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

[Shilei Tian via llvm-commits]

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@@ -437,6 +437,13 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     setOperationAction(Op, MVT::f128, Expand);
   }
 
+  // FIXME: If a target has F16C, it needs to be Custom.
+  setOperationAction(ISD::STRICT_FP_TO_BF16, MVT::f32, Expand);
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shiltian wrote:

Someone with X86 backend expertise needs to change this to `Custom` and implement `case ISD::STRICT_BF16_TO_FP:  return LowerBF16_TO_FP(Op, DAG);` in `LowerOperation` below.

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