Index: llvm/include/llvm/Transforms/Utils/Cloning.h
===================================================================
--- llvm/include/llvm/Transforms/Utils/Cloning.h
+++ llvm/include/llvm/Transforms/Utils/Cloning.h
@@ -295,6 +295,13 @@
 void identifyNoAliasScopesToClone(
     ArrayRef<BasicBlock *> BBs, SmallVectorImpl<MDNode *> &NoAliasDeclScopes);
 
+/// Find the 'llvm.experimental.noalias.scope.decl' intrinsics in the specified
+/// instruction range and extract their scope. These are candidates for
+/// duplication when cloning.
+void identifyNoAliasScopesToClone(
+    BasicBlock::iterator Start, BasicBlock::iterator End,
+    SmallVectorImpl<MDNode *> &NoAliasDeclScopes);
+
 /// Duplicate the specified list of noalias decl scopes.
 /// The 'Ext' string is added as an extension to the name.
 /// Afterwards, the ClonedScopes contains the mapping of the original scope
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -2076,6 +2076,15 @@
     ValueMapping[PN] = NewPN;
   }
 
+  // Clone noalias scope declarations in the threaded block. When threading a
+  // loop exit, we would otherwise end up with two idential scope declarations
+  // visible at the same time.
+  SmallVector<MDNode *> NoAliasScopes;
+  DenseMap<MDNode *, MDNode *> ClonedScopes;
+  LLVMContext &Context = PredBB->getContext();
+  identifyNoAliasScopesToClone(BI, BE, NoAliasScopes);
+  cloneNoAliasScopes(NoAliasScopes, ClonedScopes, "thread", Context);
+
   // Clone the non-phi instructions of the source basic block into NewBB,
   // keeping track of the mapping and using it to remap operands in the cloned
   // instructions.
@@ -2084,6 +2093,7 @@
     New->setName(BI->getName());
     NewBB->getInstList().push_back(New);
     ValueMapping[&*BI] = New;
+    adaptNoAliasScopes(New, ClonedScopes, Context);
 
     // Remap operands to patch up intra-block references.
     for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
Index: llvm/lib/Transforms/Utils/CloneFunction.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -1036,3 +1036,11 @@
       if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(&I))
         NoAliasDeclScopes.push_back(Decl->getScopeList());
 }
+
+void llvm::identifyNoAliasScopesToClone(
+    BasicBlock::iterator Start, BasicBlock::iterator End,
+    SmallVectorImpl<MDNode *> &NoAliasDeclScopes) {
+  for (Instruction &I : make_range(Start, End))
+    if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(&I))
+      NoAliasDeclScopes.push_back(Decl->getScopeList());
+}
Index: llvm/test/Transforms/JumpThreading/noalias-scope-decl.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/JumpThreading/noalias-scope-decl.ll
@@ -0,0 +1,63 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -jump-threading < %s | FileCheck %s
+
+define void @test(i8* %ptr) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @llvm.experimental.noalias.scope.decl(metadata !0)
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[I_INC:%.*]], [[LATCH:%.*]] ]
+; CHECK-NEXT:    [[C:%.*]] = icmp eq i32 [[I]], 100
+; CHECK-NEXT:    br i1 [[C]], label [[EXIT:%.*]], label [[LATCH]]
+; CHECK:       latch:
+; CHECK-NEXT:    call void @llvm.experimental.noalias.scope.decl(metadata !3)
+; CHECK-NEXT:    store i8 0, i8* [[PTR:%.*]], align 1, !noalias !0
+; CHECK-NEXT:    store i8 1, i8* [[PTR]], align 1, !noalias !3
+; CHECK-NEXT:    [[I_INC]] = add i32 [[I]], 1
+; CHECK-NEXT:    br label [[LOOP]]
+; CHECK:       exit:
+; CHECK-NEXT:    call void @llvm.experimental.noalias.scope.decl(metadata !5)
+; CHECK-NEXT:    store i8 0, i8* [[PTR]], align 1, !noalias !0
+; CHECK-NEXT:    store i8 1, i8* [[PTR]], align 1, !noalias !5
+; CHECK-NEXT:    ret void
+;
+entry:
+  call void @llvm.experimental.noalias.scope.decl(metadata !0)
+  br label %loop
+
+loop:
+  %i = phi i32 [ 0, %entry ], [ %i.inc, %latch ]
+  %c = icmp eq i32 %i, 100
+  br i1 %c, label %if, label %latch
+
+if:
+  br label %latch
+
+latch:
+  %p = phi i1 [ true, %if ], [ false, %loop ]
+  call void @llvm.experimental.noalias.scope.decl(metadata !3)
+  store i8 0, i8* %ptr, !noalias !0
+  store i8 1, i8* %ptr, !noalias !3
+  %i.inc = add i32 %i, 1
+  br i1 %p, label %exit, label %loop
+
+exit:
+  ret void
+}
+
+declare void @llvm.experimental.noalias.scope.decl(metadata)
+
+!0 = !{!1}
+!1 = distinct !{!1, !2, !"scope1"}
+!2 = distinct !{!2, !"domain"}
+!3 = !{!4}
+!4 = distinct !{!4, !2, !"scope2"}
+
+; CHECK: !0 = !{!1}
+; CHECK: !1 = distinct !{!1, !2, !"scope1"}
+; CHECK: !2 = distinct !{!2, !"domain"}
+; CHECK: !3 = !{!4}
+; CHECK: !4 = distinct !{!4, !2, !"scope2"}
+; CHECK: !5 = !{!6}
+; CHECK: !6 = distinct !{!6, !2, !"scope2:thread"}