LLVM  10.0.0svn
LineTable.h
Go to the documentation of this file.
1 //===- LineTable.h ----------------------------------------------*- 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 #ifndef LLVM_DEBUGINFO_GSYM_LINETABLE_H
10 #define LLVM_DEBUGINFO_GSYM_LINETABLE_H
11 
13 #include "llvm/Support/Error.h"
14 #include <cstdint>
15 #include <vector>
16 
17 namespace llvm {
18 namespace gsym {
19 
20 struct FunctionInfo;
21 class FileWriter;
22 
23 /// LineTable class contains deserialized versions of line tables for each
24 /// function's address ranges.
25 ///
26 /// When saved to disk, the line table is encoded using a modified version of
27 /// the DWARF line tables that only tracks address to source file and line.
28 ///
29 /// ENCODING
30 ///
31 /// The line table starts with a small prolog that contains the following
32 /// values:
33 ///
34 /// ENCODING NAME DESCRIPTION
35 /// ======== =========== ====================================================
36 /// SLEB MinDelta The min line delta for special opcodes that advance
37 /// the address and line number.
38 /// SLEB MaxDelta The max line delta for single byte opcodes that
39 /// advance the address and line number.
40 /// ULEB FirstLine The value of the first source line number to
41 /// initialize the LineEntry with.
42 ///
43 /// Once these prolog items are read, we initialize a LineEntry struct with
44 /// the start address of the function from the FunctionInfo's address range,
45 /// a default file index of 1, and the line number set to "FirstLine" from
46 /// the prolog above:
47 ///
48 /// LineEntry Row(BaseAddr, 1, FirstLine);
49 ///
50 /// The line table state machine is now initialized and ready to be parsed.
51 /// The stream that follows this encodes the line entries in a compact
52 /// form. Some opcodes cause "Row" to be modified and some opcodes may also
53 /// push "Row" onto the end of the "LineTable.Lines" vector. The end result
54 /// is a vector of LineEntry structs that is sorted in ascending address
55 /// order.
56 ///
57 /// NORMAL OPCODES
58 ///
59 /// The opcodes 0 through 3 are normal in opcodes. Their encoding and
60 /// descriptions are listed below:
61 ///
62 /// ENCODING ENUMERATION VALUE DESCRIPTION
63 /// ======== ================ ===== ========================================
64 /// LTOC_EndSequence 0x00 Parsing is done.
65 /// ULEB LTOC_SetFile 0x01 Row.File = ULEB
66 /// ULEB LTOC_AdvancePC 0x02 Row.Addr += ULEB, push "Row".
67 /// SLEB LTOC_AdvanceLine 0x03 Row.Line += SLEB
68 /// LTOC_FirstSpecial 0x04 First special opcode (see SPECIAL
69 /// OPCODES below).
70 ///
71 /// SPECIAL OPCODES
72 ///
73 /// Opcodes LTOC_FirstSpecial through 255 are special opcodes that always
74 /// increment both the Row.Addr and Row.Line and push "Row" onto the
75 /// LineEntry.Lines array. They do this by using some of the bits to
76 /// increment/decrement the source line number, and some of the bits to
77 /// increment the address. Line numbers can go up or down when making line
78 /// tables, where addresses always only increase since line tables are sorted
79 /// by address.
80 ///
81 /// In order to calculate the amount to increment the line and address for
82 /// these special opcodes, we calculate the number of values reserved for the
83 /// line increment/decrement using the "MinDelta" and "MaxDelta" from the
84 /// prolog:
85 ///
86 /// const int64_t LineRange = MaxDelta - MinDelta + 1;
87 ///
88 /// Then we can adjust the opcode to not include any of the normal opcodes:
89 ///
90 /// const uint8_t AdjustedOp = Opcode - LTOC_FirstSpecial;
91 ///
92 /// And we can calculate the line offset, and address offset:
93 ///
94 /// const int64_t LineDelta = MinDelta + (AdjustedOp % LineRange);
95 /// const uint64_t AddrDelta = (AdjustedOp / LineRange);
96 ///
97 /// And use these to modify our "Row":
98 ///
99 /// Row.Line += LineDelta;
100 /// Row.Addr += AddrDelta;
101 ///
102 /// And push a row onto the line table:
103 ///
104 /// Lines.push_back(Row);
105 ///
106 /// This is verify similar to the way that DWARF encodes its line tables. The
107 /// only difference is the DWARF line tables have more normal opcodes and the
108 /// "Row" contains more members, like source column number, bools for end of
109 /// prologue, beginnging of epilogue, is statement and many others. There are
110 /// also more complex rules that happen for the extra normal opcodes. By
111 /// leaving these extra opcodes out, we leave more bits for the special
112 /// opcodes that allows us to encode line tables in fewer bytes than standard
113 /// DWARF encodings.
