LLVM 20.0.0git
DwarfExpression.h
Go to the documentation of this file.
1//===- llvm/CodeGen/DwarfExpression.h - Dwarf Compile Unit ------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains support for writing dwarf compile unit.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
14#define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
15
16#include "ByteStreamer.h"
17#include "llvm/ADT/ArrayRef.h"
20#include <cassert>
21#include <cstdint>
22#include <iterator>
23#include <optional>
24
25namespace llvm {
26
27class AsmPrinter;
28class APInt;
29class DwarfCompileUnit;
30class DIELoc;
31class TargetRegisterInfo;
32class MachineLocation;
33
34/// Base class containing the logic for constructing DWARF expressions
35/// independently of whether they are emitted into a DIE or into a .debug_loc
36/// entry.
37///
38/// Some DWARF operations, e.g. DW_OP_entry_value, need to calculate the size
39/// of a succeeding DWARF block before the latter is emitted to the output.
40/// To handle such cases, data can conditionally be emitted to a temporary
41/// buffer, which can later on be committed to the main output. The size of the
42/// temporary buffer is queryable, allowing for the size of the data to be
43/// emitted before the data is committed.
45protected:
46 /// Holds information about all subregisters comprising a register location.
47 struct Register {
49 unsigned SubRegSize;
50 const char *Comment;
51
52 /// Create a full register, no extra DW_OP_piece operators necessary.
53 static Register createRegister(int RegNo, const char *Comment) {
54 return {RegNo, 0, Comment};
55 }
56
57 /// Create a subregister that needs a DW_OP_piece operator with SizeInBits.
58 static Register createSubRegister(int RegNo, unsigned SizeInBits,
59 const char *Comment) {
60 return {RegNo, SizeInBits, Comment};
61 }
62
63 bool isSubRegister() const { return SubRegSize; }
64 };
65
66 /// Whether we are currently emitting an entry value operation.
68
70
71 /// The register location, if any.
73
74 /// Current Fragment Offset in Bits.
76
77 /// Sometimes we need to add a DW_OP_bit_piece to describe a subregister.
78 unsigned SubRegisterSizeInBits : 16;
80
81 /// The kind of location description being produced.
83
84 /// Additional location flags which may be combined with any location kind.
85 /// Currently, entry values are not supported for the Memory location kind.
86 enum { EntryValue = 1 << 0, Indirect = 1 << 1, CallSiteParamValue = 1 << 2 };
87
88 unsigned LocationKind : 3;
89 unsigned SavedLocationKind : 3;
90 unsigned LocationFlags : 3;
91 unsigned DwarfVersion : 4;
92
93public:
94 /// Set the location (\p Loc) and \ref DIExpression (\p DIExpr) to describe.
95 void setLocation(const MachineLocation &Loc, const DIExpression *DIExpr);
96
97 bool isUnknownLocation() const { return LocationKind == Unknown; }
98
99 bool isMemoryLocation() const { return LocationKind == Memory; }
100
101 bool isRegisterLocation() const { return LocationKind == Register; }
102
103 bool isImplicitLocation() const { return LocationKind == Implicit; }
104
105 bool isEntryValue() const { return LocationFlags & EntryValue; }
106
107 bool isIndirect() const { return LocationFlags & Indirect; }
108
110
111 std::optional<uint8_t> TagOffset;
112
113protected:
114 /// Push a DW_OP_piece / DW_OP_bit_piece for emitting later, if one is needed
115 /// to represent a subregister.
116 void setSubRegisterPiece(unsigned SizeInBits, unsigned OffsetInBits) {
117 assert(SizeInBits < 65536 && OffsetInBits < 65536);
118 SubRegisterSizeInBits = SizeInBits;
120 }
121
122 /// Add masking operations to stencil out a subregister.
123 void maskSubRegister();
124
125 /// Output a dwarf operand and an optional assembler comment.
