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

[olegendo at gcc dot gnu.org]

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

--- Comment #45 from Oleg Endo <olegendo at gcc dot gnu.org> ---
>From my point of view, this PR can be closed as fixed.  The ISR related
failures were just issues w.r.t. how the the expected code sequences are
matched in the test cases.
I've created followup PR 64305 and PR 64299, which are issues that can be
addressed separately.