[llvm] Preserve range metadata when load is narrowed (PR #128144)

[via llvm-commits]

LU-JOHN wrote:

> Can we just get the ConstantRange and trunc() it? I really don't think trying to preserve the sub-ranges is worthwhile.

Make one new range to cover all previous sub-ranges.


https://github.com/llvm/llvm-project/pull/128144