[RISCV] Promote i32 ISD::VAARG to i64 for -riscv-experimental-rv64-legal-i32.

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -263,6 +263,8 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
   setOperationAction(ISD::VASTART, MVT::Other, Custom);
   setOperationAction({ISD::VAARG, ISD::VACOPY, ISD::VAEND}, MVT::Other, Expand);
+  if (RV64LegalI32 && Subtarget.is64Bit())
+    setOperationAction(ISD::VAARG, MVT::i32, Promote);
 
   setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);