diff --git a/llvm/lib/Target/TVM/TVMStack.cpp b/llvm/lib/Target/TVM/TVMStack.cpp
index 50197dc6d0b2..ffe2af9bff36 100644
--- a/llvm/lib/Target/TVM/TVMStack.cpp
+++ b/llvm/lib/Target/TVM/TVMStack.cpp
@@ -284,7 +284,8 @@ void Stack::dump() const {
 #endif
 
 void Stack::printElement(raw_ostream &OS, const StackVreg &Vreg) const {
-  if (Vreg.VirtReg == TVMFunctionInfo::UnusedReg) {
+  if (Vreg.VirtReg == TVMFunctionInfo::UnusedReg ||
+      Vreg.VirtReg >= TRI->getNumRegs()) {
     OS << "x";
     return;
   }
diff --git a/llvm/lib/Target/TVM/TVMStackFixup.cpp b/llvm/lib/Target/TVM/TVMStackFixup.cpp
index 4a71f9a4b57b..6ac908780fa0 100644
--- a/llvm/lib/Target/TVM/TVMStackFixup.cpp
+++ b/llvm/lib/Target/TVM/TVMStackFixup.cpp
@@ -95,7 +95,8 @@ StackFixup StackFixup::Diff(const Stack &to, const Stack &from) {
 
   // Generate changes to re-order
   assert(llvm::size(unmaskedTo) == llvm::size(curStack));
-  generateVagonXchgs(rv, curStack, unmaskedTo);
+  if (llvm::size(curStack) > 0)
+    generateVagonXchgs(rv, curStack, unmaskedTo);
   rv.optimize();
   return rv;
 }
@@ -225,6 +226,7 @@ void StackFixup::generateVagonXchgs(StackFixup &rv, const Stack &from,
 
   auto Tr = Train::build(curStack, to);
   auto restVagons = llvm::make_range(Tr.Vagons.begin(), Tr.Vagons.end());
+  assert(restVagons.begin() != restVagons.end());
   auto V = *restVagons.begin();
   if (V.DeepIdx + 1 == Sz && !V.Inverted) {
     restVagons = drop_begin(restVagons, 1);