xref: /freebsd/contrib/llvm-project/llvm/include/llvm/DebugInfo/DWARF/DWARFAbbreviationDeclaration.h (revision 700637cbb5e582861067a11aaca4d053546871d2) 
1 //===- DWARFAbbreviationDeclaration.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_DWARF_DWARFABBREVIATIONDECLARATION_H
10 #define LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H
11 
12 #include "llvm/ADT/SmallVector.h"
13 #include "llvm/ADT/iterator_range.h"
14 #include "llvm/BinaryFormat/Dwarf.h"
15 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
16 #include "llvm/Support/Compiler.h"
17 #include <cassert>
18 #include <cstddef>
19 #include <cstdint>
20 
21 namespace llvm {
22 
23 class DataExtractor;
24 class DWARFUnit;
25 class raw_ostream;
26 
27 class DWARFAbbreviationDeclaration {
28 public:
29   enum class ExtractState { Complete, MoreItems };
30   struct AttributeSpec {
AttributeSpecAttributeSpec31     AttributeSpec(dwarf::Attribute A, dwarf::Form F, int64_t Value)
32         : Attr(A), Form(F), Value(Value) {
33       assert(isImplicitConst());
34     }
AttributeSpecAttributeSpec35     AttributeSpec(dwarf::Attribute A, dwarf::Form F,
36                   std::optional<uint8_t> ByteSize)
37         : Attr(A), Form(F) {
38       assert(!isImplicitConst());
39       this->ByteSize.HasByteSize = ByteSize.has_value();
40       if (this->ByteSize.HasByteSize)
41         this->ByteSize.ByteSize = *ByteSize;
42     }
43 
getFormValueAttributeSpec44     DWARFFormValue getFormValue() const {
45       if (Form == dwarf::DW_FORM_implicit_const)
46         return DWARFFormValue::createFromSValue(Form, getImplicitConstValue());
47 
48       return DWARFFormValue(Form);
49     }
50 
51     dwarf::Attribute Attr;
52     dwarf::Form Form;
53 
54   private:
55     /// The following field is used for ByteSize for non-implicit_const
56     /// attributes and as value for implicit_const ones, indicated by
57     /// Form == DW_FORM_implicit_const.
58     /// The following cases are distinguished:
59     /// * Form != DW_FORM_implicit_const and HasByteSize is true:
60     ///     ByteSize contains the fixed size in bytes for the Form in this
61     ///     object.
62     /// * Form != DW_FORM_implicit_const and HasByteSize is false:
63     ///     byte size of Form either varies according to the DWARFUnit
64     ///     that it is contained in or the value size varies and must be
65     ///     decoded from the debug information in order to determine its size.
66     /// * Form == DW_FORM_implicit_const:
67     ///     Value contains value for the implicit_const attribute.
68     struct ByteSizeStorage {
69       bool HasByteSize;
70       uint8_t ByteSize;
71     };
72     union {
73       ByteSizeStorage ByteSize;
74       int64_t Value;
75     };
76 
77   public:
isImplicitConstAttributeSpec78     bool isImplicitConst() const {
79       return Form == dwarf::DW_FORM_implicit_const;
80     }
81 
getImplicitConstValueAttributeSpec82     int64_t getImplicitConstValue() const {
83       assert(isImplicitConst());
84       return Value;
85     }
86 
87     /// Get the fixed byte size of this Form if possible. This function might
88     /// use the DWARFUnit to calculate the size of the Form, like for
89     /// DW_AT_address and DW_AT_ref_addr, so this isn't just an accessor for
90     /// the ByteSize member.
91     LLVM_ABI std::optional<int64_t> getByteSize(const DWARFUnit &U) const;
92   };
93   using AttributeSpecVector = SmallVector<AttributeSpec, 8>;
94 
95   LLVM_ABI DWARFAbbreviationDeclaration();
96 
getCode()97   uint32_t getCode() const { return Code; }
getCodeByteSize()98   uint8_t getCodeByteSize() const { return CodeByteSize; }
getTag()99   dwarf::Tag getTag() const { return Tag; }
hasChildren()100   bool hasChildren() const { return HasChildren; }
101 
102   using attr_iterator_range =
103       iterator_range<AttributeSpecVector::const_iterator>;
104 
attributes()105   attr_iterator_range attributes() const {
106     return attr_iterator_range(AttributeSpecs.begin(), AttributeSpecs.end());
107   }
108 
getFormByIndex(uint32_t idx)109   dwarf::Form getFormByIndex(uint32_t idx) const {
110     assert(idx < AttributeSpecs.size());
111     return AttributeSpecs[idx].Form;
112   }
113 
getNumAttributes()114   size_t getNumAttributes() const {
115     return AttributeSpecs.size();
116   }
117 
getAttrByIndex(uint32_t idx)118   dwarf::Attribute getAttrByIndex(uint32_t idx) const {
119     assert(idx < AttributeSpecs.size());
120     return AttributeSpecs[idx].Attr;
121   }
122 
getAttrIsImplicitConstByIndex(uint32_t idx)123   bool getAttrIsImplicitConstByIndex(uint32_t idx) const {
124     assert(idx < AttributeSpecs.size());
125     return AttributeSpecs[idx].isImplicitConst();
126   }
127 
getAttrImplicitConstValueByIndex(uint32_t idx)128   int64_t getAttrImplicitConstValueByIndex(uint32_t idx) const {
129     assert(idx < AttributeSpecs.size());
130     return AttributeSpecs[idx].getImplicitConstValue();
131   }
132 
133   /// Get the index of the specified attribute.
