https://github.com/jeffreytan81 created https://github.com/llvm/llvm-project/pull/70231
While using dwarf5 `.debug_names` in internal large targets, we noticed a performance issue (around 10 seconds delay) while `lldb-vscode` tries to show `scopes` for a compile unit. Profiling shows the bottleneck is inside `DebugNamesDWARFIndex::GetGlobalVariables` which linearly search all index entries belongs to a compile unit. This patch improves the performance by using the compile units list to filter first before checking index entries. This significantly improves the performance (drops from 10 seconds => under 1 second) in the split dwarf situation because each compile unit has its own named index. >From c8d9a1f7387e3e4944d92ccb33699b6a9d0dcf89 Mon Sep 17 00:00:00 2001 From: jeffreytan81 <jeffrey...@fb.com> Date: Wed, 25 Oct 2023 10:21:06 -0700 Subject: [PATCH] Improve debug names index fetching global variables performance --- .../Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp index 292ea2806c59dc7..f94491b29bdbe14 100644 --- a/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp +++ b/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp @@ -130,6 +130,17 @@ void DebugNamesDWARFIndex::GetGlobalVariables( uint64_t cu_offset = cu.GetOffset(); bool found_entry_for_cu = false; for (const DebugNames::NameIndex &ni: *m_debug_names_up) { + // Check if this name index contains an entry for the given CU. + bool has_match_cu = false; + for (uint32_t i = 0;i < ni.getCUCount();++i) { + if (ni.getCUOffset(i) == cu_offset) { + has_match_cu = true; + break; + } + } + if (!has_match_cu) + continue; + for (DebugNames::NameTableEntry nte: ni) { uint64_t entry_offset = nte.getEntryOffset(); llvm::Expected<DebugNames::Entry> entry_or = ni.getEntry(&entry_offset); _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits