Build a test program for testing TLS support

Dockerfile

@@ -250,7 +250,7 @@ RUN cd libcxx && \
 
 RUN cd $TOOLCHAIN_PREFIX/include && ln -s ../$(echo $TOOLCHAIN_ARCHS | awk '{print $1}')-w64-mingw32/include/c++ .
 
-COPY hello.c hello.cpp hello-exception.cpp /build/hello/
+COPY hello.c hello.cpp hello-exception.cpp hello-tls.c /build/hello/
 RUN cd hello && \
     for arch in $TOOLCHAIN_ARCHS; do \
         $arch-w64-mingw32-clang hello.c -o hello-$arch.exe || exit 1; \
@@ -266,6 +266,11 @@ RUN cd hello && \
         $arch-w64-mingw32-clang++ hello-exception.cpp -o hello-exception-$arch.exe || exit 1; \
     done
 
+RUN cd hello && \
+    for arch in $TOOLCHAIN_ARCHS; do \
+        $arch-w64-mingw32-clang hello-tls.c -o hello-tls-$arch.exe || exit 1; \
+    done
+
 ENV AR=llvm-ar
 ENV RANLIB=llvm-ranlib
 ENV AS=llvm-as

hello-tls.c

@@ -0,0 +1,37 @@
+#include <windows.h>
+#include <stdio.h>
+#include <process.h>
+
+#if defined(_MSC_VER)
+static __declspec(thread) int tlsvar = 1;
+#else
+static __thread int tlsvar = 1;
+#endif
+
+static unsigned __stdcall threadfunc(void* arg) {
+	int id = (int)arg;
+	printf("thread %d, tlsvar %p %d\n", id, &tlsvar, tlsvar);
+	tlsvar = id + 100;
+	for (int i = 0; i < 5; i++) {
+		printf("thread %d, tlsvar %p %d\n", id, &tlsvar, tlsvar);
+		tlsvar += 10;
+		Sleep(1000);
+	}
+	return 0;
+}
+
+int main(int argc, char* argv[]) {
+	HANDLE threads[5];
+
+	for (int i = 0; i < 5; i++) {
+		printf("mainthread, tlsvar %p %d\n", &tlsvar, tlsvar);
+		tlsvar += 10;
+		threads[i] = (HANDLE)_beginthreadex(NULL, 0, threadfunc, (void*)(intptr_t) (i + 1), 0, NULL);
+		Sleep(750);
+	}
+	for (int i = 0; i < 5; i++) {
+		WaitForSingleObject(threads[i], INFINITE);
+		CloseHandle(threads[i]);
+	}
+	return 0;
+}