Index: clang/lib/CodeGen/BackendUtil.cpp
===================================================================
--- clang/lib/CodeGen/BackendUtil.cpp
+++ clang/lib/CodeGen/BackendUtil.cpp
@@ -81,6 +81,7 @@
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/LowerMatrixIntrinsics.h"
 #include "llvm/Transforms/Utils.h"
+#include "llvm/Transforms/Utils/CGSectionFuncComdatCreator.h"
 #include "llvm/Transforms/Utils/CanonicalizeAliases.h"
 #include "llvm/Transforms/Utils/Debugify.h"
 #include "llvm/Transforms/Utils/EntryExitInstrumenter.h"
@@ -1415,6 +1416,10 @@
       MPM.addPass(createModuleToFunctionPassAdaptor(MemProfilerPass()));
       MPM.addPass(ModuleMemProfilerPass());
     }
+
+    if (CodeGenOpts.CallGraphSection) {
+      MPM.addPass(CGSectionFuncComdatCreatorPass());
+    }
   }
 
   // FIXME: We still use the legacy pass manager to do code generation. We
Index: llvm/include/llvm/Transforms/Utils/CGSectionFuncComdatCreator.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/Transforms/Utils/CGSectionFuncComdatCreator.h
@@ -0,0 +1,32 @@
+//===-- CGSectionFuncComdatCreator.h - CG func comdat creator ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass creates comdats for functions whose symbols will be referenced
+// from the call graph section. These comdats are used to create the call graph
+// sections, so that, the sections can get discarded by the linker if the
+// functions get removed.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_CGSECTIONFUNCCOMDATCREATOR_H
+#define LLVM_TRANSFORMS_UTILS_CGSECTIONFUNCCOMDATCREATOR_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+class CGSectionFuncComdatCreatorPass
+    : public PassInfoMixin<CGSectionFuncComdatCreatorPass> {
+public:
+  PreservedAnalyses run(Module &, ModuleAnalysisManager &);
+};
+
+} // namespace llvm
+
+#endif // LLVM_TRANSFORMS_UTILS_CGSECTIONFUNCCOMDATCREATOR_H
+
Index: llvm/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/lib/Passes/PassBuilder.cpp
+++ llvm/lib/Passes/PassBuilder.cpp
@@ -211,6 +211,7 @@
 #include "llvm/Transforms/Utils/AddDiscriminators.h"
 #include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
 #include "llvm/Transforms/Utils/BreakCriticalEdges.h"
+#include "llvm/Transforms/Utils/CGSectionFuncComdatCreator.h"
 #include "llvm/Transforms/Utils/CanonicalizeAliases.h"
 #include "llvm/Transforms/Utils/CanonicalizeFreezeInLoops.h"
 #include "llvm/Transforms/Utils/EntryExitInstrumenter.h"
Index: llvm/lib/Passes/PassRegistry.def
===================================================================
--- llvm/lib/Passes/PassRegistry.def
+++ llvm/lib/Passes/PassRegistry.def
@@ -45,6 +45,7 @@
 MODULE_PASS("attributor", AttributorPass())
 MODULE_PASS("annotation2metadata", Annotation2MetadataPass())
 MODULE_PASS("openmp-opt", OpenMPOptPass())
+MODULE_PASS("cg-section-func-comdat-creator", CGSectionFuncComdatCreatorPass())
 MODULE_PASS("called-value-propagation", CalledValuePropagationPass())
 MODULE_PASS("canonicalize-aliases", CanonicalizeAliasesPass())
 MODULE_PASS("cg-profile", CGProfilePass())
Index: llvm/lib/Transforms/Utils/CGSectionFuncComdatCreator.cpp
===================================================================
--- /dev/null
+++ llvm/lib/Transforms/Utils/CGSectionFuncComdatCreator.cpp
@@ -0,0 +1,98 @@
+//===-- CGSectionFuncComdatCreator.cpp - CG section func comdat creator ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass creates comdats for functions whose symbols will be referenced
+// from the call graph section. These comdats are used to create the call graph
+// sections, so that, the sections can get discarded by the linker if the
+// functions get removed.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/CGSectionFuncComdatCreator.h"
+
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/Instructions.h"
+
+namespace llvm {
+
+namespace {
+class ModuleCGSectionFuncComdatCreator {
+public:
+  bool instrumentModule(Module &);
+
+private:
+  bool createFunctionComdat(Function &F, const Triple &T) const;
+  bool hasIndirectCalls(const Function &F) const;
+  bool isTargetToIndirectCalls(const Function &F) const;
+};
+
+bool ModuleCGSectionFuncComdatCreator::createFunctionComdat(
+    Function &F, const Triple &T) const {
+  if (auto *Comdat = F.getComdat())
+    return false;
+  assert(F.hasName());
+  Module *M = F.getParent();
+
+  // Make a new comdat for the function. Use the "no duplicates" selection kind
+  // if the object file format supports it. For COFF we restrict it to non-weak
+  // symbols.
