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"
19 #include "llvm/CodeGen/MachineBasicBlock.h"
20 #include "llvm/CodeGen/MachineFunctionPass.h"
21 #include "llvm/CodeGen/MachineInstr.h"
22 #include "llvm/CodeGen/MachineInstrBundleIterator.h"
23 #include "llvm/Support/GenericDomTree.h"
24 #include "llvm/Support/GenericDomTreeConstruction.h"
25 #include <cassert>
26 #include <memory>
27
28 namespace llvm {
29 class AnalysisUsage;
30 class MachineFunction;
31 class Module;
32 class raw_ostream;
33
34 template <>
addRoot(MachineBasicBlock * MBB)35 inline void DominatorTreeBase<MachineBasicBlock, false>::addRoot(
36 MachineBasicBlock *MBB) {
37 this->Roots.push_back(MBB);
38 }
39
40 extern template class DomTreeNodeBase<MachineBasicBlock>;
41 extern template class DominatorTreeBase<MachineBasicBlock, false>; // DomTree
42 extern template class DominatorTreeBase<MachineBasicBlock, true>; // PostDomTree
43
44 using MachineDomTree = DomTreeBase<MachineBasicBlock>;
45 using MachineDomTreeNode = DomTreeNodeBase<MachineBasicBlock>;
46
47 //===-------------------------------------
48 /// DominatorTree Class - Concrete subclass of DominatorTreeBase that is used to
49 /// compute a normal dominator tree.
50 ///
51 class MachineDominatorTree : public MachineFunctionPass {
52 /// Helper structure used to hold all the basic blocks
53 /// involved in the split of a critical edge.
54 struct CriticalEdge {
55 MachineBasicBlock *FromBB;
56 MachineBasicBlock *ToBB;
57 MachineBasicBlock *NewBB;
58 };
59
60 /// Pile up all the critical edges to be split.
61 /// The splitting of a critical edge is local and thus, it is possible
62 /// to apply several of those changes at the same time.
63 mutable SmallVector<CriticalEdge, 32> CriticalEdgesToSplit;
64
65 /// Remember all the basic blocks that are inserted during
66 /// edge splitting.
67 /// Invariant: NewBBs == all the basic blocks contained in the NewBB
68 /// field of all the elements of CriticalEdgesToSplit.
69 /// I.e., forall elt in CriticalEdgesToSplit, it exists BB in NewBBs
70 /// such as BB == elt.NewBB.
71 mutable SmallSet<MachineBasicBlock *, 32> NewBBs;
72
73 /// The DominatorTreeBase that is used to compute a normal dominator tree.
74 std::unique_ptr<MachineDomTree> DT;
75
76 /// Apply all the recorded critical edges to the DT.
77 /// This updates the underlying DT information in a way that uses
78 /// the fast query path of DT as much as possible.
79 ///
80 /// \post CriticalEdgesToSplit.empty().
81 void applySplitCriticalEdges() const;
82
83 public:
84 static char ID; // Pass ID, replacement for typeid
85
86 MachineDominatorTree();
MachineDominatorTree(MachineFunction & MF)87 explicit MachineDominatorTree(MachineFunction &MF) : MachineFunctionPass(ID) {
88 calculate(MF);
89 }
90
getBase()91 MachineDomTree &getBase() {
92 if (!DT)
93 DT.reset(new MachineDomTree());
94 applySplitCriticalEdges();
95 return *DT;
96 }
97
98 void getAnalysisUsage(AnalysisUsage &AU) const override;
99
getRoot()100 MachineBasicBlock *getRoot() const {
101 applySplitCriticalEdges();
102 return DT->getRoot();
103 }
104
getRootNode()105 MachineDomTreeNode *getRootNode() const {
106 applySplitCriticalEdges();
107 return DT->getRootNode();
108 }
109
110 bool runOnMachineFunction(MachineFunction &F) override;
111
112 void calculate(MachineFunction &F);
113
dominates(const MachineDomTreeNode * A,const MachineDomTreeNode * B)114 bool dominates(const MachineDomTreeNode *A,
115 const MachineDomTreeNode *B) const {
116 applySplitCriticalEdges();
117 return DT->dominates(A, B);
118 }
119
getDescendants(MachineBasicBlock * A,SmallVectorImpl<MachineBasicBlock * > & Result)120 void getDescendants(MachineBasicBlock *A,
121 SmallVectorImpl<MachineBasicBlock *> &Result) {
122 applySplitCriticalEdges();
123 DT->getDescendants(A, Result);
124 }
125
dominates(const MachineBasicBlock * A,const MachineBasicBlock * B)126 bool dominates(const MachineBasicBlock *A, const MachineBasicBlock *B) const {
127 applySplitCriticalEdges();
128 return DT->dominates(A, B);
129 }
130
131 // dominates - Return true if A dominates B. This performs the
132 // special checks necessary if A and B are in the same basic block.
dominates(const MachineInstr * A,const MachineInstr * B)133 bool dominates(const MachineInstr *A, const MachineInstr *B) const {
134 applySplitCriticalEdges();
135 const MachineBasicBlock *BBA = A->getParent(), *BBB = B->getParent();
136 if (BBA != BBB) return DT->dominates(BBA, BBB);
137
138 // Loop through the basic block until we find A or B.
