[llvm] [RISCV][Zicfilp] Codegen LPAD insns by looking at module flags (PR #152121)

[Ming-Yi Lai via llvm-commits]

mylai-mtk wrote:

@topperc 

> Do you plan to also address the code that uses Subtarget.hasStdExtZicfilp() in RISCVISelLowering and these patterns in RISCVInstrInfo.td

It looks like I have to, otherwise tests would just fail. As a result, I reviewed all behaviors that depended on `hasStdExtZicfilp()` and changed them to `hasZicfilpCFI()`, which is a new predicate also defined on the `RISCVSubtarget` class but has its returned value determined solely by the `Function`'s (`Module`'s) cf flags (Zicfilp ext availability is not taken into consideration). I guess I would need to rewrite the PR commit messages as the modified scope is now significantly larger.

https://github.com/llvm/llvm-project/pull/152121