aprantl created this revision.
aprantl added reviewers: JDevlieghere, friss, jasonmolenda, jingham.
Herald added a subscriber: arphaman.
When debugging a large program like clang and doing "frame variable *this", the
ValueObject pretty printer is doing hundreds of scoped FindTypes lookups. The
ones that take longest are the ones where the DWARFDeclContext ends in
something like `::Iterator` which produces many false positives that need to be
filtered out *after* extracting the DIEs. This patch demonstrates a way to
filter out false positives at the accerator table lookup step.
With this patch `lldb clang-10 -o "b EmitFunctionStart" -o r -o "f 2" -o "fr v
*this" -b -- ...` goes from 5.6s -> 4.83s or wall clock 6.979s -> 5.99s.
There are probably other good heuristics, too, and I should also implement this
for DWARF 5 debug_names.
https://reviews.llvm.org/D68678
Files:
lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
Index: lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
@@ -110,6 +110,17 @@
const bool has_qualified_name_hash =
m_apple_types_up->GetHeader().header_data.ContainsAtom(
DWARFMappedHash::eAtomTypeQualNameHash);
+
+ // When searching for "std::vector<int>::const_iterator", reject any
+ // files without "vector<int>" early, since there will be many other
+ // "const_iterators".
+ if (context.GetSize() > 1 && context[1].tag == DW_TAG_class_type) {
+ DIEArray class_matches;
+ m_apple_types_up->FindByName(context[1].name, class_matches);
+ if (class_matches.empty())
+ return;
+ }
+
const ConstString type_name(context[0].name);
const dw_tag_t tag = context[0].tag;
if (has_tag && has_qualified_name_hash) {
Index: lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/AppleDWARFIndex.cpp
@@ -110,6 +110,17 @@
const bool has_qualified_name_hash =
m_apple_types_up->GetHeader().header_data.ContainsAtom(
DWARFMappedHash::eAtomTypeQualNameHash);
+
+ // When searching for "std::vector<int>::const_iterator", reject any
+ // files without "vector<int>" early, since there will be many other
+ // "const_iterators".
+ if (context.GetSize() > 1 && context[1].tag == DW_TAG_class_type) {
+ DIEArray class_matches;
+ m_apple_types_up->FindByName(context[1].name, class_matches);
+ if (class_matches.empty())
+ return;
+ }
+
const ConstString type_name(context[0].name);
const dw_tag_t tag = context[0].tag;
if (has_tag && has_qualified_name_hash) {
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