Fix C2712 build error on Windows

[kzhuravl]

Summary

Move the try/except block outside of the set_thread_name function to avoid a conflict with object unwinding due to the use of the llvm::Storage.

[zturner]

Good catch, thanks.

lib/Support/Windows/Threading.inc

 }
 
 uint64_t llvm::get_threadid() {
   return uint64_t(::GetCurrentThreadId());
 }
 
 uint32_t llvm::get_max_thread_name_length() { return 0; }
 
-void llvm::set_thread_name(const Twine &Name) {
 #if defined(_MSC_VER)
-  // Make sure the input is null terminated.
-  SmallString<64> Storage;
-  StringRef NameStr = Name.toNullTerminatedStringRef(Storage);
+static void SetThreadName(DWORD Id, LPCSTR Name) {
   constexpr DWORD MS_VC_EXCEPTION = 0x406D1388;
 
 #pragma pack(push, 8)
   struct THREADNAME_INFO {
     DWORD dwType;     // Must be 0x1000.
     LPCSTR szName;    // Pointer to thread name
     DWORD dwThreadId; // Thread ID (-1 == current thread)
     DWORD dwFlags;    // Reserved.  Do not use.
   };
 #pragma pack(pop)
 
   THREADNAME_INFO info;
   info.dwType = 0x1000;
-  info.szName = NameStr.data();
-  info.dwThreadId = ::GetCurrentThreadId();
+  info.szName = Name;
+  info.dwThreadId = Id;
   info.dwFlags = 0;
 
   __try {
     ::RaiseException(MS_VC_EXCEPTION, 0, sizeof(info) / sizeof(ULONG_PTR),
       (ULONG_PTR *)&info);
   }
   __except (EXCEPTION_EXECUTE_HANDLER) {
   }
+}
+#endif
+
+void llvm::set_thread_name(const Twine &Name) {
+#if defined(_MSC_VER)
+  // Make sure the input is null terminated.
+  SmallString<64> Storage;
+  StringRef NameStr = Name.toNullTerminatedStringRef(Storage);
+  SetThreadName(::GetCurrentThreadId(), NameStr.data());
 #endif
 }
 
 void llvm::get_thread_name(SmallVectorImpl<char> &Name) {
   // "Name" is not an inherent property of a thread on Windows.  In fact, when
   // you "set" the name, you are only firing a one-time message to a debugger
   // which it interprets as a program setting its threads' name.  We may be
   // able to get fancy by creating a TLS entry when someone calls
   // set_thread_name so that subsequent calls to get_thread_name return this
   // value.
   Name.clear();
 }