diff --git a/llvm/lib/CodeGen/VirtRegMap.cpp b/llvm/lib/CodeGen/VirtRegMap.cpp
index d10ca1a..124c279 100644
--- a/llvm/lib/CodeGen/VirtRegMap.cpp
+++ b/llvm/lib/CodeGen/VirtRegMap.cpp
@@ -72,6 +72,17 @@
   Virt2SplitMap.resize(NumRegs);
 }
 
+void VirtRegMap::assignVirt2Phys(unsigned virtReg, MCPhysReg physReg) {
+  assert(TargetRegisterInfo::isVirtualRegister(virtReg) &&
+         TargetRegisterInfo::isPhysicalRegister(physReg));
+  assert(Virt2PhysMap[virtReg] == NO_PHYS_REG &&
+         "attempt to assign physical register to already mapped "
+         "virtual register");
+  assert(!getRegInfo().isReserved(physReg) &&
+         "Attempt to map virtReg to a reserved physReg");
+  Virt2PhysMap[virtReg] = physReg;
+}
+
 unsigned VirtRegMap::createSpillSlot(const TargetRegisterClass *RC) {
   unsigned Size = TRI->getSpillSize(*RC);
   unsigned Align = TRI->getSpillAlignment(*RC);