LLVM 17.0.0git
Dominators.h
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1//===- Dominators.h - Dominator Info 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 the DominatorTree class, which provides fast and efficient
10// dominance queries.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_IR_DOMINATORS_H
15#define LLVM_IR_DOMINATORS_H
16
17#include "llvm/ADT/APInt.h"
18#include "llvm/ADT/ArrayRef.h"
19#include "llvm/ADT/DenseMap.h"
22#include "llvm/ADT/Hashing.h"
25#include "llvm/ADT/Twine.h"
28#include "llvm/IR/BasicBlock.h"
29#include "llvm/IR/CFG.h"
30#include "llvm/IR/PassManager.h"
31#include "llvm/IR/Use.h"
32#include "llvm/Pass.h"
37#include <algorithm>
38#include <utility>
39#include <vector>
40
41namespace llvm {
42
43class Function;
44class Instruction;
45class Module;
46class Value;
47class raw_ostream;
48template <class GraphType> struct GraphTraits;
49
50extern template class DomTreeNodeBase<BasicBlock>;
51extern template class DominatorTreeBase<BasicBlock, false>; // DomTree
52extern template class DominatorTreeBase<BasicBlock, true>; // PostDomTree
53
54extern template class cfg::Update<BasicBlock *>;
55
56namespace DomTreeBuilder {
59
61
64
65extern template void Calculate<BBDomTree>(BBDomTree &DT);
66extern template void CalculateWithUpdates<BBDomTree>(BBDomTree &DT,
67 BBUpdates U);
68
69extern template void Calculate<BBPostDomTree>(BBPostDomTree &DT);
70
71extern template void InsertEdge<BBDomTree>(BBDomTree &DT, BasicBlock *From,
72 BasicBlock *To);
73extern template void InsertEdge<BBPostDomTree>(BBPostDomTree &DT,
75 BasicBlock *To);
76
77extern template void DeleteEdge<BBDomTree>(BBDomTree &DT, BasicBlock *From,
78 BasicBlock *To);
79extern template void DeleteEdge<BBPostDomTree>(BBPostDomTree &DT,
81 BasicBlock *To);
82
83extern template void ApplyUpdates<BBDomTree>(BBDomTree &DT,
86extern template void ApplyUpdates<BBPostDomTree>(BBPostDomTree &DT,
89
90extern template bool Verify<BBDomTree>(const BBDomTree &DT,
92extern template bool Verify<BBPostDomTree>(const BBPostDomTree &DT,
94} // namespace DomTreeBuilder
95
97
99 const BasicBlock *Start;
100 const BasicBlock *End;
101
102public:
103 BasicBlockEdge(const BasicBlock *Start_, const BasicBlock *End_) :
104 Start(Start_), End(End_) {}
105
106 BasicBlockEdge(const std::pair<BasicBlock *, BasicBlock *> &Pair)
107 : Start(Pair.first), End(Pair.second) {}
108
109 BasicBlockEdge(const std::pair<const BasicBlock *, const BasicBlock *> &Pair)
110 : Start(Pair.first), End(Pair.second) {}
111
112 const BasicBlock *getStart() const {
113 return Start;
114 }
115
116 const BasicBlock *getEnd() const {
117 return End;
118 }
119
120 /// Check if this is the only edge between Start and End.
121 bool isSingleEdge() const;
122};
123
126
127 static unsigned getHashValue(const BasicBlockEdge *V);
128
129 static inline BasicBlockEdge getEmptyKey() {
130 return BasicBlockEdge(BBInfo::getEmptyKey(), BBInfo::getEmptyKey());
131 }
132
134 return BasicBlockEdge(BBInfo::getTombstoneKey(), BBInfo::getTombstoneKey());
135 }
136
137 static unsigned getHashValue(const BasicBlockEdge &Edge) {
138 return hash_combine(BBInfo::getHashValue(Edge.getStart()),
139 BBInfo::getHashValue(Edge.getEnd()));
140 }
141
142 static bool isEqual(const BasicBlockEdge &LHS, const BasicBlockEdge &RHS) {
143 return BBInfo::isEqual(LHS.getStart(), RHS.getStart()) &&
144 BBInfo::isEqual(LHS.getEnd(), RHS.getEnd());
145 }
146};
147
148/// Concrete subclass of DominatorTreeBase that is used to compute a
149/// normal dominator tree.
