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