https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107172
--- Comment #18 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Segher Boessenkool from comment #16)
> Hi Roger,
>
> (In reply to Roger Sayle from comment #15)
> > Yes, a COMPARE rtx can be used to set various flags on x86, but many other
> > operations also legitimately set and/or use MODE_CC, often in a parallel
> > with the primary operation.
>
> *Any* MODE_CC setter sets the flags as-if from a compare. This is what
> MODE_CC *is*.
>
> Setting something as ne:CC and then using it as somethingelse:CC has no
> defined meaning.
This
(parallel [
(set (reg:SI 97)
(neg:SI (ltu:SI (reg:CCC 17 flags)
(const_int 0 [0]))))
(clobber (reg:CC 17 flags))
])
still won't work correctly if reg:CCC 17 flags is set by a compare of
2 known values.
