[RISCV] Simplify some code in lowering vector int<->fp conversions. NFC

Don't call EltVT.getSizeInBits() or SrcEltVT.getSizeInBits() a second
time. They are already in EltSize or SrcEltSize variables.

Refactor some comparisons to use multiply instead of division.

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -3381,10 +3381,10 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
 
     bool IsInt2FP = SrcEltVT.isInteger();
     // Widening conversions
-    if (EltSize > SrcEltSize && (EltSize / SrcEltSize >= 4)) {
+    if (EltSize > (2 * SrcEltSize)) {
       if (IsInt2FP) {
         // Do a regular integer sign/zero extension then convert to float.
-        MVT IVecVT = MVT::getVectorVT(MVT::getIntegerVT(EltVT.getSizeInBits()),
+        MVT IVecVT = MVT::getVectorVT(MVT::getIntegerVT(EltSize),
                                       VT.getVectorElementCount());
         unsigned ExtOpcode = Op.getOpcode() == ISD::UINT_TO_FP
                                  ? ISD::ZERO_EXTEND
@@ -3402,7 +3402,7 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
     }
 
     // Narrowing conversions
-    if (SrcEltSize > EltSize && (SrcEltSize / EltSize >= 4)) {
+    if (SrcEltSize > (2 * EltSize)) {
       if (IsInt2FP) {
         // One narrowing int_to_fp, then an fp_round.
         assert(EltVT == MVT::f16 && "Unexpected [US]_TO_FP lowering");
@@ -3413,9 +3413,8 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
       // FP2Int
       // One narrowing fp_to_int, then truncate the integer. If the float isn't
       // representable by the integer, the result is poison.
-      MVT IVecVT =
-          MVT::getVectorVT(MVT::getIntegerVT(SrcEltVT.getSizeInBits() / 2),
-                           VT.getVectorElementCount());
+      MVT IVecVT = MVT::getVectorVT(MVT::getIntegerVT(SrcEltSize / 2),
+                                    VT.getVectorElementCount());
       SDValue FP2Int = DAG.getNode(Op.getOpcode(), DL, IVecVT, Src);
       return DAG.getNode(ISD::TRUNCATE, DL, VT, FP2Int);
     }