Are any relevant GPUs VLIW anymore? As far as I'm aware they all dropped it too, moving to scalar ISAs on SIMT hardware. The last VLIW GPU I remember was AMD TeraScale, replaced by GCN where one of the most important architecture changes was dropping VLIW.

I mean, there is a reason why these sorts of constructs are UB, even if they work on popular architectures. The problems aren’t unique to IA64, either; the better solution is to be aware that UB means UB and to avoid it studiously. (Unfortunately, that’s also hard to do in C).