diff --git a/llvm/include/llvm/Transforms/IPO/HotColdSplitting.h b/llvm/include/llvm/Transforms/IPO/HotColdSplitting.h
--- a/llvm/include/llvm/Transforms/IPO/HotColdSplitting.h
+++ b/llvm/include/llvm/Transforms/IPO/HotColdSplitting.h
@@ -12,7 +12,9 @@
 #ifndef LLVM_TRANSFORMS_IPO_HOTCOLDSPLITTING_H
 #define LLVM_TRANSFORMS_IPO_HOTCOLDSPLITTING_H
 
+#include "llvm/ADT/StringSet.h"
 #include "llvm/IR/PassManager.h"
+#include "llvm/Support/SpecialCaseList.h"
 
 namespace llvm {
 
@@ -37,7 +39,8 @@
                    function_ref<TargetTransformInfo &(Function &)> GTTI,
                    std::function<OptimizationRemarkEmitter &(Function &)> *GORE,
                    function_ref<AssumptionCache *(Function &)> LAC)
-      : PSI(ProfSI), GetBFI(GBFI), GetTTI(GTTI), GetORE(GORE), LookupAC(LAC) {}
+      : PSI(ProfSI), GetBFI(GBFI), GetTTI(GTTI), GetORE(GORE), LookupAC(LAC),
+        FileMarkedColdFunctions(nullptr) {}
   bool run(Module &M);
 
 private:
@@ -55,6 +58,8 @@
   function_ref<TargetTransformInfo &(Function &)> GetTTI;
   std::function<OptimizationRemarkEmitter &(Function &)> *GetORE;
   function_ref<AssumptionCache *(Function &)> LookupAC;
+  StringSet<> CmdMarkedColdFunctions;
+  std::unique_ptr<SpecialCaseList> FileMarkedColdFunctions;
 };
 
 /// Pass to outline cold regions.
@@ -66,4 +71,3 @@
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_IPO_HOTCOLDSPLITTING_H
-
diff --git a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
--- a/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
+++ b/llvm/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -29,6 +29,7 @@
 #include "llvm/ADT/PostOrderIterator.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/BlockFrequencyInfo.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
@@ -59,6 +60,8 @@
 #include "llvm/Support/BranchProbability.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/SpecialCaseList.h"
+#include "llvm/Support/VirtualFileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/Scalar.h"
@@ -69,6 +72,10 @@
 #include "llvm/Transforms/Utils/ValueMapper.h"
 #include <algorithm>
 #include <cassert>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <string>
 
 #define DEBUG_TYPE "hotcoldsplit"
 
@@ -85,6 +92,18 @@
                        cl::desc("Base penalty for splitting cold code (as a "
                                 "multiple of TCC_Basic)"));
 
+static cl::opt<std::string>
+    ColdFunctionsList("cold-functions-list", cl::init(""), cl::Hidden,
+                      cl::desc("Comma-separated list of functions to mark"
+                               " as cold during hot/cold splitting."));
+
+static cl::opt<std::string>
+    ColdFunctionsFile("cold-functions-file", cl::init(""), cl::Hidden,
+                      cl::desc("File name containing a newline-separated list"
+                               " of function names to mark as cold during"
+                               " hot/cold splitting."));
+
+
 namespace {
 // Same as blockEndsInUnreachable in CodeGen/BranchFolding.cpp. Do not modify
 // this function unless you modify the MBB version as well.
@@ -202,6 +221,22 @@
   if (PSI->isFunctionEntryCold(&F))
     return true;
 
+  // Alternatively, if user supplies any extra information
+  // on cold functions via command-line or file input,
+  // use them to determine if function is cold or not.
+  if (CmdMarkedColdFunctions.find(F.getName()) !=
+      CmdMarkedColdFunctions.end()) {
+    LLVM_DEBUG(dbgs() << "isFunctionCold: " << F.getName() << " is cold "
+                      << " via command line info.\n");
+    return true;
+  }
+
+  if (FileMarkedColdFunctions &&
+      FileMarkedColdFunctions->inSection("", "", F.getName())) {
+    LLVM_DEBUG(dbgs() << "isFunctionCold: " << F.getName() << " is cold "
+                      << " via file info.\n");
+    return true;
+  }
   return false;
 }
 
@@ -656,6 +691,32 @@
 bool HotColdSplitting::run(Module &M) {
   bool Changed = false;
   bool HasProfileSummary = (M.getProfileSummary(/* IsCS */ false) != nullptr);
+
+  // Read in user-defined cold function names, if any.
+  if (ColdFunctionsList != "") {
+    LLVM_DEBUG(dbgs() << "Reading in cold functions from command line.\n");
+    std::stringstream CFStream(ColdFunctionsList);
+    while (CFStream.good()) {
+      std::string CFName;
+      std::getline(CFStream, CFName, ',');
+      LLVM_DEBUG(dbgs() << " Function " << CFName
+                        << " listed as cold from command line.\n");
+      CmdMarkedColdFunctions.insert(CFName);
+    }
+  }
+
+  // Read in user-defined cold function names supplied
+  // by a file.
+  if (ColdFunctionsFile != "") {
+    // Use the SpecialCaseList helper to read in the
+    // cold functions file.
+    LLVM_DEBUG(dbgs() << "Reading in functions from file "
+                      << ColdFunctionsFile);
+    std::unique_ptr<vfs::FileSystem> FS = vfs::createPhysicalFileSystem();
+    FileMarkedColdFunctions =
+        SpecialCaseList::createOrDie({ColdFunctionsFile}, *FS);
+  }
+
   for (auto It = M.begin(), End = M.end(); It != End; ++It) {
     Function &F = *It;