Index: llvm/include/llvm/IR/RuntimeLibcalls.def
===================================================================
--- llvm/include/llvm/IR/RuntimeLibcalls.def
+++ llvm/include/llvm/IR/RuntimeLibcalls.def
@@ -522,6 +522,18 @@
 // Deoptimization
 HANDLE_LIBCALL(DEOPTIMIZE, "__llvm_deoptimize")
 
+// Entry/exit instrumentation (lib/Transforms/Utils/EntryExitInstrumenter.cpp).
+HANDLE_LIBCALL(ENTRYEXIT1, "mcount")
+HANDLE_LIBCALL(ENTRYEXIT2, ".mcount")
+HANDLE_LIBCALL(ENTRYEXIT3, "\01__gnu_mcount_nc")
+HANDLE_LIBCALL(ENTRYEXIT4, "\01_mcount")
+HANDLE_LIBCALL(ENTRYEXIT5, "\01mcount")
+HANDLE_LIBCALL(ENTRYEXIT6, "__mcount")
+HANDLE_LIBCALL(ENTRYEXIT7, "_mcount")
+HANDLE_LIBCALL(ENTRYEXIT8, "__cyg_profile_func_enter_bare")
+HANDLE_LIBCALL(ENTRYEXIT9, "__cyg_profile_func_enter")
+HANDLE_LIBCALL(ENTRYEXIT10, "__cyg_profile_func_exit")
+
 HANDLE_LIBCALL(UNKNOWN_LIBCALL, nullptr)
 
 #undef HANDLE_LIBCALL
Index: llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp
===================================================================
--- llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp
+++ llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp
@@ -20,6 +20,9 @@
 
 static void insertCall(Function &CurFn, StringRef Func,
                        Instruction *InsertionPt, DebugLoc DL) {
+  // If you add code to recognize a new instrumentation function here, the
+  // function also needs to be added to include/llvm/IR/RuntimeLibcalls.def
+  // so that it is handled correctly by LTO.
   Module &M = *InsertionPt->getParent()->getParent()->getParent();
   LLVMContext &C = InsertionPt->getParent()->getContext();