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

[David Hildenbrand]

On 25.02.19 17:14, Richard Henderson wrote:
> On 2/25/19 3:55 AM, David Hildenbrand wrote:
>> +uint64_t HELPER(lcbb)(uint64_t addr, uint32_t m3)
>> +{
>> +    const uint32_t block_size = 1ul << (m3 + 6);
>> +    const uint64_t rounded_addr = ROUND_UP(addr, block_size);
>> +    uint32_t to_load = 16;
>> +
>> +    if (rounded_addr != addr) {
>> +        to_load = MIN(rounded_addr - addr, to_load);
>> +    }
>> +    return to_load;
>> +}
> 
> 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?

-- 

Thanks,

David / dhildenb