139 MachineBasicBlock::const_iterator I = BBA->begin();
140 for (; &*I != A && &*I != B; ++I)
141 /*empty*/ ;
142
143 return &*I == A;
144 }
145
properlyDominates(const MachineDomTreeNode * A,const MachineDomTreeNode * B)146 bool properlyDominates(const MachineDomTreeNode *A,
147 const MachineDomTreeNode *B) const {
148 applySplitCriticalEdges();
149 return DT->properlyDominates(A, B);
150 }
151
properlyDominates(const MachineBasicBlock * A,const MachineBasicBlock * B)152 bool properlyDominates(const MachineBasicBlock *A,
153 const MachineBasicBlock *B) const {
154 applySplitCriticalEdges();
155 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.
findNearestCommonDominator(MachineBasicBlock * A,MachineBasicBlock * B)160 MachineBasicBlock *findNearestCommonDominator(MachineBasicBlock *A,
161 MachineBasicBlock *B) {
162 applySplitCriticalEdges();
163 return DT->findNearestCommonDominator(A, B);
164 }
165
166 MachineDomTreeNode *operator[](MachineBasicBlock *BB) const {
167 applySplitCriticalEdges();
168 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 ///
getNode(MachineBasicBlock * BB)174 MachineDomTreeNode *getNode(MachineBasicBlock *BB) const {
175 applySplitCriticalEdges();
176 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.
addNewBlock(MachineBasicBlock * BB,MachineBasicBlock * DomBB)182 MachineDomTreeNode *addNewBlock(MachineBasicBlock *BB,
183 MachineBasicBlock *DomBB) {
184 applySplitCriticalEdges();
185 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 ///
changeImmediateDominator(MachineBasicBlock * N,MachineBasicBlock * NewIDom)191 void changeImmediateDominator(MachineBasicBlock *N,
192 MachineBasicBlock *NewIDom) {
193 applySplitCriticalEdges();
194 DT->changeImmediateDominator(N, NewIDom);
195 }
196
changeImmediateDominator(MachineDomTreeNode * N,MachineDomTreeNode * NewIDom)197 void changeImmediateDominator(MachineDomTreeNode *N,
198 MachineDomTreeNode *NewIDom) {
199 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.
eraseNode(MachineBasicBlock * BB)206 void eraseNode(MachineBasicBlock *BB) {
207 applySplitCriticalEdges();
208 DT->eraseNode(BB);
209 }
210
211 /// splitBlock - BB is split and now it has one successor. Update dominator
212 /// tree to reflect this change.
splitBlock(MachineBasicBlock * NewBB)213 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.
isReachableFromEntry(const MachineBasicBlock * A)220 bool isReachableFromEntry(const MachineBasicBlock *A) {
221 applySplitCriticalEdges();
222 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.
recordSplitCriticalEdge(MachineBasicBlock * FromBB,MachineBasicBlock * ToBB,MachineBasicBlock * NewBB)243 void recordSplitCriticalEdge(MachineBasicBlock *FromBB,
244 MachineBasicBlock *ToBB,
245 MachineBasicBlock *NewBB) {
246 bool Inserted = NewBBs.insert(NewBB).second;
247 (void)Inserted;
248 assert(Inserted &&
249 "A basic block inserted via edge splitting cannot appear twice");
250 CriticalEdgesToSplit.push_back({FromBB, ToBB, NewBB});
251 }
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
getEntryNodeMachineDomTreeGraphTraitsBase264 static NodeRef getEntryNode(NodeRef N) { return N; }
child_beginMachineDomTreeGraphTraitsBase265 static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
child_endMachineDomTreeGraphTraitsBase266 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::const_iterator> {
275 };
276
277 template <>
278 struct GraphTraits<const MachineDomTreeNode *>
279 : public MachineDomTreeGraphTraitsBase<const MachineDomTreeNode,
280 MachineDomTreeNode::const_iterator> {
281 };
282
283 template <> struct GraphTraits<MachineDominatorTree*>
284 : public GraphTraits<MachineDomTreeNode *> {
285 static NodeRef getEntryNode(MachineDominatorTree *DT) {
286 return DT->getRootNode();
287 }
288 };
289
290 } // end namespace llvm
291
292 #endif // LLVM_CODEGEN_MACHINEDOMINATORS_H
293