[PATCH] D82258: [RegisterCoalescer] Fix IMPLICIT_DEF init removal for a register on joining

[Valery Pykhtin via Phabricator via llvm-commits]

vpykhtin added a comment.

In D82258#2148331 <https://reviews.llvm.org/D82258#2148331>, @arsenm wrote:

> It would help if 9d7bc0874cf20f44cd331c77f5a003b4c4b262bd had a test...
>
> I'm somewhat suspicious, since I have seen cases where the implicit def is needed in cases where the full register is never fully covered. However, it's possible this is still a leftover from before DetectDeadLanes was added


Do you mean there might be a situation when some lane becomes unitialized after RenameIndpendentSubregs? I checked RenameIndpendentSubregs pass - it has dedicated code in computeMainRangesFixFlags (line 310 ..) that creates IMPLICIT_DEF initialization for indpendent lanes.


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https://reviews.llvm.org/D82258