Re: [qemu-s390x] [Qemu-devel] [PATCH v1 7/7] s390x/tcg: Implement LOAD COUNT TO BLOCK BOUNDARY

[David Hildenbrand]

On 25.02.19 17:40, Richard Henderson wrote:
> On 2/25/19 8:17 AM, David Hildenbrand wrote:
>> On 25.02.19 17:14, Richard Henderson wrote:
>>> I don't understand all of this "blocksize" business, when they are all 
>>> powers
>>> of two, and the maximum value returned is 16.
>>>
>>> As far as I can see, the result is obtained by -(addr | -16) regardless of 
>>> the
>>> value of m3.
>>
>> Let's assume we have addr = 63;
>>
>> Assume block size is 64:
>> -> to_load = 1
>>
>> Assume block size is 128:
>> -> to_load = 16
>>
>> Or am i missing something?
> 
> No, just me.
> 
> You can still do the computation inline, with
> 
>     tcg_gen_ori_i64(tmp, addr, -blocksize);
>     tcg_gen_neg_i64(tmp, tmp);
>     sixteen = tcg_const_i64(16);
>     tcg_gen_umin_i64(tmp, sixteen);
> 

Nice trick, works fine, thanks :)

> 
> r~
> 


-- 

Thanks,

David / dhildenb