1//===- DWARFDebugAranges.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/DWARFDebugAranges.h"
10#include "llvm/DebugInfo/DWARF/DWARFCompileUnit.h"
11#include "llvm/DebugInfo/DWARF/DWARFContext.h"
12#include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
13#include "llvm/Support/DataExtractor.h"
14#include "llvm/Support/WithColor.h"
15#include <algorithm>
16#include <cassert>
17#include <cstdint>
18#include <set>
19#include <vector>
20
21using namespace llvm;
22
23void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
24  if (!DebugArangesData.isValidOffset(0))
25    return;
26  uint64_t Offset = 0;
27  DWARFDebugArangeSet Set;
28
29  while (Set.extract(DebugArangesData, &Offset)) {
30    uint64_t CUOffset = Set.getCompileUnitDIEOffset();
31    for (const auto &Desc : Set.descriptors()) {
32      uint64_t LowPC = Desc.Address;
33      uint64_t HighPC = Desc.getEndAddress();
34      appendRange(CUOffset, LowPC, HighPC);
35    }
36    ParsedCUOffsets.insert(CUOffset);
37  }
38}
39
40void DWARFDebugAranges::generate(DWARFContext *CTX) {
41  clear();
42  if (!CTX)
43    return;
44
45  // Extract aranges from .debug_aranges section.
46  DataExtractor ArangesData(CTX->getDWARFObj().getArangesSection(),
47                            CTX->isLittleEndian(), 0);
48  extract(ArangesData);
49
50  // Generate aranges from DIEs: even if .debug_aranges section is present,
51  // it may describe only a small subset of compilation units, so we need to
52  // manually build aranges for the rest of them.
53  for (const auto &CU : CTX->compile_units()) {
54    uint64_t CUOffset = CU->getOffset();
55    if (ParsedCUOffsets.insert(CUOffset).second) {
56      Expected<DWARFAddressRangesVector> CURanges = CU->collectAddressRanges();
57      if (!CURanges)
58        WithColor::error() << toString(CURanges.takeError()) << '\n';
59      else
60        for (const auto &R : *CURanges)
61          appendRange(CUOffset, R.LowPC, R.HighPC);
62    }
63  }
64
65  construct();
66}
67
68void DWARFDebugAranges::clear() {
69  Endpoints.clear();
70  Aranges.clear();
71  ParsedCUOffsets.clear();
72}
73
74void DWARFDebugAranges::appendRange(uint64_t CUOffset, uint64_t LowPC,
75                                    uint64_t HighPC) {
76  if (LowPC >= HighPC)
77    return;
78  Endpoints.emplace_back(LowPC, CUOffset, true);
79  Endpoints.emplace_back(HighPC, CUOffset, false);
80}
81
82void DWARFDebugAranges::construct() {
83  std::multiset<uint64_t> ValidCUs;  // Maintain the set of CUs describing
84                                     // a current address range.
85  llvm::sort(Endpoints);
86  uint64_t PrevAddress = -1ULL;
87  for (const auto &E : Endpoints) {
88    if (PrevAddress < E.Address && !ValidCUs.empty()) {
89      // If the address range between two endpoints is described by some
90      // CU, first try to extend the last range in Aranges. If we can't
91      // do it, start a new range.
92      if (!Aranges.empty() && Aranges.back().HighPC() == PrevAddress &&
93          ValidCUs.find(Aranges.back().CUOffset) != ValidCUs.end()) {
94        Aranges.back().setHighPC(E.Address);
95      } else {
96        Aranges.emplace_back(PrevAddress, E.Address, *ValidCUs.begin());
97      }
98    }
99    // Update the set of valid CUs.
100    if (E.IsRangeStart) {
101      ValidCUs.insert(E.CUOffset);
102    } else {
103      auto CUPos = ValidCUs.find(E.CUOffset);
104      assert(CUPos != ValidCUs.end());
105      ValidCUs.erase(CUPos);
106    }
107    PrevAddress = E.Address;
108  }
109  assert(ValidCUs.empty());
110
111  // Endpoints are not needed now.
112  Endpoints.clear();
113  Endpoints.shrink_to_fit();
114}
115
116uint64_t DWARFDebugAranges::findAddress(uint64_t Address) const {
117  RangeCollIterator It =
118      partition_point(Aranges, [=](Range R) { return R.HighPC() <= Address; });
119  if (It != Aranges.end() && It->LowPC <= Address)
120    return It->CUOffset;
121  return -1ULL;
122}
123