On Fri, 29 Sep 2017, Segher Boessenkool wrote: > How do other ports deal with this? Insns with a specific rounding mode? > Have a separate unspec for every operation? Not very nice either :-(
Well, ideally you'd have a machine-independent representation of constant rounding modes that could be used with the TS 18661-1 FENV_ROUND pragma, respectively FENV_DEC_ROUND for decimal floating point (as the standard machine-independent way of accessing such a facility at the C language level - you'd then need to extend it to handle round-to-odd, but given the basic facility, accepting additional rounding mode names with it should be easy). But I don't know what that would look like in either GIMPLE or RTL, and I'd certainly expect it to be a large project (quite likely depending on other large projects to handle dynamic rounding modes properly through optimizers). So you probably can't do much better than lots of unspecs and machine-specific built-in functions at present. -- Joseph S. Myers jos...@codesourcery.com
