DWARFDebugAranges.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
1//===-- DWARFDebugAranges.cpp -----------------------------------*- C++ -*-===//
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 "DWARFDebugAranges.h"
11#include "DWARFCompileUnit.h"
12#include "DWARFContext.h"
13#include "llvm/Support/Format.h"
14#include "llvm/Support/raw_ostream.h"
15#include <algorithm>
16#include <cassert>
17using namespace llvm;
18
19void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
20  if (!DebugArangesData.isValidOffset(0))
21    return;
22  uint32_t Offset = 0;
23  typedef std::vector<DWARFDebugArangeSet> RangeSetColl;
24  RangeSetColl Sets;
25  DWARFDebugArangeSet Set;
26  uint32_t TotalRanges = 0;
27
28  while (Set.extract(DebugArangesData, &Offset)) {
29    Sets.push_back(Set);
30    TotalRanges += Set.getNumDescriptors();
31  }
32  if (TotalRanges == 0)
33    return;
34
35  Aranges.reserve(TotalRanges);
36  for (const auto &I : Sets) {
37    uint32_t CUOffset = I.getCompileUnitDIEOffset();
38
39    for (const auto &Desc : I.descriptors()) {
40      uint64_t LowPC = Desc.Address;
41      uint64_t HighPC = Desc.getEndAddress();
42      appendRange(CUOffset, LowPC, HighPC);
43    }
44  }
45}
46
47void DWARFDebugAranges::generate(DWARFContext *CTX) {
48  clear();
49  if (!CTX)
50    return;
51
52  // Extract aranges from .debug_aranges section.
53  DataExtractor ArangesData(CTX->getARangeSection(), CTX->isLittleEndian(), 0);
54  extract(ArangesData);
55
56  // Generate aranges from DIEs: even if .debug_aranges section is present,
57  // it may describe only a small subset of compilation units, so we need to
58  // manually build aranges for the rest of them.
59  for (const auto &CU : CTX->compile_units()) {
60    uint32_t CUOffset = CU->getOffset();
61    if (ParsedCUOffsets.insert(CUOffset).second)
62      CU->buildAddressRangeTable(this, true, CUOffset);
63  }
64
65  sortAndMinimize();
66}
67
68void DWARFDebugAranges::appendRange(uint32_t CUOffset, uint64_t LowPC,
69                                    uint64_t HighPC) {
70  if (!Aranges.empty()) {
71    if (Aranges.back().CUOffset == CUOffset &&
72        Aranges.back().HighPC() == LowPC) {
73      Aranges.back().setHighPC(HighPC);
74      return;
75    }
76  }
77  Aranges.push_back(Range(LowPC, HighPC, CUOffset));
78}
79
80void DWARFDebugAranges::sortAndMinimize() {
81  const size_t orig_arange_size = Aranges.size();
82  // Size of one? If so, no sorting is needed
83  if (orig_arange_size <= 1)
84    return;
85  // Sort our address range entries
86  std::stable_sort(Aranges.begin(), Aranges.end());
87
88  // Most address ranges are contiguous from function to function
89  // so our new ranges will likely be smaller. We calculate the size
90  // of the new ranges since although std::vector objects can be resized,
91  // the will never reduce their allocated block size and free any excesss
92  // memory, so we might as well start a brand new collection so it is as
93  // small as possible.
94
95  // First calculate the size of the new minimal arange vector
96  // so we don't have to do a bunch of re-allocations as we
97  // copy the new minimal stuff over to the new collection.
98  size_t minimal_size = 1;
99  for (size_t i = 1; i < orig_arange_size; ++i) {
100    if (!Range::SortedOverlapCheck(Aranges[i-1], Aranges[i]))
101      ++minimal_size;
102  }
103
104  // If the sizes are the same, then no consecutive aranges can be
105  // combined, we are done.
106  if (minimal_size == orig_arange_size)
107    return;
108
109  // Else, make a new RangeColl that _only_ contains what we need.
110  RangeColl minimal_aranges;
111  minimal_aranges.resize(minimal_size);
112  uint32_t j = 0;
113  minimal_aranges[j] = Aranges[0];
114  for (size_t i = 1; i < orig_arange_size; ++i) {
115    if (Range::SortedOverlapCheck(minimal_aranges[j], Aranges[i])) {
116      minimal_aranges[j].setHighPC(Aranges[i].HighPC());
117    } else {
118      // Only increment j if we aren't merging
119      minimal_aranges[++j] = Aranges[i];
120    }
121  }
122  assert(j+1 == minimal_size);
123
124  // Now swap our new minimal aranges into place. The local
125  // minimal_aranges will then contian the old big collection
126  // which will get freed.
127  minimal_aranges.swap(Aranges);
128}
129
130uint32_t DWARFDebugAranges::findAddress(uint64_t Address) const {
131  if (!Aranges.empty()) {
132    Range range(Address);
133    RangeCollIterator begin = Aranges.begin();
134    RangeCollIterator end = Aranges.end();
135    RangeCollIterator pos =
136        std::lower_bound(begin, end, range);
137
138    if (pos != end && pos->containsAddress(Address)) {
139      return pos->CUOffset;
140    } else if (pos != begin) {
141      --pos;
142      if (pos->containsAddress(Address))
143        return pos->CUOffset;
144    }
145  }
146  return -1U;
147}
148