Hi! On Wed, Jun 14, 2023 at 10:04:20AM +0100, Richard Sandiford wrote: > I'd also understood it to be either. As in, it is a may-clobber > that can be used for must-clobber. Alternatively: the value stored > is unpredictable, and can therefore be the same as the current value.
Yes, it is a set with an unspecified RHS. > I think the main difference between: > > (clobber (mem:BLK …)) > > and > > (set (mem:BLK …) (unspec:BLK …)) > > is that the latter must happen for correctness (unless something > that understands the unspec proves otherwise) whereas a clobber > can validly be dropped. So for something like stack_tie, a set > seems more correct than a clobber. No, the latter can be removed as well, under exactly the same conditions: if no code after it reads what was written. This happens in branches marked dead. Segher
