Re: [Qemu-devel] [RFC][PATCH v2 4/4] configure: add CONFIG_QEMU_LDST_OPTIMIZATION for TCG qemu_ld/st optimization

[Laurent Desnogues]

On Thu, Jul 5, 2012 at 4:06 PM, Peter Maydell <address@hidden> wrote:
[...]
>>  case "$target_arch2" in
>>    alpha | sparc* | xtensa* | ppc*)
>>      echo "CONFIG_TCG_PASS_AREG0=y" >> $config_target_mak
>> +    # qemu_ld/st optimization is not available with CONFIG_TCG_PASS_AREG0
>> +    target_ldst_optimization="no"
>
> PASS_AREG0 is the way of the future -- you need to fix the ldst
> optimization to work with it.

Agreed.  But what's the point of speeding up on one side and
losing speed on the other side?  AREG0 slowdown would be
acceptable if the ARM target was using less helpers, until this
happens I don't think it is a good idea to push AREG0,
hence I'm not sure it is a prerequisite that Yeongkyoon Lee's
patch supports it.  By the way, it's also a good reason to have
CONFIG_QEMU_LDST_OPTIMIZATION, which you
commented on in patch 3.

Basically, and in my humble opinion, this is not a good
enough reason to reject the patch :-)  Of course the support
should be added as soon as possible once the rest has
been discussed.


Laurent