When is the hardware related register is allocated?

[Joern Rennecke]

Quoting Ian Lance Taylor <iant@google.com>:

> Offhand I don't know of any way to get the compiler to save CC for you
> around your instruction.  That's a stiff requirement.

It's easy to do under explicit control of the pattern, using (a) match_scratch
clobber(s) of (a) register(s) of the required class(es) - or if memory is
needed, the stack top can be set aside by the prologue/epilogue code.