diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -2501,6 +2501,25 @@
   RegAllocBase::init(getAnalysis<VirtRegMap>(),
                      getAnalysis<LiveIntervals>(),
                      getAnalysis<LiveRegMatrix>());
+
+  bool HasVirtRegAlloc = false;
+  for (unsigned I = 0, E = MRI->getNumVirtRegs(); I != E; ++I) {
+    Register Reg = Register::index2VirtReg(I);
+    if (MRI->reg_nodbg_empty(Reg))
+      continue;
+    const TargetRegisterClass *RC = MRI->getRegClass(Reg);
+    if (!RC)
+      continue;
+    if (ShouldAllocateClass(*TRI, *RC)) {
+      HasVirtRegAlloc = true;
+      break;
+    }
+  }
+  // Early return if there is no virtual register to be allocated to a
+  // physical register.
+  if (!HasVirtRegAlloc)
+    return false;
+
   Indexes = &getAnalysis<SlotIndexes>();
   MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
   DomTree = &getAnalysis<MachineDominatorTree>();