+  Comdat *C = M->getOrInsertComdat(F.getName());
+  if (T.isOSBinFormatELF() || (T.isOSBinFormatCOFF() && !F.isWeakForLinker()))
+    C->setSelectionKind(Comdat::NoDuplicates);
+  F.setComdat(C);
+  return true;
+}
+
+bool ModuleCGSectionFuncComdatCreator::hasIndirectCalls(
+    const Function &F) const {
+  for (const auto &I : F)
+    if (const CallInst *CI = dyn_cast<CallInst>(&I))
+      if (CI->isIndirectCall())
+        return true;
+  return false;
+}
+
+bool ModuleCGSectionFuncComdatCreator::isTargetToIndirectCalls(
+    const Function &F) const {
+  return !F.hasLocalLinkage() ||
+         F.hasAddressTaken(nullptr,
+                           /* IgnoreCallbackUses */ true,
+                           /* IgnoreAssumeLikeCalls */ true,
+                           /* IgnoreLLVMUsed */ false);
+}
+
+bool ModuleCGSectionFuncComdatCreator::instrumentModule(Module &M) {
+  Triple TargetTriple = Triple(M.getTargetTriple());
+
+  bool CreatedComdats = false;
+
+  for (Function &F : M) {
+    if (isTargetToIndirectCalls(F) || hasIndirectCalls(F)) {
+      if (TargetTriple.supportsCOMDAT() && !F.isInterposable() &&
+          !F.isDeclarationForLinker()) {
+        CreatedComdats |= createFunctionComdat(F, TargetTriple);
+      }
+    }
+  }
+
+  return CreatedComdats;
+}
+
+} // namespace
+
+PreservedAnalyses
+CGSectionFuncComdatCreatorPass::run(Module &M, ModuleAnalysisManager &AM) {
+  ModuleCGSectionFuncComdatCreator ModuleCG;
+  if (ModuleCG.instrumentModule(M)) {
+    return PreservedAnalyses::none();
+  }
+  return PreservedAnalyses::all();
+}
+
+} // namespace llvm
+
Index: llvm/lib/Transforms/Utils/CMakeLists.txt
===================================================================
--- llvm/lib/Transforms/Utils/CMakeLists.txt
+++ llvm/lib/Transforms/Utils/CMakeLists.txt
@@ -7,6 +7,7 @@
   BreakCriticalEdges.cpp
   BuildLibCalls.cpp
   BypassSlowDivision.cpp
+  CGSectionFuncComdatCreator.cpp
   CallPromotionUtils.cpp
   CallGraphUpdater.cpp
   CanonicalizeAliases.cpp
Index: llvm/test/Transforms/Util/create-function-comdats.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Util/create-function-comdats.ll
@@ -0,0 +1,21 @@
+; Tests that we create function comdats properly and only for those with no
+; comdats.
+
+; RUN: opt -passes='cg-section-func-comdat-creator' -S %s | FileCheck %s
+
+; CHECK: $f = comdat noduplicates
+; CHECK: $g = comdat any
+$g = comdat any
+
+; CHECK: define dso_local void @f() comdat {
+define dso_local void @f() {
+entry:
+  ret void
+}
+
+; CHECK: define dso_local void @g() comdat {
+define dso_local void @g() comdat {
+entry:
+  ret void
+}
+