PING^2 [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