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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/ADT/SmallVector.h"
20 : #include "llvm/CodeGen/MachineBasicBlock.h"
21 : #include "llvm/CodeGen/MachineFunctionPass.h"
22 : #include "llvm/CodeGen/MachineInstr.h"
23 : #include "llvm/Support/GenericDomTree.h"
24 : #include "llvm/Support/GenericDomTreeConstruction.h"
25 : #include <cassert>
26 : #include <memory>
27 : #include <vector>
28 :
29 : namespace llvm {
30 :
31 : template <>
32 : inline void DominatorTreeBase<MachineBasicBlock, false>::addRoot(
33 : MachineBasicBlock *MBB) {
34 0 : this->Roots.push_back(MBB);
35 : }
36 :
37 : extern template class DomTreeNodeBase<MachineBasicBlock>;
38 : extern template class DominatorTreeBase<MachineBasicBlock, false>; // DomTree
39 : extern template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTree
40 :
41 : using MachineDomTreeNode = DomTreeNodeBase<MachineBasicBlock>;
42 :
43 : //===-------------------------------------
44 : /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
45 : /// compute a normal dominator tree.
46 : ///
47 : class MachineDominatorTree : public MachineFunctionPass {
48 : /// Helper structure used to hold all the basic blocks
49 : /// involved in the split of a critical edge.
50 : struct CriticalEdge {
51 : MachineBasicBlock *FromBB;
52 : MachineBasicBlock *ToBB;
53 : MachineBasicBlock *NewBB;
54 : };
55 :
56 : /// Pile up all the critical edges to be split.
57 : /// The splitting of a critical edge is local and thus, it is possible
58 : /// to apply several of those changes at the same time.
59 : mutable SmallVector<CriticalEdge, 32> CriticalEdgesToSplit;
60 :
61 : /// Remember all the basic blocks that are inserted during
62 : /// edge splitting.
63 : /// Invariant: NewBBs == all the basic blocks contained in the NewBB
64 : /// field of all the elements of CriticalEdgesToSplit.
65 : /// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs
66 : /// such as BB == elt.NewBB.
67 : mutable SmallSet<MachineBasicBlock *, 32> NewBBs;
68 :
69 : /// The DominatorTreeBase that is used to compute a normal dominator tree
70 : std::unique_ptr<DomTreeBase<MachineBasicBlock>> DT;
71 :
72 : /// Apply all the recorded critical edges to the DT.
73 : /// This updates the underlying DT information in a way that uses
74 : /// the fast query path of DT as much as possible.
75 : ///
76 : /// \post CriticalEdgesToSplit.empty().
77 : void applySplitCriticalEdges() const;
78 :
79 : public:
80 : static char ID; // Pass ID, replacement for typeid
81 :
82 : MachineDominatorTree();
83 :
84 1362070 : DomTreeBase<MachineBasicBlock> &getBase() {
85 1362070 : if (!DT) DT.reset(new DomTreeBase<MachineBasicBlock>());
86 1362070 : applySplitCriticalEdges();
87 1362070 : return *DT;
88 : }
89 :
90 : void getAnalysisUsage(AnalysisUsage &AU) const override;
91 :
92 : /// getRoots - Return the root blocks of the current CFG. This may include
93 : /// multiple blocks if we are computing post dominators. For forward
94 : /// dominators, this will always be a single block (the entry node).
