diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -1357,11 +1357,18 @@
                          DstM.getModuleIdentifier() + "'");
     }
 
-    auto replaceDstValue = [&](MDNode *New) {
+    auto ensureDistinctOp = [&](MDNode *DstValue) {
+      assert(isa<MDTuple>(DstValue) &&
+             "Expected MDTuple when appending module flags");
+      if (DstValue->isDistinct())
+        return dyn_cast<MDTuple>(DstValue);
+      MDTuple *New = MDTuple::getDistinct(
+          DstM.getContext(), SmallVector<Metadata *, 4>(DstValue->operands()));
       Metadata *FlagOps[] = {DstOp->getOperand(0), ID, New};
-      MDNode *Flag = MDNode::get(DstM.getContext(), FlagOps);
+      MDNode *Flag = MDTuple::getDistinct(DstM.getContext(), FlagOps);
       DstModFlags->setOperand(DstIndex, Flag);
       Flags[ID].first = Flag;
+      return New;
     };
 
     // Emit a warning if the values differ and either source or destination
@@ -1438,25 +1445,20 @@
       break;
     }
     case Module::Append: {
-      MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
+      MDTuple *DstValue = ensureDistinctOp(cast<MDNode>(DstOp->getOperand(2)));
       MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
-      SmallVector<Metadata *, 8> MDs;
-      MDs.reserve(DstValue->getNumOperands() + SrcValue->getNumOperands());
-      MDs.append(DstValue->op_begin(), DstValue->op_end());
-      MDs.append(SrcValue->op_begin(), SrcValue->op_end());
-
-      replaceDstValue(MDNode::get(DstM.getContext(), MDs));
+      for (const auto &O : SrcValue->operands())
+        DstValue->push_back(O);
       break;
     }
     case Module::AppendUnique: {
       SmallSetVector<Metadata *, 16> Elts;
-      MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
+      MDTuple *DstValue = ensureDistinctOp(cast<MDNode>(DstOp->getOperand(2)));
       MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
       Elts.insert(DstValue->op_begin(), DstValue->op_end());
       Elts.insert(SrcValue->op_begin(), SrcValue->op_end());
-
-      replaceDstValue(MDNode::get(DstM.getContext(),
-                                  makeArrayRef(Elts.begin(), Elts.end())));
+      for (auto I = DstValue->getNumOperands(); I < Elts.size(); I++)
+        DstValue->push_back(Elts[I]);
       break;
     }
     }
diff --git a/llvm/lib/Transforms/Instrumentation/CGProfile.cpp b/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
--- a/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
+++ b/llvm/lib/Transforms/Instrumentation/CGProfile.cpp
@@ -39,7 +39,8 @@
     Nodes.push_back(MDNode::get(Context, Vals));
   }
 
-  M.addModuleFlag(Module::Append, "CG Profile", MDNode::get(Context, Nodes));
+  M.addModuleFlag(Module::Append, "CG Profile",
+                  MDTuple::getDistinct(Context, Nodes));
   return true;
 }
 
diff --git a/llvm/test/Instrumentation/cgprofile.ll b/llvm/test/Instrumentation/cgprofile.ll
--- a/llvm/test/Instrumentation/cgprofile.ll
+++ b/llvm/test/Instrumentation/cgprofile.ll
@@ -34,7 +34,7 @@
 
