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

Fri Jul 28 08:03:27 PDT 2023

arsenm added a comment.

In D156345#4542127 <https://reviews.llvm.org/D156345#4542127>, @qcolombet wrote:

> Hi @arsenm ,
>
> A maybe more robust temporary fix may be to apply the terminal rule (`applyTerminalRule`) only on `isCopy` instructions (right now it is on `isCopyLike`).
>
> I could be wrong, but I wouldn't be surprised if this is the entry point of the problematic coalesced SUBREG_TO_REGs. And clearly without your fixes, the terminal rule is incorrect on SUBREG_TO_REG.

"UseTerminalRule" is false by default. Swapping the isCopyLike in copyCoalesceInMBB for isCopy induces about 850 test failures

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https://reviews.llvm.org/D156345