PING^1 [PATCH v4] rs6000: Adjust mov optabs for opaque modes [PR103353]

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi,

Gentle ping https://gcc.gnu.org/pipermail/gcc-patches/2022-June/597286.html

BR,
Kewen

on 2022/6/27 10:47, Kewen.Lin via Gcc-patches wrote:
> Hi Segher!
> 
> on 2022/6/25 00:49, Segher Boessenkool wrote:
>> Hi!
>>
>> On Fri, Jun 24, 2022 at 09:03:59AM +0800, Kewen.Lin wrote:
>>> on 2022/6/24 03:06, Segher Boessenkool wrote:
>>>> On Wed, May 18, 2022 at 10:07:48PM +0800, Kewen.Lin wrote:
>>>>> As PR103353 shows, we may want to continue to expand a MMA built-in
>>>>> function like a normal function, even if we have already emitted
>>>>> error messages about some missing required conditions.  As shown in
>>>>> that PR, without one explicit mov optab on OOmode provided, it would
>>>>> call emit_move_insn recursively.
>>>>
>>>> First off: lxvp is a VSX insn, not an MMA insn.  So please don't call it
>>>> that -- this confusion is what presumably caused the problem here, so it
>>>> would be good to root it out :-)
>>>
>>> I guess the "it" in "don't call it call" is for "MMA built-in function"?
>>> It comes from the current code:
>>
>> Your proposed commit message says "MMA built-in function".  It is not
>> an MMA builtin, or rather, it should not be.
>>
>>>>> +  /* Opaque modes are only expected to be available when MMA is supported,
>>>>
>>>> Why do people expect that?  It is completely wrong.  The name "opaque"
>>>> itself already says this is not just for MMA, but perhaps more
>>>> importantly, it is a basic VSX insn, doesn't touch any MMA resources,
>>>> and is useful in other contexts as well.
>>>
>>> ... The above statements are also based on current code, for now, the
>>> related things like built-in functions, mov optab, hard_regno_ok etc.
>>> for these two modes are guarded by TARGET_MMA.
>>
>> Opaque modes are a generic thing, not an rs6000 thing.  It is important
>> not to conflate completely different things that just happened to
>> coincide some months ago (but not anymore right now even!)
>>
>>> I think I get your points here, you want to separate these opaque
>>> modes from MMA since the underlying lxvp/stxvp are not MMA specific,
>>> so those related things (bifs, mov optabs etc.) are not necessarily
>>> guarded under MMA.
>>
>> Yup.  This can take some time of course, but in the mean time we should
>> stop pretending the status quo is correct.
>>
>>>> So this needs some bigger surgery.
>>>
>>> Yes, Peter may have more comments on this.
>>
>> Yes.  Can you do a patch that just fixes this PR103353, without adding
>> more misleading comments?  :-)
>>
> 
> Many thanks for all the further explanation above!  The attached patch
> updated the misleading comments as you pointed out and suggested, could
> you help to have another look?
> 
> BR,
> Kewen