 ; CHECK: !llvm.module.flags = !{![[cgprof:[0-9]+]]}
 ; CHECK: ![[cgprof]] = !{i32 5, !"CG Profile", ![[prof:[0-9]+]]}
-; CHECK: ![[prof]] = !{![[e0:[0-9]+]], ![[e1:[0-9]+]], ![[e2:[0-9]+]], ![[e3:[0-9]+]], ![[e4:[0-9]+]], ![[e5:[0-9]+]], ![[e6:[0-9]+]]}
+; CHECK: ![[prof]] = distinct !{![[e0:[0-9]+]], ![[e1:[0-9]+]], ![[e2:[0-9]+]], ![[e3:[0-9]+]], ![[e4:[0-9]+]], ![[e5:[0-9]+]], ![[e6:[0-9]+]]}
 ; CHECK: ![[e0]] = !{void ()* @a, void ()* @b, i64 32}
 ; CHECK: ![[e1]] = !{void (i1)* @freq, i32 ()* @func4, i64 1030}
 ; CHECK: ![[e2]] = !{void (i1)* @freq, i32 ()* @func2, i64 410}
diff --git a/llvm/test/Linker/module-flags-8-a.ll b/llvm/test/Linker/module-flags-8-a.ll
--- a/llvm/test/Linker/module-flags-8-a.ll
+++ b/llvm/test/Linker/module-flags-8-a.ll
@@ -2,10 +2,10 @@
 
 ; Test append-type module flags.
 
-; CHECK: !0 = !{i32 5, !"flag-0", !1}
-; CHECK: !1 = !{i32 0, i32 0, i32 1}
-; CHECK: !2 = !{i32 6, !"flag-1", !3}
-; CHECK: !3 = !{i32 0, i32 1, i32 2}
+; CHECK: !0 = distinct !{i32 5, !"flag-0", !1}
+; CHECK: !1 = distinct !{i32 0, i32 0, i32 1}
+; CHECK: !2 = distinct !{i32 6, !"flag-1", !3}
+; CHECK: !3 = distinct !{i32 0, i32 1, i32 2}
 ; CHECK: !llvm.module.flags = !{!0, !2}
 
 !0 = !{ i32 5, !"flag-0", !{ i32 0 } }
diff --git a/llvm/test/Linker/module-flags-dont-change-others.ll b/llvm/test/Linker/module-flags-dont-change-others.ll
--- a/llvm/test/Linker/module-flags-dont-change-others.ll
+++ b/llvm/test/Linker/module-flags-dont-change-others.ll
@@ -5,7 +5,7 @@
 ; happen to also serve as module flags.
 
 ; CHECK: !named = !{!0, !1, !2, !3, !4, !5}
-; CHECK: !llvm.module.flags = !{!6, !7, !8}
+; CHECK: !llvm.module.flags = !{!6, !7, !9}
 !named = !{!0, !1, !2, !3, !4, !5}
 !llvm.module.flags = !{!3, !4, !5}
 
@@ -16,8 +16,10 @@
 ; CHECK: !4 = !{i32 5, !"bar", !0}
 ; CHECK: !5 = !{i32 6, !"baz", !1}
 ; CHECK: !6 = !{i32 4, !"foo", i32 37}
-; CHECK: !7 = !{i32 5, !"bar", !1}
-; CHECK: !8 = !{i32 6, !"baz", !2}
+; CHECK: !7 = distinct !{i32 5, !"bar", !8}
+; CHECK: !8 = distinct !{!0}
+; CHECK: !9 = distinct !{i32 6, !"baz", !10}
+; CHECK: !10 = distinct !{!0, !1}
 !0 = !{}
 !1 = !{!0}
 !2 = !{!0, !1}
diff --git a/llvm/test/Transforms/FunctionImport/cg_profile.ll b/llvm/test/Transforms/FunctionImport/cg_profile.ll
--- a/llvm/test/Transforms/FunctionImport/cg_profile.ll
+++ b/llvm/test/Transforms/FunctionImport/cg_profile.ll
@@ -9,7 +9,7 @@
 
 ; CHECK:      !0 = !{i32 1, !"EnableSplitLTOUnit", i32 0}
 ; CHECK-NEXT: !1 = !{i32 5, !"CG Profile", !2}
-; CHECK-NEXT: !2 = !{!3}
+; CHECK-NEXT: !2 = distinct !{!3}
 ; CHECK-NEXT: !3 = !{void ()* @foo, void (%class.A*)* bitcast (void (%class.A.0*)* @bar to void (%class.A*)*), i64 2753}
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"