1 //===-- llvm/CodeGen/DebugLocEntry.h - Entry in debug_loc list -*- 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 #ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DEBUGLOCENTRY_H
11 #define LLVM_LIB_CODEGEN_ASMPRINTER_DEBUGLOCENTRY_H
12 #include "llvm/ADT/SmallString.h"
13 #include "llvm/IR/Constants.h"
14 #include "llvm/IR/DebugInfo.h"
15 #include "llvm/MC/MCSymbol.h"
16 #include "llvm/MC/MachineLocation.h"
17 
18 namespace llvm {
19 class AsmPrinter;
20 class MDNode;
21 /// \brief This struct describes location entries emitted in the .debug_loc
22 /// section.
23 class DebugLocEntry {
24   /// Begin and end symbols for the address range that this location is valid.
25   const MCSymbol *Begin;
26   const MCSymbol *End;
27 
28 public:
29   /// \brief A single location or constant.
30   struct Value {
31     Value(const MDNode *Var, const MDNode *Expr, int64_t i)
32         : Variable(Var), Expression(Expr), EntryKind(E_Integer) {
33       Constant.Int = i;
34     }
35     Value(const MDNode *Var, const MDNode *Expr, const ConstantFP *CFP)
36         : Variable(Var), Expression(Expr), EntryKind(E_ConstantFP) {
37       Constant.CFP = CFP;
38     }
39     Value(const MDNode *Var, const MDNode *Expr, const ConstantInt *CIP)
40         : Variable(Var), Expression(Expr), EntryKind(E_ConstantInt) {
41       Constant.CIP = CIP;
42     }
43     Value(const MDNode *Var, const MDNode *Expr, MachineLocation Loc)
44         : Variable(Var), Expression(Expr), EntryKind(E_Location), Loc(Loc) {
45       assert(isa<MDLocalVariable>(Var));
46       assert(cast<MDExpression>(Expr)->isValid());
47     }
48 
49     /// The variable to which this location entry corresponds.
50     const MDNode *Variable;
51 
52     /// Any complex address location expression for this Value.
53     const MDNode *Expression;
54 
55     /// Type of entry that this represents.
56     enum EntryType { E_Location, E_Integer, E_ConstantFP, E_ConstantInt };
57     enum EntryType EntryKind;
58 
59     /// Either a constant,
60     union {
61       int64_t Int;
62       const ConstantFP *CFP;
63       const ConstantInt *CIP;
64     } Constant;
65 
66     // Or a location in the machine frame.
67     MachineLocation Loc;
68 
69     bool isLocation() const { return EntryKind == E_Location; }
70     bool isInt() const { return EntryKind == E_Integer; }
71     bool isConstantFP() const { return EntryKind == E_ConstantFP; }
72     bool isConstantInt() const { return EntryKind == E_ConstantInt; }
73     int64_t getInt() const { return Constant.Int; }
74     const ConstantFP *getConstantFP() const { return Constant.CFP; }
75     const ConstantInt *getConstantInt() const { return Constant.CIP; }
76     MachineLocation getLoc() const { return Loc; }
77     const MDNode *getVariableNode() const { return Variable; }
78     DIVariable getVariable() const { return cast<MDLocalVariable>(Variable); }
79     bool isBitPiece() const { return getExpression().isBitPiece(); }
80     DIExpression getExpression() const {
81       return cast_or_null<MDExpression>(Expression);
82     }
83     friend bool operator==(const Value &, const Value &);
84     friend bool operator<(const Value &, const Value &);
85   };
86 
87 private:
88   /// A nonempty list of locations/constants belonging to this entry,
89   /// sorted by offset.
90   SmallVector<Value, 1> Values;
91   SmallString<8> DWARFBytes;
92   SmallVector<std::string, 1> Comments;
93 
94 public:
95   DebugLocEntry(const MCSymbol *B, const MCSymbol *E, Value Val)
96       : Begin(B), End(E) {
97     Values.push_back(std::move(Val));
98   }
99 
100   /// \brief If this and Next are describing different pieces of the same
101   /// variable, merge them by appending Next's values to the current
102   /// list of values.
