[PATCH] D112852: [GlobalISel] Allow DBG_VALUE to use invalid vregs throughout pipeline

[Amara Emerson via Phabricator via llvm-commits]

aemerson added a comment.

In D112852#3146936 <https://reviews.llvm.org/D112852#3146936>, @MatzeB wrote:

> Requesting changes for the missing MIR serialization of the new property.
>
>> The issue here is determining where the barrier for disallowing these undefined vregs should be. LiveDebugVariables naturally discards these particular uses, so this is sufficient based on my knowledge.
>
> Well to me this feels like we are making the intermediate representation more complicated (I consider it more complicated because DBG_VALUE instructions are special with lifetime rules now) for a very small gain.
>
> That said I don't feel strongly about this. If others think this is benefitial then we can go ahead.

We haven’t changed the meaning of the MIR, we just clarified the existing semantics on the RFC thread. There’s no middle ground here as far as I can see, either it’s valid to have undefined uses or not. If it is, then we’re free to do anything that leaves them around.


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  https://reviews.llvm.org/D112852/new/

https://reviews.llvm.org/D112852