Re: [Qemu-devel] [PATCH v3 05/20] tcg-arm: Handle constant arguments to add2/sub2

[Richard Henderson <rth@twiddle.net>]

On 03/28/2013 08:56 AM, Peter Maydell wrote:
>> +#define TO_CPSR (1 << 20)
> 
> This is the S bit; I think it would be helpful if our #define
> had a name that made that clearer...

Suggestions?  I thought "TO_CPSR" was clear...

>> +    ARITH_TST = 0x8 << 21 | TO_CPSR,
>> +    ARITH_CMP = 0xa << 21 | TO_CPSR,
>> +    ARITH_CMN = 0xb << 21 | TO_CPSR,
>> +    ARITH_ORR = 0xc << 21,
>> +    ARITH_MOV = 0xd << 21,
>> +    ARITH_BIC = 0xe << 21,
>> +    ARITH_MVN = 0xf << 21,
>>  };
> 
> It feels a little ugly to OR in the S bit in this enum, but I guess
> it works.

I think it actually makes everything a lot cleaner myself.  Especially given
the previous definition that required runtime checks for TST et al.

> Maybe we should add ARITH_TEQ at some point?

Given that it's the only one left out, sure.  I can't imagine what context it
would be useful within tcg though -- it's main use seems to be doing an
equality comparison while preserving the C flag.



r~