[llvm-dev] Can DBG_VALUE instructions use undefined vregs?

[Amara Emerson via llvm-dev]

One GlobalISel compile time optimization patch (https://reviews.llvm.org/D109750 <https://reviews.llvm.org/D109750>) has generated some debate over whether it’s semantically allowed/not-an-error for a DBG_VALUE machine instruction to have a use of a vreg that doesn’t have a corresponding definition.

We talked internally with Adrian and Vedant and didn’t come to a strong conclusion either way. Does anyone have thoughts here?

Thanks,
Amara
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