[llvm] CodeGen: Don't assert when printing null GlobalAddress operands (PR #115531)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> So how do you run into this problem?

Bugs

> It sounds to me that we shouldn't produce nullptr for GlobalAddress in a normal compilation flow.

Yes, but this is in debug printing. -debug causing new crashes to appear is a bad property 

https://github.com/llvm/llvm-project/pull/115531