[llvm] MIPS: Support isLegalICmpImmediate and isLegalAddImmediate (PR #133400)

[YunQiang Su via llvm-commits]

wzssyqa wrote:

> Testcase? I'd expect that implementing these functions has some effect on generated code, even if you're not explicitly using them in the MIPS backend.

I agree, and I think that it is due to that we have a test case can cover it.

https://github.com/llvm/llvm-project/pull/133400