126 virtual void emitOp(uint8_t Op, const char *Comment = nullptr) = 0;
127
128 /// Emit a raw signed value.
129 virtual void emitSigned(int64_t Value) = 0;
130
131 /// Emit a raw unsigned value.
132 virtual void emitUnsigned(uint64_t Value) = 0;
133
134 virtual void emitData1(uint8_t Value) = 0;
135
136 virtual void emitBaseTypeRef(uint64_t Idx) = 0;
137
138 /// Start emitting data to the temporary buffer. The data stored in the
139 /// temporary buffer can be committed to the main output using
140 /// commitTemporaryBuffer().
141 virtual void enableTemporaryBuffer() = 0;
142
143 /// Disable emission to the temporary buffer. This does not commit data
144 /// in the temporary buffer to the main output.
145 virtual void disableTemporaryBuffer() = 0;
146
147 /// Return the emitted size, in number of bytes, for the data stored in the
148 /// temporary buffer.
149 virtual unsigned getTemporaryBufferSize() = 0;
150
151 /// Commit the data stored in the temporary buffer to the main output.
152 virtual void commitTemporaryBuffer() = 0;
153
154 /// Emit a normalized unsigned constant.
156
157 /// Return whether the given machine register is the frame register in the
158 /// current function.
160 llvm::Register MachineReg) = 0;
161
162 /// Emit a DW_OP_reg operation. Note that this is only legal inside a DWARF
163 /// register location description.
164 void addReg(int DwarfReg, const char *Comment = nullptr);
165
166 /// Emit a DW_OP_breg operation.
167 void addBReg(int DwarfReg, int Offset);
168
169 /// Emit DW_OP_fbreg <Offset>.
170 void addFBReg(int Offset);
171
172 /// Emit a partial DWARF register operation.
173 ///
174 /// \param MachineReg The register number.
175 /// \param MaxSize If the register must be composed from
176 /// sub-registers this is an upper bound
177 /// for how many bits the emitted DW_OP_piece
178 /// may cover.
179 ///
180 /// If size and offset is zero an operation for the entire register is
181 /// emitted: Some targets do not provide a DWARF register number for every
182 /// register. If this is the case, this function will attempt to emit a DWARF
183 /// register by emitting a fragment of a super-register or by piecing together
184 /// multiple subregisters that alias the register.
185 ///
186 /// \return false if no DWARF register exists for MachineReg.
187 bool addMachineReg(const TargetRegisterInfo &TRI, llvm::Register MachineReg,
188 unsigned MaxSize = ~1U);
189
190 /// Emit a DW_OP_piece or DW_OP_bit_piece operation for a variable fragment.
191 /// \param OffsetInBits This is an optional offset into the location that
192 /// is at the top of the DWARF stack.
193 void addOpPiece(unsigned SizeInBits, unsigned OffsetInBits = 0);
194
195 /// Emit a shift-right dwarf operation.
196 void addShr(unsigned ShiftBy);
197
198 /// Emit a bitwise and dwarf operation.
199 void addAnd(unsigned Mask);
200
201 /// Emit a DW_OP_stack_value, if supported.
202 ///
203 /// The proper way to describe a constant value is DW_OP_constu <const>,
204 /// DW_OP_stack_value. Unfortunately, DW_OP_stack_value was not available
205 /// until DWARF 4, so we will continue to generate DW_OP_constu <const> for
206 /// DWARF 2 and DWARF 3. Technically, this is incorrect since DW_OP_const
207 /// <const> actually describes a value at a constant address, not a constant
208 /// value. However, in the past there was no better way to describe a
209 /// constant value, so the producers and consumers started to rely on
210 /// heuristics to disambiguate the value vs. location status of the
211 /// expression. See PR21176 for more details.
212 void addStackValue();
213
214 /// Finalize an entry value by emitting its size operand, and committing the
215 /// DWARF block which has been emitted to the temporary buffer.
