Thanks for the reviews. Jeff Law <jeffreya...@gmail.com> writes: > On 11/5/23 11:48, Richard Sandiford wrote: >> The mode-switching pass already had hooks to say what mode >> an entity is in on entry to a function and what mode it must >> be in on return. For SME, we also want to say what mode an >> entity is guaranteed to be in on entry to an exception handler. >> >> gcc/ >> * target.def (mode_switching.eh_handler): New hook. >> * doc/tm.texi.in (TARGET_MODE_EH_HANDLER): New @hook. >> * doc/tm.texi: Regenerate. >> * mode-switching.cc (optimize_mode_switching): Use eh_handler >> to get the mode on entry to an exception handler. > Can we ever have a path to the exception handler triggered by a normal > control flow and if so, presumably we want this to apply in that case too?
Not directly AFAIK. The handler has to handle the EH_DATA_REGNOs, call __cxa_begin_catch, etc. So even if there is fall-through at the source level, I think there'd always be a block that is only reached through abnormal control flow. So... > It looks like that's the semantics of the implementation by way to using > bb_has_eh_pred. Just want to make sure that's the semantics you want in > that oddball case. > > Assuming it is the semantics you want, it's OK for the trunk, though you > might want to twiddle the docs slightly to mention that case. ...I think these EH blocks are pure re-entry points. I suppose some targets might have entities whose state is call-preserved, so that it's not changed by EH edges. But that might also apply to other abnormal control flow too, so it's probably a separate issue/feature. Thanks, Richard
