[llvm] [DAG] fold `avgu(sext(x), sext(y))` -> `sext(avgu(x, y))` (PR #95365)

[Jay Foad via llvm-commits]

jayfoad wrote:

> [DAG] fold avgu(sext(x), sext(y)) -> sext(avgu(x, y))

No, this needs to be: avg**s**(sext(x), sext(y)) -> sext(avg**s**(x, y))

https://github.com/llvm/llvm-project/pull/95365