[Lldb-commits] [lldb] Improve type and namespace lookup using parent chain (PR #108907)

[via lldb-commits]

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@@ -374,25 +377,40 @@ void DebugNamesDWARFIndex::GetFullyQualifiedType(
   m_fallback.GetFullyQualifiedType(context, callback);
 }
 
+bool DebugNamesDWARFIndex::SameAsEntryATName(
+    llvm::StringRef query_name, const DebugNames::Entry &entry) const {
+  auto maybe_dieoffset = entry.getDIEUnitOffset();
+  if (!maybe_dieoffset)
+    return false;
+
+  // [Optimization] instead of parsing the entry from dwo file, we simply
+  // check if the query_name can point to an entry of the same DIE offset.
+  // This greatly reduced number of dwo file parsed and thus improved the
+  // performance.
+  for (const DebugNames::Entry &query_entry :
+       entry.getNameIndex()->equal_range(query_name)) {
+    auto query_dieoffset = query_entry.getDIEUnitOffset();
+    if (!query_dieoffset)
+      continue;
+
+    if (*query_dieoffset == *maybe_dieoffset) {
+      return true;
+    } else if (*query_dieoffset > *maybe_dieoffset) {
+      // The pool entries of the same name are sequentially cluttered together
+      // so if the query name from `query_name` is after the target entry, this
+      // is definitely not the correct one, we can stop searching.
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jeffreytan81 wrote:

@labath, @felipepiovezan, ah, you are right. This check is a bad implementation. The optimization I want to express here is that: the "pool entries" in `.debug_names` are cluttered together (which is stated by spec) while the code incorrectly checks that the "die offsets" in `.debug_info` pointed to by `.debug_names` "pool entries" are sorted (which definitely has no guarantee). 

>From the existing API it is not that simple to express the intention I want to express, and the performance testing shows this check does not affect wall-time (at least in our cases) so I will remove this check in this iteration but add a TODO to look into in future. 

For splitting PRs, that makes sense. This PR just shares big picture and gathers feedback so that I can refactor more effectively. 

https://github.com/llvm/llvm-project/pull/108907