[Lldb-commits] [PATCH] D68655: Trust the arange accelerator tables in dSYMs

[Adrian Prantl via Phabricator via lldb-commits]

aprantl created this revision.
aprantl added reviewers: jasonmolenda, jingham, friss.
Herald added a subscriber: JDevlieghere.
Herald added a reviewer: JDevlieghere.

When ingesting aranges from a dSYM it makes sense to always trust the contents of the accelerator table since it always comes from dsymutil. According to Instruments, skipping the decoding of all CU DIEs to get at the DW_AT_ranges attribute removes ~3.5 seconds from setting a breakpoint by file/line when debugging clang with a dSYM. Interestingly on the wall clock the speedup is less noticeable, but still present.

rdar://problem/56057688


https://reviews.llvm.org/D68655

Files:
  lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp


Index: lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -54,13 +54,19 @@
 
   // Manually build arange data for everything that wasn't in the
   // .debug_aranges table.
-  const size_t num_units = GetNumUnits();
-  for (size_t idx = 0; idx < num_units; ++idx) {
-    DWARFUnit *cu = GetUnitAtIndex(idx);
-
-    dw_offset_t offset = cu->GetOffset();
-    if (cus_with_data.find(offset) == cus_with_data.end())
-      cu->BuildAddressRangeTable(m_cu_aranges_up.get());
+  //
+  // This step is skipped for dSYMs and other debug-info-only
+  // objects, which are always trusted to have a complete table.
+  auto *obj = m_dwarf.GetObjectFile();
+  if (!obj || obj->GetType() != ObjectFile::eTypeDebugInfo) {
+    const size_t num_units = GetNumUnits();
+    for (size_t idx = 0; idx < num_units; ++idx) {
+      DWARFUnit *cu = GetUnitAtIndex(idx);
+
+      dw_offset_t offset = cu->GetOffset();
+      if (cus_with_data.find(offset) == cus_with_data.end())
+        cu->BuildAddressRangeTable(m_cu_aranges_up.get());
+    }
   }
 
   const bool minimize = true;


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