xref: /llvm-project/lldb/source/Plugins/SymbolFile/DWARF/DIERef.h (revision fb8df8cb658278ceba9ef4b96e0b448aed32c1f6)
1 //===-- DIERef.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 LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DIEREF_H
10 #define LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DIEREF_H
11 
12 #include "lldb/Core/dwarf.h"
13 #include "lldb/lldb-defines.h"
14 #include "lldb/lldb-types.h"
15 #include <cassert>
16 #include <optional>
17 
18 namespace lldb_private::plugin {
19 namespace dwarf {
20 /// Identifies a DWARF debug info entry within a given Module. It contains three
21 /// "coordinates":
22 /// - file_index: identifies the separate stand alone debug info file
23 ///   that is referred to by the main debug info file. This will be the
24 ///   index of a DWO file for fission, or the .o file on mac when not
25 ///   using a dSYM file. If this field is not set, then this references
26 ///   a DIE inside the original object file.
27 /// - section: identifies the section of the debug info entry in the given file:
28 ///   debug_info or debug_types.
29 /// - die_offset: The offset of the debug info entry as an absolute offset from
30 ///   the beginning of the section specified in the section field.
31 class DIERef {
32 public:
33   enum Section : uint8_t { DebugInfo, DebugTypes };
34   DIERef(std::optional<uint32_t> file_index, Section section,
35          dw_offset_t die_offset)
36       : m_die_offset(die_offset), m_file_index(file_index.value_or(0)),
37         m_file_index_valid(file_index ? true : false), m_section(section) {
38     assert(this->file_index() == file_index && "File Index is out of range?");
39   }
40 
41   explicit DIERef(lldb::user_id_t uid) {
42     m_die_offset = uid & k_die_offset_mask;
43     m_file_index_valid = (uid & k_file_index_valid_bit) != 0;
44     m_file_index = m_file_index_valid
45                        ? (uid >> k_die_offset_bit_size) & k_file_index_mask
46                        : 0;
47     m_section =
48         (uid & k_section_bit) != 0 ? Section::DebugTypes : Section::DebugInfo;
49   }
50 
51   lldb::user_id_t get_id() const {
52     if (m_die_offset == k_die_offset_mask)
53       return LLDB_INVALID_UID;
54 
55     return lldb::user_id_t(file_index().value_or(0)) << k_die_offset_bit_size |
56            die_offset() | (m_file_index_valid ? k_file_index_valid_bit : 0) |
57            (section() == Section::DebugTypes ? k_section_bit : 0);
58   }
59 
60   std::optional<uint32_t> file_index() const {
61     if (m_file_index_valid)
62       return m_file_index;
63     return std::nullopt;
64   }
65 
66   Section section() const { return static_cast<Section>(m_section); }
67 
68   dw_offset_t die_offset() const { return m_die_offset; }
69 
70   bool operator<(DIERef other) const {
71     if (m_file_index_valid != other.m_file_index_valid)
72       return m_file_index_valid < other.m_file_index_valid;
73     if (m_file_index_valid && (m_file_index != other.m_file_index))
74       return m_file_index < other.m_file_index;
75     if (m_section != other.m_section)
76       return m_section < other.m_section;
77     return m_die_offset < other.m_die_offset;
78   }
79 
80   bool operator==(const DIERef &rhs) const {
81     return file_index() == rhs.file_index() && m_section == rhs.m_section &&
82            m_die_offset == rhs.m_die_offset;
83   }
84 
85   bool operator!=(const DIERef &rhs) const { return !(*this == rhs); }
86 
87   /// Decode a serialized version of this object from data.
88   ///
89   /// \param data
90   ///   The decoder object that references the serialized data.
91   ///
92   /// \param offset_ptr
93   ///   A pointer that contains the offset from which the data will be decoded
94   ///   from that gets updated as data gets decoded.
95   ///
96   /// \return
97   ///   Returns a valid DIERef if decoding succeeded, std::nullopt if there was
98   ///   unsufficient or invalid values that were decoded.
99   static std::optional<DIERef> Decode(const DataExtractor &data,
100                                       lldb::offset_t *offset_ptr);
101 
102   /// Encode this object into a data encoder object.
103   ///
104   /// This allows this object to be serialized to disk.
105   ///
106   /// \param encoder
107   ///   A data encoder object that serialized bytes will be encoded into.
108   ///
109   void Encode(DataEncoder &encoder) const;
110 
111   static constexpr uint64_t k_die_offset_bit_size = DW_DIE_OFFSET_MAX_BITSIZE;
112   static constexpr uint64_t k_file_index_bit_size =
113       64 - DW_DIE_OFFSET_MAX_BITSIZE - /* size of control bits */ 2;
114 
115   static constexpr uint64_t k_file_index_valid_bit =
116       (1ull << (k_file_index_bit_size + k_die_offset_bit_size));
117   static constexpr uint64_t k_section_bit =
118       (1ull << (k_file_index_bit_size + k_die_offset_bit_size + 1));
119   static constexpr uint64_t
120       k_file_index_mask = (~0ull) >> (64 - k_file_index_bit_size); // 0x3fffff;
121   static constexpr uint64_t k_die_offset_mask = (~0ull) >>
122                                                 (64 - k_die_offset_bit_size);
123 
124 private:
125   // Allow 2TB of .debug_info/.debug_types offset
126   dw_offset_t m_die_offset : k_die_offset_bit_size;
127   // Used for DWO index or for .o file index on mac
128   dw_offset_t m_file_index : k_file_index_bit_size;
129   // Set to 1 if m_file_index is a DWO number
130   dw_offset_t m_file_index_valid : 1;
131   // Set to 0 for .debug_info 1 for .debug_types,
132   dw_offset_t m_section : 1;
133 };
134 static_assert(sizeof(DIERef) == 8);
135 
136 typedef std::vector<DIERef> DIEArray;
137 } // namespace dwarf
138 } // namespace lldb_private::plugin
139 
140 namespace llvm {
141 template <> struct format_provider<lldb_private::plugin::dwarf::DIERef> {
142   static void format(const lldb_private::plugin::dwarf::DIERef &ref,
143                      raw_ostream &OS, StringRef Style);
144 };
145 } // namespace llvm
146 
147 #endif // LLDB_SOURCE_PLUGINS_SYMBOLFILE_DWARF_DIEREF_H
148