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From: David Hildenbrand <david@redhat.com>
Message-ID: <99906aad-e22a-8cc3-8c49-4e2a2ce3d0e9@redhat.com>
Date: Wed, 13 Feb 2019 20:53:16 +0100
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Subject: Re: [Qemu-devel] [PATCH v2 12/15] s390x/tcg: Implement XxC and
 checks for most FP instructions
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To: Richard Henderson <richard.henderson@linaro.org>, qemu-devel@nongnu.org
Cc: qemu-s390x@nongnu.org, Thomas Huth <thuth@redhat.com>, Halil Pasic <pasic@linux.ibm.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Janosch Frank <frankja@linux.ibm.com>, Cornelia Huck <cohuck@redhat.com>

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 <david@redhat.com>
> 
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> 
>> +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