114 ///
115 /// Opcodes that will push "Row" onto the LineEntry.Lines include the
116 /// LTOC_AdvancePC opcode and all special opcodes. All other opcodes
117 /// only modify the current "Row", or cause the line table to end.
118 class LineTable {
119  typedef std::vector<gsym::LineEntry> Collection;
120  Collection Lines; ///< All line entries in the line table.
121 public:
122  static LineEntry lookup(DataExtractor &Data, uint64_t BaseAddr,
123  uint64_t Addr);
124 
125  /// Decode an LineTable object from a binary data stream.
126  ///
127  /// \param Data The binary stream to read the data from. This object must
128  /// have the data for the LineTable object starting at offset zero. The data
129  /// can contain more data than needed.
130  ///
131  /// \param BaseAddr The base address to use when decoding the line table.
132  /// This will be the FunctionInfo's start address and will be used to
133  /// initialize the line table row prior to parsing any opcodes.
134  ///
135  /// \returns An LineTable or an error describing the issue that was
136  /// encountered during decoding.
138  uint64_t BaseAddr);
139  /// Encode this LineTable object into FileWriter stream.
140  ///
141  /// \param O The binary stream to write the data to at the current file
142  /// position.
143  ///
144  /// \param BaseAddr The base address to use when decoding the line table.
145  /// This will be the FunctionInfo's start address.
146  ///
147  /// \returns An error object that indicates success or failure or the
148  /// encoding process.
149  llvm::Error encode(FileWriter &O, uint64_t BaseAddr) const;
150  bool empty() const { return Lines.empty(); }
151  void clear() { Lines.clear(); }
152  void push(const LineEntry &LE) {
153  Lines.push_back(LE);
154  }
155  size_t isValid() const {
156  return !Lines.empty();
157  }
158  size_t size() const {
159  return Lines.size();
160  }
161  LineEntry &get(size_t i) {
162  assert(i < Lines.size());
163  return Lines[i];
164  }
165  const LineEntry &get(size_t i) const {
166  assert(i < Lines.size());
167  return Lines[i];
168  }
169  LineEntry &operator[](size_t i) {
170  return get(i);
171  }
172  const LineEntry &operator[](size_t i) const {
173  return get(i);
174  }
175  bool operator==(const LineTable &RHS) const {
176  return Lines == RHS.Lines;
177  }
178  bool operator!=(const LineTable &RHS) const {
179  return Lines != RHS.Lines;
180  }
181  bool operator<(const LineTable &RHS) const {
182  const auto LHSSize = Lines.size();
183  const auto RHSSize = RHS.Lines.size();
184  if (LHSSize == RHSSize)
185  return Lines < RHS.Lines;
186  return LHSSize < RHSSize;
187  }
188  Collection::const_iterator begin() const { return Lines.begin(); }
189  Collection::const_iterator end() const { return Lines.end(); }
190 
191 };
192 
194 
195 } // namespace gsym
196 } // namespace llvm
197 
198 #endif // #ifndef LLVM_DEBUGINFO_GSYM_LINETABLE_H
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void push(const LineEntry &LE)
Definition: LineTable.h:152
const LineEntry & operator[](size_t i) const
Definition: LineTable.h:172
bool operator<(const LineTable &RHS) const
Definition: LineTable.h:181
size_t size() const
Definition: LineTable.h:158
Line entries are used to encode the line tables in FunctionInfo objects.
Definition: LineEntry.h:22
bool operator==(const LineTable &RHS) const
Definition: LineTable.h:175
Collection::const_iterator end() const
Definition: LineTable.h:189
Tagged union holding either a T or a Error.
Definition: yaml2obj.h:21
LineTable class contains deserialized versions of line tables for each function&#39;s address ranges...
Definition: LineTable.h:118
size_t isValid() const
Definition: LineTable.h:155
A simplified binary data writer class that doesn&#39;t require targets, target definitions, architectures, or require any other optional compile time libraries to be enabled via the build process.
Definition: FileWriter.h:29
static llvm::Expected< LineTable > decode(DataExtractor &Data, uint64_t BaseAddr)
Decode an LineTable object from a binary data stream.
Definition: LineTable.cpp:251
llvm::Error encode(FileWriter &O, uint64_t BaseAddr) const
Encode this LineTable object into FileWriter stream.
Definition: LineTable.cpp:122
bool empty() const
Definition: LineTable.h:150
LineEntry & operator[](size_t i)
Definition: LineTable.h:169
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:45
static LineEntry lookup(DataExtractor &Data, uint64_t BaseAddr, uint64_t Addr)
Definition: LineTable.cpp:266
bool operator!=(const LineTable &RHS) const
Definition: LineTable.h:178
raw_ostream & operator<<(raw_ostream &OS, const FunctionInfo &R)
Collection::const_iterator begin() const
Definition: LineTable.h:188