134   ///
135   /// Searches the this abbreviation declaration for the index of the specified
136   /// attribute.
137   ///
138   /// \param attr DWARF attribute to search for.
139   /// \returns Optional index of the attribute if found, std::nullopt otherwise.
140   LLVM_ABI std::optional<uint32_t>
141   findAttributeIndex(dwarf::Attribute attr) const;
142 
143   /// Extract a DWARF form value from a DIE specified by DIE offset.
144   ///
145   /// Extract an attribute value for a DWARFUnit given the DIE offset and the
146   /// attribute.
147   ///
148   /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
149   /// code in the .debug_info data.
150   /// \param Attr DWARF attribute to search for.
151   /// \param U the DWARFUnit the contains the DIE.
152   /// \returns Optional DWARF form value if the attribute was extracted.
153   LLVM_ABI std::optional<DWARFFormValue>
154   getAttributeValue(const uint64_t DIEOffset, const dwarf::Attribute Attr,
155                     const DWARFUnit &U) const;
156 
157   /// Compute an offset from a DIE specified by DIE offset and attribute index.
158   ///
159   /// \param AttrIndex an index of DWARF attribute.
160   /// \param DIEOffset the DIE offset that points to the ULEB128 abbreviation
161   /// code in the .debug_info data.
162   /// \param U the DWARFUnit the contains the DIE.
163   /// \returns an offset of the attribute.
164   LLVM_ABI uint64_t getAttributeOffsetFromIndex(uint32_t AttrIndex,
165                                                 uint64_t DIEOffset,
166                                                 const DWARFUnit &U) const;
167 
168   /// Extract a DWARF form value from a DIE speccified by attribute index and
169   /// its offset.
170   ///
171   /// \param AttrIndex an index of DWARF attribute.
172   /// \param Offset offset of the attribute.
173   /// \param U the DWARFUnit the contains the DIE.
174   /// \returns Optional DWARF form value if the attribute was extracted.
175   LLVM_ABI std::optional<DWARFFormValue>
176   getAttributeValueFromOffset(uint32_t AttrIndex, uint64_t Offset,
177                               const DWARFUnit &U) const;
178 
179   LLVM_ABI llvm::Expected<ExtractState> extract(DataExtractor Data,
180                                                 uint64_t *OffsetPtr);
181   LLVM_ABI void dump(raw_ostream &OS) const;
182 
183   // Return an optional byte size of all attribute data in this abbreviation
184   // if a constant byte size can be calculated given a DWARFUnit. This allows
185   // DWARF parsing to be faster as many DWARF DIEs have a fixed byte size.
186   LLVM_ABI std::optional<size_t>
187   getFixedAttributesByteSize(const DWARFUnit &U) const;
188 
189 private:
190   void clear();
191 
192   /// A helper structure that can quickly determine the size in bytes of an
193   /// abbreviation declaration.
194   struct FixedSizeInfo {
195     /// The fixed byte size for fixed size forms.
196     uint16_t NumBytes = 0;
197     /// Number of DW_FORM_address forms in this abbrevation declaration.
198     uint8_t NumAddrs = 0;
199     /// Number of DW_FORM_ref_addr forms in this abbrevation declaration.
200     uint8_t NumRefAddrs = 0;
201     /// Number of 4 byte in DWARF32 and 8 byte in DWARF64 forms.
202     uint8_t NumDwarfOffsets = 0;
203 
204     FixedSizeInfo() = default;
205 
206     /// Calculate the fixed size in bytes given a DWARFUnit.
207     ///
208     /// \param U the DWARFUnit to use when determing the byte size.
209     /// \returns the size in bytes for all attribute data in this abbreviation.
210     /// The returned size does not include bytes for the  ULEB128 abbreviation
211     /// code
212     LLVM_ABI size_t getByteSize(const DWARFUnit &U) const;
213   };
214 
215   uint32_t Code;
216   dwarf::Tag Tag;
217   uint8_t CodeByteSize;
218   bool HasChildren;
219   AttributeSpecVector AttributeSpecs;
220   /// If this abbreviation has a fixed byte size then FixedAttributeSize member
221   /// variable below will have a value.
222   std::optional<FixedSizeInfo> FixedAttributeSize;
223 };
224 
225 } // end namespace llvm
226 
227 #endif // LLVM_DEBUGINFO_DWARF_DWARFABBREVIATIONDECLARATION_H
228