Hi Carl,
On Thu, Mar 12, 2020 at 09:57:06AM -0700, Carl Love wrote:
> > From the GCC manual:
> >
> > -mmfcrf p4 2.01
> > -mpopcntb p5 2.02
> > -mfprnd p5+ 2.04 ("info gcc" says 2.03, that's wrong? But the
> > ISA
> > says this is 2.02 even? Now what!)
> > -mcmpb p6 2.05
> > -mpopcntd p7 2.06
> >
> > (and there are more, in fact).
>
> <snip>
>
> > It would be better if you disallowed this option combination? Don't
> > allow an options that says ISA X insns are allowed, but ISA Y insns
> > are
> > not, with Y < X. In this case X is 2.06 and Y is 2.02 or 2.03 or
> > 2.04.
>
> My fix was very specific to the builtin and the command line argument
> as pointed out in the bug report.
>
> Sounds like you are implying we should take a much more general
> approach to checking the command line args against the ISA level. Such
> a test would need to go somewhere else not in the builtin expansion
> call. We may want a routine that just does these checks which can then
> be called from the appropriate place. Let me go look at the GCC manual
> and see about what all needs testing.
Yes, but only for this fprnd vs. 2.06 (vsx) situation. Like we already
have:
if (TARGET_DIRECT_MOVE && !TARGET_VSX)
{
if (rs6000_isa_flags_explicit & OPTION_MASK_DIRECT_MOVE)
error ("%qs requires %qs", "-mdirect-move", "-mvsx");
rs6000_isa_flags &= ~OPTION_MASK_DIRECT_MOVE;
}
(and many other cases there), we could do this there as well (so, don't
allow -mvsx (maybe via a -mcpu= etc.) at the same time as -mno-fprnd).
Do you see problems with that?
Segher
