1//===- LexicalScopes.cpp - Collecting lexical scope info --------*- 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 implements LexicalScopes analysis.
10//
11// This pass collects lexical scope information and maps machine instructions
12// to respective lexical scopes.
13//
14//===----------------------------------------------------------------------===//
15
16#ifndef LLVM_CODEGEN_LEXICALSCOPES_H
17#define LLVM_CODEGEN_LEXICALSCOPES_H
18
19#include "llvm/ADT/ArrayRef.h"
20#include "llvm/ADT/DenseMap.h"
21#include "llvm/ADT/SmallPtrSet.h"
22#include "llvm/ADT/SmallVector.h"
23#include "llvm/IR/DebugInfoMetadata.h"
24#include <cassert>
25#include <unordered_map>
26#include <utility>
27
28namespace llvm {
29
30class MachineBasicBlock;
31class MachineFunction;
32class MachineInstr;
33class MDNode;
34
35//===----------------------------------------------------------------------===//
36/// InsnRange - This is used to track range of instructions with identical
37/// lexical scope.
38///
39using InsnRange = std::pair<const MachineInstr *, const MachineInstr *>;
40
41//===----------------------------------------------------------------------===//
42/// LexicalScope - This class is used to track scope information.
43///
44class LexicalScope {
45public:
46  LexicalScope(LexicalScope *P, const DILocalScope *D, const DILocation *I,
47               bool A)
48      : Parent(P), Desc(D), InlinedAtLocation(I), AbstractScope(A) {
49    assert(D);
50    assert(D->getSubprogram()->getUnit()->getEmissionKind() !=
51           DICompileUnit::NoDebug &&
52           "Don't build lexical scopes for non-debug locations");
53    assert(D->isResolved() && "Expected resolved node");
54    assert((!I || I->isResolved()) && "Expected resolved node");
55    if (Parent)
56      Parent->addChild(this);
57  }
58
59  // Accessors.
60  LexicalScope *getParent() const { return Parent; }
61  const MDNode *getDesc() const { return Desc; }
62  const DILocation *getInlinedAt() const { return InlinedAtLocation; }
63  const DILocalScope *getScopeNode() const { return Desc; }
64  bool isAbstractScope() const { return AbstractScope; }
65  SmallVectorImpl<LexicalScope *> &getChildren() { return Children; }
66  SmallVectorImpl<InsnRange> &getRanges() { return Ranges; }
67
68  /// addChild - Add a child scope.
69  void addChild(LexicalScope *S) { Children.push_back(S); }
70
71  /// openInsnRange - This scope covers instruction range starting from MI.
72  void openInsnRange(const MachineInstr *MI) {
73    if (!FirstInsn)
74      FirstInsn = MI;
75
76    if (Parent)
77      Parent->openInsnRange(MI);
78  }
79
80  /// extendInsnRange - Extend the current instruction range covered by
81  /// this scope.
82  void extendInsnRange(const MachineInstr *MI) {
83    assert(FirstInsn && "MI Range is not open!");
84    LastInsn = MI;
85    if (Parent)
86      Parent->extendInsnRange(MI);
87  }
88
89  /// closeInsnRange - Create a range based on FirstInsn and LastInsn collected
90  /// until now. This is used when a new scope is encountered while walking
91  /// machine instructions.
92  void closeInsnRange(LexicalScope *NewScope = nullptr) {
93    assert(LastInsn && "Last insn missing!");
94    Ranges.push_back(InsnRange(FirstInsn, LastInsn));
95    FirstInsn = nullptr;
96    LastInsn = nullptr;
97    // If Parent dominates NewScope then do not close Parent's instruction
98    // range.
99    if (Parent && (!NewScope || !Parent->dominates(NewScope)))
100      Parent->closeInsnRange(NewScope);
101  }
102
103  /// dominates - Return true if current scope dominates given lexical scope.
104  bool dominates(const LexicalScope *S) const {
105    if (S == this)
106      return true;
107    if (DFSIn < S->getDFSIn() && DFSOut > S->getDFSOut())
108      return true;
109    return false;
110  }
111
112  // Depth First Search support to walk and manipulate LexicalScope hierarchy.
113  unsigned getDFSOut() const { return DFSOut; }
114  void setDFSOut(unsigned O) { DFSOut = O; }
115  unsigned getDFSIn() const { return DFSIn; }
116  void setDFSIn(unsigned I) { DFSIn = I; }
117
118  /// dump - print lexical scope.
119  void dump(unsigned Indent = 0) const;
120
121private:
122  LexicalScope *Parent;                        // Parent to this scope.
123  const DILocalScope *Desc;                    // Debug info descriptor.
124  const DILocation *InlinedAtLocation;         // Location at which this
125                                               // scope is inlined.
126  bool AbstractScope;                          // Abstract Scope
127  SmallVector<LexicalScope *, 4> Children;     // Scopes defined in scope.
128                                               // Contents not owned.
129  SmallVector<InsnRange, 4> Ranges;
130
131  const MachineInstr *LastInsn = nullptr;  // Last instruction of this scope.
132  const MachineInstr *FirstInsn = nullptr; // First instruction of this scope.
133  unsigned DFSIn = 0; // In & Out Depth use to determine scope nesting.
134  unsigned DFSOut = 0;
135};
136
137//===----------------------------------------------------------------------===//
138/// LexicalScopes -  This class provides interface to collect and use lexical
139/// scoping information from machine instruction.
