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