[NVPTX] Expand VSELECT on v2f32 and other types

VSELECT instructions are always expanded because the predicate type they
use (vNi1) is unsupported by our backend. However, TLI doesn't check the
predicate type when determining whether to rewrite certain operations
(ex: FMAX/FMIN) as a VSELECT, only the value type. So in the case of
FMAX/FMIN on v2f32, the value type is now legal and therefore TLI thinks
it can rewrite it as VSELECT. Eventually this is scalarized into setp,
which is not what we want.

Author: Prince781

llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp

@@ -683,6 +683,7 @@ NVPTXTargetLowering::NVPTXTargetLowering(const NVPTXTargetMachine &TM,
   for (MVT VT : {MVT::bf16, MVT::f16, MVT::v2bf16, MVT::v2f16, MVT::f32,
                  MVT::v2f32, MVT::f64, MVT::i1, MVT::i8, MVT::i16, MVT::v2i16,
                  MVT::v4i8, MVT::i32, MVT::i64}) {
+    setOperationAction(ISD::VSELECT, VT, Expand);
     setOperationAction(ISD::SELECT_CC, VT, Expand);
     setOperationAction(ISD::BR_CC, VT, Expand);
   }