Re: [Qemu-devel] [PATCH] cpu: Move tcg_exit_req to the end of CPUState

[Andreas Färber]

Am 19.03.2014 22:04, schrieb Richard Henderson:
> Ping?  This is a significant TCG code size regression
> for ARM, AArch64, and Sparc hosts.  It helps x86 too,
> though that's not as severe.

Sorry, applied to qom-cpu now:
https://github.com/afaerber/qemu-cpu/commits/qom-cpu

How did you find this? Was there some assertion on one target, or do you
have some analysis code that you could share?

Thanks,
Andreas

> 
> 
> r~
> 
> On 03/14/2014 03:30 PM, Richard Henderson wrote:
>> Reverse an increase in the size of generated code.
>>
>> Cc: Andreas Färber <address@hidden>
>> Signed-off-by: Richard Henderson <address@hidden>
>> ---
>>  include/qom/cpu.h | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
>> index 06ee263..f99885a 100644
>> --- a/include/qom/cpu.h
>> +++ b/include/qom/cpu.h
>> @@ -227,7 +227,6 @@ struct CPUState {
>>      bool stop;
>>      bool stopped;
>>      volatile sig_atomic_t exit_request;
>> -    volatile sig_atomic_t tcg_exit_req;
>>      uint32_t interrupt_request;
>>      int singlestep_enabled;
>>      int64_t icount_extra;
>> @@ -272,6 +271,12 @@ struct CPUState {
>>      } icount_decr;
>>      uint32_t can_do_io;
>>      int32_t exception_index; /* used by m68k TCG */
>> +
>> +    /* Note that this is accessed at the start of every TB via a negative
>> +       offset from AREG0.  Leave this field at the end so as to make the
>> +       (absolute value) offset as small as possible.  This reduces code
>> +       size, especially for hosts without large memory offsets.  */
>> +    volatile sig_atomic_t tcg_exit_req;
>>  };
>>  
>>  QTAILQ_HEAD(CPUTailQ, CPUState);
>>
> 
> 


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