[llvm] [MIPS] match llvm.{min, max}num with {min, max}.fmt for R6 (PR #89021)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

We need a real regression test for fmax/fmin. Please add a new one.
Maybe `RISCV/float-maximum-minimum.ll` is a good example.

https://github.com/llvm/llvm-project/pull/89021