Re: [Qemu-devel] [PATCH] target-mips: Fix incorrect shift for SHILO and SHILOV

[Andreas Färber]

Am 04.12.2012 20:48, schrieb Jovanovic, Petar:
>> diff --git a/target-mips/dsp_helper.c b/target-mips/dsp_helper.c
>> index e7949c2..f8a7a9f 100644
>> --- a/target-mips/dsp_helper.c
>> +++ b/target-mips/dsp_helper.c
>> @@ -3814,17 +3814,17 @@ void helper_shilo(target_ulong ac, target_ulong rs, 
>> CPUMIPSState *env)
>>
>>      rs5_0 = rs & 0x3F;
>>      rs5_0 = (int8_t)(rs5_0 << 2) >> 2;
>> -    rs5_0 = MIPSDSP_ABS(rs5_0);
>> +
>> +    if (rs5_0 == 0)
>> +        return;
> 
>> The check should be moved to translation time so that the call to this
>> helper is not generated at all.
> 
> This case is not likely so generation of unnecessary call is unlikely too.
> Let me know what you think.

FWIW you could use our unlikely() macro then to aid branch prediction.

Andreas

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