[llvm] [TTI] Check type legalization of both src and result for fpto{u|s}i.sat. (PR #147657)

[David Green via llvm-commits]

davemgreen wrote:

I might be wrong about what is going on, but yes I assumed that the backends marking those opcodes as Custom (https://github.com/llvm/llvm-project/blob/20becf373edcf9d568f8904c2b473e6b48500787/llvm/lib/Target/ARM/ARMISelLowering.cpp#L327, https://github.com/llvm/llvm-project/blob/20becf373edcf9d568f8904c2b473e6b48500787/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp#L2060, https://github.com/llvm/llvm-project/blob/20becf373edcf9d568f8904c2b473e6b48500787/llvm/lib/Target/RISCV/RISCVISelLowering.cpp#L835) makes the cost model use the isOperationCustom cost of 2 in the code you pointed to. That might not be very useful for a lot of types though (it doesn't consider the Tys[0], only RetTy), and maybe for this particular operation it isn't going to be correct enough to be useful.

https://github.com/llvm/llvm-project/pull/147657