[llvm] [SelectionDAG] Add `STRICT_BF16_TO_FP` and `STRICT_FP_TO_BF16` (PR #80056)

[Shilei Tian via llvm-commits]

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@@ -393,7 +393,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
   }
 
   for (auto Op : {ISD::FP16_TO_FP, ISD::STRICT_FP16_TO_FP, ISD::FP_TO_FP16,
-                  ISD::STRICT_FP_TO_FP16}) {
+                  ISD::STRICT_FP_TO_FP16, ISD::STRICT_FP_TO_BF16}) {
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shiltian wrote:

@phoebewang Do you mean here, we need to drop `Custom` for `Subtarget.hasF16C()` if `Op` is `ISD::STRICT_FP_TO_BF16`? If yes, I will take it out of the loop.

https://github.com/llvm/llvm-project/pull/80056