As a former embedded engineer on older Motorola and ARM processors I have seen reordering happening, and more than once had to check the generated assembly code

As a former embedded engineer on older Motorola and ARM processors I have seen reordering happening, and more than once had to check the generated assembly code, the other items more or less makes sense if you don't expect too much from your compiler, for example using volatile to get atomicity. Using volatile on multi-threaded code is ok as long as you know what you are doing, for example kicking a watchdog at a defined physical address could be fine from different threads.