[llvm] [llubi] Add basic support for vector and aggregate ops (PR #181544)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> I didn't understand why you need constant expressions to test scalable vector support.

I used to think zeroinitializer will be expanded to insertelement+shufflevector idiom without `use-constant-int-for-scalable-splat`...

https://github.com/llvm/llvm-project/pull/181544