[SDAGBuilder] Make the AArch64 builder happier.

I intended this loop to only unwrap SplitVector actions, but it
was more broad than that, such as unwrapping WidenVector actions,
which makes operations seem legal when they're not.

llvm-svn: 237457
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 1915a43..3c5d32f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2278,11 +2278,11 @@
 
     EVT VT = ValueVTs[0];
     LLVMContext &Ctx = *DAG.getContext();
-    while (DAG.getTargetLoweringInfo().getTypeToTransformTo(Ctx, VT) != VT)
-      VT = DAG.getTargetLoweringInfo().getTypeToTransformTo(Ctx, VT);
+    auto &TLI = DAG.getTargetLoweringInfo();
+    while (TLI.getTypeAction(Ctx, VT) == TargetLoweringBase::TypeSplitVector)
+      VT = TLI.getTypeToTransformTo(Ctx, VT);
 
-    if (Opc != ISD::DELETED_NODE &&
-        DAG.getTargetLoweringInfo().isOperationLegalOrCustom(Opc, VT)) {
+    if (Opc != ISD::DELETED_NODE && TLI.isOperationLegalOrCustom(Opc, VT)) {
       OpCode = Opc;
       LHSVal = getValue(LHS);
       RHSVal = getValue(RHS);