7061197: ThreadLocalStorage sp map table should be optional

Reviewed-by: dholmes, never, jwilhelm, kvn

hotspot/src/os_cpu/linux_x86/vm/assembler_linux_x86.cpp

@@ -33,6 +33,28 @@ void MacroAssembler::int3() {
   call(RuntimeAddress(CAST_FROM_FN_PTR(address, os::breakpoint)));
 }
 
+#ifdef MINIMIZE_RAM_USAGE
+
+void MacroAssembler::get_thread(Register thread) {
+  // call pthread_getspecific
+  // void * pthread_getspecific(pthread_key_t key);
+  if (thread != rax) push(rax);
+  push(rcx);
+  push(rdx);
+
+  push(ThreadLocalStorage::thread_index());
+  call(RuntimeAddress(CAST_FROM_FN_PTR(address, pthread_getspecific)));
+  increment(rsp, wordSize);
+
+  pop(rdx);
+  pop(rcx);
+  if (thread != rax) {
+    mov(thread, rax);
+    pop(rax);
+  }
+}
+
+#else
 void MacroAssembler::get_thread(Register thread) {
   movl(thread, rsp);
   shrl(thread, PAGE_SHIFT);
@@ -43,6 +65,7 @@ void MacroAssembler::get_thread(Register thread) {
 
   movptr(thread, tls);
 }
+#endif // MINIMIZE_RAM_USAGE
 #else
 void MacroAssembler::int3() {
   call(RuntimeAddress(CAST_FROM_FN_PTR(address, os::breakpoint)));

hotspot/src/os_cpu/linux_x86/vm/threadLS_linux_x86.cpp

@@ -52,25 +52,20 @@
 // MADV_DONTNEED on Linux keeps the virtual memory mapping, but zaps the
 // physical memory page (i.e. similar to MADV_FREE on Solaris).
 
-#ifndef AMD64
+#if !defined(AMD64) && !defined(MINIMIZE_RAM_USAGE)
 Thread* ThreadLocalStorage::_sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)];
-#endif // !AMD64
 
 void ThreadLocalStorage::generate_code_for_get_thread() {
     // nothing we can do here for user-level thread
 }
 
 void ThreadLocalStorage::pd_init() {
-#ifndef AMD64
   assert(align_size_down(os::vm_page_size(), PAGE_SIZE) == os::vm_page_size(),
          "page size must be multiple of PAGE_SIZE");
-#endif // !AMD64
 }
 
 void ThreadLocalStorage::pd_set_thread(Thread* thread) {
   os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
-
-#ifndef AMD64
   address stack_top = os::current_stack_base();
   size_t stack_size = os::current_stack_size();
 
@@ -88,5 +83,17 @@ void ThreadLocalStorage::pd_set_thread(Thread* thread) {
            "thread exited without detaching from VM??");
     _sp_map[(uintptr_t)p >> PAGE_SHIFT] = thread;
   }
-#endif // !AMD64
 }
+#else
+
+void ThreadLocalStorage::generate_code_for_get_thread() {
+    // nothing we can do here for user-level thread
+}
+
+void ThreadLocalStorage::pd_init() {
+}
+
+void ThreadLocalStorage::pd_set_thread(Thread* thread) {
+  os::thread_local_storage_at_put(ThreadLocalStorage::thread_index(), thread);
+}
+#endif // !AMD64 && !MINIMIZE_RAM_USAGE

hotspot/src/os_cpu/linux_x86/vm/threadLS_linux_x86.hpp

@@ -27,28 +27,32 @@
 
   // Processor dependent parts of ThreadLocalStorage
 
-#ifndef AMD64
+#if !defined(AMD64) && !defined(MINIMIZE_RAM_USAGE)
+
   // map stack pointer to thread pointer - see notes in threadLS_linux_x86.cpp
   #define SP_BITLENGTH  32
   #define PAGE_SHIFT    12
   #define PAGE_SIZE     (1UL << PAGE_SHIFT)
   static Thread* _sp_map[1UL << (SP_BITLENGTH - PAGE_SHIFT)];
-#endif // !AMD64
 
 public:
 
-#ifndef AMD64
   static Thread** sp_map_addr() { return _sp_map; }
-#endif // !AMD64
 
   static Thread* thread() {
-#ifdef AMD64
-    return (Thread*) os::thread_local_storage_at(thread_index());
-#else
     uintptr_t sp;
     __asm__ volatile ("movl %%esp, %0" : "=r" (sp));
     return _sp_map[sp >> PAGE_SHIFT];
-#endif // AMD64
   }
 
+#else
+
+public:
+
+   static Thread* thread() {
+     return (Thread*) os::thread_local_storage_at(thread_index());
+   }
+
+#endif // AMD64 || MINIMIZE_RAM_USAGE
+
 #endif // OS_CPU_LINUX_X86_VM_THREADLS_LINUX_X86_HPP