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