Re: [PATCH] rs6000: fmr gets used instead of faster xxlor [PR93571]

[Ajit Agarwal via Gcc-patches]

On 21/02/23 7:39 pm, Segher Boessenkool wrote:
> On Tue, Feb 21, 2023 at 06:00:52PM +0530, Ajit Agarwal wrote:
>> On 21/02/23 4:34 pm, Segher Boessenkool wrote:
>>> Please domn't use a switch, it isn't needed.  Instead use the "isa"
>>> attribute (with p7v here), and put the preferred alternative first.
>>
>> I am not sure how this is possible without switch and using only "isa".
> 
> You have the "p7v" "xxlor" alternative earlier than the "*" "fmr"
> alternative.  You can have an "xxlor" for contraints "d", but probably
> the best (and certainly the easiest) is to just move the existing
> xxlor to before fmr.
> 
> Oh, the existing xxlor alternative is implicitly isa p7v, the "wa"
> constraint causes that.  It may be nicer to mark it explicitly p7v as
> well, nicer for the reader.
> 

If I do the above, for power9 it selects xxlor instead of fmr.

> Btw, please update the other similar patterns at the same time?  There
> are eight patterns with fmr in rs6000.md (the four in dfp.md should
> probably not be touched); not all are similar so should be in separate
> patches, if changed at all, but a bunch are completely analogous so
> should not diverge.
> 
> (It is fine to first do this one pattern only, until we have worked out
> all kinks, but all should be committed at the same time).
> 
> Thanks,
> 
> 
> Segher