diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index d415955b6093..492b2ad80166 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/lld/COFF/InputFiles.cpp
@@ -25,6 +25,7 @@
 #include "llvm/DebugInfo/PDB/Native/NativeSession.h"
 #include "llvm/DebugInfo/PDB/Native/PDBFile.h"
 #include "llvm/IR/Mangler.h"
+#include "llvm/IR/RuntimeLibcalls.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Object/Binary.h"
 #include "llvm/Object/COFF.h"
@@ -1395,6 +1396,8 @@ void BitcodeFile::parse() {
     // FIXME: Check nodeduplicate
     comdat[i] =
         symtab.addComdat(this, saver.save(obj->getComdatTable()[i].first));
+  Triple tt(obj->getTargetTriple());
+  RTLIB::RuntimeLibcallsInfo libcalls(tt);
   for (const lto::InputFile::Symbol &objSym : obj->symbols()) {
     StringRef symName = saver.save(objSym.getName());
     int comdatIndex = objSym.getComdatIndex();
@@ -1444,7 +1447,7 @@ void BitcodeFile::parse() {
           symtab.addRegular(this, symName, nullptr, fakeSC, 0, objSym.isWeak());
     }
     symbols.push_back(sym);
-    if (objSym.isUsed())
+    if (objSym.isUsed() || objSym.isLibcall(libcalls))
       symtab.ctx.config.gcroot.push_back(sym);
   }
   directives = saver.save(obj->getCOFFLinkerOpts());
diff --git a/llvm/include/llvm/LTO/LTO.h b/llvm/include/llvm/LTO/LTO.h
index cba5cf7eb9e6..4011065ec37a 100644
--- a/llvm/include/llvm/LTO/LTO.h
+++ b/llvm/include/llvm/LTO/LTO.h
@@ -16,6 +16,7 @@
 #define LLVM_LTO_LTO_H
 
 #include "llvm/IR/LLVMRemarkStreamer.h"
+#include "llvm/IR/RuntimeLibcalls.h"
 #include "llvm/Support/Compiler.h"
 #include <memory>
 
@@ -167,6 +168,12 @@ public:
     using irsymtab::Symbol::getSectionName;
     using irsymtab::Symbol::isExecutable;
     using irsymtab::Symbol::isUsed;
+
+    // Returns whether this symbol is a library call that LTO code generation
+    // may emit references to. Such symbols must be considered external, as
+    // removing them or modifying their interfaces would invalidate the code
+    // generator's knowledge about them.
+    bool isLibcall(const RTLIB::RuntimeLibcallsInfo &Libcalls) const;
   };
 
   /// A range over the symbols in this InputFile.
@@ -583,7 +590,7 @@ private:
 
   void addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
                             ArrayRef<SymbolResolution> Res, unsigned Partition,
-                            bool InSummary);
+                            bool InSummary, const Triple &TT);
 
   // These functions take a range of symbol resolutions and consume the
   // resolutions used by a single input module. Functions return ranges refering
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 955a19db4860..152b2beeae12 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -597,6 +597,11 @@ Expected<std::unique_ptr<InputFile>> InputFile::create(MemoryBufferRef Object) {
   return std::move(File);
 }
 
+bool InputFile::Symbol::isLibcall(
+    const RTLIB::RuntimeLibcallsInfo &Libcalls) const {
+  return Libcalls.getSupportedLibcallImpl(IRName) != RTLIB::Unsupported;
+}
+
 StringRef InputFile::getName() const {
   return Mods[0].getModuleIdentifier();
 }
@@ -642,11 +647,13 @@ LTO::~LTO() = default;
 // their partitions.
 void LTO::addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
                                ArrayRef<SymbolResolution> Res,
-                               unsigned Partition, bool InSummary) {
+                               unsigned Partition, bool InSummary,
+                               const Triple &TT) {
   llvm::TimeTraceScope timeScope("LTO add module to global resolution");
   auto *ResI = Res.begin();
   auto *ResE = Res.end();
   (void)ResE;
+  RTLIB::RuntimeLibcallsInfo Libcalls(TT);
   for (const InputFile::Symbol &Sym : Syms) {
     assert(ResI != ResE);
     SymbolResolution Res = *ResI++;
@@ -689,11 +696,14 @@ void LTO::addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
       GlobalRes.VisibleOutsideSummary = true;
     }
 
