Generic dominator tree construction - This file provides routines to construct immediate dominator in...
static NodeRef getEntryNode(MachineDominatorTree *DT)
MachineDomTreeNode * getRootNode() const
bool dominates(const MachineDomTreeNode *A, const MachineDomTreeNode *B) const
static ChildIteratorType child_begin(NodeRef N)
bool properlyDominates(const MachineDomTreeNode *A, const MachineDomTreeNode *B) const
const MachineBasicBlock * getParent() const
Definition: MachineInstr.h:255
Representation of each machine instruction.
Definition: MachineInstr.h:63
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
DominatorTree GraphTraits specialization so the DominatorTree can be iterable by generic graph iterat...
void changeImmediateDominator(MachineBasicBlock *N, MachineBasicBlock *NewIDom)
changeImmediateDominator - This method is used to update the dominator tree information when a node&#39;s...
bool isReachableFromEntry(const MachineBasicBlock *A)
isReachableFromEntry - Return true if A is dominated by the entry block of the function containing it...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
aarch64 promote const
typename std::vector< DomTreeNodeBase * >::iterator iterator
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
This file defines a set of templates that efficiently compute a dominator tree over a generic graph...
MachineDomTreeNode * addNewBlock(MachineBasicBlock *BB, MachineBasicBlock *DomBB)
addNewBlock - Add a new node to the dominator tree information.
DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to compute a normal dominat...