[RISCV] Disable hasAllNBitUsers for vector types.

RISCVGenDAGISel.inc can call this before it checks the node type.
Ensure the type is scalar before wasting time to do the more
computationally expensive checks.

This also avoids an assertion if we hit a VMV_X_S instruction
which doesn't have a VL operand which vectorPseudoHasAllNBitUsers
expects.

Author: topperc

llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp

@@ -2878,6 +2878,11 @@ bool RISCVDAGToDAGISel::hasAllNBitUsers(SDNode *Node, unsigned Bits,
   if (Depth >= SelectionDAG::MaxRecursionDepth)
     return false;
 
+  // The PatFrags that call this may run before RISCVGenDAGISel.inc has checked
+  // the VT. Ensure the type is scalar to avoid wasting time on vectors.
+  if (!Node->getValueType(0).isScalarInteger())
+    return false;
+
   for (auto UI = Node->use_begin(), UE = Node->use_end(); UI != UE; ++UI) {
     SDNode *User = *UI;
     // Users of this node should have already been instruction selected