diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -165,7 +165,7 @@
 void initializeFinalizeMachineBundlesPass(PassRegistry&);
 void initializeFixIrreduciblePass(PassRegistry &);
 void initializeFixupStatepointCallerSavedPass(PassRegistry&);
-void initializeFlattenCFGPassPass(PassRegistry&);
+void initializeFlattenCFGLegacyPassPass(PassRegistry &);
 void initializeFloat2IntLegacyPassPass(PassRegistry&);
 void initializeForceFunctionAttrsLegacyPassPass(PassRegistry&);
 void initializeForwardControlFlowIntegrityPass(PassRegistry&);
diff --git a/llvm/include/llvm/Transforms/Scalar/FlattenCFG.h b/llvm/include/llvm/Transforms/Scalar/FlattenCFG.h
new file mode 100644
--- /dev/null
+++ b/llvm/include/llvm/Transforms/Scalar/FlattenCFG.h
@@ -0,0 +1,25 @@
+//===- FlattenCFG.h -------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// The FlattenCFG pass flattens a function's CFG using the FlattenCFG utility
+// function, iteratively flattening until no further changes are made.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_FLATTENCFG_H
+#define LLVM_TRANSFORMS_SCALAR_FLATTENCFG_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+struct FlattenCFGPass : PassInfoMixin<FlattenCFGPass> {
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+} // namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_FLATTENCFG_H
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -152,6 +152,7 @@
 #include "llvm/Transforms/Scalar/DeadStoreElimination.h"
 #include "llvm/Transforms/Scalar/DivRemPairs.h"
 #include "llvm/Transforms/Scalar/EarlyCSE.h"
+#include "llvm/Transforms/Scalar/FlattenCFG.h"
 #include "llvm/Transforms/Scalar/Float2Int.h"
 #include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar/GuardWidening.h"
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -254,6 +254,7 @@
 FUNCTION_PASS("dot-cfg", CFGPrinterPass())
 FUNCTION_PASS("dot-cfg-only", CFGOnlyPrinterPass())
 FUNCTION_PASS("fix-irreducible", FixIrreduciblePass())
+FUNCTION_PASS("flattencfg", FlattenCFGPass())
 FUNCTION_PASS("make-guards-explicit", MakeGuardsExplicitPass())
 FUNCTION_PASS("gvn-hoist", GVNHoistPass())
 FUNCTION_PASS("gvn-sink", GVNSinkPass())
diff --git a/llvm/lib/Transforms/Scalar/FlattenCFGPass.cpp b/llvm/lib/Transforms/Scalar/FlattenCFGPass.cpp
--- a/llvm/lib/Transforms/Scalar/FlattenCFGPass.cpp
+++ b/llvm/lib/Transforms/Scalar/FlattenCFGPass.cpp
@@ -13,10 +13,12 @@
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/InstrTypes.h"
+#include "llvm/IR/PassManager.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Scalar/FlattenCFG.h"
 #include "llvm/Transforms/Utils/Local.h"
 
 using namespace llvm;
@@ -24,11 +26,11 @@
 #define DEBUG_TYPE "flattencfg"
 
 namespace {
-struct FlattenCFGPass : public FunctionPass {
+struct FlattenCFGLegacyPass : public FunctionPass {
   static char ID; // Pass identification, replacement for typeid
 public:
-  FlattenCFGPass() : FunctionPass(ID) {
-    initializeFlattenCFGPassPass(*PassRegistry::getPassRegistry());
+  FlattenCFGLegacyPass() : FunctionPass(ID) {
+    initializeFlattenCFGLegacyPassPass(*PassRegistry::getPassRegistry());
   }
   bool runOnFunction(Function &F) override;
 
@@ -39,21 +41,10 @@
 private:
   AliasAnalysis *AA;
 };
-}
-
-char FlattenCFGPass::ID = 0;
-INITIALIZE_PASS_BEGIN(FlattenCFGPass, "flattencfg", "Flatten the CFG", false,
-                      false)
-INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
-INITIALIZE_PASS_END(FlattenCFGPass, "flattencfg", "Flatten the CFG", false,
-                    false)
-
-// Public interface to the FlattenCFG pass
-FunctionPass *llvm::createFlattenCFGPass() { return new FlattenCFGPass(); }
 
 /// iterativelyFlattenCFG - Call FlattenCFG on all the blocks in the function,
 /// iterating until no more changes are made.
-static bool iterativelyFlattenCFG(Function &F, AliasAnalysis *AA) {
+bool iterativelyFlattenCFG(Function &F, AliasAnalysis *AA) {
   bool Changed = false;
   bool LocalChange = true;
 
@@ -78,8 +69,22 @@
   }
   return Changed;
 }
+} // namespace
 
-bool FlattenCFGPass::runOnFunction(Function &F) {
+char FlattenCFGLegacyPass::ID = 0;
+
+INITIALIZE_PASS_BEGIN(FlattenCFGLegacyPass, "flattencfg", "Flatten the CFG",
+                      false, false)
+INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
+INITIALIZE_PASS_END(FlattenCFGLegacyPass, "flattencfg", "Flatten the CFG",
+                    false, false)
+
+// Public interface to the FlattenCFG pass
+FunctionPass *llvm::createFlattenCFGPass() {
+  return new FlattenCFGLegacyPass();
+}
+
+bool FlattenCFGLegacyPass::runOnFunction(Function &F) {
   AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
   bool EverChanged = false;
   // iterativelyFlattenCFG can make some blocks dead.
@@ -89,3 +94,15 @@
   }
   return EverChanged;
 }
+
+PreservedAnalyses FlattenCFGPass::run(Function &F,
+                                      FunctionAnalysisManager &AM) {
+  bool EverChanged = false;
+  AliasAnalysis *AA = &AM.getResult<AAManager>(F);
+  // iterativelyFlattenCFG can make some blocks dead.
+  while (iterativelyFlattenCFG(F, AA)) {
+    removeUnreachableBlocks(F);
+    EverChanged = true;
+  }
+  return EverChanged ? PreservedAnalyses::none() : PreservedAnalyses::all();
+}
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -54,7 +54,7 @@
   initializeMakeGuardsExplicitLegacyPassPass(Registry);
   initializeGVNHoistLegacyPassPass(Registry);
   initializeGVNSinkLegacyPassPass(Registry);
-  initializeFlattenCFGPassPass(Registry);
+  initializeFlattenCFGLegacyPassPass(Registry);
   initializeIRCELegacyPassPass(Registry);
   initializeIndVarSimplifyLegacyPassPass(Registry);
   initializeInferAddressSpacesPass(Registry);
diff --git a/llvm/test/Transforms/Util/flattencfg.ll b/llvm/test/Transforms/Util/flattencfg.ll
--- a/llvm/test/Transforms/Util/flattencfg.ll
+++ b/llvm/test/Transforms/Util/flattencfg.ll
@@ -1,4 +1,5 @@
 ; RUN: opt -flattencfg -S < %s -enable-new-pm=0 | FileCheck %s
+; RUN: opt -passes=flattencfg -S < %s | FileCheck %s
 
 
 ; This test checks whether the pass completes without a crash.