Move pthread TLS state native code using wasm globals

This moves pthead_self and other thread state into
native code.

Author: sbc100

emcc.py

@@ -1577,9 +1577,10 @@ def filter_out_duplicate_dynamic_libs(inputs):
       # manually export them
 
       shared.Settings.EXPORTED_FUNCTIONS += [
+        '__emscripten_thread_init',
         '_emscripten_get_global_libc',
         '___pthread_tsd_run_dtors',
-        'registerPthreadPtr', '_pthread_self',
+        '_pthread_self',
         '___emscripten_pthread_data_constructor',
         '_emscripten_futex_wake',
         '_emscripten_stack_set_limits',

src/library_pthread.js

@@ -6,7 +6,7 @@
 
 var LibraryPThread = {
   $PThread__postset: 'if (!ENVIRONMENT_IS_PTHREAD) PThread.initMainThreadBlock();',
-  $PThread__deps: ['$registerPthreadPtr',
+  $PThread__deps: ['_emscripten_thread_init',
                    '$ERRNO_CODES', 'emscripten_futex_wake', '$killThread',
                    '$cancelThread', '$cleanupThread',
 #if USE_ASAN || USE_LSAN
@@ -81,10 +81,10 @@ var LibraryPThread = {
       });
 #endif
 
-      // Pass the thread address inside the asm.js scope to store it for fast
-      // access that avoids the need for a FFI out.  Global constructors trying
+      // Pass the thread address to the native code where they stored in wasm
+      // globals which act as a form of TLS. Global constructors trying
       // to access this value will read the wrong value, but that is UB anyway.
-      registerPthreadPtr(PThread.mainThreadBlock, /*isMainBrowserThread=*/!ENVIRONMENT_IS_WORKER, /*isMainRuntimeThread=*/1);
+      __emscripten_thread_init(PThread.mainThreadBlock, /*isMainBrowserThread=*/!ENVIRONMENT_IS_WORKER, /*isMainRuntimeThread=*/1);
       _emscripten_register_main_browser_thread_id(PThread.mainThreadBlock);
     },
     initWorker: function() {
@@ -218,7 +218,7 @@ var LibraryPThread = {
         PThread.runExitHandlers();
 
         _emscripten_futex_wake(tb + {{{ C_STRUCTS.pthread.threadStatus }}}, {{{ cDefine('INT_MAX') }}});
-        registerPthreadPtr(0, 0, 0); // Unregister the thread block also inside the asm.js scope.
+        __emscripten_thread_init(0, 0, 0); // Unregister the thread block also inside the asm.js scope.
         threadInfoStruct = 0;
         if (ENVIRONMENT_IS_PTHREAD) {
           // Note: in theory we would like to return any offscreen canvases back to the main thread,
@@ -234,7 +234,7 @@ var LibraryPThread = {
       Atomics.store(HEAPU32, (threadInfoStruct + {{{ C_STRUCTS.pthread.threadStatus }}} ) >> 2, 1); // Mark the thread as no longer running.
       _emscripten_futex_wake(threadInfoStruct + {{{ C_STRUCTS.pthread.threadStatus }}}, {{{ cDefine('INT_MAX') }}}); // wake all threads
       threadInfoStruct = selfThreadId = 0; // Not hosting a pthread anymore in this worker, reset the info structures to null.
-      registerPthreadPtr(0, 0, 0); // Unregister the thread block also inside the asm.js scope.
+      __emscripten_thread_init(0, 0, 0); // Unregister the thread block also inside the asm.js scope.
       postMessage({ 'cmd': 'cancelDone' });
     },
 
@@ -1005,46 +1005,9 @@ var LibraryPThread = {
     throw 'unwind';
   },
 
-  _pthread_ptr: 0,
   _pthread_is_main_runtime_thread: 0,
   _pthread_is_main_browser_thread: 0,
 
