[llvm] [X86] Lower bf16->f32/f64 fpext without a GPR round-trip (PR #218359)

[Phoebe Wang via llvm-commits]

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@@ -462,6 +462,11 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     setOperationAction(ISD::BF16_TO_FP, VT, Expand);
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phoebewang wrote:

We declare BF16 type is supported only on SSE2+ in psABI and checked it in the FE. I forgot the bfloat-calling-conv-no-sse2.ll test. Actually I disagreed with the author to test non SSE2 case.. Let's keep it pass anyway.

https://github.com/llvm/llvm-project/pull/218359