[llvm] [Bitcode] Fix constexpr expansion creating invalid PHIs (PR #141560)

[Nikita Popov via llvm-commits]

================
@@ -0,0 +1,32 @@
+; RUN: opt -expand-constant-exprs -p verify %s.bc
----------------
nikic wrote:

```suggestion
; RUN: opt -S -expand-constant-exprs %s.bc
```
`-p verify` is implied for opt.

https://github.com/llvm/llvm-project/pull/141560