Implement initialization for local-exec TLS (#8976)

Author: quantum5

ChangeLog.md

@@ -21,6 +21,8 @@ Current Trunk
 
  - LLVM backend pthread builds no longer use external memory initialization
    files, replacing them with passive data segments.
+ - LLVM backend now supports thread local storage via the C extension `__thread`
+   and C11/C++11 keyword `thread_local`. (#8976)
 
 v1.38.39: 07/16/2019
 --------------------

src/worker.js

@@ -207,6 +207,9 @@ this.onmessage = function(e) {
       // Also call inside JS module to set up the stack frame for this pthread in JS module scope
       Module['establishStackSpaceInJsModule'](e.data.stackBase, e.data.stackBase + e.data.stackSize);
 #endif
+#if WASM_BACKEND
+      Module['_emscripten_tls_init']();
+#endif
 #if STACK_OVERFLOW_CHECK
       {{{ makeAsmGlobalAccessInPthread('writeStackCookie') }}}();
 #endif

system/lib/libc/musl/src/misc/emscripten_pthread.c

@@ -25,7 +25,7 @@ EM_JS(void, initPthreadsJS, (void), {
 })
 
 EMSCRIPTEN_KEEPALIVE
-__attribute__((constructor(100))) // This must run before any userland ctors
+__attribute__((constructor(99))) // This must run before any userland ctors
 void __emscripten_pthread_data_constructor(void) {
   initPthreadsJS();
   pthread_self()->locale = &libc.global_locale;

system/lib/pthread/library_pthread_wasm.c

@@ -168,3 +168,17 @@ uint32_t emscripten_atomic_xor_u32(void /*uint32_t*/* addr, uint32_t val) {
 uint64_t emscripten_atomic_xor_u64(void /*uint64_t*/* addr, uint64_t val) {
   return __c11_atomic_fetch_xor((_Atomic uint64_t*)addr, val, __ATOMIC_SEQ_CST);
 }
+
+extern void __wasm_init_tls(void *memory);
+void *emscripten_builtin_malloc(size_t size);
+void emscripten_builtin_free(void *memory);
+
+__attribute__((constructor(100)))
+void EMSCRIPTEN_KEEPALIVE emscripten_tls_init(void) {
+  size_t tls_size = __builtin_wasm_tls_size();
+  if (tls_size) {
+    void *tls_block = emscripten_builtin_malloc(tls_size);
+    __wasm_init_tls(tls_block);
+    pthread_cleanup_push(emscripten_builtin_free, tls_block);
+  }
+}

tests/pthread/test_pthread_tls.cpp

@@ -0,0 +1,32 @@
+#include <thread>
+#include <cstdio>
+
+thread_local int tls;
+thread_local struct {
+  int a;
+  double b;
+} data = {1, 2};
+thread_local int array[10];
+
+void thread(void) {
+  ++tls;
+  data.a = 3;
+  data.b = 4;
+  assert(tls == 1);
+  assert(data.a == 3);
+  assert(data.b == 4);
+  assert(array[9] == 0);
+}
+
+int main(void) {
+  array[9] = 1337;
+  std::thread t(thread);
+  t.join();
+  assert(tls == 0);
+  assert(data.a == 1);
+  assert(data.b == 2);
+  assert(array[9] == 1337);
+#ifdef REPORT_RESULT
+  REPORT_RESULT(1337);
+#endif
+}

tests/pthread/test_pthread_tls_main.cpp

@@ -0,0 +1,16 @@
+#include <thread>
+#include <cstdio>
+
+thread_local int tls = 1330;
+thread_local int tls2;
+
+__attribute__((constructor))
+void init_tls2(void) {
+  tls2 = 7;
+}
+
+int main(void) {
+#ifdef REPORT_RESULT
+  REPORT_RESULT(tls + tls2);
+#endif
+}

tests/test_browser.py

@@ -3892,6 +3892,18 @@ def test_pthread_utf8_funcs(self):
   def test_pthread_wake_all(self):
     self.btest(path_from_root('tests', 'pthread', 'test_futex_wake_all.cpp'), expected='0', args=['-O3', '-s', 'USE_PTHREADS=1', '-s', 'TOTAL_MEMORY=64MB', '-s', 'NO_EXIT_RUNTIME=1'], also_asmjs=True)
 
+  # Test that real `thread_local` works.
+  @no_fastcomp('thread_local is only supported on WASM backend')
+  @requires_threads
+  def test_pthread_tls(self):
+    self.btest(path_from_root('tests', 'pthread', 'test_pthread_tls.cpp'), expected='1337', args=['-s', 'PROXY_TO_PTHREAD', '-s', 'USE_PTHREADS', '-std=c++11'])
+
+  # Test that real `thread_local` works in main thread without PROXY_TO_PTHREAD.
+  @no_fastcomp('thread_local is only supported on WASM backend')
+  @requires_threads
+  def test_pthread_tls_main(self):
+    self.btest(path_from_root('tests', 'pthread', 'test_pthread_tls_main.cpp'), expected='1337', args=['-s', 'USE_PTHREADS', '-std=c++11'])
+
   # Tests MAIN_THREAD_EM_ASM_INT() function call signatures.
   @no_wasm_backend('MAIN_THREAD_EM_ASM() not yet implemented in Wasm backend')
   def test_main_thread_em_asm_signatures(self):