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