95 : ///
96 : inline const SmallVectorImpl<MachineBasicBlock*> &getRoots() const {
97 : applySplitCriticalEdges();
98 : return DT->getRoots();
99 : }
100 :
101 : inline MachineBasicBlock *getRoot() const {
102 3285 : applySplitCriticalEdges();
103 : return DT->getRoot();
104 : }
105 :
106 : inline MachineDomTreeNode *getRootNode() const {
107 307640 : applySplitCriticalEdges();
108 307640 : return DT->getRootNode();
109 : }
110 :
111 : bool runOnMachineFunction(MachineFunction &F) override;
112 :
113 : inline bool dominates(const MachineDomTreeNode* A,
114 : const MachineDomTreeNode* B) const {
115 32988 : applySplitCriticalEdges();
116 32988 : return DT->dominates(A, B);
117 : }
118 :
119 : inline bool dominates(const MachineBasicBlock* A,
120 : const MachineBasicBlock* B) const {
121 87719 : applySplitCriticalEdges();
122 87719 : return DT->dominates(A, B);
123 : }
124 :
125 : // dominates - Return true if A dominates B. This performs the
126 : // special checks necessary if A and B are in the same basic block.
127 57916 : bool dominates(const MachineInstr *A, const MachineInstr *B) const {
128 57916 : applySplitCriticalEdges();
129 57916 : const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent();
130 57916 : if (BBA != BBB) return DT->dominates(BBA, BBB);
131 :
132 : // Loop through the basic block until we find A or B.
133 : MachineBasicBlock::const_iterator I = BBA->begin();
134 14077319 : for (; &*I != A && &*I != B; ++I)
135 : /*empty*/ ;
136 :
137 : //if(!DT.IsPostDominators) {
138 : // A dominates B if it is found first in the basic block.
139 57521 : return &*I == A;
140 : //} else {
141 : // // A post-dominates B if B is found first in the basic block.
142 : // return &*I == B;
143 : //}
144 : }
145 :
146 : inline bool properlyDominates(const MachineDomTreeNode* A,
147 : const MachineDomTreeNode* B) const {
148 : applySplitCriticalEdges();
149 : return DT->properlyDominates(A, B);
150 : }
151 :
152 : inline bool properlyDominates(const MachineBasicBlock* A,
153 : const MachineBasicBlock* B) const {
154 13692 : applySplitCriticalEdges();
155 13692 : return DT->properlyDominates(A, B);
156 : }
157 :
158 : /// findNearestCommonDominator - Find nearest common dominator basic block
159 : /// for basic block A and B. If there is no such block then return NULL.
160 : inline MachineBasicBlock *findNearestCommonDominator(MachineBasicBlock *A,
161 : MachineBasicBlock *B) {
162 7966 : applySplitCriticalEdges();
163 7966 : return DT->findNearestCommonDominator(A, B);
164 : }
165 :
166 129908 : inline MachineDomTreeNode *operator[](MachineBasicBlock *BB) const {
167 129908 : applySplitCriticalEdges();
168 129908 : return DT->getNode(BB);
169 : }
170 :
171 : /// getNode - return the (Post)DominatorTree node for the specified basic
172 : /// block. This is the same as using operator[] on this class.
173 : ///
174 527807 : inline MachineDomTreeNode *getNode(MachineBasicBlock *BB) const {
175 527807 : applySplitCriticalEdges();
176 527807 : return DT->getNode(BB);
177 : }
178 :
179 : /// addNewBlock - Add a new node to the dominator tree information. This
180 : /// creates a new node as a child of DomBB dominator node,linking it into
181 : /// the children list of the immediate dominator.
182 : inline MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB,
183 : MachineBasicBlock *DomBB) {
184 44 : applySplitCriticalEdges();
185 44 : return DT->addNewBlock(BB, DomBB);
186 : }
187 :
188 : /// changeImmediateDominator - This method is used to update the dominator
189 : /// tree information when a node's immediate dominator changes.
190 : ///
191 : inline void changeImmediateDominator(MachineBasicBlock *N,
192 : MachineBasicBlock* NewIDom) {
193 31 : applySplitCriticalEdges();
194 31 : DT->changeImmediateDominator(N, NewIDom);
195 : }
196 :
197 : inline void changeImmediateDominator(MachineDomTreeNode *N,
198 : MachineDomTreeNode* NewIDom) {
199 0 : applySplitCriticalEdges();
200 : DT->changeImmediateDominator(N, NewIDom);
201 : }
202 :
203 : /// eraseNode - Removes a node from the dominator tree. Block must not
204 : /// dominate any other blocks. Removes node from its immediate dominator's
205 : /// children list. Deletes dominator node associated with basic block BB.