-  $registerPthreadPtr__deps: ['_pthread_ptr', '_pthread_is_main_runtime_thread', '_pthread_is_main_browser_thread'],
-  $registerPthreadPtr__asm: true,
-  $registerPthreadPtr__sig: 'viii',
-  $registerPthreadPtr: function(pthreadPtr, isMainBrowserThread, isMainRuntimeThread) {
-    pthreadPtr = pthreadPtr|0;
-    isMainBrowserThread = isMainBrowserThread|0;
-    isMainRuntimeThread = isMainRuntimeThread|0;
-    __pthread_ptr = pthreadPtr;
-    __pthread_is_main_browser_thread = isMainBrowserThread;
-    __pthread_is_main_runtime_thread = isMainRuntimeThread;
-  },
-
-  // Public pthread_self() function which returns a unique ID for the thread.
-  pthread_self__deps: ['_pthread_ptr'],
-  pthread_self__asm: true,
-  pthread_self__sig: 'i',
-  pthread_self: function() {
-    return __pthread_ptr|0;
-  },
-
-  emscripten_is_main_runtime_thread__asm: true,
-  emscripten_is_main_runtime_thread__sig: 'i',
-  emscripten_is_main_runtime_thread__deps: ['_pthread_is_main_runtime_thread'],
-  emscripten_is_main_runtime_thread: function() {
-    // Semantically the same as testing "!ENVIRONMENT_IS_PTHREAD" outside the asm.js scope
-    return __pthread_is_main_runtime_thread|0;
-  },
-
-  emscripten_is_main_browser_thread__asm: true,
-  emscripten_is_main_browser_thread__sig: 'i',
-  emscripten_is_main_browser_thread__deps: ['_pthread_is_main_browser_thread'],
-  emscripten_is_main_browser_thread: function() {
-    // Semantically the same as testing "!ENVIRONMENT_IS_WORKER" outside the asm.js scope
-    return __pthread_is_main_browser_thread|0;
-  },
-
   pthread_getschedparam: function(thread, policy, schedparam) {
     if (!policy && !schedparam) return ERRNO_CODES.EINVAL;
 

src/postamble_minimal.js

@@ -62,7 +62,7 @@ function initRuntime(asm) {
   Module['_emscripten_tls_init'] = _emscripten_tls_init;
   Module['HEAPU32'] = HEAPU32;
   Module['dynCall'] = dynCall;
-  Module['registerPthreadPtr'] = registerPthreadPtr;
+  Module['__emscripten_thread_init'] = __emscripten_thread_init;
   Module['_pthread_self'] = _pthread_self;
 
   if (ENVIRONMENT_IS_PTHREAD) {
@@ -72,7 +72,7 @@ function initRuntime(asm) {
 
   // Pass the thread address inside the asm.js scope to store it for fast access
   // that avoids the need for a FFI out.
-  registerPthreadPtr(PThread.mainThreadBlock, /*isMainBrowserThread=*/!ENVIRONMENT_IS_WORKER, /*isMainRuntimeThread=*/1);
+  __emscripten_thread_init(PThread.mainThreadBlock, /*isMainBrowserThread=*/!ENVIRONMENT_IS_WORKER, /*isMainRuntimeThread=*/1);
   _emscripten_register_main_browser_thread_id(PThread.mainThreadBlock);
 #endif
 

src/worker.js

@@ -155,7 +155,7 @@ this.onmessage = function(e) {
       threadInfoStruct = e.data.threadInfoStruct;
 
       // Pass the thread address inside the asm.js scope to store it for fast access that avoids the need for a FFI out.
-      Module['registerPthreadPtr'](threadInfoStruct, /*isMainBrowserThread=*/0, /*isMainRuntimeThread=*/0);
+      Module['__emscripten_thread_init'](threadInfoStruct, /*isMainBrowserThread=*/0, /*isMainRuntimeThread=*/0);
 
       selfThreadId = e.data.selfThreadId;
       parentThreadId = e.data.parentThreadId;

system/lib/pthread/pthread_self.s

@@ -0,0 +1,39 @@
+.globaltype thread_id, i32
+thread_id:
+
+.globaltype is_main_thread, i32
+is_main_thread:
+
+.globaltype is_runtime_thread, i32
+is_runtime_thread:
+
+.globl pthread_self
+pthread_self:
+  .functype pthread_self () -> (i32)
+  global.get thread_id
+  end_function
+
+.globl _emscripten_thread_init
+_emscripten_thread_init:
+  .functype _emscripten_thread_init (i32, i32, i32) -> ()
+  local.get 0
+  global.set thread_id
+  local.get 1
+  global.set is_main_thread
+  local.get 2
+  global.set is_runtime_thread
+  end_function
+
+# Semantically the same as testing "!ENVIRONMENT_IS_PTHREAD" in JS
+.globl emscripten_is_main_runtime_thread
+emscripten_is_main_runtime_thread:
+  .functype emscripten_is_main_runtime_thread () -> (i32)
+  global.get is_runtime_thread
+  end_function
+
+# Semantically the same as testing "!ENVIRONMENT_IS_WORKER" in JS
+.globl emscripten_is_main_browser_thread
+emscripten_is_main_browser_thread:
+  .functype emscripten_is_main_browser_thread () -> (i32)
+  global.get is_browser_thread
+  end_function

tools/system_libs.py

@@ -1200,6 +1200,7 @@ def get_files(self):
           'library_pthread.c',
           'emscripten_atomic.c',
           'emscripten_tls_init.c',
+          'pthread_self.s',
         ])
       return files
     else: