llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-lldb Author: None (jeffreytan81) <details> <summary>Changes</summary> 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. --- Full diff: https://github.com/llvm/llvm-project/pull/70231.diff 1 Files Affected: - (modified) lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp (+13-2) ``````````diff diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp index 292ea2806c59dc7..4fc3866a3b608fd 100644 --- a/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp +++ b/lldb/source/Plugins/SymbolFile/DWARF/DebugNamesDWARFIndex.cpp @@ -129,8 +129,19 @@ void DebugNamesDWARFIndex::GetGlobalVariables( DWARFUnit &cu, llvm::function_ref<bool(DWARFDIE die)> callback) { uint64_t cu_offset = cu.GetOffset(); bool found_entry_for_cu = false; - for (const DebugNames::NameIndex &ni: *m_debug_names_up) { - for (DebugNames::NameTableEntry nte: ni) { + for (const DebugNames::NameIndex &ni : *m_debug_names_up) { + // Check if this name index contains an entry for the given CU. + bool cu_matches = false; + for (uint32_t i = 0; i < ni.getCUCount(); ++i) { + if (ni.getCUOffset(i) == cu_offset) { + cu_matches = true; + break; + } + } + if (!cu_matches) + continue; + + for (DebugNames::NameTableEntry nte : ni) { uint64_t entry_offset = nte.getEntryOffset(); llvm::Expected<DebugNames::Entry> entry_or = ni.getEntry(&entry_offset); for (; entry_or; entry_or = ni.getEntry(&entry_offset)) { `````````` </details> https://github.com/llvm/llvm-project/pull/70231 _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