216 void finalizeEntryValue();
217
218 /// Cancel the emission of an entry value.
219 void cancelEntryValue();
220
221 ~DwarfExpression() = default;
222
223public:
228
229 /// This needs to be called last to commit any pending changes.
230 void finalize();
231
232 /// Emit a signed constant.
233 void addSignedConstant(int64_t Value);
234
235 /// Emit an unsigned constant.
237
238 /// Emit an unsigned constant.
239 void addUnsignedConstant(const APInt &Value);
240
241 /// Emit an floating point constant.
242 void addConstantFP(const APFloat &Value, const AsmPrinter &AP);
243
244 /// Lock this down to become a memory location description.
248 }
249
250 /// Lock this down to become an entry value location.
251 void setEntryValueFlags(const MachineLocation &Loc);
252
253 /// Lock this down to become a call site parameter location.
255
256 /// Emit a machine register location. As an optimization this may also consume
257 /// the prefix of a DwarfExpression if a more efficient representation for
258 /// combining the register location and the first operation exists.
259 ///
260 /// \param FragmentOffsetInBits If this is one fragment out of a
261 /// fragmented
262 /// location, this is the offset of the
263 /// fragment inside the entire variable.
264 /// \return false if no DWARF register exists
265 /// for MachineReg.
267 DIExpressionCursor &Expr,
268 llvm::Register MachineReg,
269 unsigned FragmentOffsetInBits = 0);
270
271 /// Begin emission of an entry value dwarf operation. The entry value's
272 /// first operand is the size of the DWARF block (its second operand),
273 /// which needs to be calculated at time of emission, so we don't emit
274 /// any operands here.
276
277 /// Return the index of a base type with the given properties and
278 /// create one if necessary.
279 unsigned getOrCreateBaseType(unsigned BitSize, dwarf::TypeKind Encoding);
280
281 /// Emit all remaining operations in the DIExpressionCursor. The
282 /// cursor must not contain any DW_OP_LLVM_arg operations.
284
285 /// Emit all remaining operations in the DIExpressionCursor.
286 /// DW_OP_LLVM_arg operations are resolved by calling (\p InsertArg).
287 //
288 /// \return false if any call to (\p InsertArg) returns false.
289 bool addExpression(
290 DIExpressionCursor &&Expr,
291 llvm::function_ref<bool(unsigned, DIExpressionCursor &)> InsertArg);
292
293 /// If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to
294 /// the fragment described by \c Expr.
295 void addFragmentOffset(const DIExpression *Expr);
296
297 void emitLegacySExt(unsigned FromBits);
298 void emitLegacyZExt(unsigned FromBits);
299
300 /// Emit location information expressed via WebAssembly location + offset
301 /// The Index is an identifier for locals, globals or operand stack.
302 void addWasmLocation(unsigned Index, uint64_t Offset);
303};
304
305/// DwarfExpression implementation for .debug_loc entries.
307
308 struct TempBuffer {
309 SmallString<32> Bytes;
310 std::vector<std::string> Comments;
312
313 TempBuffer(bool GenerateComments) : BS(Bytes, Comments, GenerateComments) {}
314 };
315
316 std::unique_ptr<TempBuffer> TmpBuf;
317 BufferByteStreamer &OutBS;
318 bool IsBuffering = false;
319
320 /// Return the byte streamer that currently is being emitted to.
321 ByteStreamer &getActiveStreamer() { return IsBuffering ? TmpBuf->BS : OutBS; }
322
323 void emitOp(uint8_t Op, const char *Comment = nullptr) override;
324 void emitSigned(int64_t Value) override;
325 void emitUnsigned(uint64_t Value) override;
326 void emitData1(uint8_t Value) override;
327 void emitBaseTypeRef(uint64_t Idx) override;
328
329 void enableTemporaryBuffer() override;
330 void disableTemporaryBuffer() override;
331 unsigned getTemporaryBufferSize() override;
332 void commitTemporaryBuffer() override;
333
334 bool isFrameRegister(const TargetRegisterInfo &TRI,
335 llvm::Register MachineReg) override;
336
337public:
340 : DwarfExpression(DwarfVersion, CU), OutBS(BS) {}
341};
342
343/// DwarfExpression implementation for singular DW_AT_location.
