Re: Multiplexed registers and invalidating the register cache

[Andrew Cagney <cagney@gnu.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