Re: [Qemu-devel] [PATCH 5/7] tcg-i386: Implement deposit operation.

[Alexander Graf <agraf@suse.de>]

Richard Henderson wrote:
> On 01/26/2011 10:27 AM, Alexander Graf wrote:
>   
>> What do I do on a page fault now? I could rerun the translator to find
>> out which registers would be stuck in a temporary, but I have no way to
>> actually read the temporary's value, as all register state is thrown
>> away on a page fault IIUC.
>>     
>
> When does a page-fault happen?
>
> As far as I know, it does not happen at random.  Which seems to be 
> what you are suggesting.
>   

It happens on load/store and potentially helpers. The main difference
IIUC between globals and temps is that globals are kept in registers as
long as possible (read: until load/store or helper or tb end gets
emitted) while temporaries are not stored back to any memory, so they
are lost on load/store.

So what you are suggesting is basically to use a different set of
globals for regs32 and to keep track of their usage throughout the TB,
so we can convert on demand. We can't use temporaries for that unless we
manually store them off on load/store/helper/tb end which means we'd
rewrite the globals treatment in target code :).


Alex