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

[Yeongkyoon Lee <yeongkyoon.lee@samsung.com>]

On 2012년 07월 05일 23:06, Peter Maydell wrote:
> On 5 July 2012 14:23, Yeongkyoon Lee <yeongkyoon.lee@samsung.com> wrote:
>> Add an option "--enable-ldst-optimization" to enable CONFIG_QEMU_LDST_OPTIMIZATION macro for TCG qemu_ld/st optimization. It only works with CONFIG_SOFTMMU and doesn't work with CONFIG_TCG_PASS_AREG0.
> This shouldn't be a user settable config option -- we should
> just identify what the optimal setting is for the guest/target
> combination and use it.

It looks better remove the option after it is confirmed that it works 
well for all the guest target architectures.

>>   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.

There are two reasons to prevent working with PASS_AREG0.
The first one is I'm not sure the history and future PASS_AREG0 and have 
not tested PASS_AREG0 which is only enabled for some guest architectures..
The second is a problem of too many conditional paths in sources.
I think it is not late to combine the ldst optimization with PASS_AREG0 
after the ldst optimization agreed as default.