1 //===- DWARFDebugInfoEntry.cpp --------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h"
11 #include "llvm/ADT/Optional.h"
12 #include "llvm/DebugInfo/DWARF/DWARFDebugAbbrev.h"
13 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
14 #include "llvm/DebugInfo/DWARF/DWARFUnit.h"
15 #include "llvm/Support/DataExtractor.h"
16 #include <cstddef>
17 #include <cstdint>
18 
19 using namespace llvm;
20 using namespace dwarf;
21 
22 bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U,
23                                              uint32_t *OffsetPtr) {
24   DataExtractor DebugInfoData = U.getDebugInfoExtractor();
25   const uint32_t UEndOffset = U.getNextUnitOffset();
26   return extractFast(U, OffsetPtr, DebugInfoData, UEndOffset, 0);
27 }
28 
29 bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U, uint32_t *OffsetPtr,
30                                       const DataExtractor &DebugInfoData,
31                                       uint32_t UEndOffset, uint32_t D) {
32   Offset = *OffsetPtr;
33   Depth = D;
34   if (Offset >= UEndOffset || !DebugInfoData.isValidOffset(Offset))
35     return false;
36   uint64_t AbbrCode = DebugInfoData.getULEB128(OffsetPtr);
37   if (0 == AbbrCode) {
38     // NULL debug tag entry.
39     AbbrevDecl = nullptr;
40     return true;
41   }
42   AbbrevDecl = U.getAbbreviations()->getAbbreviationDeclaration(AbbrCode);
43   if (nullptr == AbbrevDecl) {
44     // Restore the original offset.
45     *OffsetPtr = Offset;
46     return false;
47   }
48   // See if all attributes in this DIE have fixed byte sizes. If so, we can
49   // just add this size to the offset to skip to the next DIE.
50   if (Optional<size_t> FixedSize = AbbrevDecl->getFixedAttributesByteSize(U)) {
51     *OffsetPtr += *FixedSize;
52     return true;
53   }
54 
55   // Skip all data in the .debug_info for the attributes
56   for (const auto &AttrSpec : AbbrevDecl->attributes()) {
57     // Check if this attribute has a fixed byte size.
58     if (auto FixedSize = AttrSpec.getByteSize(U)) {
59       // Attribute byte size if fixed, just add the size to the offset.
60       *OffsetPtr += *FixedSize;
61     } else if (!DWARFFormValue::skipValue(AttrSpec.Form, DebugInfoData,
62                                           OffsetPtr, &U)) {
63       // We failed to skip this attribute's value, restore the original offset
64       // and return the failure status.
65       *OffsetPtr = Offset;
66       return false;
67     }
68   }
69   return true;
70 }
71