ntdll: Use .seh handler instead of __TRY in RtlUserThreadStart() on x64.

dlls/ntdll/thread.c

@@ -285,7 +285,41 @@ void DECLSPEC_HIDDEN call_thread_func( PRTL_THREAD_START_ROUTINE entry, void *ar
     __ENDTRY
 }
 
-#else  /* __i386__ */
+#elif /* __i386__ */ defined(__x86_64__) && defined(__ASM_SEH_SUPPORTED)
+EXCEPTION_DISPOSITION WINAPI call_thread_func_handler( EXCEPTION_RECORD *rec, ULONG64 frame,
+                                                       CONTEXT *context, DISPATCHER_CONTEXT *dispatch )
+{
+    EXCEPTION_POINTERS ep = { rec, context };
+
+    WARN( "Unhandled exception, calling filter.\n" );
+
+    switch (call_unhandled_exception_filter( &ep ))
+    {
+        case EXCEPTION_CONTINUE_SEARCH:
+            return ExceptionContinueSearch;
+        case EXCEPTION_CONTINUE_EXECUTION:
+            return ExceptionContinueExecution;
+        case EXCEPTION_EXECUTE_HANDLER:
+            break;
+    }
+    NtTerminateProcess( GetCurrentProcess(), rec->ExceptionCode );
+    return ExceptionContinueExecution;
+}
+
+extern void WINAPI RtlUserThreadStart( PRTL_THREAD_START_ROUTINE entry, void *arg );
+__ASM_GLOBAL_FUNC( RtlUserThreadStart,
+                  "subq $0x28,%rsp\n\t"
+                  ".seh_stackalloc 0x28\n\t"
+                  ".seh_endprologue\n\t"
+                  "movq %rdx,%r8\n\t"
+                  "movq %rcx,%rdx\n\t"
+                  "xorq %rcx,%rcx\n\t"
+                  "movq " __ASM_NAME( "pBaseThreadInitThunk" ) "(%rip),%r9\n\t"
+                  "call *%r9\n\t"
+                  "int3\n\t"
+                  ".seh_handler call_thread_func_handler, @except\n\t" )
+
+#else /* defined(__x86_64__) && defined(__ASM_SEH_SUPPORTED) */
 
 void WINAPI RtlUserThreadStart( PRTL_THREAD_START_ROUTINE entry, void *arg )
 {

include/wine/asm.h

@@ -54,6 +54,7 @@
 #  define __ASM_SEH(str)
 # else
 #  define __ASM_SEH(str) str
+#  define __ASM_SEH_SUPPORTED
 # endif
 #else
 # define __ASM_SEH(str)