345 const AsmPrinter &AP;
346 DIELoc &OutDIE;
347 DIELoc TmpDIE;
348 bool IsBuffering = false;
349
350 /// Return the DIE that currently is being emitted to.
351 DIELoc &getActiveDIE() { return IsBuffering ? TmpDIE : OutDIE; }
352
353 void emitOp(uint8_t Op, const char *Comment = nullptr) override;
354 void emitSigned(int64_t Value) override;
355 void emitUnsigned(uint64_t Value) override;
356 void emitData1(uint8_t Value) override;
357 void emitBaseTypeRef(uint64_t Idx) override;
358
359 void enableTemporaryBuffer() override;
360 void disableTemporaryBuffer() override;
361 unsigned getTemporaryBufferSize() override;
362 void commitTemporaryBuffer() override;
363
364 bool isFrameRegister(const TargetRegisterInfo &TRI,
365 llvm::Register MachineReg) override;
366
367public:
369
372 return &OutDIE;
373 }
374};
375
376} // end namespace llvm
377
378#endif // LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H
Returns the sub type a function will return at a given Idx Should correspond to the result type of an ExtractValue instruction executed with just that one unsigned Idx
unsigned const TargetRegisterInfo * TRI
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file defines the SmallVector class.
Class for arbitrary precision integers.
Definition: APInt.h:78
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:86
DwarfExpression implementation for singular DW_AT_location.
DIELoc - Represents an expression location.
Definition: DIE.h:1010
A structured debug information entry.
Definition: DIE.h:819
Holds a DIExpression and keeps track of how many operands have been consumed so far.
DWARF expression.
This class represents an Operation in the Expression.
DwarfExpression implementation for .debug_loc entries.
DebugLocDwarfExpression(unsigned DwarfVersion, BufferByteStreamer &BS, DwarfCompileUnit &CU)
Base class containing the logic for constructing DWARF expressions independently of whether they are ...
void addAnd(unsigned Mask)
Emit a bitwise and dwarf operation.
void setLocation(const MachineLocation &Loc, const DIExpression *DIExpr)
Set the location (Loc) and DIExpression (DIExpr) to describe.
virtual void emitOp(uint8_t Op, const char *Comment=nullptr)=0
Output a dwarf operand and an optional assembler comment.
virtual void disableTemporaryBuffer()=0
Disable emission to the temporary buffer.
bool isUnknownLocation() const
virtual unsigned getTemporaryBufferSize()=0
Return the emitted size, in number of bytes, for the data stored in the temporary buffer.
uint64_t OffsetInBits
Current Fragment Offset in Bits.
virtual bool isFrameRegister(const TargetRegisterInfo &TRI, llvm::Register MachineReg)=0
Return whether the given machine register is the frame register in the current function.
void finalize()
This needs to be called last to commit any pending changes.
void addFragmentOffset(const DIExpression *Expr)
If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to the fragment described by Ex...
void emitLegacySExt(unsigned FromBits)
void cancelEntryValue()
Cancel the emission of an entry value.
bool isRegisterLocation() const
void setMemoryLocationKind()
Lock this down to become a memory location description.
virtual void emitBaseTypeRef(uint64_t Idx)=0
virtual void emitData1(uint8_t Value)=0
bool addMachineReg(const TargetRegisterInfo &TRI, llvm::Register MachineReg, unsigned MaxSize=~1U)
Emit a partial DWARF register operation.
void addReg(int DwarfReg, const char *Comment=nullptr)
Emit a DW_OP_reg operation.
std::optional< uint8_t > TagOffset
DwarfCompileUnit & CU
bool isImplicitLocation() const
void setCallSiteParamValueFlag()
Lock this down to become a call site parameter location.
virtual void emitUnsigned(uint64_t Value)=0
Emit a raw unsigned value.
void addConstantFP(const APFloat &Value, const AsmPrinter &AP)
Emit an floating point constant.
void maskSubRegister()
Add masking operations to stencil out a subregister.
