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 {
ValueValue31     Value(const MDNode *Var, const MDNode *Expr, int64_t i)
32         : Variable(Var), Expression(Expr), EntryKind(E_Integer) {
33       Constant.Int = i;
34     }
ValueValue35     Value(const MDNode *Var, const MDNode *Expr, const ConstantFP *CFP)
36         : Variable(Var), Expression(Expr), EntryKind(E_ConstantFP) {
37       Constant.CFP = CFP;
38     }
ValueValue39     Value(const MDNode *Var, const MDNode *Expr, const ConstantInt *CIP)
40         : Variable(Var), Expression(Expr), EntryKind(E_ConstantInt) {
41       Constant.CIP = CIP;
42     }
ValueValue43     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 
isLocationValue69     bool isLocation() const { return EntryKind == E_Location; }
isIntValue70     bool isInt() const { return EntryKind == E_Integer; }
isConstantFPValue71     bool isConstantFP() const { return EntryKind == E_ConstantFP; }
isConstantIntValue72     bool isConstantInt() const { return EntryKind == E_ConstantInt; }
getIntValue73     int64_t getInt() const { return Constant.Int; }
getConstantFPValue74     const ConstantFP *getConstantFP() const { return Constant.CFP; }
getConstantIntValue75     const ConstantInt *getConstantInt() const { return Constant.CIP; }
getLocValue76     MachineLocation getLoc() const { return Loc; }
getVariableValue77     DIVariable getVariable() const { return cast<MDLocalVariable>(Variable); }
isBitPieceValue78     bool isBitPiece() const { return getExpression()->isBitPiece(); }
getExpressionValue79     DIExpression getExpression() const {
80       return cast_or_null<MDExpression>(Expression);
81     }
82     friend bool operator==(const Value &, const Value &);
83     friend bool operator<(const Value &, const Value &);
84   };
85 
86 private:
87   /// A nonempty list of locations/constants belonging to this entry,
88   /// sorted by offset.
89   SmallVector<Value, 1> Values;
90   SmallString<8> DWARFBytes;
91   SmallVector<std::string, 1> Comments;
92 
93 public:
DebugLocEntry(const MCSymbol * B,const MCSymbol * E,Value Val)94   DebugLocEntry(const MCSymbol *B, const MCSymbol *E, Value Val)
95       : Begin(B), End(E) {
96     Values.push_back(std::move(Val));
97   }
98 
99   /// \brief If this and Next are describing different pieces of the same
100   /// variable, merge them by appending Next's values to the current
101   /// list of values.
102   /// Return true if the merge was successful.
MergeValues(const DebugLocEntry & Next)103   bool MergeValues(const DebugLocEntry &Next) {
104     if (Begin == Next.Begin) {
105       DIExpression Expr = cast_or_null<MDExpression>(Values[0].Expression);
106       DIVariable Var = cast_or_null<MDLocalVariable>(Values[0].Variable);
107       DIExpression NextExpr =
108           cast_or_null<MDExpression>(Next.Values[0].Expression);
109       DIVariable NextVar = cast_or_null<MDLocalVariable>(Next.Values[0].Variable);
110       if (Var == NextVar && Expr->isBitPiece() && NextExpr->isBitPiece()) {
111         addValues(Next.Values);
112         End = Next.End;
113         return true;
114       }
115     }
116     return false;
117   }
118 
119   /// \brief Attempt to merge this DebugLocEntry with Next and return
120   /// true if the merge was successful. Entries can be merged if they
121   /// share the same Loc/Constant and if Next immediately follows this
122   /// Entry.
MergeRanges(const DebugLocEntry & Next)123   bool MergeRanges(const DebugLocEntry &Next) {
124     // If this and Next are describing the same variable, merge them.
125     if ((End == Next.Begin && Values == Next.Values)) {
126       End = Next.End;
127       return true;
128     }
129     return false;
130   }
131 
getBeginSym()132   const MCSymbol *getBeginSym() const { return Begin; }
getEndSym()133   const MCSymbol *getEndSym() const { return End; }
getValues()134   ArrayRef<Value> getValues() const { return Values; }
addValues(ArrayRef<DebugLocEntry::Value> Vals)135   void addValues(ArrayRef<DebugLocEntry::Value> Vals) {
136     Values.append(Vals.begin(), Vals.end());
137     sortUniqueValues();
138     assert(std::all_of(Values.begin(), Values.end(), [](DebugLocEntry::Value V){
139           return V.isBitPiece();
140         }) && "value must be a piece");
141   }
142 
143   // \brief Sort the pieces by offset.
144   // Remove any duplicate entries by dropping all but the first.
sortUniqueValues()145   void sortUniqueValues() {
146     std::sort(Values.begin(), Values.end());
147     Values.erase(std::unique(Values.begin(), Values.end(),
148                              [](const Value &A, const Value &B) {
149                    return A.getVariable() == B.getVariable() &&
150                           A.getExpression() == B.getExpression();
151                  }),
152                  Values.end());
153   }
154 
155   /// \brief Lower this entry into a DWARF expression.
156   void finalize(const AsmPrinter &AP,
157                 const DITypeIdentifierMap &TypeIdentifierMap);
158 
159   /// \brief Return the lowered DWARF expression.
getDWARFBytes()160   StringRef getDWARFBytes() const { return DWARFBytes; }
161   /// \brief Return the assembler comments for the lowered DWARF expression.
getComments()162   const SmallVectorImpl<std::string> &getComments() const { return Comments; }
163 };
164 
165 /// \brief Compare two Values for equality.
166 inline bool operator==(const DebugLocEntry::Value &A,
167                        const DebugLocEntry::Value &B) {
168   if (A.EntryKind != B.EntryKind)
169     return false;
170 
171   if (A.Expression != B.Expression)
172     return false;
173 
174   if (A.Variable != B.Variable)
175     return false;
176 
177   switch (A.EntryKind) {
178   case DebugLocEntry::Value::E_Location:
179     return A.Loc == B.Loc;
180   case DebugLocEntry::Value::E_Integer:
181     return A.Constant.Int == B.Constant.Int;
182   case DebugLocEntry::Value::E_ConstantFP:
183     return A.Constant.CFP == B.Constant.CFP;
184   case DebugLocEntry::Value::E_ConstantInt:
185     return A.Constant.CIP == B.Constant.CIP;
186   }
187   llvm_unreachable("unhandled EntryKind");
188 }
189 
190 /// \brief Compare two pieces based on their offset.
191 inline bool operator<(const DebugLocEntry::Value &A,
192                       const DebugLocEntry::Value &B) {
193   return A.getExpression()->getBitPieceOffset() <
194          B.getExpression()->getBitPieceOffset();
195 }
196 
197 }
198 
199 #endif
200