DWP parsing: Use the index by hash when available

Rather than looking up by offset - actually use the hash table to
perform faster lookup where possible. (for DWARFv4 DWP compilation units
the hash isn't in the header - it's in the root DIE, but to parse the
DIE you need the abbrev section and to get the abbrev section you need
the index - so in that case lookup by offset is required)

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
index 295433d..04ccd32 100644 (file)
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFUnit.cpp
@@ -865,14 +865,24 @@ DWARFUnitHeader::extract(const DWARFDataExtractor &data,
         section == DIERef::Section::DebugTypes ? DW_UT_type : DW_UT_compile;
   }
 
+  if (header.IsTypeUnit()) {
+    header.m_type_hash = data.GetU64(offset_ptr);
+    header.m_type_offset = data.GetDWARFOffset(offset_ptr);
+  }
+
   if (context.isDwo()) {
+    const llvm::DWARFUnitIndex *Index;
     if (header.IsTypeUnit()) {
-      header.m_index_entry =
-          context.GetAsLLVM().getTUIndex().getFromOffset(header.m_offset);
+      Index = &context.GetAsLLVM().getTUIndex();
+      if (*Index)
+        header.m_index_entry = Index->getFromHash(header.m_type_hash);
     } else {
-      header.m_index_entry =
-          context.GetAsLLVM().getCUIndex().getFromOffset(header.m_offset);
+      Index = &context.GetAsLLVM().getCUIndex();
+      if (*Index && header.m_version >= 5)
+        header.m_index_entry = Index->getFromHash(header.m_dwo_id);
     }
+    if (!header.m_index_entry)
+      header.m_index_entry = Index->getFromOffset(header.m_offset);
   }
 
   if (header.m_index_entry) {
@@ -895,10 +905,6 @@ DWARFUnitHeader::extract(const DWARFDataExtractor &data,
     }
     header.m_abbr_offset = abbr_entry->Offset;
   }
-  if (header.IsTypeUnit()) {
-    header.m_type_hash = data.GetU64(offset_ptr);
-    header.m_type_offset = data.GetDWARFOffset(offset_ptr);
-  }
 
   bool length_OK = data.ValidOffset(header.GetNextUnitOffset() - 1);
   bool version_OK = SymbolFileDWARF::SupportedVersion(header.m_version);