1 //===- DWARFDebugAranges.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/DWARFDebugAranges.h"
11 #include "llvm/DebugInfo/DWARF/DWARFCompileUnit.h"
12 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
13 #include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
14 #include "llvm/Support/DataExtractor.h"
15 #include <algorithm>
16 #include <cassert>
17 #include <cstdint>
18 #include <set>
19 #include <vector>
20 
21 using namespace llvm;
22 
23 void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
24   if (!DebugArangesData.isValidOffset(0))
25     return;
26   uint32_t Offset = 0;
27   DWARFDebugArangeSet Set;
28 
29   while (Set.extract(DebugArangesData, &Offset)) {
30     uint32_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 
40 void DWARFDebugAranges::generate(DWARFContext *CTX) {
41   clear();
42   if (!CTX)
43     return;
44 
45   // Extract aranges from .debug_aranges section.
46   DataExtractor ArangesData(CTX->getARangeSection(), CTX->isLittleEndian(), 0);
47   extract(ArangesData);
48 
49   // Generate aranges from DIEs: even if .debug_aranges section is present,
50   // it may describe only a small subset of compilation units, so we need to
51   // manually build aranges for the rest of them.
52   for (const auto &CU : CTX->compile_units()) {
53     uint32_t CUOffset = CU->getOffset();
54     if (ParsedCUOffsets.insert(CUOffset).second) {
55       DWARFAddressRangesVector CURanges;
56       CU->collectAddressRanges(CURanges);
57       for (const auto &R : CURanges)
58         appendRange(CUOffset, R.LowPC, R.HighPC);
59     }
60   }
61 
62   construct();
63 }
64 
65 void DWARFDebugAranges::clear() {
66   Endpoints.clear();
67   Aranges.clear();
68   ParsedCUOffsets.clear();
69 }
70 
71 void DWARFDebugAranges::appendRange(uint32_t CUOffset, uint64_t LowPC,
72                                     uint64_t HighPC) {
73   if (LowPC >= HighPC)
74     return;
75   Endpoints.emplace_back(LowPC, CUOffset, true);
76   Endpoints.emplace_back(HighPC, CUOffset, false);
77 }
78 
79 void DWARFDebugAranges::construct() {
80   std::multiset<uint32_t> ValidCUs;  // Maintain the set of CUs describing
81                                      // a current address range.
82   std::sort(Endpoints.begin(), Endpoints.end());
83   uint64_t PrevAddress = -1ULL;
84   for (const auto &E : Endpoints) {
85     if (PrevAddress < E.Address && !ValidCUs.empty()) {
86       // If the address range between two endpoints is described by some
87       // CU, first try to extend the last range in Aranges. If we can't
88       // do it, start a new range.
89       if (!Aranges.empty() && Aranges.back().HighPC() == PrevAddress &&
90           ValidCUs.find(Aranges.back().CUOffset) != ValidCUs.end()) {
91         Aranges.back().setHighPC(E.Address);
92       } else {
93         Aranges.emplace_back(PrevAddress, E.Address, *ValidCUs.begin());
94       }
95     }
96     // Update the set of valid CUs.
97     if (E.IsRangeStart) {
98       ValidCUs.insert(E.CUOffset);
99     } else {
100       auto CUPos = ValidCUs.find(E.CUOffset);
101       assert(CUPos != ValidCUs.end());
102       ValidCUs.erase(CUPos);
103     }
104     PrevAddress = E.Address;
105   }
106   assert(ValidCUs.empty());
107 
108   // Endpoints are not needed now.
109   std::vector<RangeEndpoint> EmptyEndpoints;
110   EmptyEndpoints.swap(Endpoints);
111 }
112 
113 uint32_t DWARFDebugAranges::findAddress(uint64_t Address) const {
114   if (!Aranges.empty()) {
115     Range range(Address);
116     RangeCollIterator begin = Aranges.begin();
117     RangeCollIterator end = Aranges.end();
118     RangeCollIterator pos =
119         std::lower_bound(begin, end, range);
120 
121     if (pos != end && pos->containsAddress(Address)) {
122       return pos->CUOffset;
123     } else if (pos != begin) {
124       --pos;
125       if (pos->containsAddress(Address))
126         return pos->CUOffset;
127     }
128   }
129   return -1U;
130 }
131