[llvm] AMDGPU: Make v2f32 -> v2f16 legal when target supports v_cvt_pk_f16_f32 (PR #139956)

[Matt Arsenault via llvm-commits]

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@@ -6899,10 +6902,16 @@ SDValue SITargetLowering::getFPExtOrFPRound(SelectionDAG &DAG, SDValue Op,
 SDValue SITargetLowering::lowerFP_ROUND(SDValue Op, SelectionDAG &DAG) const {
   SDValue Src = Op.getOperand(0);
   EVT SrcVT = Src.getValueType();
+  EVT DstVT = Op.getValueType();
+
+  if (DstVT == MVT::v2f16) {
+    assert(Subtarget->hasCvtPkF16F32Inst() && "support v_cvt_pk_f16_f32");
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arsenm wrote:

The same should apply to all vector types.

https://github.com/llvm/llvm-project/pull/139956