[PATCH] D156345: RegisterCoalescer: Add implicit-def of super register when coalescing SUBREG_TO_REG

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet added a comment.

> In my mind, if we have implicit defs on a copy, then we should probably not consider the related instruction as a copy to begin with.

Essentially that's the difference between `isCopy` and `isCopyLike`.
`isCopyLike` requires more careful handling.

Maybe that's the root cause of the problem. We're using `isCopyInstr` for `isCopyLike` instructions at places where `isCopy` (i.e., true copies, nothing else) was only supported. It's also possible that over the years we used `isCopyLike` in places where `isCopy` is the only thing supported. (I may be guilty of that :)).

Now, it shouldn't be that easy to shoot ourselves in the foot.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D156345/new/

https://reviews.llvm.org/D156345