Re: [Qemu-devel] [RFC 00/16] TCG indirect registers

[Richard Henderson <rth@twiddle.net>]

On 09/23/2013 10:23 AM, Blue Swirl wrote:
> On Fri, Sep 20, 2013 at 12:24 AM, Richard Henderson <rth@twiddle.net> wrote:
>>
>> This is an attempt to improve performance of target-sparc
>> by exposing the windowed registers as TCG globals, and all
>> the optimization that we can do there.
>>
>> This is done via allowing tcg_global_mem_new to be used
>> with any base pointer, not just off of a fixed register.
>> Thus the sparc windowed registers are globals off cpu_regwptr.
> 
> Nice and simple.
> 
> Would it be possible to eliminate regwptr and perform the calculation
> of the effective register set during compile time? We could get rid of
> register shuffling (memcpy32) and register access would be much
> simpler. The downside would be that code which is called from
> different register window level would need to be recompiled.

An interesting idea.  Yes, it would be possible to grab some bits
from TB->flags and encode the register window setting.  I suppose
it all depends on how much overhead there is from the recompilation
as opposed to the indirection + memcpys.


r~