Index: llvm/lib/IR/AutoUpgrade.cpp
===================================================================
--- llvm/lib/IR/AutoUpgrade.cpp
+++ llvm/lib/IR/AutoUpgrade.cpp
@@ -4453,12 +4453,16 @@
 }
 
 MDNode *llvm::UpgradeTBAANode(MDNode &MD) {
+  const unsigned NumOperands = MD.getNumOperands();
+  if (NumOperands == 0)
+    return nullptr;
+
   // Check if the tag uses struct-path aware TBAA format.
-  if (isa<MDNode>(MD.getOperand(0)) && MD.getNumOperands() >= 3)
+  if (isa<MDNode>(MD.getOperand(0)) && NumOperands >= 3)
     return &MD;
 
   auto &Context = MD.getContext();
-  if (MD.getNumOperands() == 3) {
+  if (NumOperands == 3) {
     Metadata *Elts[] = {MD.getOperand(0), MD.getOperand(1)};
     MDNode *ScalarType = MDNode::get(Context, Elts);
     // Create a MDNode <ScalarType, ScalarType, offset 0, const>
Index: llvm/test/Bitcode/tbaa-empty-arg-autoupgrade-crash.ll
===================================================================
--- /dev/null
+++ llvm/test/Bitcode/tbaa-empty-arg-autoupgrade-crash.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as -o - < %s | llvm-dis | FileCheck %s
+
+; Test there's no crash if tbaa has an empty argument.
+; CHECK: store i32 %arg0, ptr addrspace(1) %arg1, align 4{{$}}
+
+define void @tbaa_empty_arg(i32 %arg0, ptr addrspace(1) %arg1) {
+  store i32 %arg0, ptr addrspace(1) %arg1, align 4, !tbaa !0
+  ret void
+}
+
+!0 = !{}