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Re: [qemu-s390x] [PATCH v1 03/41] s390x/tcg: Implement VECTOR ADD COMPUT

From: David Hildenbrand
Subject: Re: [qemu-s390x] [PATCH v1 03/41] s390x/tcg: Implement VECTOR ADD COMPUTE CARRY
Date: Tue, 16 Apr 2019 10:46:25 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1

On 16.04.19 10:43, Richard Henderson wrote:
> On 4/15/19 10:33 PM, David Hildenbrand wrote:
>>>> Indeed, I didn't really explore vector operations yet. This is more
>>>> compact than I expected :)
>>> :-)
>>> That said, in implementing vector variable shifts today,
>>> I've come up with a representational problem here.
>>> You may want to hold off on these until I can address them.
>> I assume you mean vector helpers *in general* in this file. Yes, we can
>> add them later.
>> What exact problem are you dealing with?
> The .opc field lets you only specify one opcode which is optional in the
> backend on which you depend.  In writing support for AArch64 USHL, I find that
> I needed 3 optional opcodes.

I was asking myself this exact thing when looking at the opc field in
the example you gave ("which instruction is one supposed to indicate
here") :)

> I'm thinking of a mass change whereby .opc becomes a pointer to an array with
> terminator.  But then, for debugging purposes, I think I need to validate that
> array, so that it's not missing things that ought to be specified, but which
> happen to be supported by the current host.

Makes sense!



David / dhildenb

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