Index: llvm/lib/Transforms/Utils/FunctionComparator.cpp
===================================================================
--- llvm/lib/Transforms/Utils/FunctionComparator.cpp
+++ llvm/lib/Transforms/Utils/FunctionComparator.cpp
@@ -787,6 +787,14 @@
   if (ConstR)
     return -1;
 
+  if (auto LIL = dyn_cast<LoadInst>(L), LIR = dyn_cast<LoadInst>(R);
+      LIL && LIR) {
+    auto NNL = bool(LIL->getMetadata(LLVMContext::MD_nonnull));
+    auto NNR = bool(LIR->getMetadata(LLVMContext::MD_nonnull));
+    if (NNL != NNR)
+      return NNL - NNR;
+  }
+
   const InlineAsm *InlineAsmL = dyn_cast<InlineAsm>(L);
   const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
 
Index: llvm/test/Transforms/MergeFunc/mergefunc-preserve-nonnull.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/MergeFunc/mergefunc-preserve-nonnull.ll
@@ -0,0 +1,48 @@
+; 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, i64 }, ptr }
+
+define hidden void @f1(ptr noalias nocapture noundef sret(%1) dereferenceable(24) %0, ptr noalias nocapture noundef dereferenceable(24) %1) unnamed_addr #0 {
+  ; CHECK-LABEL: @f1(
+  ; CHECK: %8 = load ptr, ptr %7, align 8, !nonnull !2, !align !6, !noundef !2
+  %3 = getelementptr inbounds { ptr, i64 }, ptr %1, i32 0, i32 0
+  %4 = load ptr, ptr %3, align 8, !nonnull !2, !align !3, !noundef !2
+  %5 = getelementptr inbounds { ptr, i64 }, ptr %1, i32 0, i32 1
+  %6 = load i64, ptr %5, align 8
+  %7 = getelementptr inbounds { { ptr, i64 }, ptr }, ptr %1, i32 0, i32 1
+  %8 = load ptr, ptr %7, align 8, !nonnull !2, !align !6, !noundef !2
+  %9 = getelementptr inbounds { ptr, i64 }, ptr %0, i32 0, i32 0
+  store ptr %4, ptr %9, align 8
+  %10 = getelementptr inbounds { ptr, i64 }, ptr %0, i32 0, i32 1
+  store i64 %6, ptr %10, align 8
+  %11 = getelementptr inbounds %1, ptr %0, i32 0, i32 1
+  store ptr %8, ptr %11, align 8
+  ret void
+}
+
+define hidden void @f2(ptr noalias nocapture noundef sret(%1) dereferenceable(24) %0, ptr noalias nocapture noundef dereferenceable(24) %1) unnamed_addr #0 {
+  ; CHECK-LABEL: @f2(
+  ; %8 = load ptr, ptr %7, align 8, !align !6
+  %3 = getelementptr inbounds { ptr, i64 }, ptr %1, i32 0, i32 0
+  %4 = load ptr, ptr %3, align 8, !nonnull !2, !align !3, !noundef !2
+  %5 = getelementptr inbounds { ptr, i64 }, ptr %1, i32 0, i32 1
+  %6 = load i64, ptr %5, align 8
+  %7 = getelementptr inbounds { { ptr, i64 }, ptr }, ptr %1, i32 0, i32 1
+  %8 = load ptr, ptr %7, align 8, !align !6
+  %9 = getelementptr inbounds { ptr, i64 }, ptr %0, i32 0, i32 0
+  store ptr %4, ptr %9, align 8
+  %10 = getelementptr inbounds { ptr, i64 }, ptr %0, i32 0, i32 1
+  store i64 %6, ptr %10, align 8
+  %11 = getelementptr inbounds %1, ptr %0, i32 0, i32 1
+  store ptr %8, ptr %11, align 8
+  ret void
+}
+
+!2 = !{}
+!3 = !{i64 1}
+!6 = !{i64 8}