103   /// Return true if the merge was successful.
104   bool MergeValues(const DebugLocEntry &Next) {
105     if (Begin == Next.Begin) {
106       DIExpression Expr = cast_or_null<MDExpression>(Values[0].Expression);
107       DIVariable Var = cast_or_null<MDLocalVariable>(Values[0].Variable);
108       DIExpression NextExpr =
109           cast_or_null<MDExpression>(Next.Values[0].Expression);
110       DIVariable NextVar = cast_or_null<MDLocalVariable>(Next.Values[0].Variable);
111       if (Var == NextVar && Expr.isBitPiece() &&
112           NextExpr.isBitPiece()) {
113         addValues(Next.Values);
114         End = Next.End;
115         return true;
116       }
117     }
118     return false;
119   }
120 
121   /// \brief Attempt to merge this DebugLocEntry with Next and return
122   /// true if the merge was successful. Entries can be merged if they
123   /// share the same Loc/Constant and if Next immediately follows this
124   /// Entry.
125   bool MergeRanges(const DebugLocEntry &Next) {
126     // If this and Next are describing the same variable, merge them.
127     if ((End == Next.Begin && Values == Next.Values)) {
128       End = Next.End;
129       return true;
130     }
131     return false;
132   }
133 
134   const MCSymbol *getBeginSym() const { return Begin; }
135   const MCSymbol *getEndSym() const { return End; }
136   ArrayRef<Value> getValues() const { return Values; }
137   void addValues(ArrayRef<DebugLocEntry::Value> Vals) {
138     Values.append(Vals.begin(), Vals.end());
139     sortUniqueValues();
140     assert(std::all_of(Values.begin(), Values.end(), [](DebugLocEntry::Value V){
141           return V.isBitPiece();
142         }) && "value must be a piece");
143   }
144 
145   // \brief Sort the pieces by offset.
146   // Remove any duplicate entries by dropping all but the first.
147   void sortUniqueValues() {
148     std::sort(Values.begin(), Values.end());
149     Values.erase(std::unique(Values.begin(), Values.end(),
150                              [](const Value &A, const Value &B) {
151                    return A.getVariable() == B.getVariable() &&
152                           A.getExpression() == B.getExpression();
153                  }),
154                  Values.end());
155   }
156 
157   /// \brief Lower this entry into a DWARF expression.
158   void finalize(const AsmPrinter &AP,
159                 const DITypeIdentifierMap &TypeIdentifierMap);
160 
161   /// \brief Return the lowered DWARF expression.
162   StringRef getDWARFBytes() const { return DWARFBytes; }
163   /// \brief Return the assembler comments for the lowered DWARF expression.
164   const SmallVectorImpl<std::string> &getComments() const { return Comments; }
165 };
166 
167 /// \brief Compare two Values for equality.
168 inline bool operator==(const DebugLocEntry::Value &A,
169                        const DebugLocEntry::Value &B) {
170   if (A.EntryKind != B.EntryKind)
171     return false;
172 
173   if (A.Expression != B.Expression)
174     return false;
175 
176   if (A.Variable != B.Variable)
177     return false;
178 
179   switch (A.EntryKind) {
180   case DebugLocEntry::Value::E_Location:
181     return A.Loc == B.Loc;
182   case DebugLocEntry::Value::E_Integer:
183     return A.Constant.Int == B.Constant.Int;
184   case DebugLocEntry::Value::E_ConstantFP:
185     return A.Constant.CFP == B.Constant.CFP;
186   case DebugLocEntry::Value::E_ConstantInt:
187     return A.Constant.CIP == B.Constant.CIP;
188   }
189   llvm_unreachable("unhandled EntryKind");
190 }
191 
192 /// \brief Compare two pieces based on their offset.
193 inline bool operator<(const DebugLocEntry::Value &A,
194                       const DebugLocEntry::Value &B) {
195   return A.getExpression().getBitPieceOffset() <
196          B.getExpression().getBitPieceOffset();
197 }
198 
199 }
200 
201 #endif
202