Index: llvm/include/llvm/IR/StructuralHash.h
===================================================================
--- /dev/null
+++ llvm/include/llvm/IR/StructuralHash.h
@@ -0,0 +1,40 @@
+//===- llvm/IR/StructuralHash.h - Hash Function & Module for expensive checks
+//--*- 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 file provides hashing of the LLVM IR structure to be used to check
+// Passes modification status.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_IR_STRUCTURALHASH_H
+#define LLVM_IR_STRUCTURALHASH_H
+
+#include <cstdint>
+
+// This header is only meant to be used when -DEXPENSIVE_CHECKS is set
+namespace llvm {
+
+class Function;
+class Module;
+
+#ifdef EXPENSIVE_CHECKS
+
+uint64_t StructuralHash(Function const &F);
+uint64_t StructuralHash(Module const &M);
+
+#else
+
+static inline uint64_t StructuralHash(Function const &F) { return 0; }
+static inline uint64_t StructuralHash(Module const &M) { return 0; }
+
+#endif
+
+} // end namespace llvm
+
+#endif // LLVM_IR_STRUCTURALHASH_H
Index: llvm/lib/Analysis/CallGraphSCCPass.cpp
===================================================================
--- llvm/lib/Analysis/CallGraphSCCPass.cpp
+++ llvm/lib/Analysis/CallGraphSCCPass.cpp
@@ -28,6 +28,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/OptBisect.h"
 #include "llvm/IR/PassTimingInfo.h"
+#include "llvm/IR/StructuralHash.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -466,10 +467,15 @@
 
     initializeAnalysisImpl(P);
 
+    uint64_t RefHash = StructuralHash(CG.getModule());
+
     // Actually run this pass on the current SCC.
     bool LocalChanged =
         RunPassOnSCC(P, CurSCC, CG, CallGraphUpToDate, DevirtualizedCall);
 
+    assert((LocalChanged || (RefHash == StructuralHash(CG.getModule()))) &&
+           "Pass modifies its input and doesn't report it.");
+
     Changed |= LocalChanged;
 
     if (LocalChanged)
Index: llvm/lib/Analysis/LoopPass.cpp
===================================================================
--- llvm/lib/Analysis/LoopPass.cpp
+++ llvm/lib/Analysis/LoopPass.cpp
@@ -20,6 +20,7 @@
 #include "llvm/IR/OptBisect.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/PassTimingInfo.h"
+#include "llvm/IR/StructuralHash.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/TimeProfiler.h"
@@ -191,7 +192,14 @@
       {
         PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
         TimeRegion PassTimer(getPassTimer(P));
+
+        uint64_t RefHash = StructuralHash(F);
+
         LocalChanged = P->runOnLoop(CurrentLoop, *this);
+
+        assert((LocalChanged || (RefHash == StructuralHash(F))) &&
+               "Pass modifies its input and doesn't report it.");
+
         Changed |= LocalChanged;
         if (EmitICRemark) {
           unsigned NewSize = F.getInstructionCount();
Index: llvm/lib/Analysis/RegionPass.cpp
===================================================================
--- llvm/lib/Analysis/RegionPass.cpp
+++ llvm/lib/Analysis/RegionPass.cpp
@@ -15,6 +15,7 @@
 #include "llvm/Analysis/RegionPass.h"
 #include "llvm/IR/OptBisect.h"
 #include "llvm/IR/PassTimingInfo.h"
+#include "llvm/IR/StructuralHash.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Timer.h"
 #include "llvm/Support/raw_ostream.h"
@@ -94,9 +95,14 @@
       {
         PassManagerPrettyStackEntry X(P, *CurrentRegion->getEntry());
 
+        uint64_t RefHash = StructuralHash(F);
+
         TimeRegion PassTimer(getPassTimer(P));
         LocalChanged = P->runOnRegion(CurrentRegion, *this);
         Changed |= LocalChanged;
+
+        assert((LocalChanged || (RefHash == StructuralHash(F))) &&
+               "Pass modifies its input and doesn't report it.");
       }
 
       if (isPassDebuggingExecutionsOrMore()) {
Index: llvm/lib/IR/CMakeLists.txt
===================================================================
--- llvm/lib/IR/CMakeLists.txt
+++ llvm/lib/IR/CMakeLists.txt
@@ -47,6 +47,7 @@
   SafepointIRVerifier.cpp
   ProfileSummary.cpp
   Statepoint.cpp
+  StructuralHash.cpp
   Type.cpp
   TypeFinder.cpp
   Use.cpp
Index: llvm/lib/IR/LegacyPassManager.cpp
===================================================================
--- llvm/lib/IR/LegacyPassManager.cpp
+++ llvm/lib/IR/LegacyPassManager.cpp
@@ -20,6 +20,7 @@
 #include "llvm/IR/LegacyPassNameParser.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/PassTimingInfo.h"
+#include "llvm/IR/StructuralHash.h"
 #include "llvm/Support/Chrono.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -1475,75 +1476,6 @@
   }
 }
 
