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Re: [Qemu-devel] [PATCH v1 1/5] s390x/tcg: Implement VECTOR FIND ANY ELE


From: David Hildenbrand
Subject: Re: [Qemu-devel] [PATCH v1 1/5] s390x/tcg: Implement VECTOR FIND ANY ELEMENT EQUAL
Date: Wed, 22 May 2019 13:01:03 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1

> I also think that, if we create a bunch more of these wrappers:
> 
>> +DEF_VFAE_HELPER(8)
>> +DEF_VFAE_HELPER(16)
>> +DEF_VFAE_HELPER(32)
> 
> then RT and ZS can be passed in as constant parameters to the above, and then
> the compiler will fold away all of the stuff that's not needed for each
> different case.  Which, I think, is significant.  These are practically
> different instructions with the different modifiers.
> 

So, we have 4 flags, resulting in 16 variants. Times 3 element sizes ...
48 helpers in total. Do we really want to go down that path?

I can also go ahead any try to identify the most frequent users (in
Linux) and only specialize that one.

-- 

Thanks,

David / dhildenb



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