[RISCV][GISEL] Add IRTranslation for insertelement with scalable vector type (#80377)

This patch is stacked on #80372, #80307, and #80306.

Author: michaelmaitland

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -2965,7 +2965,8 @@ bool IRTranslator::translateInsertElement(const User &U,
                                           MachineIRBuilder &MIRBuilder) {
   // If it is a <1 x Ty> vector, use the scalar as it is
   // not a legal vector type in LLT.
-  if (cast<FixedVectorType>(U.getType())->getNumElements() == 1)
+  if (auto *FVT = dyn_cast<FixedVectorType>(U.getType());
+      FVT && FVT->getNumElements() == 1)
     return translateCopy(U, *U.getOperand(1), MIRBuilder);
 
   Register Res = getOrCreateVReg(U);

llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp

@@ -1287,8 +1287,8 @@ MachineIRBuilder::buildInstr(unsigned Opc, ArrayRef<DstOp> DstOps,
                SrcOps[1].getLLTTy(*getMRI()) &&
            "Type mismatch");
     assert(SrcOps[2].getLLTTy(*getMRI()).isScalar() && "Invalid index");
-    assert(DstOps[0].getLLTTy(*getMRI()).getNumElements() ==
-               SrcOps[0].getLLTTy(*getMRI()).getNumElements() &&
+    assert(DstOps[0].getLLTTy(*getMRI()).getElementCount() ==
+               SrcOps[0].getLLTTy(*getMRI()).getElementCount() &&
            "Type mismatch");
     break;
   }

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -20729,11 +20729,11 @@ unsigned RISCVTargetLowering::getCustomCtpopCost(EVT VT,
 
 bool RISCVTargetLowering::fallBackToDAGISel(const Instruction &Inst) const {
 
-  // GISel support is in progress or complete for G_ADD, G_SUB, G_AND, G_OR, and
-  // G_XOR.
+  // GISel support is in progress or complete for these opcodes.
   unsigned Op = Inst.getOpcode();
   if (Op == Instruction::Add || Op == Instruction::Sub ||
-      Op == Instruction::And || Op == Instruction::Or || Op == Instruction::Xor)
+      Op == Instruction::And || Op == Instruction::Or ||
+      Op == Instruction::Xor || Op == Instruction::InsertElement)
     return false;
 
   if (Inst.getType()->isScalableTy())