[PATCH] D97054: [MachineVerifier] Confirm that both ends of a tied def/use are live together

Mon Feb 22 16:44:06 PST 2021

arsenm added a comment.

In D97054#2579436 <https://reviews.llvm.org/D97054#2579436>, @reames wrote:

> In D97054#2574843 <https://reviews.llvm.org/D97054#2574843>, @arsenm wrote:
>
>> Testcase?
>
> Not sure how to honestly.  The whole idea is that an invalid live range should be impossible to construct, but that we want to catch it in verification if the register allocator does so.

We have unit tests in unittests/MI/LiveIntervalTest

>> I also think this won't handle subregister indexes correctly. How does the x86 test fail?
>
> Can you expand on this a bit?  I'm not sure what you mean by handling subregisters.  What are the expectations for tied subregisters?

I believe the tied operands should have the same subregister index (although I'm not sure this is enforced). The same rules should apply, just on the subrange

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