[PATCH 2/3] VAX: Handle constant 0 with QMATH DImode add/sub

[Maciej W. Rozycki]

On Sun, 13 Dec 2020, Jeff Law wrote:

> > 	gcc/
> > 	* config/vax/vax.c (vax_expand_addsub_di_operands): Handle the 
> > 	addition or subtraction of 0.
> OK, though I would have generally expected something to catch this earlier.

 Doesn't it matter that this pattern is produced in the context of atomic 
intrinsics?

 It is also not invalid even if silly and the !QMATH VAX implementation 
(the older one, presumably) lets it through just fine.  Last but not least 
the operation does not make it to assembly output; I could perhaps trace 
it through the RTL passes, but so far I have decided it doesn't really 
matter which specific pass makes it disappear.

 Either way thanks for your review, I have pushed this and the remaining 
five changes.

  Maciej