stdlib: generalise TLS to support Windows

Rename the explicit `pthread` to `thread` to indicate that this is not
`pthread` specifically.  This allows us to implement the TLS support for
Windows using Fibers.

Author: compnerd

stdlib/public/SwiftShims/LibcShims.h

@@ -114,28 +114,28 @@ double _swift_stdlib_squareRoot(double _self) {
 // TLS - thread local storage
 
 #if defined(__ANDROID__)
-typedef int __swift_pthread_key_t;
+typedef int __swift_thread_key_t;
 #elif defined(__linux__)
-typedef unsigned int __swift_pthread_key_t;
+typedef unsigned int __swift_thread_key_t;
 #elif defined(__FreeBSD__)
-typedef int __swift_pthread_key_t;
+typedef int __swift_thread_key_t;
+#elif defined(_WIN32)
+typedef unsigned long __swift_thread_key_t;
 #else
-typedef unsigned long __swift_pthread_key_t;
+typedef unsigned long __swift_thread_key_t;
 #endif
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-int _swift_stdlib_pthread_key_create(
-  __swift_pthread_key_t * _Nonnull key, void
-  (* _Nullable destructor)(void * _Nullable )
-);
+int
+_swift_stdlib_thread_key_create(__swift_thread_key_t * _Nonnull key,
+                                void (* _Nullable destructor)(void * _Nullable));
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-void * _Nullable _swift_stdlib_pthread_getspecific(__swift_pthread_key_t key);
+void * _Nullable _swift_stdlib_thread_getspecific(__swift_thread_key_t key);
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-int _swift_stdlib_pthread_setspecific(
-  __swift_pthread_key_t key, const void * _Nullable value
-);
+int _swift_stdlib_thread_setspecific(__swift_thread_key_t key,
+                                     const void * _Nullable value);
 
 // TODO: Remove horrible workaround when importer does Float80 <-> long double.
 #if (defined __i386__ || defined __x86_64__) && !defined _MSC_VER

stdlib/public/core/ThreadLocalStorage.swift

@@ -64,7 +64,7 @@ internal struct _ThreadLocalStorage {
   static internal func getPointer()
     -> UnsafeMutablePointer<_ThreadLocalStorage>
   {
-    let tlsRawPtr = _swift_stdlib_pthread_getspecific(_tlsKey)
+    let tlsRawPtr = _swift_stdlib_thread_getspecific(_tlsKey)
     if _fastPath(tlsRawPtr != nil) {
       return tlsRawPtr._unsafelyUnwrappedUnchecked.assumingMemoryBound(
         to: _ThreadLocalStorage.self)
@@ -116,10 +116,10 @@ internal func _destroyTLS(_ ptr: UnsafeMutableRawPointer?) {
 }
 
 // Lazily created global key for use with pthread TLS
-internal let _tlsKey: __swift_pthread_key_t = {
-  let sentinelValue = __swift_pthread_key_t.max
-  var key: __swift_pthread_key_t = sentinelValue
-  let success = _swift_stdlib_pthread_key_create(&key, _destroyTLS)
+internal let _tlsKey: __swift_thread_key_t = {
+  let sentinelValue = __swift_thread_key_t.max
+  var key: __swift_thread_key_t = sentinelValue
+  let success = _swift_stdlib_thread_key_create(&key, _destroyTLS)
   _sanityCheck(success == 0, "somehow failed to create TLS key")
   _sanityCheck(key != sentinelValue, "Didn't make a new key")
   return key
@@ -129,7 +129,7 @@ internal let _tlsKey: __swift_pthread_key_t = {
 internal func _initializeThreadLocalStorage()
   -> UnsafeMutablePointer<_ThreadLocalStorage>
 {
-  _sanityCheck(_swift_stdlib_pthread_getspecific(_tlsKey) == nil,
+  _sanityCheck(_swift_stdlib_thread_getspecific(_tlsKey) == nil,
     "already initialized")
 