206 : inline void eraseNode(MachineBasicBlock *BB) {
207 67 : applySplitCriticalEdges();
208 67 : DT->eraseNode(BB);
209 : }
210 :
211 : /// splitBlock - BB is split and now it has one successor. Update dominator
212 : /// tree to reflect this change.
213 : inline void splitBlock(MachineBasicBlock* NewBB) {
214 : applySplitCriticalEdges();
215 : DT->splitBlock(NewBB);
216 : }
217 :
218 : /// isReachableFromEntry - Return true if A is dominated by the entry
219 : /// block of the function containing it.
220 : bool isReachableFromEntry(const MachineBasicBlock *A) {
221 298067 : applySplitCriticalEdges();
222 298067 : return DT->isReachableFromEntry(A);
223 : }
224 :
225 : void releaseMemory() override;
226 :
227 : void verifyAnalysis() const override;
228 :
229 : void print(raw_ostream &OS, const Module*) const override;
230 :
231 : /// Record that the critical edge (FromBB, ToBB) has been
232 : /// split with NewBB.
233 : /// This is best to use this method instead of directly update the
234 : /// underlying information, because this helps mitigating the
235 : /// number of time the DT information is invalidated.
236 : ///
237 : /// \note Do not use this method with regular edges.
238 : ///
239 : /// \note To benefit from the compile time improvement incurred by this
240 : /// method, the users of this method have to limit the queries to the DT
241 : /// interface between two edges splitting. In other words, they have to
242 : /// pack the splitting of critical edges as much as possible.
243 33630 : void recordSplitCriticalEdge(MachineBasicBlock *FromBB,
244 : MachineBasicBlock *ToBB,
245 : MachineBasicBlock *NewBB) {
246 33630 : bool Inserted = NewBBs.insert(NewBB).second;
247 : (void)Inserted;
248 : assert(Inserted &&
249 : "A basic block inserted via edge splitting cannot appear twice");
250 33630 : CriticalEdgesToSplit.push_back({FromBB, ToBB, NewBB});
251 33630 : }
252 : };
253 :
254 : //===-------------------------------------
255 : /// DominatorTree GraphTraits specialization so the DominatorTree can be
256 : /// iterable by generic graph iterators.
257 : ///
258 :
259 : template <class Node, class ChildIterator>
260 : struct MachineDomTreeGraphTraitsBase {
261 : using NodeRef = Node *;
262 : using ChildIteratorType = ChildIterator;
263 :
264 : static NodeRef getEntryNode(NodeRef N) { return N; }
265 : static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
266 : static ChildIteratorType child_end(NodeRef N) { return N->end(); }
267 : };
268 :
269 : template <class T> struct GraphTraits;
270 :
271 : template <>
272 : struct GraphTraits<MachineDomTreeNode *>
273 : : public MachineDomTreeGraphTraitsBase<MachineDomTreeNode,
274 : MachineDomTreeNode::iterator> {};
275 :
276 : template <>
277 : struct GraphTraits<const MachineDomTreeNode *>
278 : : public MachineDomTreeGraphTraitsBase<const MachineDomTreeNode,
279 : MachineDomTreeNode::const_iterator> {
280 : };
281 :
282 : template <> struct GraphTraits<MachineDominatorTree*>
283 : : public GraphTraits<MachineDomTreeNode *> {
284 : static NodeRef getEntryNode(MachineDominatorTree *DT) {
285 : return DT->getRootNode();
286 : }
287 : };
288 :
289 : } // end namespace llvm
290 :
291 : #endif // LLVM_CODEGEN_MACHINEDOMINATORS_H
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