[OpenBIOS] [PATCH 2/4] ppc: add new context handler

[Segher Boessenkool]

On Tue, May 03, 2016 at 09:03:48PM +0100, Mark Cave-Ayland wrote:
> >> So the optimiser has decided to remove the storage to/from the lr stack
> >> variable which of course means that the lr value isn't being preserved.
> >> Do I somehow need to mark the "r" (lr) as clobbered or something else?
> > 
> > Oh, yeah, that's another problem: a call can clobber all volatile
> > (caller-save) registers.  The best solution is to write this whole
> > thing in actual assembler, instead of fighting the compiler to get
> > just the assembler you want ;-)
> 
> Heh actually the bug was a missing volatile qualifier from the __context
> pointer which is interesting since this code is used almost boilerplate
> for other architectures - I'll spin up a patch to update the other archs
> once this has gone in. The v2 version of the patchset contains this
> correction though.

That is just a workaround.  It might well work, and it can also break
at any time.


Segher