Re: [Qemu-devel] [PATCH 0/7] Define "deposit" tcg operation, v2

[Aurelien Jarno <aurelien@aurel32.net>]

On Mon, Jan 10, 2011 at 07:23:41PM -0800, Richard Henderson wrote:
> Changes since v1:
>   * No attempt to pack pos+len into one operand.  Updated backends
>     to match this change.
> 
>   * Example in the README is a bit more complex.
> 
>   * Define an official tcg_scratch_alloc routine, used by the i386
>     target for the case in which we need a scratch register.  I had
>     said that triggering this wasn't possible with mainline, but I
>     was wrong.  The rlwimi example I posted in the other thread hits
>     this case.
> 
> Aurelien suggested using a shorter name like "dep", but I think that
> would be more confusing than not.  This opcode is not really used
> enough to warrent cropping 4 characters, in my opinion.
> 

It was just a suggestion, I am also fine with "deposit".

The implementation of the deposit op (that is the first patch) looks 
fine to me, and I am convince this new op is useful. It's probably going
to be useful for the s390 target, that tried to solve the same problem 
with a sync op.

To go further, I think we should split the patch series into two (no
need to resend it), the op itself, and the implementation/usage in
various host/targets. The latter can go part by part, so the various
persons can review them separately. The whole series is still useful 
anyway to see the potential of such a new op.

Even if the code for the new op is quite simple, adding a new op has
some consequences (the main one being is that it's difficult to remove 
it latter), so I propose that it is reviewed/acked by a few persons
before being committed. People, please do that or send your comments.

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net