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From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] [PATCH for-2.5 08/30] m68k: update CPU flags
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To: Laurent Vivier <laurent@vivier.eu>, qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, Andreas Schwab <schwab@linux-m68k.org>, gerg@uclinux.org

On 08/12/2015 01:56 PM, Laurent Vivier wrote:
>>> -DEF_HELPER_2(flush_flags, void, env, i32)
>>> +DEF_HELPER_2(flush_flags, i32, env, i32)
>>
>> Modify to use DEF_HELPER_FLAGS while you're at it.  At the moment it
>> reads some globals, but doesn't write any, or have any other side effects.
>
> It writes "env->cc_x", so I guess I can't use DEF_HELPER_FLAGS ?

Ah, missed that.  So, no, not usefully.

>> That const needs to be freed.
>
> perhaps I'm wrong, what I had understood is:
>
> tcg_const_i32() creates a tcg_temp_new_i32(), and tcg_temp_new_i32() are
> automatically freed at end of tcg block (whereas tcg_const_local adn
> tcg_temp_local are not).

They are freed at the end of a basic block.  But the total number of temps 
affects the speed of the tcg code generator.  So you can improve the speed of 
qemu by freeing temporaries that are no longer needed.


r~