[RISCV] Expand scalable vector bswap. Fix crash for bitreverse.

Fix LegalizeVectorOps to not try shuffle or unrolling expansions for
scalable vectors.

Differential Revision: https://reviews.llvm.org/D112236

Author: topperc

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

@@ -1095,6 +1095,10 @@ static void createBSWAPShuffleMask(EVT VT, SmallVectorImpl<int> &ShuffleMask) {
 SDValue VectorLegalizer::ExpandBSWAP(SDNode *Node) {
   EVT VT = Node->getValueType(0);
 
+  // Scalable vectors can't use shuffle expansion.
+  if (VT.isScalableVector())
+    return TLI.expandBSWAP(Node, DAG);
+
   // Generate a byte wise shuffle mask for the BSWAP.
   SmallVector<int, 16> ShuffleMask;
   createBSWAPShuffleMask(VT, ShuffleMask);
@@ -1124,6 +1128,12 @@ void VectorLegalizer::ExpandBITREVERSE(SDNode *Node,
                                        SmallVectorImpl<SDValue> &Results) {
   EVT VT = Node->getValueType(0);
 
+  // We can't unroll or use shuffles for scalable vectors.
+  if (VT.isScalableVector()) {
+    Results.push_back(TLI.expandBITREVERSE(Node, DAG));
+    return;
+  }
+
   // If we have the scalar operation, it's probably cheaper to unroll it.
   if (TLI.isOperationLegalOrCustom(ISD::BITREVERSE, VT.getScalarType())) {
     SDValue Tmp = DAG.UnrollVectorOp(Node);

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -545,6 +545,8 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
       setOperationAction(ISD::CTLZ, VT, Expand);
       setOperationAction(ISD::CTPOP, VT, Expand);
 
+      setOperationAction(ISD::BSWAP, VT, Expand);
+
       // Custom-lower extensions and truncations from/to mask types.
       setOperationAction(ISD::ANY_EXTEND, VT, Custom);
       setOperationAction(ISD::SIGN_EXTEND, VT, Custom);