[PATCH] D90131: [PowerPC] Add folding patterns for rlwinm + andi_rec.

Thu Dec 3 23:47:26 PST 2020

Esme added inline comments.

================
Comment at: llvm/test/CodeGen/PowerPC/p10-spill-crlt.ll:78
+; CHECK-NEXT:    rlwinm. r3, r30, 0, 30, 30
+; CHECK-NEXT:    rlwinm r29, r30, 0, 24, 22
 ; CHECK-NEXT:    mcrf cr2, cr0
----------------
nemanjai wrote:
> nemanjai wrote:
> > Well this is less than ideal. Perhaps we should only do this if the GPR that the `andi.` defines is dead?
> Sorry, this was meant to say that we should check that the GPR that `andi.` **uses** is killed.
> Sorry, this was meant to say that we should check that the GPR that `andi.` **uses** is killed.

@nemanjai Sorry, although I have updated the revision, I am actually a bit confused about this fix. As the comment added in last version (Diff 308919), I assumed the deg was caused by RA. 
```
; FIXME: A redundant COPY was generated during RA.
; i.e.   rlwinm r29, r30, 0, 24, 22
;        mr r30, r29
```
Checking the GPR that andi. uses is killed can skip folding the case and avoid the deg, however is it the cause of the deg? I would be thankful if you have more comments about this issue.

Repository:
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  https://reviews.llvm.org/D90131/new/

https://reviews.llvm.org/D90131