140///
141class LexicalScopes {
142public:
143  LexicalScopes() = default;
144
145  /// initialize - Scan machine function and constuct lexical scope nest, resets
146  /// the instance if necessary.
147  void initialize(const MachineFunction &);
148
149  /// releaseMemory - release memory.
150  void reset();
151
152  /// empty - Return true if there is any lexical scope information available.
153  bool empty() { return CurrentFnLexicalScope == nullptr; }
154
155  /// getCurrentFunctionScope - Return lexical scope for the current function.
156  LexicalScope *getCurrentFunctionScope() const {
157    return CurrentFnLexicalScope;
158  }
159
160  /// getMachineBasicBlocks - Populate given set using machine basic blocks
161  /// which have machine instructions that belong to lexical scope identified by
162  /// DebugLoc.
163  void getMachineBasicBlocks(const DILocation *DL,
164                             SmallPtrSetImpl<const MachineBasicBlock *> &MBBs);
165
166  /// dominates - Return true if DebugLoc's lexical scope dominates at least one
167  /// machine instruction's lexical scope in a given machine basic block.
168  bool dominates(const DILocation *DL, MachineBasicBlock *MBB);
169
170  /// findLexicalScope - Find lexical scope, either regular or inlined, for the
171  /// given DebugLoc. Return NULL if not found.
172  LexicalScope *findLexicalScope(const DILocation *DL);
173
174  /// getAbstractScopesList - Return a reference to list of abstract scopes.
175  ArrayRef<LexicalScope *> getAbstractScopesList() const {
176    return AbstractScopesList;
177  }
178
179  /// findAbstractScope - Find an abstract scope or return null.
180  LexicalScope *findAbstractScope(const DILocalScope *N) {
181    auto I = AbstractScopeMap.find(N);
182    return I != AbstractScopeMap.end() ? &I->second : nullptr;
183  }
184
185  /// findInlinedScope - Find an inlined scope for the given scope/inlined-at.
186  LexicalScope *findInlinedScope(const DILocalScope *N, const DILocation *IA) {
187    auto I = InlinedLexicalScopeMap.find(std::make_pair(N, IA));
188    return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
189  }
190
191  /// findLexicalScope - Find regular lexical scope or return null.
192  LexicalScope *findLexicalScope(const DILocalScope *N) {
193    auto I = LexicalScopeMap.find(N);
194    return I != LexicalScopeMap.end() ? &I->second : nullptr;
195  }
196
197  /// dump - Print data structures to dbgs().
198  void dump() const;
199
200  /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
201  LexicalScope *getOrCreateAbstractScope(const DILocalScope *Scope);
202
203private:
204  /// getOrCreateLexicalScope - Find lexical scope for the given Scope/IA. If
205  /// not available then create new lexical scope.
206  LexicalScope *getOrCreateLexicalScope(const DILocalScope *Scope,
207                                        const DILocation *IA = nullptr);
208  LexicalScope *getOrCreateLexicalScope(const DILocation *DL) {
209    return DL ? getOrCreateLexicalScope(DL->getScope(), DL->getInlinedAt())
210              : nullptr;
211  }
212
213  /// getOrCreateRegularScope - Find or create a regular lexical scope.
214  LexicalScope *getOrCreateRegularScope(const DILocalScope *Scope);
215
216  /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
217  LexicalScope *getOrCreateInlinedScope(const DILocalScope *Scope,
218                                        const DILocation *InlinedAt);
219
220  /// extractLexicalScopes - Extract instruction ranges for each lexical scopes
221  /// for the given machine function.
222  void extractLexicalScopes(SmallVectorImpl<InsnRange> &MIRanges,
223                            DenseMap<const MachineInstr *, LexicalScope *> &M);
224  void constructScopeNest(LexicalScope *Scope);
225  void
226  assignInstructionRanges(SmallVectorImpl<InsnRange> &MIRanges,
227                          DenseMap<const MachineInstr *, LexicalScope *> &M);
228
229  const MachineFunction *MF = nullptr;
230
231  /// LexicalScopeMap - Tracks the scopes in the current function.
232  // Use an unordered_map to ensure value pointer validity over insertion.
233  std::unordered_map<const DILocalScope *, LexicalScope> LexicalScopeMap;
234
235  /// InlinedLexicalScopeMap - Tracks inlined function scopes in current
236  /// function.
237  std::unordered_map<std::pair<const DILocalScope *, const DILocation *>,
238                     LexicalScope,
239                     pair_hash<const DILocalScope *, const DILocation *>>
240      InlinedLexicalScopeMap;
241
242  /// AbstractScopeMap - These scopes are  not included LexicalScopeMap.
243  // Use an unordered_map to ensure value pointer validity over insertion.
244  std::unordered_map<const DILocalScope *, LexicalScope> AbstractScopeMap;
245
246  /// AbstractScopesList - Tracks abstract scopes constructed while processing
247  /// a function.
248  SmallVector<LexicalScope *, 4> AbstractScopesList;
249
250  /// CurrentFnLexicalScope - Top level scope for the current function.
251  ///
252  LexicalScope *CurrentFnLexicalScope = nullptr;
253};
254
255} // end namespace llvm
256
257#endif // LLVM_CODEGEN_LEXICALSCOPES_H
258