1 //===-- llvm/CodeGen/DwarfExpression.h - Dwarf Compile Unit ---*- 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 contains support for writing dwarf compile unit.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
15 #define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
16 
17 #include "llvm/IR/DebugInfo.h"
18 #include "llvm/Support/DataTypes.h"
19 
20 namespace llvm {
21 
22 class AsmPrinter;
23 class ByteStreamer;
24 class TargetRegisterInfo;
25 class DwarfUnit;
26 class DIELoc;
27 
28 /// Base class containing the logic for constructing DWARF expressions
29 /// independently of whether they are emitted into a DIE or into a .debug_loc
30 /// entry.
31 class DwarfExpression {
32 protected:
33   // Various convenience accessors that extract things out of AsmPrinter.
34   const TargetRegisterInfo &TRI;
35   unsigned DwarfVersion;
36 
37 public:
38   DwarfExpression(const TargetRegisterInfo &TRI,
39                   unsigned DwarfVersion)
40     : TRI(TRI), DwarfVersion(DwarfVersion) {}
41   virtual ~DwarfExpression() {}
42 
43   /// Output a dwarf operand and an optional assembler comment.
44   virtual void EmitOp(uint8_t Op, const char *Comment = nullptr) = 0;
45   /// Emit a raw signed value.
46   virtual void EmitSigned(int Value) = 0;
47   /// Emit a raw unsigned value.
48   virtual void EmitUnsigned(unsigned Value) = 0;
49   /// Return whether the given machine register is the frame register in the
50   /// current function.
51   virtual bool isFrameRegister(unsigned MachineReg) = 0;
52 
53   /// Emit a dwarf register operation.
54   void AddReg(int DwarfReg, const char *Comment = nullptr);
55   /// Emit an (double-)indirect dwarf register operation.
56   void AddRegIndirect(int DwarfReg, int Offset, bool Deref = false);
57 
58   /// Emit a dwarf register operation for describing
59   /// - a small value occupying only part of a register or
60   /// - a register representing only part of a value.
61   void AddOpPiece(unsigned SizeInBits, unsigned OffsetInBits = 0);
62   /// Emit a shift-right dwarf expression.
63   void AddShr(unsigned ShiftBy);
64 
65   /// Emit an indirect dwarf register operation for the given machine register.
66   /// \return false if no DWARF register exists for MachineReg.
67   bool AddMachineRegIndirect(unsigned MachineReg, int Offset = 0);
68 
69   /// \brief Emit a partial DWARF register operation.
70   /// \param MachineReg        the register
71   /// \param PieceSizeInBits   size and
72   /// \param PieceOffsetInBits offset of the piece in bits, if this is one
73   ///                          piece of an aggregate value.
74   ///
75   /// If size and offset is zero an operation for the entire
76   /// register is emitted: Some targets do not provide a DWARF
77   /// register number for every register.  If this is the case, this
78   /// function will attempt to emit a DWARF register by emitting a
79   /// piece of a super-register or by piecing together multiple
80   /// subregisters that alias the register.
81   ///
82   /// \return false if no DWARF register exists for MachineReg.
83   bool AddMachineRegPiece(unsigned MachineReg, unsigned PieceSizeInBits = 0,
84                           unsigned PieceOffsetInBits = 0);
85 
86   /// Emit a signed constant.
87   void AddSignedConstant(int Value);
88   /// Emit an unsigned constant.
89   void AddUnsignedConstant(unsigned Value);
90 
91   /// Emit an entire DIExpression on top of a machine register location.
92   /// \param PieceOffsetInBits If this is one piece out of a fragmented
93   /// location, this is the offset of the piece inside the entire variable.
94   /// \return false if no DWARF register exists for MachineReg.
95   bool AddMachineRegExpression(DIExpression Expr, unsigned MachineReg,
96                                unsigned PieceOffsetInBits = 0);
97   /// Emit a the operations remaining the DIExpressionIterator I.
98   /// \param PieceOffsetInBits If this is one piece out of a fragmented
99   /// location, this is the offset of the piece inside the entire variable.
100   void AddExpression(DIExpression::iterator I, DIExpression::iterator E,
101                      unsigned PieceOffsetInBits = 0);
102 };
103 
104 /// DwarfExpression implementation for .debug_loc entries.
105 class DebugLocDwarfExpression : public DwarfExpression {
106   ByteStreamer &BS;
107 
108 public:
109   DebugLocDwarfExpression(const TargetRegisterInfo &TRI,
110                           unsigned DwarfVersion, ByteStreamer &BS)
111     : DwarfExpression(TRI, DwarfVersion), BS(BS) {}
112 
113   void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
114   void EmitSigned(int Value) override;
115   void EmitUnsigned(unsigned Value) override;
116   bool isFrameRegister(unsigned MachineReg) override;
117 };
118 
119 /// DwarfExpression implementation for singular DW_AT_location.
120 class DIEDwarfExpression : public DwarfExpression {
121 const AsmPrinter ≈
122   DwarfUnit &DU;
123   DIELoc ¨
124 
125 public:
126   DIEDwarfExpression(const AsmPrinter &AP, DwarfUnit &DU, DIELoc &DIE);
127   void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
128   void EmitSigned(int Value) override;
129   void EmitUnsigned(unsigned Value) override;
130   bool isFrameRegister(unsigned MachineReg) override;
131 };
132 }
133 
134 #endif
135