On Mon, 13 Feb 2023, Jakub Jelinek wrote: > On Mon, Feb 13, 2023 at 12:00:56PM +0100, Richard Biener wrote: > > DCE now chokes on indirect setjmp calls becoming direct because > > that exposes them too late to be subject to abnormal edge creation. > > The following patch honors gimple_call_ctrl_altering for those and > > _not_ treat formerly indirect calls to setjmp as calls to setjmp. > > > > Unfortunately there's no way to have an indirect call to setjmp > > properly annotated (the returns_twice attribute is ignored on types). > > > > RTL expansion late discovers returns-twice for the purpose of > > adding REG_SETJMP notes and also sets ->calls_setjmp > > (instead of asserting it is set). There's no good way to > > transfer proper knowledge around here so I'm using ->calls_setjmp > > as a flag to indicate whether gimple_call_ctrl_altering was set. > > > > Comments on what's the most sensible thing to do here? Supporting > > returns_twice on indirect calls wouldn't be difficult, so we're > > talking about how to handle this kind of "legacy" situation? > > One thing is supporting returns_twice on function types, but another one > is that initially none of the calls will be marked that way and even later, > it is up to the user if they mark it or not.
Yep. > Could we e.g. prevent turning such indirect calls into direct calls? We do exactly have gimple_call_fntype and gimple_call_ctrl_altering_p to not require special-casing indirect to direct call promotion here. > Anyway, notice_special_calls is called in various spots, not just DCE, > wouldn't it be better to simply not set calls_setjmp flag in there if > the current function already has cfg and the call isn't ctrl altering? I thought about changing gimple_call_flags instead, filtering out ECF_RETURNS_TWICE. I just didn't make up my mind on what property to key at (and to require 'cfun' to be set to query it). But sure, changing notice_special_calls also works - the only other relevant caller is the inliner I think, and that could be replaced by caller |= callee of the two flags tracked instead of re-scanning each inlined stmt. Would you be happy with changing notice_special_calls, dropping the DCE hunk but keeping the cfgexpand/calls.cc hunks? Thanks, Richard.
