[Bug target/53513] [SH] Add support for fschg and fpchg insns and improve fenv support

[kkojima at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53513

--- Comment #30 from Kazumoto Kojima <kkojima at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #29)
> With this patch there are no new failures for -m4 -ml and -m4 -mb here,
> except the ISR failures.  I'll also test it for the other combinations
> later.  I'd like to get the current sh4 working version first.  Then fix
> other niche problems with ISRs or SH2E.  Kaz, what do you think?

Sounds reasonable.  Please go ahead.