Remove incorrect and superfluous caching in Mangled.

There was a global cache for Swift display names, however, it didn't
take the symbol context into account, which means the demangling
result is non-deterministic depending on whether the symbol context
had the necessary debug info to resolve the names of archetypes or
not.

In addition to that Display names are not supposed to be on a hot path
(unlike names, which are used to resolve breakpoints).

Author: adrian-prantl

lldb/source/Core/Mangled.cpp

@@ -45,23 +45,6 @@ static inline bool cstring_is_mangled(llvm::StringRef s) {
   return Mangled::GetManglingScheme(s) != Mangled::eManglingSchemeNone;
 }
 
-#ifdef LLDB_ENABLE_SWIFT
-#pragma mark DisplayDemangledNamesCache
-
-// make the key type be a const char* because that gives us usable
-// DenseMapInfo for free making DenseMap work for ConstString requires
-// us to provide two "invalid" values: the empty key and the tombstone
-// key; but for ConstString, we really don't have any well-known
-// invalid value other than ConstString(nullptr) so, just use const
-// char* as the key as LLVM knows how to do proper DenseMapInfo for
-// pointers
-static ThreadSafeDenseMap<const char *, ConstString>&
-GetDisplayDemangledNamesCache() {
-  static ThreadSafeDenseMap<const char *, ConstString> g_cache;
-  return g_cache;
-}
-#endif // LLDB_ENABLE_SWIFT
-
 #pragma mark Mangled
 
 Mangled::ManglingScheme Mangled::GetManglingScheme(llvm::StringRef const name) {
@@ -346,39 +329,15 @@ ConstString Mangled::GetDemangledName(// BEGIN SWIFT
 
 ConstString Mangled::GetDisplayDemangledName(
 // BEGIN SWIFT
-                                             const SymbolContext *sc
-                                             ) const {
-  ConstString demangled;
+    const SymbolContext *sc) const {
 #ifdef LLDB_ENABLE_SWIFT
-  if (m_mangled) {
-    do {
-      const char *mangled = m_mangled.GetCString();
-
-      if (mangled) {
-        if (SwiftLanguageRuntime::IsSwiftMangledName(m_mangled.GetStringRef())) {
-          auto& display_cache = ::GetDisplayDemangledNamesCache();
-          if (display_cache.Lookup(mangled, demangled) &&
-              demangled)
-            break;
-
-          std::string demangled_std =
-              SwiftLanguageRuntime::DemangleSymbolAsString(
-                  m_mangled.GetStringRef(), SwiftLanguageRuntime::eSimplified,
-                  sc);
-          if (!demangled_std.empty()) {
-            demangled.SetCString(demangled_std.c_str());
-            display_cache.Insert(mangled, demangled);
-            break;
-          }
-        }
-      }
-    } while (0);
-  }
+  if (m_mangled &&
+      SwiftLanguageRuntime::IsSwiftMangledName(m_mangled.GetStringRef()))
+    return ConstString(SwiftLanguageRuntime::DemangleSymbolAsString(
+        m_mangled.GetStringRef(), SwiftLanguageRuntime::eSimplified, sc));
 #endif // LLDB_ENABLE_SWIFT
-  if (!demangled)
-    demangled = GetDemangledName();
-  return demangled ? demangled : m_mangled;
 // END SWIFT
+  return GetDemangledName();
 }
 
 bool Mangled::NameMatches(const RegularExpression &regex) const {