[llvm] [InstCombine] Fold `(op x, ({z,s}ext (icmp eq x, C)))` to select (PR #89020)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> @dtcxzyw can you re-run this. If we don't hit any non `add` patterns ill close this and post nikic's simplification.

Confirmed that most of cases are `add` patterns except bench/spdlog/optimized/async.cpp.ll. I cannot tell which pattern is folded based on the ir diff.


https://github.com/llvm/llvm-project/pull/89020