Remove dlsym() lookup for TSan functions from common path (#36478)

* Move TSan function lookup out of the common path

Move TSan function lookup via `dlsym()` out of the common path.  The
TSan runtime will now call `__tsan_on_initialize()` which we can use to
initialize the TSan functions in the Swift runtime.

This avoids paying the cost of `dlsym()` in the common, non-TSan case.

Depends on: https://reviews.llvm.org/D98810

rdar://75493372

* Remove Windows code

Thread Sanitizer is not supported on Windows.

Co-authored-by: Julian Lettner <[email protected]>

Author: yln

stdlib/public/Concurrency/ThreadSanitizer.cpp

@@ -10,54 +10,39 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Thread Sanitizer support for the Swift Task runtime
+// Thread Sanitizer support for the Swift Task runtime.
 //
 //===----------------------------------------------------------------------===//
 
 #include "TaskPrivate.h"
 
+// Thread Sanitizer is not supported on Windows.
 #if defined(_WIN32)
-#define NOMINMAX
-#include <windows.h>
+void swift::_swift_tsan_acquire(void *addr) {}
+void swift::_swift_tsan_release(void *addr) {}
 #else
 #include <dlfcn.h>
-#endif
 
 namespace {
 using TSanFunc = void(void *);
 TSanFunc *tsan_acquire, *tsan_release;
-
-TSanFunc *loadSymbol(const char *name) {
-#if defined(_WIN32)
-  return (TSanFunc *)GetProcAddress(GetModuleHandle(NULL), name);
-#else
-  return (TSanFunc *)dlsym(RTLD_DEFAULT, name);
-#endif
-}
-
-swift::swift_once_t initOnceToken;
-void initializeThreadSanitizer(void *unused) {
-  tsan_acquire = loadSymbol("__tsan_acquire");
-  tsan_release = loadSymbol("__tsan_release");
-}
 } // anonymous namespace
 
 void swift::_swift_tsan_acquire(void *addr) {
-  swift_once(&initOnceToken, initializeThreadSanitizer, nullptr);
   if (tsan_acquire) {
     tsan_acquire(addr);
   }
 }
 
 void swift::_swift_tsan_release(void *addr) {
-  swift_once(&initOnceToken, initializeThreadSanitizer, nullptr);
   if (tsan_release) {
     tsan_release(addr);
   }
 }
 
 SWIFT_EXPORT_FROM(swift_Concurrency) SWIFT_CC(c)
-void swift_task_set_tsan_hooks(TSanFunc *acquire, TSanFunc *release) {
-  tsan_acquire = acquire;
-  tsan_release = release;
+void __tsan_on_initialize() {
+  tsan_acquire = (TSanFunc *)dlsym(RTLD_DEFAULT, "__tsan_acquire");
+  tsan_release = (TSanFunc *)dlsym(RTLD_DEFAULT, "__tsan_release");
 }
+#endif