SmallVector< Register, 2 > DwarfRegs
The register location, if any.
bool addMachineRegExpression(const TargetRegisterInfo &TRI, DIExpressionCursor &Expr, llvm::Register MachineReg, unsigned FragmentOffsetInBits=0)
Emit a machine register location.
~DwarfExpression()=default
void addStackValue()
Emit a DW_OP_stack_value, if supported.
void finalizeEntryValue()
Finalize an entry value by emitting its size operand, and committing the DWARF block which has been e...
void addBReg(int DwarfReg, int Offset)
Emit a DW_OP_breg operation.
bool isMemoryLocation() const
void addUnsignedConstant(uint64_t Value)
Emit an unsigned constant.
unsigned SubRegisterSizeInBits
Sometimes we need to add a DW_OP_bit_piece to describe a subregister.
void addFBReg(int Offset)
Emit DW_OP_fbreg <Offset>.
void setSubRegisterPiece(unsigned SizeInBits, unsigned OffsetInBits)
Push a DW_OP_piece / DW_OP_bit_piece for emitting later, if one is needed to represent a subregister.
void addExpression(DIExpressionCursor &&Expr)
Emit all remaining operations in the DIExpressionCursor.
unsigned getOrCreateBaseType(unsigned BitSize, dwarf::TypeKind Encoding)
Return the index of a base type with the given properties and create one if necessary.
void addSignedConstant(int64_t Value)
Emit a signed constant.
void emitLegacyZExt(unsigned FromBits)
bool IsEmittingEntryValue
Whether we are currently emitting an entry value operation.
virtual void emitSigned(int64_t Value)=0
Emit a raw signed value.
unsigned SubRegisterOffsetInBits
void setEntryValueFlags(const MachineLocation &Loc)
Lock this down to become an entry value location.
virtual void commitTemporaryBuffer()=0
Commit the data stored in the temporary buffer to the main output.
void addShr(unsigned ShiftBy)
Emit a shift-right dwarf operation.
DwarfExpression(unsigned DwarfVersion, DwarfCompileUnit &CU)
void addWasmLocation(unsigned Index, uint64_t Offset)
Emit location information expressed via WebAssembly location + offset The Index is an identifier for ...
virtual void enableTemporaryBuffer()=0
Start emitting data to the temporary buffer.
void emitConstu(uint64_t Value)
Emit a normalized unsigned constant.
void beginEntryValueExpression(DIExpressionCursor &ExprCursor)
Begin emission of an entry value dwarf operation.
void addOpPiece(unsigned SizeInBits, unsigned OffsetInBits=0)
Emit a DW_OP_piece or DW_OP_bit_piece operation for a variable fragment.
Wrapper class representing virtual and physical registers.
Definition: Register.h:19
SmallString - A SmallString is just a SmallVector with methods and accessors that make it work better...
Definition: SmallString.h:26
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
TargetRegisterInfo base class - We assume that the target defines a static array of TargetRegisterDes...
LLVM Value Representation.
Definition: Value.h:74
An efficient, type-erasing, non-owning reference to a callable.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
@ Offset
Definition: DWP.cpp:480
Holds information about all subregisters comprising a register location.
static Register createRegister(int RegNo, const char *Comment)
Create a full register, no extra DW_OP_piece operators necessary.
static Register createSubRegister(int RegNo, unsigned SizeInBits, const char *Comment)
Create a subregister that needs a DW_OP_piece operator with SizeInBits.