[llvm] [ValueTracking] Handle not cond to assume. (PR #127140)

[Nikita Popov via llvm-commits]

nikic wrote:

See https://github.com/llvm/llvm-project/issues/128152 for another ephemeral value problem. This is why I think special casing not is not a solution.

I briefly tried the variant where we don't consider extra uses at https://github.com/nikic/llvm-project/commit/37f1d405e40d9a12c0de48acd3bcb15a01d88f25 / https://github.com/dtcxzyw/llvm-opt-benchmark/pull/2135. That would need more work, but I think that's the general direction we should go to resolve this more thoroughly.

https://github.com/llvm/llvm-project/pull/127140