Re: [Qemu-devel] TCG: AREG0 removal planning

[Lluís]

Blue Swirl writes:

> On Wed, May 11, 2011 at 12:28 AM, Paul Brook <address@hidden> wrote:
>> In practice generated code probably accesses CPUState often enough that a
>> dedicated register isn't a bad idea.  My guess is that eliminating it from C
>> code gets us almost all of the useful benefit.  Removing it from the code
>> generator (i.e. TCG_AREG0) may be more pain that it's worth.

> I don't think moving the helpers from op_helper.c to helper.c will be
> a performance win if AREG0 is not eliminated. The code gets to use one
> register more, but AREG0 needs to be moved to a function argument
> register in most cases and AREG0 has to be restored. I think the
> benefit should come from generated code getting one more available
> register.

So, it all boils down to the amount of register spilling that can be
avoided in TCG-generated code when eliminating the reserved register for
AREG0. Am I right?


Lluis

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