On Mon, Jul 12, 2021 at 08:20:14AM +0200, Richard Biener wrote: > On Fri, 9 Jul 2021, Segher Boessenkool wrote: > > Almost all targets just use Pmode, but there is no such guarantee I > > think, and esp. some targets that do not have machine insns for this > > (but want to generate different code for this anyway) can do pretty much > > anything. > > > > Maybe using just Pmode here is good enough though? > > I think Pmode is a particularly bad choice and I'd prefer word_mode > if we go for any hardcoded mode.
In many important cases you use a pointer as iteration variable. Is word_mode register size on most current targets? > s390x for example seems to handle > both SImode and DImode (but names the helper gen_doloop_si64 > for SImode?!). Yes, so Pmode will work fine for 390. It would be nice if we could allow multiple modes here, certainly. Can we? > But indeed it looks like somehow querying doloop_end > is going to be difficult since the expander doesn't have any mode, > so we'd have to actually try emit RTL here. Or add a well-designed target macro for this. "Which modes do we like for IVs", perhaps? Segher
