Re: [Qemu-devel] [PATCH v2 12/15] s390x/tcg: Implement XxC and checks for most FP instructions

[David Hildenbrand]

On 13.02.19 20:31, Richard Henderson wrote:
> On 2/13/19 6:33 AM, David Hildenbrand wrote:
>> With the floating-point extension facility
>> - CONVERT FROM LOGICAL
>> - CONVERT TO LOGICAL
>> - CONVERT TO FIXED
>> - CONVERT FROM FIXED
>> - LOAD FP INTEGER
>> have both, a rounding mode specification and the inexact-exception control
>> (XxC). Other instructions will be handled separatly.
>>
>> Check for valid rounding modes and forward also the XxC (via m4). To avoid
>> a lot of boilerplate code and changes to the helpers, combine both, the
>> m3 and m4 field in a combined 32 bit TCG variable. Perform checks at
>> a central place, taking in account if the m3 or m4 field was ignore
>> before the floating-point extension facility was introduced.
>>
>> Signed-off-by: David Hildenbrand <address@hidden>
> 
> Reviewed-by: Richard Henderson <address@hidden>
> 
>> +static inline bool xxc_from_m34(uint32_t m34)
>> +{
>> +    /* XxC is bit 1 of m4 */
>> +    return (extract32(m34, 4, 4) & 0x4) != 0;
> 
> Better as extract32(m32, 6, 1);

Is it "better as" that or "better written as" that?

I think "extract32(m34, 4, 4) & 0x4" is slightly easier to understand.
(get m4 field and take the bit number 1)

Thanks!

> 
> 
> r~
> 


-- 

Thanks,

David / dhildenb