1 //===-- llvm/CodeGen/DwarfExpression.h - Dwarf Compile Unit ---*- C++ -*--===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains support for writing dwarf compile unit.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
15 #define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
17 #include "llvm/IR/DebugInfo.h"
18 #include "llvm/Support/DataTypes.h"
24 class TargetRegisterInfo;
28 /// Holds a DIExpression and keeps track of how many operands have been consumed
30 class DIExpressionCursor {
31 DIExpression::expr_op_iterator Start, End;
33 DIExpressionCursor(const DIExpression *Expr) {
38 Start = Expr->expr_op_begin();
39 End = Expr->expr_op_end();
42 DIExpressionCursor(ArrayRef<uint64_t> Expr)
43 : Start(Expr.begin()), End(Expr.end()) {}
45 /// Consume one operation.
46 Optional<DIExpression::ExprOperand> take() {
52 /// Consume N operations.
53 void consume(unsigned N) { std::advance(Start, N); }
55 /// Return the current operation.
56 Optional<DIExpression::ExprOperand> peek() const {
62 /// Return the next operation.
63 Optional<DIExpression::ExprOperand> peekNext() const {
67 auto Next = Start.getNext();
73 /// Determine whether there are any operations left in this expression.
74 operator bool() const { return Start != End; }
76 /// Retrieve the fragment information, if any.
77 Optional<DIExpression::FragmentInfo> getFragmentInfo() const {
78 return DIExpression::getFragmentInfo(Start, End);
82 /// Base class containing the logic for constructing DWARF expressions
83 /// independently of whether they are emitted into a DIE or into a .debug_loc
85 class DwarfExpression {
87 unsigned DwarfVersion;
88 /// Current Fragment Offset in Bits.
89 uint64_t OffsetInBits = 0;
91 /// Sometimes we need to add a DW_OP_bit_piece to describe a subregister.
92 unsigned SubRegisterSizeInBits = 0;
93 unsigned SubRegisterOffsetInBits = 0;
95 /// Push a DW_OP_piece / DW_OP_bit_piece for emitting later, if one is needed
96 /// to represent a subregister.
97 void setSubRegisterPiece(unsigned SizeInBits, unsigned OffsetInBits) {
98 SubRegisterSizeInBits = SizeInBits;
99 SubRegisterOffsetInBits = OffsetInBits;
103 DwarfExpression(unsigned DwarfVersion) : DwarfVersion(DwarfVersion) {}
104 virtual ~DwarfExpression() {};
106 /// This needs to be called last to commit any pending changes.
109 /// Output a dwarf operand and an optional assembler comment.
110 virtual void EmitOp(uint8_t Op, const char *Comment = nullptr) = 0;
111 /// Emit a raw signed value.
112 virtual void EmitSigned(int64_t Value) = 0;
113 /// Emit a raw unsigned value.
114 virtual void EmitUnsigned(uint64_t Value) = 0;
115 /// Return whether the given machine register is the frame register in the
116 /// current function.
117 virtual bool isFrameRegister(const TargetRegisterInfo &TRI, unsigned MachineReg) = 0;
119 /// Emit a dwarf register operation.
120 void AddReg(int DwarfReg, const char *Comment = nullptr);
121 /// Emit an (double-)indirect dwarf register operation.
122 void AddRegIndirect(int DwarfReg, int Offset, bool Deref = false);
124 /// Emit a DW_OP_piece or DW_OP_bit_piece operation for a variable fragment.
125 /// \param OffsetInBits This is an optional offset into the location that
126 /// is at the top of the DWARF stack.
127 void AddOpPiece(unsigned SizeInBits, unsigned OffsetInBits = 0);
129 /// Emit a shift-right dwarf expression.
130 void AddShr(unsigned ShiftBy);
132 /// Emit a DW_OP_stack_value, if supported.
