Re: rs6000: Prefer assigning the MMA vector operands to altivec registers [PR105556]

[Peter Bergner <bergner@linux.ibm.com>]

On 5/10/22 5:35 PM, Segher Boessenkool wrote:
> If you want to use this same message as commit message, you shouldn't
> say "this patch".  Also, try not to use lines more than 72 positions
> wide (which handily is also a good maximum length for email messages,
> that way it can be quoted a few times without wrapping).

Sure, I can reword that.


> And I assume generated code still looks at least as good otherwise?

If you are asking whether we get the code we want generated with the
patch, the answer is yes.  Otherwise, I'm not sure what you're asking. :-)

 

> This is more involved than just replacing one constrait with two.  You
> shoould say that in the changelog (and in your message).

Ok, I can expand on that.


> Out of interest, did you try using v,?wa (so just two alternatives, not
> four)?  Or did you think it wouldresult in  measurably worse code?  Or
> did you decide it is not such bad backend code size explosion after
> all :-)

I have not tried that, but I will and see what happens.
I'm slightly worried that since 'v' is part of 'wa', then saying
'?wa' might just cancel the 'v' usage, but I'll see how it works.
If it works and simplifies the patch, great!  I'll report back.


> Okay for trunk with a slightly better changelog.  Thanks!

If it doesn't work, I'll go with the code as is, modulo the
changes you asked for.  Thanks.


Peter