[Bug target/52941] SH Target: Add support for movco.l / movli.l atomics on SH4A

[kkojima at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52941

--- Comment #1 from Kazumoto Kojima <kkojima at gcc dot gnu.org> 2012-04-12 01:18:42 UTC ---
(In reply to comment #0)
> Other than that, should we add another option '-mhard-atomic' (which would
> enable the movco/movli atomics on SH4A and disable all atomic insns for
> non-SH4A)?

I think so.

> Actually, I think the options should be '-msp-atomic' and '-mmp-atomic', where
> '-msp-atomic' would be the current '-msoft-atomic'.

I don't think that -msp/mmp-atomic are good naming here.  SP/MP notion
is not directory connected with the soft/hard implementation of atomics,
even if soft atomics are impossible for real MP system.  Hard atomics
should work with both SP and MP.  I guess that the point is the necessity
of kernel (i.e. software) services.  If the atomics require kernel services,
they are "soft" atomics even some of them utilize the LL/SC-like insns.
If they don't require any kernel services, they are "hard" atomics.
Using -msp-atomic for "soft" atomics looks a bit misleading, from this point
of view.
Perhaps an unsupprising way would be enable movco/movli on SH4A with both
-msoft-atomic/-mhard-atomic if we can.