text: //===- DWARFDebugAranges.cpp ----------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/DebugInfo/DWARF/DWARFDebugAranges.h"
  #include "llvm/DebugInfo/DWARF/DWARFCompileUnit.h"
  #include "llvm/DebugInfo/DWARF/DWARFContext.h"
  #include "llvm/DebugInfo/DWARF/DWARFDebugArangeSet.h"
  #include "llvm/Support/DataExtractor.h"
  #include "llvm/Support/WithColor.h"
  #include <algorithm>
  #include <cassert>
  #include <cstdint>
  #include <set>
  #include <vector>
  
  using namespace llvm;
  
  void DWARFDebugAranges::extract(DataExtractor DebugArangesData) {
    if (!DebugArangesData.isValidOffset(0))
      return;
    uint32_t Offset = 0;
    DWARFDebugArangeSet Set;
  
    while (Set.extract(DebugArangesData, &Offset)) {
      uint32_t CUOffset = Set.getCompileUnitDIEOffset();
      for (const auto &Desc : Set.descriptors()) {
        uint64_t LowPC = Desc.Address;
        uint64_t HighPC = Desc.getEndAddress();
        appendRange(CUOffset, LowPC, HighPC);
      }
      ParsedCUOffsets.insert(CUOffset);
    }
  }
  
  void DWARFDebugAranges::generate(DWARFContext *CTX) {
    clear();
    if (!CTX)
      return;
  
    // Extract aranges from .debug_aranges section.
    DataExtractor ArangesData(CTX->getDWARFObj().getARangeSection(),
                              CTX->isLittleEndian(), 0);
    extract(ArangesData);
  
    // Generate aranges from DIEs: even if .debug_aranges section is present,
    // it may describe only a small subset of compilation units, so we need to
    // manually build aranges for the rest of them.
    for (const auto &CU : CTX->compile_units()) {
      uint32_t CUOffset = CU->getOffset();
      if (ParsedCUOffsets.insert(CUOffset).second) {
        Expected<DWARFAddressRangesVector> CURanges = CU->collectAddressRanges();
        if (!CURanges)
          WithColor::error() << toString(CURanges.takeError()) << '\n';
        else
          for (const auto &R : *CURanges)
            appendRange(CUOffset, R.LowPC, R.HighPC);
      }
    }
  
    construct();
  }
  
  void DWARFDebugAranges::clear() {
    Endpoints.clear();
    Aranges.clear();
    ParsedCUOffsets.clear();
  }
  
  void DWARFDebugAranges::appendRange(uint32_t CUOffset, uint64_t LowPC,
                                      uint64_t HighPC) {
    if (LowPC >= HighPC)
      return;
    Endpoints.emplace_back(LowPC, CUOffset, true);
    Endpoints.emplace_back(HighPC, CUOffset, false);
  }
  
  void DWARFDebugAranges::construct() {
    std::multiset<uint32_t> ValidCUs;  // Maintain the set of CUs describing
                                       // a current address range.
    llvm::sort(Endpoints);
    uint64_t PrevAddress = -1ULL;
    for (const auto &E : Endpoints) {
      if (PrevAddress < E.Address && !ValidCUs.empty()) {
        // If the address range between two endpoints is described by some
        // CU, first try to extend the last range in Aranges. If we can't
        // do it, start a new range.
        if (!Aranges.empty() && Aranges.back().HighPC() == PrevAddress &&
            ValidCUs.find(Aranges.back().CUOffset) != ValidCUs.end()) {
          Aranges.back().setHighPC(E.Address);
        } else {
          Aranges.emplace_back(PrevAddress, E.Address, *ValidCUs.begin());
        }
      }
      // Update the set of valid CUs.
      if (E.IsRangeStart) {
        ValidCUs.insert(E.CUOffset);
      } else {
        auto CUPos = ValidCUs.find(E.CUOffset);
        assert(CUPos != ValidCUs.end());
        ValidCUs.erase(CUPos);
      }
      PrevAddress = E.Address;
    }
    assert(ValidCUs.empty());
  
    // Endpoints are not needed now.
    Endpoints.clear();
    Endpoints.shrink_to_fit();
  }
  
  uint32_t DWARFDebugAranges::findAddress(uint64_t Address) const {
    if (!Aranges.empty()) {
      Range range(Address);
      RangeCollIterator begin = Aranges.begin();
      RangeCollIterator end = Aranges.end();
      RangeCollIterator pos =
          std::lower_bound(begin, end, range);
  
      if (pos != end && pos->containsAddress(Address)) {
        return pos->CUOffset;
      } else if (pos != begin) {
        --pos;
        if (pos->containsAddress(Address))
          return pos->CUOffset;
      }
    }
    return -1U;
  }
  