Index: llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
+++ llvm/trunk/lib/CodeGen/MIRCanonicalizerPass.cpp
@@ -483,18 +483,14 @@
   unsigned virtualVRegNumber;
 
 public:
-  NamedVRegCursor(MachineRegisterInfo &MRI) : MRI(MRI) {
-    unsigned VRegGapIndex = 0;
-    const unsigned VR_GAP = (++VRegGapIndex * 1000);
-
-    unsigned I = MRI.createIncompleteVirtualRegister();
-    const unsigned E = (((I + VR_GAP) / VR_GAP) + 1) * VR_GAP;
-
-    virtualVRegNumber = E;
-  }
+  NamedVRegCursor(MachineRegisterInfo &MRI) : MRI(MRI), virtualVRegNumber(0) {}
 
   void SkipVRegs() {
     unsigned VRegGapIndex = 1;
+    if (!virtualVRegNumber) {
+      VRegGapIndex = 0;
+      virtualVRegNumber = MRI.createIncompleteVirtualRegister();
+    }
     const unsigned VR_GAP = (++VRegGapIndex * 1000);
 
     unsigned I = virtualVRegNumber;
@@ -511,6 +507,8 @@
   }
 
   unsigned createVirtualRegister(unsigned VReg) {
+    if (!virtualVRegNumber)
+      SkipVRegs();
     std::string S;
     raw_string_ostream OS(S);
     OS << "namedVReg" << (virtualVRegNumber & ~0x80000000);
Index: llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
===================================================================
--- llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
+++ llvm/trunk/test/CodeGen/MIR/AArch64/multiple-lhs-operands.mir
@@ -2,6 +2,9 @@
 # This test ensures that the MIR parser can parse multiple register machine
 # operands before '='.
 
+# This tests that a MIR file with no vregs does not get altered by mir-canon.
+# RUN: llc -mtriple=aarch64 -o - -run-pass mir-canonicalizer -verify-machineinstrs %s
+
 --- |
 
   declare void @foo()