Re: Multiplexed registers and invalidating the register cache

[Andrew Cagney <cagney at gnu dot org>]

> Orjan Friberg wrote:
>
> > Daniel Jacobowitz wrote:
> >
> > > I think you should make this change unconditionally - and flush the
> > > entire frame cache.
> >
> >
> >
> > Pardon my ignorance, but why should the entire frame cache be flushed, instead of just invalidating the current set of registers?  Is it because frame pointer/return address registers (or something else affecting other frames) might change?

Consider the effect of modifying the $sp.

While it might in theory be possible to implement some sort of 
complicated look-aside cache schema, in reality there is zero return on 
investment.  Since recovery from the flush can't be slower than recovery 
from single-step, and single step is way way more critical, we should 
focus on single step.

Andrew