[llvm] [llubi] Use correct tag bitwidth to recover provenances (PR #230852)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> (Though I'm not sure if LLVM really intends to support non-byte-sized pointers, that seems pretty weird...)

Only LLMs could conceive of this :)
 

https://github.com/llvm/llvm-project/pull/230852