Index: llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
+++ llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
@@ -104,6 +104,8 @@
                     "Rename Register Operands Canonically", false, false)
 
 static std::vector<MachineBasicBlock *> GetRPOList(MachineFunction &MF) {
+  if (MF.empty())
+    return {};
   ReversePostOrderTraversal<MachineBasicBlock *> RPOT(&*MF.begin());
   std::vector<MachineBasicBlock *> RPOList;
   for (auto MBB : RPOT) {
Index: llvm/trunk/test/CodeGen/MIR/AArch64/empty-MF.mir
===================================================================
--- llvm/trunk/test/CodeGen/MIR/AArch64/empty-MF.mir
+++ llvm/trunk/test/CodeGen/MIR/AArch64/empty-MF.mir
@@ -0,0 +1,11 @@
+# RUN: llc -mtriple aarch64-- -run-pass mir-canonicalizer %s -o - | FileCheck %s
+# CHECK: ...
+# CHECK-NEXT: ---
+# CHECK-NEXT: name:            foo
+# CHECK: body:             |
+# CHECK-EMPTY:
+# CHECK-NEXT: ...
+---
+name: foo
+body:             |
+...