150///
151/// Definition: A block is said to be forward statically reachable if there is
152/// a path from the entry of the function to the block. A statically reachable
153/// block may become statically unreachable during optimization.
154///
155/// A forward unreachable block may appear in the dominator tree, or it may
156/// not. If it does, dominance queries will return results as if all reachable
157/// blocks dominate it. When asking for a Node corresponding to a potentially
158/// unreachable block, calling code must handle the case where the block was
159/// unreachable and the result of getNode() is nullptr.
160///
161/// Generally, a block known to be unreachable when the dominator tree is
162/// constructed will not be in the tree. One which becomes unreachable after
163/// the dominator tree is initially constructed may still exist in the tree,
164/// even if the tree is properly updated. Calling code should not rely on the
165/// preceding statements; this is stated only to assist human understanding.
167 public:
169
170 DominatorTree() = default;
171 explicit DominatorTree(Function &F) { recalculate(F); }
173 recalculate(*DT.Parent, U);
174 }
175
176 /// Handle invalidation explicitly.
177 bool invalidate(Function &F, const PreservedAnalyses &PA,
179
180 // Ensure base-class overloads are visible.
181 using Base::dominates;
182
183 /// Return true if the (end of the) basic block BB dominates the use U.
184 bool dominates(const BasicBlock *BB, const Use &U) const;
185
186 /// Return true if value Def dominates use U, in the sense that Def is
187 /// available at U, and could be substituted as the used value without
188 /// violating the SSA dominance requirement.
189 ///
190 /// In particular, it is worth noting that:
191 /// * Non-instruction Defs dominate everything.
192 /// * Def does not dominate a use in Def itself (outside of degenerate cases
193 /// like unreachable code or trivial phi cycles).
194 /// * Invoke/callbr Defs only dominate uses in their default destination.
195 bool dominates(const Value *Def, const Use &U) const;
196 /// Return true if value Def dominates all possible uses inside instruction
197 /// User. Same comments as for the Use-based API apply.
198 bool dominates(const Value *Def, const Instruction *User) const;
199
200 /// Returns true if Def would dominate a use in any instruction in BB.
201 /// If Def is an instruction in BB, then Def does not dominate BB.
202 ///
203 /// Does not accept Value to avoid ambiguity with dominance checks between
204 /// two basic blocks.
205 bool dominates(const Instruction *Def, const BasicBlock *BB) const;
206
207 /// Return true if an edge dominates a use.
208 ///
209 /// If BBE is not a unique edge between start and end of the edge, it can
210 /// never dominate the use.
211 bool dominates(const BasicBlockEdge &BBE, const Use &U) const;
212 bool dominates(const BasicBlockEdge &BBE, const BasicBlock *BB) const;
213 /// Returns true if edge \p BBE1 dominates edge \p BBE2.
214 bool dominates(const BasicBlockEdge &BBE1, const BasicBlockEdge &BBE2) const;
215
216 // Ensure base class overloads are visible.
217 using Base::isReachableFromEntry;
218
219 /// Provide an overload for a Use.
220 bool isReachableFromEntry(const Use &U) const;
221
222 // Ensure base class overloads are visible.
223 using Base::findNearestCommonDominator;
224
225 /// Find the nearest instruction I that dominates both I1 and I2, in the sense
226 /// that a result produced before I will be available at both I1 and I2.
227 Instruction *findNearestCommonDominator(Instruction *I1,
228 Instruction *I2) const;
229
230 // Pop up a GraphViz/gv window with the Dominator Tree rendered using `dot`.
231 void viewGraph(const Twine &Name, const Twine &Title);
232 void viewGraph();
233};
234
235//===-------------------------------------
236// DominatorTree GraphTraits specializations so the DominatorTree can be
237// iterable by generic graph iterators.
