Index: llvm/include/llvm/Transforms/Utils/FunctionComparator.h
===================================================================
--- llvm/include/llvm/Transforms/Utils/FunctionComparator.h
+++ llvm/include/llvm/Transforms/Utils/FunctionComparator.h
@@ -333,6 +333,7 @@
   int cmpInlineAsm(const InlineAsm *L, const InlineAsm *R) const;
   int cmpAttrs(const AttributeList L, const AttributeList R) const;
   int cmpRangeMetadata(const MDNode *L, const MDNode *R) const;
+  int cmpLoadInstMetadata(LoadInst const *L, LoadInst const *R) const;
   int cmpOperandBundlesSchema(const CallBase &LCS, const CallBase &RCS) const;
 
   /// Compare two GEPs for equivalent pointer arithmetic.
Index: llvm/lib/Transforms/Utils/FunctionComparator.cpp
===================================================================
--- llvm/lib/Transforms/Utils/FunctionComparator.cpp
+++ llvm/lib/Transforms/Utils/FunctionComparator.cpp
@@ -184,6 +184,44 @@
   return 0;
 }
 
+int FunctionComparator::cmpLoadInstMetadata(LoadInst const *L,
+                                            LoadInst const *R) const {
+  if (L == R)
+    return 0;
+  if (!L)
+    return -1;
+  if (!R)
+    return 1;
+
+  /// Compare metadata with empty nodes
+  /// These metadata affects the other optimization passes by making assertions
+  /// or constraints.
+  /// Values that carries different expectations should be considered different.
+  /// First, check metadata with empty nodes:
+  for (auto Kind : {LLVMContext::MD_nonnull, LLVMContext::MD_invariant_group,
+                    LLVMContext::MD_invariant_load, LLVMContext::MD_noundef}) {
+    auto ML = bool(L->getMetadata(Kind));
+    auto MR = bool(R->getMetadata(Kind));
+    if (ML != MR)
+      return ML - MR;
+  }
+  /// We are left with `dereferenceable` and `dereferenceable_or_null`,
+  /// which carries a single parameter for the size of dereferenceable
+  /// data behind the result:
+  for (auto Kind : {LLVMContext::MD_dereferenceable,
+                    LLVMContext::MD_dereferenceable_or_null}) {
+    auto ML = L->getMetadata(Kind);
+    auto MR = R->getMetadata(Kind);
+    if (ML == MR)
+      continue;
+    auto VL = mdconst::extract<ConstantInt>(ML->getOperand(0));
+    auto VR = mdconst::extract<ConstantInt>(MR->getOperand(0));
+    if (int Res = cmpAPInts(VL->getValue(), VR->getValue()))
+      return Res;
+  }
+  return 0;
+}
+
 int FunctionComparator::cmpOperandBundlesSchema(const CallBase &LCS,
                                                 const CallBase &RCS) const {
   assert(LCS.getOpcode() == RCS.getOpcode() && "Can't compare otherwise!");
@@ -586,9 +624,11 @@
     if (int Res = cmpNumbers(LI->getSyncScopeID(),
                              cast<LoadInst>(R)->getSyncScopeID()))
       return Res;
-    return cmpRangeMetadata(
-        LI->getMetadata(LLVMContext::MD_range),
-        cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range));
+    if (int Res = cmpRangeMetadata(
+            LI->getMetadata(LLVMContext::MD_range),
+            cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range)))
+      return Res;
+    return cmpLoadInstMetadata(LI, cast<LoadInst>(R));
   }
   if (const StoreInst *SI = dyn_cast<StoreInst>(L)) {
     if (int Res =
Index: llvm/test/Transforms/MergeFunc/mergefunc-preserve-nonnull.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/MergeFunc/mergefunc-preserve-nonnull.ll
@@ -0,0 +1,36 @@
+; RUN: opt -passes=mergefunc -S < %s | FileCheck %s
+
+; This test makes sure that the mergefunc pass does not merge functions
+; that have different nonnull assertions.
+
+target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+
+%1 = type ptr
+
+define void @f1(ptr noalias nocapture noundef sret(%1) dereferenceable(8) %0, ptr noalias nocapture noundef dereferenceable(24) %1) {
+  ; CHECK-LABEL: @f1(
+  ; CHECK: %3 = load ptr, ptr %1, align 8, !nonnull !0
+  %3 = load ptr, ptr %1, align 8, !nonnull !0
+  store ptr %3, ptr %0, align 8
+  ret void
+}
+
+define void @f2(ptr noalias nocapture noundef sret(%1) dereferenceable(8) %0, ptr noalias nocapture noundef dereferenceable(24) %1) {
+  ; CHECK-LABEL: @f2(
+  ; CHECK: %3 = load ptr, ptr %1, align 8
+  %3 = load ptr, ptr %1, align 8
+  store ptr %3, ptr %0, align 8
+  ret void
+}
+
+define void @f3(ptr noalias nocapture noundef sret(%1) dereferenceable(8) %0, ptr noalias nocapture noundef dereferenceable(24) %1) {
+  ; CHECK-LABEL: @f3(
+  ; CHECK: %3 = load ptr, ptr %1, align 8, !noundef !0
+  %3 = load ptr, ptr %1, align 8, !noundef !0
+  store ptr %3, ptr %0, align 8
+  ret void
+}
+
+!0 = !{}
+!1 = !{i64 1}
+!2 = !{i64 8}