On Thu, Aug 08, 2019 at 01:26:42PM -0500, Segher Boessenkool wrote: > LABEL_REF_P works out nicely because it is referring to something that > is data, is not an operator. "Leaves" in an RTL expression, if you want > to look at it that way. > > Predicates for other RTX codes aren't always as obvious, see CONST_P as > example. PLUS_P would be a bit borderline. > > Part of the reason why REG_P and MEM_P and the like are nice, is that > these predicates are often used in bigger conditions, maybe together > with some XEXP and whatnot. Is that the case for PLUS_P? >
Yes, it's used quite often in more complex conditions checking the operands (eg to see whether they're constants), or applied to XEXP's itself. But I'm in agreement that PLUS_P just seems odd somehow. The leaf/data vs operator distinction makes sense, maybe RTXOP_PLUS_P, but then you'd want that to check if it was being called on an operator, so I don't know if you'd do it unless/until we eventually have an rtx_op class and have done the other bits of converting to C++.
