[Lldb-commits] [PATCH] D11390: Optimize GetCompileUnitContainingDIE with a lookup table

[Greg Clayton]

clayborg requested changes to this revision.
clayborg added a comment.
This revision now requires changes to proceed.

No need for an extra map. A local C++ guru a while back told me about being able to use a comparison function with two different types if you use std::lower_bound() or std::upper_bound(). Since m_compiler_units is sorted, we can just do:

  static bool CompileUnitOffsetLessThan (dw_offset_t die_offset, const DWARFCompileUnitSP& cu_sp)
  {
      return die_offset < cu_sp->GetOffset();
  }
  
  DWARFCompileUnitSP
  DWARFDebugInfo::GetCompileUnitContainingDIE(dw_offset_t die_offset)
  {
      DWARFCompileUnitSP cu_sp;
      if (die_offset != DW_INVALID_OFFSET)
      {
          ParseCompileUnitHeadersIfNeeded();
  
          // Watch out for single compile unit executable as they are pretty common
          const size_t num_cus = m_compile_units.size();
          if (num_cus == 1)
          {
              if (m_compile_units[0]->ContainsDIEOffset(die_offset))
                  cu_sp = m_compile_units[0];
          }
          else if (num_cus)
          {
              CompileUnitColl::const_iterator end_pos = m_compile_units.end();
              CompileUnitColl::const_iterator begin_pos = m_compile_units.begin();
              CompileUnitColl::const_iterator pos = std::upper_bound(begin_pos, end_pos, die_offset, CompileUnitOffsetLessThan);
              if (pos != begin_pos)
              {
                  --pos;
                  if ((*pos)->ContainsDIEOffset(die_offset))
                      cu_sp = *pos;
              }
          }
      }
      return cu_sp;
  }

Try out the changes and make sure they work and then switch to using the code above.


http://reviews.llvm.org/D11390