[dsymutil] Avoid repeated hash lookups (NFC) (#126190) (#126346)

Author: kazutakahirata

llvm/tools/dsymutil/BinaryHolder.cpp

@@ -176,8 +176,8 @@ BinaryHolder::ArchiveEntry::getObjectEntry(StringRef Filename,
 
   // Try the cache first.
   std::lock_guard<std::mutex> Lock(MemberCacheMutex);
-  if (MemberCache.count(Key))
-    return *MemberCache[Key];
+  if (auto It = MemberCache.find(Key); It != MemberCache.end())
+    return *It->second;
 
   // Create a new ObjectEntry, but don't add it to the cache yet. Loading of
   // the archive members might fail and we don't want to lock the whole archive
@@ -228,8 +228,7 @@ BinaryHolder::ArchiveEntry::getObjectEntry(StringRef Filename,
   if (OE->Objects.empty())
     return errorCodeToError(errc::no_such_file_or_directory);
 
-  MemberCache[Key] = std::move(OE);
-  return *MemberCache[Key];
+  return *(MemberCache[Key] = std::move(OE));
 }
 
 Expected<const BinaryHolder::ObjectEntry &>