[Bug target/99937] Optimization needed for ARM with single cycle multiplier

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99937

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to mike.robins from comment #2)
> (In reply to Richard Biener from comment #1)
> > You need to adjust RTX costing accordingly which likely means adding a new
> > subtarget tuning.
> 
> Hi Richard
> Are you saying that this would have to be added at the GCC source level
> somehow. I.e that there is no existing -mtune... or -f... to achieve this?
> Mike

Generally yes.  I don't know the arm backend enough to tell whether there
exists an ARM variant with the multiplier behaving in this way (I suppose an
in-order,
non-pipelined m0 core might behave this way ...)