238
239template <class Node, class ChildIterator> struct DomTreeGraphTraitsBase {
240 using NodeRef = Node *;
241 using ChildIteratorType = ChildIterator;
243
244 static NodeRef getEntryNode(NodeRef N) { return N; }
245 static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
246 static ChildIteratorType child_end(NodeRef N) { return N->end(); }
247
249 return df_begin(getEntryNode(N));
250 }
251
252 static nodes_iterator nodes_end(NodeRef N) { return df_end(getEntryNode(N)); }
253};
254
255template <>
258};
259
260template <>
262 : public DomTreeGraphTraitsBase<const DomTreeNode,
264
265template <> struct GraphTraits<DominatorTree*>
267 static NodeRef getEntryNode(DominatorTree *DT) { return DT->getRootNode(); }
268
270 return df_begin(getEntryNode(N));
271 }
272
274 return df_end(getEntryNode(N));
275 }
276};
277
278/// Analysis pass which computes a \c DominatorTree.
279class DominatorTreeAnalysis : public AnalysisInfoMixin<DominatorTreeAnalysis> {
281 static AnalysisKey Key;
282
283public:
284 /// Provide the result typedef for this analysis pass.
286
287 /// Run the analysis pass over a function and produce a dominator tree.
289};
290
291/// Printer pass for the \c DominatorTree.
293 : public PassInfoMixin<DominatorTreePrinterPass> {
294 raw_ostream &OS;
295
296public:
298
300};
301
302/// Verifier pass for the \c DominatorTree.
303struct DominatorTreeVerifierPass : PassInfoMixin<DominatorTreeVerifierPass> {
305};
306
307/// Enables verification of dominator trees.
308///
309/// This check is expensive and is disabled by default. `-verify-dom-info`
310/// allows selectively enabling the check without needing to recompile.
311extern bool VerifyDomInfo;
312
313/// Legacy analysis pass which computes a \c DominatorTree.
315 DominatorTree DT;
316
317public:
318 static char ID;
319
321
322 DominatorTree &getDomTree() { return DT; }
323 const DominatorTree &getDomTree() const { return DT; }
324
325 bool runOnFunction(Function &F) override;
326
327 void verifyAnalysis() const override;
328
329 void getAnalysisUsage(AnalysisUsage &AU) const override {
330 AU.setPreservesAll();
331 }
332
333 void releaseMemory() override { DT.reset(); }
334
335 void print(raw_ostream &OS, const Module *M = nullptr) const override;
336};
337} // end namespace llvm
338
339#endif // LLVM_IR_DOMINATORS_H
aarch64 promote const
This file implements a class to represent arbitrary precision integral constant values and operations...
BlockVerifier::State From
This file defines DenseMapInfo traits for DenseMap.
This file defines the DenseMap class.
This file builds on the ADT/GraphTraits.h file to build generic depth first graph iterator.
std::string Name
Generic dominator tree construction - this file provides routines to construct immediate dominator in...
This file defines a set of templates that efficiently compute a dominator tree over a generic graph.
This file provides various utilities for inspecting and working with the control flow graph in LLVM I...
#define F(x, y, z)
Definition: MD5.cpp:55
Machine Check Debug Module
This header defines various interfaces for pass management in LLVM.
This file defines the PointerIntPair class.
static bool dominates(MachineBasicBlock &MBB, MachineBasicBlock::const_iterator A, MachineBasicBlock::const_iterator B)
This file defines the SmallVector class.
This defines the Use class.
Value * RHS
Value * LHS
API to communicate dependencies between analyses during invalidation.
Definition: PassManager.h:661
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:620
Represent the analysis usage information of a pass.
void setPreservesAll()
Set by analyses that do not transform their input at all.
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
const BasicBlock * getEnd() const
Definition: Dominators.h:116
const BasicBlock * getStart() const
Definition: Dominators.h:112
BasicBlockEdge(const std::pair< const BasicBlock *, const BasicBlock * > &Pair)
Definition: Dominators.h:109
BasicBlockEdge(const BasicBlock *Start_, const BasicBlock *End_)
Definition: Dominators.h:103
BasicBlockEdge(const std::pair< BasicBlock *, BasicBlock * > &Pair)
Definition: Dominators.h:106
LLVM Basic Block Representation.