134 /// The proper way to describe a constant value is DW_OP_constu <const>,
135 /// DW_OP_stack_value. Unfortunately, DW_OP_stack_value was not available
136 /// until DWARF 4, so we will continue to generate DW_OP_constu <const> for
137 /// DWARF 2 and DWARF 3. Technically, this is incorrect since DW_OP_const
138 /// <const> actually describes a value at a constant addess, not a constant
139 /// value. However, in the past there was no better way to describe a
140 /// constant value, so the producers and consumers started to rely on
141 /// heuristics to disambiguate the value vs. location status of the
142 /// expression. See PR21176 for more details.
143 void AddStackValue();
145 /// Emit an indirect dwarf register operation for the given machine register.
146 /// \return false if no DWARF register exists for MachineReg.
147 bool AddMachineRegIndirect(const TargetRegisterInfo &TRI, unsigned MachineReg,
150 /// Emit a partial DWARF register operation.
152 /// \param MachineReg The register number.
153 /// \param MaxSize If the register must be composed from
154 /// sub-registers this is an upper bound
155 /// for how many bits the emitted DW_OP_piece
158 /// If size and offset is zero an operation for the entire register is
159 /// emitted: Some targets do not provide a DWARF register number for every
160 /// register. If this is the case, this function will attempt to emit a DWARF
161 /// register by emitting a fragment of a super-register or by piecing together
162 /// multiple subregisters that alias the register.
164 /// \return false if no DWARF register exists for MachineReg.
165 bool AddMachineReg(const TargetRegisterInfo &TRI, unsigned MachineReg,
166 unsigned MaxSize = ~1U);
168 /// Emit a signed constant.
169 void AddSignedConstant(int64_t Value);
170 /// Emit an unsigned constant.
171 void AddUnsignedConstant(uint64_t Value);
172 /// Emit an unsigned constant.
173 void AddUnsignedConstant(const APInt &Value);
175 /// Emit a machine register location. As an optimization this may also consume
176 /// the prefix of a DwarfExpression if a more efficient representation for
177 /// combining the register location and the first operation exists.
179 /// \param FragmentOffsetInBits If this is one fragment out of a fragmented
180 /// location, this is the offset of the
181 /// fragment inside the entire variable.
182 /// \return false if no DWARF register exists
184 bool AddMachineRegExpression(const TargetRegisterInfo &TRI,
185 DIExpressionCursor &Expr, unsigned MachineReg,
186 unsigned FragmentOffsetInBits = 0);
187 /// Emit all remaining operations in the DIExpressionCursor.
189 /// \param FragmentOffsetInBits If this is one fragment out of multiple
190 /// locations, this is the offset of the
191 /// fragment inside the entire variable.
192 void AddExpression(DIExpressionCursor &&Expr,
193 unsigned FragmentOffsetInBits = 0);
195 /// If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to
196 /// the fragment described by \c Expr.
197 void addFragmentOffset(const DIExpression *Expr);
200 /// DwarfExpression implementation for .debug_loc entries.
201 class DebugLocDwarfExpression : public DwarfExpression {
205 DebugLocDwarfExpression(unsigned DwarfVersion, ByteStreamer &BS)
206 : DwarfExpression(DwarfVersion), BS(BS) {}
208 void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
209 void EmitSigned(int64_t Value) override;
210 void EmitUnsigned(uint64_t Value) override;
211 bool isFrameRegister(const TargetRegisterInfo &TRI,
212 unsigned MachineReg) override;
215 /// DwarfExpression implementation for singular DW_AT_location.
216 class DIEDwarfExpression : public DwarfExpression {
217 const AsmPrinter &AP;
222 DIEDwarfExpression(const AsmPrinter &AP, DwarfUnit &DU, DIELoc &DIE);
223 void EmitOp(uint8_t Op, const char *Comment = nullptr) override;
224 void EmitSigned(int64_t Value) override;
225 void EmitUnsigned(uint64_t Value) override;
226 bool isFrameRegister(const TargetRegisterInfo &TRI,
227 unsigned MachineReg) override;
229 DwarfExpression::finalize();