   // Create and initialize one.
@@ -146,7 +146,7 @@ internal func _initializeThreadLocalStorage()
   tlsPtr.initialize(
     to: _ThreadLocalStorage(_uBreakIterator: newUBreakIterator)
   )
-  let success = _swift_stdlib_pthread_setspecific(_tlsKey, tlsPtr)
+  let success = _swift_stdlib_thread_setspecific(_tlsKey, tlsPtr)
   _sanityCheck(success == 0, "setspecific failed")
   return tlsPtr
 }

stdlib/public/stubs/LibcShims.cpp

@@ -15,10 +15,12 @@
 #include <cmath>
 #if defined(_WIN32)
 #include <io.h>
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
 #else
 #include <unistd.h>
-#endif
 #include <pthread.h>
+#endif
 
 #include <stdlib.h>
 #include <stdio.h>
@@ -60,7 +62,7 @@ __swift_size_t swift::_swift_stdlib_strlen(const char *s) {
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
 __swift_size_t swift::_swift_stdlib_strlen_unsigned(const unsigned char *s) {
-  return strlen((char *)s);
+  return strlen(reinterpret_cast<const char *>(s));
 }
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
@@ -98,34 +100,57 @@ int swift::_swift_stdlib_close(int fd) {
 #endif
 }
 
-// Guard compilation on the typedef for __swift_pthread_key_t in LibcShims.h
+#if defined(_WIN32)
+static_assert(std::is_same<__swift_thread_key_t, DWORD>::value,
+              "__swift_thread_key_t is not a DWORD");
+
+SWIFT_RUNTIME_STDLIB_INTERFACE
+int
+swift::_swift_stdlib_thread_key_create(__swift_thread_key_t * _Nonnull key,
+                                       void (* _Nullable destructor)(void *)) {
+  // TODO(compnerd) account for x86 CC violation (__stdcall)
+  *key = FlsAlloc(reinterpret_cast<PFLS_CALLBACK_FUNCTION>(destructor));
+  return *key != FLS_OUT_OF_INDEXES;
+}
+
+SWIFT_RUNTIME_STDLIB_INTERFACE
+void * _Nullable
+swift::_swift_stdlib_thread_getspecific(__swift_thread_key_t key) {
+  return FlsGetValue(key);
+}
+
+SWIFT_RUNTIME_STDLIB_INTERFACE
+int swift::_swift_stdlib_thread_setspecific(__swift_thread_key_t key,
+                                            const void * _Nullable value) {
+  return FlsSetValue(key, const_cast<void *>(value)) == TRUE;
+}
+#else
+// Guard compilation on the typedef for __swift_thread_key_t in LibcShims.h
 // being identical to the platform's pthread_key_t
-static_assert(std::is_same<__swift_pthread_key_t, pthread_key_t>::value,
+static_assert(std::is_same<__swift_thread_key_t, pthread_key_t>::value,
               "This platform's pthread_key_t differs. If you hit this assert, "
               "fix __swift_pthread_key_t's typedef in LibcShims.h by adding an "
               "#if guard and definition for your platform");
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-int swift::_swift_stdlib_pthread_key_create(
-  __swift_pthread_key_t * _Nonnull key,
-  void (* _Nullable destructor)(void *)
-) {
+int
+swift::_swift_stdlib_thread_key_create(__swift_thread_key_t * _Nonnull key,
+                                       void (* _Nullable destructor)(void *)) {
   return pthread_key_create(key, destructor);
 }
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-void * _Nullable swift::_swift_stdlib_pthread_getspecific(
-  __swift_pthread_key_t key
-) {
+void * _Nullable
+swift::_swift_stdlib_thread_getspecific(__swift_thread_key_t key) {
   return pthread_getspecific(key);
 }
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-int swift::_swift_stdlib_pthread_setspecific(
-  __swift_pthread_key_t key, const void * _Nullable value
-) {
+int swift::_swift_stdlib_thread_setspecific(__swift_thread_key_t key,
+                                            const void * _Nullable value) {
   return pthread_setspecific(key, value);
 }
+#endif
 
 #if defined(__APPLE__)
 #include <malloc/malloc.h>