Definition: BasicBlock.h:56
typename SmallVector< DomTreeNodeBase *, 4 >::const_iterator const_iterator
Analysis pass which computes a DominatorTree.
Definition: Dominators.h:279
DominatorTree run(Function &F, FunctionAnalysisManager &)
Run the analysis pass over a function and produce a dominator tree.
Definition: Dominators.cpp:385
Core dominator tree base class.
DomTreeNodeBase< NodeT > * getRootNode()
getRootNode - This returns the entry node for the CFG of the function.
Printer pass for the DominatorTree.
Definition: Dominators.h:293
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: Dominators.cpp:396
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:314
bool runOnFunction(Function &F) override
runOnFunction - Virtual method overriden by subclasses to do the per-function processing of the pass.
void print(raw_ostream &OS, const Module *M=nullptr) const override
print - Print out the internal state of the pass.
Definition: Dominators.cpp:442
DominatorTree & getDomTree()
Definition: Dominators.h:322
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: Dominators.h:329
const DominatorTree & getDomTree() const
Definition: Dominators.h:323
void releaseMemory() override
releaseMemory() - This member can be implemented by a pass if it wants to be able to release its memo...
Definition: Dominators.h:333
void verifyAnalysis() const override
verifyAnalysis() - This member can be implemented by a analysis pass to check state of analysis infor...
Definition: Dominators.cpp:435
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
Definition: Dominators.h:166
DominatorTree()=default
DominatorTree(Function &F)
Definition: Dominators.h:171
DominatorTree(DominatorTree &DT, DomTreeBuilder::BBUpdates U)
Definition: Dominators.h:172
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:308
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:152
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
A Use represents the edge between a Value definition and its users.
Definition: Use.h:43
LLVM Value Representation.
Definition: Value.h:74
This class implements an extremely fast bulk output stream that can only output to a stream.
Definition: raw_ostream.h:52
This provides a very simple, boring adaptor for a begin and end iterator into a range type.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
df_iterator< T > df_begin(const T &G)
DomTreeNodeBase< BasicBlock > DomTreeNode
Definition: Dominators.h:96
bool VerifyDomInfo
Enables verification of dominator trees.
Definition: Dominators.cpp:39
df_iterator< T > df_end(const T &G)
hash_code hash_combine(const Ts &...args)
Combine values into a single hash_code.
Definition: Hashing.h:608
#define N
A CRTP mix-in that provides informational APIs needed for analysis passes.
Definition: PassManager.h:394
A special type used by analysis passes to provide an address that identifies that particular analysis...
Definition: PassManager.h:69
static BasicBlockEdge getEmptyKey()
Definition: Dominators.h:129
static BasicBlockEdge getTombstoneKey()
Definition: Dominators.h:133
static unsigned getHashValue(const BasicBlockEdge *V)
static unsigned getHashValue(const BasicBlockEdge &Edge)
Definition: Dominators.h:137
static bool isEqual(const BasicBlockEdge &LHS, const BasicBlockEdge &RHS)
Definition: Dominators.h:142
An information struct used to provide DenseMap with the various necessary components for a given valu...
Definition: DenseMapInfo.h:51
static ChildIteratorType child_end(NodeRef N)
Definition: Dominators.h:246
static NodeRef getEntryNode(NodeRef N)
Definition: Dominators.h:244
ChildIterator ChildIteratorType
Definition: Dominators.h:241
static nodes_iterator nodes_begin(NodeRef N)
Definition: Dominators.h:248
static nodes_iterator nodes_end(NodeRef N)
Definition: Dominators.h:252
static ChildIteratorType child_begin(NodeRef N)
Definition: Dominators.h:245
Verifier pass for the DominatorTree.
Definition: Dominators.h:303
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
Definition: Dominators.cpp:404
static nodes_iterator nodes_end(DominatorTree *N)
Definition: Dominators.h:273
static NodeRef getEntryNode(DominatorTree *DT)
Definition: Dominators.h:267
static nodes_iterator nodes_begin(DominatorTree *N)
Definition: Dominators.h:269
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:371