Register Cache.

[Fernando Nasser]

Steven Johnson wrote:
> 
> Fernando Nasser wrote:
> >   However, I vaguely remember our register cache being a
> > "write-through" cache.
> 
> It is, unless the data you are writing is already believed to be in the
> register.
> 
> ie, Register contains 0xAA55
> 
> Write 0x55AA to Register, and GDB updates target register with 0x55AA
> 
> Write 0x55AA to Register again, and GDB checks it's cache, determines
> the value is already 0x55AA and does NOT write.
> 

That is true.  I forgot this little detail.


> I have gotten around the issues by invalidating the register cache
> between writes. This is obviously sub-optimal but it works OK.
> 
> A better implementation would be to allow a setting on a register by
> register basis that sets how it will be cached by reg-cache.  At the
> time of the original post, this was a fairly major undertaking.
> Regcache currently seems to be undergoing changes that will make
> implementing this easier but for the moment flushing works fine.
> 

Yes, like "not cached" :-)  For hardware/control registers caching is
just not good.

-- 
Fernando Nasser
Red Hat Canada Ltd.                     E-Mail:  fnasser@redhat.com
2323 Yonge Street, Suite #300
Toronto, Ontario   M4P 2C9