[NVPTX] expand trunc v2i32->v2i16

llvm#153478 made v2i32 legal on newer GPUs, but we can not lower all operations yet.
Expand the `trunc` operation until we implement efficient lowering.

Author: Artem-B

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

@@ -638,6 +638,9 @@ NVPTXTargetLowering::NVPTXTargetLowering(const NVPTXTargetMachine &TM,
   // No support for these operations with v2f32/v2i32
   setOperationAction(ISD::INSERT_VECTOR_ELT, {MVT::v2f32, MVT::v2i32}, Expand);
   setOperationAction(ISD::VECTOR_SHUFFLE, {MVT::v2f32, MVT::v2i32}, Expand);
+
+  setOperationAction(ISD::TRUNCATE, MVT::v2i16, Expand);
+
   // Need custom lowering in case the index is dynamic.
   if (STI.hasF32x2Instructions())
     setOperationAction(ISD::EXTRACT_VECTOR_ELT, {MVT::v2f32, MVT::v2i32},