-#ifdef EXPENSIVE_CHECKS
-namespace {
-namespace details {
-
-// Basic hashing mechanism to detect structural change to the IR, used to verify
-// pass return status consistency with actual change. Loosely copied from
-// llvm/lib/Transforms/Utils/FunctionComparator.cpp
-
-class StructuralHash {
-  uint64_t Hash = 0x6acaa36bef8325c5ULL;
-
-  void update(uint64_t V) { Hash = hashing::detail::hash_16_bytes(Hash, V); }
-
-public:
-  StructuralHash() = default;
-
-  void update(Function &F) {
-    if (F.empty())
-      return;
-
-    update(F.isVarArg());
-    update(F.arg_size());
-
-    SmallVector<const BasicBlock *, 8> BBs;
-    SmallPtrSet<const BasicBlock *, 16> VisitedBBs;
-
-    BBs.push_back(&F.getEntryBlock());
-    VisitedBBs.insert(BBs[0]);
-    while (!BBs.empty()) {
-      const BasicBlock *BB = BBs.pop_back_val();
-      update(45798); // Block header
-      for (auto &Inst : *BB)
-        update(Inst.getOpcode());
-
-      const Instruction *Term = BB->getTerminator();
-      for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
-        if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
-          continue;
-        BBs.push_back(Term->getSuccessor(i));
-      }
-    }
-  }
-
-  void update(Module &M) {
-    for (Function &F : M)
-      update(F);
-  }
-
-  uint64_t getHash() const { return Hash; }
-};
-
-} // namespace details
-
-uint64_t StructuralHash(Function &F) {
-  details::StructuralHash H;
-  H.update(F);
-  return H.getHash();
-}
-
-uint64_t StructuralHash(Module &M) {
-  details::StructuralHash H;
-  H.update(M);
-  return H.getHash();
-}
-
-} // end anonymous namespace
-
-#endif
-
 /// Execute all of the passes scheduled for execution by invoking
 /// runOnFunction method.  Keep track of whether any of the passes modifies
 /// the function, and if so, return true.
@@ -1581,15 +1513,13 @@
     {
       PassManagerPrettyStackEntry X(FP, F);
       TimeRegion PassTimer(getPassTimer(FP));
-#ifdef EXPENSIVE_CHECKS
+
       uint64_t RefHash = StructuralHash(F);
-#endif
+
       LocalChanged |= FP->runOnFunction(F);
 
-#ifdef EXPENSIVE_CHECKS
       assert((LocalChanged || (RefHash == StructuralHash(F))) &&
              "Pass modifies its input and doesn't report it.");
-#endif
 
       if (EmitICRemark) {
         unsigned NewSize = F.getInstructionCount();
@@ -1692,16 +1622,12 @@
       PassManagerPrettyStackEntry X(MP, M);
       TimeRegion PassTimer(getPassTimer(MP));
 
-#ifdef EXPENSIVE_CHECKS
       uint64_t RefHash = StructuralHash(M);
-#endif
 
       LocalChanged |= MP->runOnModule(M);
 
-#ifdef EXPENSIVE_CHECKS
       assert((LocalChanged || (RefHash == StructuralHash(M))) &&
              "Pass modifies its input and doesn't report it.");
-#endif
 
       if (EmitICRemark) {
         // Update the size of the module.
Index: llvm/lib/IR/StructuralHash.cpp
===================================================================
--- /dev/null
+++ llvm/lib/IR/StructuralHash.cpp
@@ -0,0 +1,85 @@
+//===-- StructuralHash.cpp - Hash Function & Module for expensive checks
+//----------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+
+#ifdef EXPENSIVE_CHECKS
+
+#include "llvm/IR/StructuralHash.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+
+using namespace llvm;
+
+namespace {
+namespace details {
+
+// Basic hashing mechanism to detect structural change to the IR, used to verify
+// pass return status consistency with actual change. Loosely copied from
+// llvm/lib/Transforms/Utils/FunctionComparator.cpp
+
+class StructuralHash {
+  uint64_t Hash = 0x6acaa36bef8325c5ULL;
+
+  void update(uint64_t V) { Hash = hashing::detail::hash_16_bytes(Hash, V); }
+
+public:
+  StructuralHash() = default;
+
+  void update(Function const &F) {
+    if (F.empty())
+      return;
+
+    update(F.isVarArg());
+    update(F.arg_size());
+
+    SmallVector<const BasicBlock *, 8> BBs;
+    SmallPtrSet<const BasicBlock *, 16> VisitedBBs;
+
+    BBs.push_back(&F.getEntryBlock());
+    VisitedBBs.insert(BBs[0]);
+    while (!BBs.empty()) {
+      const BasicBlock *BB = BBs.pop_back_val();
+      update(45798); // Block header
+      for (auto &Inst : *BB)
+        update(Inst.getOpcode());
+
+      const Instruction *Term = BB->getTerminator();
+      for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
+        if (!VisitedBBs.insert(Term->getSuccessor(i)).second)
+          continue;
+        BBs.push_back(Term->getSuccessor(i));
+      }
+    }
+  }
+
+  void update(Module const &M) {
+    for (Function const &F : M)
+      update(F);
+  }
+
+  uint64_t getHash() const { return Hash; }
+};
+
+} // namespace details
+
+} // namespace
+
+uint64_t llvm::StructuralHash(Function const &F) {
+  details::StructuralHash H;
+  H.update(F);
+  return H.getHash();
+}
+
+uint64_t llvm::StructuralHash(Module const &M) {
+  details::StructuralHash H;
+  H.update(M);
+  return H.getHash();
+}
+
+#endif