8356394: Remove USE_LIBRARY_BASED_TLS_ONLY macro

Reviewed-by: dholmes, kbarrett, lucy

Author: MBaesken

src/hotspot/share/classfile/symbolTable.cpp

@@ -88,13 +88,9 @@ static volatile bool   _has_items_to_clean = false;
 
 static volatile bool _alt_hash = false;
 
-#ifdef USE_LIBRARY_BASED_TLS_ONLY
-static volatile bool _lookup_shared_first = false;
-#else
 // "_lookup_shared_first" can get highly contended with many cores if multiple threads
-// are updating "lookup success history" in a global shared variable. If built-in TLS is available, use it.
+// are updating "lookup success history" in a global shared variable, so use built-in TLS
 static THREAD_LOCAL bool _lookup_shared_first = false;
-#endif
 
 // Static arena for symbols that are not deallocated
 Arena* SymbolTable::_arena = nullptr;

src/hotspot/share/runtime/thread.cpp

@@ -52,10 +52,7 @@
 #include "jfr/jfr.hpp"
 #endif
 
-#ifndef USE_LIBRARY_BASED_TLS_ONLY
-// Current thread is maintained as a thread-local variable
 THREAD_LOCAL Thread* Thread::_thr_current = nullptr;
-#endif
 
 // ======= Thread ========
 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
@@ -158,20 +155,16 @@ void Thread::initialize_tlab() {
 }
 
 void Thread::initialize_thread_current() {
-#ifndef USE_LIBRARY_BASED_TLS_ONLY
   assert(_thr_current == nullptr, "Thread::current already initialized");
   _thr_current = this;
-#endif
   assert(ThreadLocalStorage::thread() == nullptr, "ThreadLocalStorage::thread already initialized");
   ThreadLocalStorage::set_thread(this);
   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 }
 
 void Thread::clear_thread_current() {
   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
-#ifndef USE_LIBRARY_BASED_TLS_ONLY
   _thr_current = nullptr;
-#endif
   ThreadLocalStorage::set_thread(nullptr);
 }
 

src/hotspot/share/runtime/thread.hpp

@@ -113,10 +113,8 @@ class Thread: public ThreadShadow {
   friend class JavaThread;
  private:
 
-#ifndef USE_LIBRARY_BASED_TLS_ONLY
   // Current thread is maintained as a thread-local variable
   static THREAD_LOCAL Thread* _thr_current;
-#endif
 
   // On AArch64, the high order 32 bits are used by a "patching epoch" number
   // which reflects if this thread has executed the required fences, after
@@ -660,14 +658,7 @@ inline Thread* Thread::current() {
 }
 
 inline Thread* Thread::current_or_null() {
-#ifndef USE_LIBRARY_BASED_TLS_ONLY
   return _thr_current;
-#else
-  if (ThreadLocalStorage::is_initialized()) {
-    return ThreadLocalStorage::thread();
-  }
-  return nullptr;
-#endif
 }
 
 inline Thread* Thread::current_or_null_safe() {