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:
DwarfExpression(const TargetRegisterInfo & TRI,unsigned DwarfVersion)38   DwarfExpression(const TargetRegisterInfo &TRI,
39                   unsigned DwarfVersion)
40     : TRI(TRI), DwarfVersion(DwarfVersion) {}
~DwarfExpression()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(int64_t Value) = 0;
47   /// Emit a raw unsigned value.
48   virtual void EmitUnsigned(uint64_t 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   /// \brief Emit an entire expression on top of a machine register location.
92   ///
93   /// \param PieceOffsetInBits If this is one piece out of a fragmented
94   /// location, this is the offset of the piece inside the entire variable.
95   /// \return false if no DWARF register exists for MachineReg.
96   bool AddMachineRegExpression(const DIExpression *Expr, unsigned MachineReg,
97                                unsigned PieceOffsetInBits = 0);
98   /// Emit a the operations remaining the DIExpressionIterator I.
99   /// \param PieceOffsetInBits If this is one piece out of a fragmented
100   /// location, this is the offset of the piece inside the entire variable.
101   void AddExpression(DIExpression::expr_op_iterator I,
102                      DIExpression::expr_op_iterator E,
103                      unsigned PieceOffsetInBits = 0);
104 };
105 
106 /// DwarfExpression implementation for .debug_loc entries.
107 class DebugLocDwarfExpression : public DwarfExpression {
108   ByteStreamer &BS;
109 
110 public:
DebugLocDwarfExpression(const TargetRegisterInfo & TRI,unsigned DwarfVersion,ByteStreamer & BS)111   DebugLocDwarfExpression(const TargetRegisterInfo &TRI,
112                           unsigned DwarfVersion, ByteStreamer &BS)
113     : DwarfExpression(TRI, DwarfVersion), BS(BS) {}
114 
115   void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
116   void EmitSigned(int64_t Value) override;
117   void EmitUnsigned(uint64_t Value) override;
118   bool isFrameRegister(unsigned MachineReg) override;
119 };
120 
121 /// DwarfExpression implementation for singular DW_AT_location.
122 class DIEDwarfExpression : public DwarfExpression {
123 const AsmPrinter ≈
124   DwarfUnit &DU;
125   DIELoc ¨
126 
127 public:
128   DIEDwarfExpression(const AsmPrinter &AP, DwarfUnit &DU, DIELoc &DIE);
129   void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
130   void EmitSigned(int64_t Value) override;
131   void EmitUnsigned(uint64_t Value) override;
132   bool isFrameRegister(unsigned MachineReg) override;
133 };
134 }
135 
136 #endif
137