DWARFDebugInfoEntry.cpp revision 360784 
1//===- DWARFDebugInfoEntry.cpp --------------------------------------------===//
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#include "llvm/DebugInfo/DWARF/DWARFDebugInfoEntry.h"
10#include "llvm/ADT/Optional.h"
11#include "llvm/DebugInfo/DWARF/DWARFDebugAbbrev.h"
12#include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
13#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
14#include "llvm/Support/DataExtractor.h"
15#include <cstddef>
16#include <cstdint>
17
18using namespace llvm;
19using namespace dwarf;
20
21bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U,
22                                             uint64_t *OffsetPtr) {
23  DWARFDataExtractor DebugInfoData = U.getDebugInfoExtractor();
24  const uint64_t UEndOffset = U.getNextUnitOffset();
25  return extractFast(U, OffsetPtr, DebugInfoData, UEndOffset, 0);
26}
27
28bool DWARFDebugInfoEntry::extractFast(const DWARFUnit &U, uint64_t *OffsetPtr,
29                                      const DWARFDataExtractor &DebugInfoData,
30                                      uint64_t UEndOffset, uint32_t D) {
31  Offset = *OffsetPtr;
32  Depth = D;
33  if (Offset >= UEndOffset || !DebugInfoData.isValidOffset(Offset))
34    return false;
35  uint64_t AbbrCode = DebugInfoData.getULEB128(OffsetPtr);
36  if (0 == AbbrCode) {
37    // NULL debug tag entry.
38    AbbrevDecl = nullptr;
39    return true;
40  }
41  AbbrevDecl = U.getAbbreviations()->getAbbreviationDeclaration(AbbrCode);
42  if (nullptr == AbbrevDecl) {
43    // Restore the original offset.
44    *OffsetPtr = Offset;
45    return false;
46  }
47  // See if all attributes in this DIE have fixed byte sizes. If so, we can
48  // just add this size to the offset to skip to the next DIE.
49  if (Optional<size_t> FixedSize = AbbrevDecl->getFixedAttributesByteSize(U)) {
50    *OffsetPtr += *FixedSize;
51    return true;
52  }
53
54  // Skip all data in the .debug_info for the attributes
55  for (const auto &AttrSpec : AbbrevDecl->attributes()) {
56    // Check if this attribute has a fixed byte size.
57    if (auto FixedSize = AttrSpec.getByteSize(U)) {
58      // Attribute byte size if fixed, just add the size to the offset.
59      *OffsetPtr += *FixedSize;
60    } else if (!DWARFFormValue::skipValue(AttrSpec.Form, DebugInfoData,
61                                          OffsetPtr, U.getFormParams())) {
62      // We failed to skip this attribute's value, restore the original offset
63      // and return the failure status.
64      *OffsetPtr = Offset;
65      return false;
66    }
67  }
68  return true;
69}
70