+    bool IsLibcall = Sym.isLibcall(Libcalls);
+
     // Set the partition to external if we know it is re-defined by the linker
     // with -defsym or -wrap options, used elsewhere, e.g. it is visible to a
     // regular object, is referenced from llvm.compiler.used/llvm.used, or was
     // already recorded as being referenced from a different partition.
     if (Res.LinkerRedefined || Res.VisibleToRegularObj || Sym.isUsed() ||
+        IsLibcall ||
         (GlobalRes.Partition != GlobalResolution::Unknown &&
          GlobalRes.Partition != Partition)) {
       GlobalRes.Partition = GlobalResolution::External;
@@ -704,7 +714,7 @@ void LTO::addModuleToGlobalRes(ArrayRef<InputFile::Symbol> Syms,
     // Flag as visible outside of summary if visible from a regular object or
     // from a module that does not have a summary.
     GlobalRes.VisibleOutsideSummary |=
-        (Res.VisibleToRegularObj || Sym.isUsed() || !InSummary);
+        (Res.VisibleToRegularObj || Sym.isUsed() || IsLibcall || !InSummary);
 
     GlobalRes.ExportDynamic |= Res.ExportDynamic;
   }
@@ -811,7 +821,7 @@ LTO::addModule(InputFile &Input, ArrayRef<SymbolResolution> InputRes,
   auto ModSyms = Input.module_symbols(ModI);
   addModuleToGlobalRes(ModSyms, Res,
                        IsThinLTO ? ThinLTO.ModuleMap.size() + 1 : 0,
-                       LTOInfo->HasSummary);
+                       LTOInfo->HasSummary, Triple(Input.getTargetTriple()));
 
   if (IsThinLTO)
     return addThinLTO(BM, ModSyms, Res);
diff --git a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
index 961dd0ee4337..93b672ae7840 100644
--- a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -290,11 +290,12 @@ static void optimizeModule(Module &TheModule, TargetMachine &TM,
 static void
 addUsedSymbolToPreservedGUID(const lto::InputFile &File,
                              DenseSet<GlobalValue::GUID> &PreservedGUID) {
-  for (const auto &Sym : File.symbols()) {
-    if (Sym.isUsed())
+  Triple TT(File.getTargetTriple());
+  RTLIB::RuntimeLibcallsInfo Libcalls(TT);
+  for (const auto &Sym : File.symbols())
+    if (Sym.isUsed() || Sym.isLibcall(Libcalls))
       PreservedGUID.insert(
           GlobalValue::getGUIDAssumingExternalLinkage(Sym.getIRName()));
-  }
 }
 
 // Convert the PreservedSymbols map from "Name" based to "GUID" based.
diff --git a/llvm/lib/Object/IRSymtab.cpp b/llvm/lib/Object/IRSymtab.cpp
index 20610262f6a1..878f4c911475 100644
--- a/llvm/lib/Object/IRSymtab.cpp
+++ b/llvm/lib/Object/IRSymtab.cpp
@@ -22,7 +22,6 @@
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
-#include "llvm/IR/RuntimeLibcalls.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Object/ModuleSymbolTable.h"
 #include "llvm/Object/SymbolicFile.h"
@@ -74,16 +73,12 @@ struct Builder {
   // so this provides somewhere to store any strings that we create.
   Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder,
           BumpPtrAllocator &Alloc, const Triple &TT)
-      : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc), TT(TT),
-        Libcalls(TT) {}
+      : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc), TT(TT) {}
 
   DenseMap<const Comdat *, int> ComdatMap;
   Mangler Mang;
   const Triple &TT;
 
-  // FIXME: This shouldn't be here.
-  RTLIB::RuntimeLibcallsInfo Libcalls;
-
   std::vector<storage::Comdat> Comdats;
   std::vector<storage::Module> Mods;
   std::vector<storage::Symbol> Syms;
@@ -94,10 +89,6 @@ struct Builder {
 
   std::vector<storage::Str> DependentLibraries;
 
-  bool isPreservedName(StringRef Name) {
-    return Libcalls.getSupportedLibcallImpl(Name) != RTLIB::Unsupported;
-  }
-
   void setStr(storage::Str &S, StringRef Value) {
     S.Offset = StrtabBuilder.add(Value);
     S.Size = Value.size();
@@ -269,7 +260,7 @@ Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
   StringRef GVName = GV->getName();
   setStr(Sym.IRName, GVName);
 
-  if (Used.count(GV) || isPreservedName(GVName))
+  if (Used.count(GV))
     Sym.Flags |= 1 << storage::Symbol::FB_used;
   if (GV->isThreadLocal())
     Sym.Flags |= 1 << storage::Symbol::FB_tls;