diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 7f8e10eb201a6..31f3ffc9da745 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1978,14 +1978,19 @@ void JumpThreadingPass::updateSSA(BasicBlock *BB, BasicBlock *NewBB,
   for (Instruction &I : *BB) {
     // Scan all uses of this instruction to see if it is used outside of its
     // block, and if so, record them in UsesToRename.
+
+    SmallVector<Instruction *> LifetimeMarkers;
     for (Use &U : I.uses()) {
       Instruction *User = cast<Instruction>(U.getUser());
-      if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
-        if (UserPN->getIncomingBlock(U) == BB)
+      if (User->isLifetimeStartOrEnd()) {
+        LifetimeMarkers.push_back(User);
+      } else {
+        if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
+          if (UserPN->getIncomingBlock(U) == BB)
+            continue;
+        } else if (User->getParent() == BB)
           continue;
-      } else if (User->getParent() == BB)
-        continue;
-
+      }
       UsesToRename.push_back(&U);
     }
 
@@ -2014,6 +2019,15 @@ void JumpThreadingPass::updateSSA(BasicBlock *BB, BasicBlock *NewBB,
       DbgVariableRecords.clear();
     }
 
+    // Lifetime markers cannot be rewritten through PHIs. If threading leaves
+    // one of them pointing at a PHI, drop the whole set.
+    bool HasPhiArg = any_of(LifetimeMarkers, [](Instruction *User) {
+      return isa<PHINode>(cast<CallBase>(User)->getOperand(0));
+    });
+    if (HasPhiArg) {
+      for (Instruction *User : LifetimeMarkers)
+        User->eraseFromParent();
+    }
     LLVM_DEBUG(dbgs() << "\n");
   }
 }
diff --git a/llvm/test/Transforms/JumpThreading/lifetime-alloca.ll b/llvm/test/Transforms/JumpThreading/lifetime-alloca.ll
new file mode 100644
index 0000000000000..81e05c70588f6
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/lifetime-alloca.ll
@@ -0,0 +1,80 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=jump-threading -S %s | FileCheck %s
+
+; Test that JumpThreading does not create a PHI node for an alloca that is
+; used by a lifetime intrinsic, which would violate the requirement that
+; lifetime markers only operate on allocas.
+
+define void @widget_dropped(i1 %arg) {
+; CHECK-LABEL: @widget_dropped(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br i1 [[ARG:%.*]], label [[BB3:%.*]], label [[BB2:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    [[ALLOCA:%.*]] = alloca [4 x [4 x i32]], align 8
+; CHECK-NEXT:    br label [[BB4:%.*]]
+; CHECK:       bb3:
+; CHECK-NEXT:    call void @dummy()
+; CHECK-NEXT:    [[ALLOCA1:%.*]] = alloca [4 x [4 x i32]], align 8
+; CHECK-NEXT:    br label [[BB4]]
+; CHECK:       bb4:
+; CHECK-NEXT:    [[ALLOCA2:%.*]] = phi ptr [ [[ALLOCA1]], [[BB3]] ], [ [[ALLOCA]], [[BB2]] ]
+; CHECK-NEXT:    ret void
+;
+bb:
+  br i1 %arg, label %bb1, label %bb2
+
+bb1:
+  call void @dummy()
+  br label %bb2
+
+bb2:
+  %alloca = alloca [4 x [4 x i32]], align 8
+  br i1 %arg, label %bb3, label %bb4
+
+bb3:
+  br label %bb4
+
+bb4:
+  call void @llvm.lifetime.start.p0(ptr %alloca)
+  call void @llvm.lifetime.end.p0(ptr %alloca)
+  ret void
+}
+
+; Because the alloca is in the entry block, it dominates all threaded blocks.
+; No PHI node is required, and the lifetime markers can be safely preserved.
+define void @widget_preserved(i1 %arg) {
+; CHECK-LABEL: @widget_preserved(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[ALLOCA:%.*]] = alloca [4 x [4 x i32]], align 8
+; CHECK-NEXT:    br i1 [[ARG:%.*]], label [[BB3:%.*]], label [[BB4:%.*]]
+; CHECK:       bb3:
+; CHECK-NEXT:    call void @dummy()
+; CHECK-NEXT:    br label [[BB4]]
+; CHECK:       bb4:
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0(ptr [[ALLOCA]])
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0(ptr [[ALLOCA]])
+; CHECK-NEXT:    ret void
+;
+bb:
+  %alloca = alloca [4 x [4 x i32]], align 8
+  br i1 %arg, label %bb1, label %bb2
+
+bb1:
+  call void @dummy()
+  br label %bb2
+
+bb2:
+  br i1 %arg, label %bb3, label %bb4
+
+bb3:
+  br label %bb4
+
+bb4:
+  call void @llvm.lifetime.start.p0(ptr %alloca)
+  call void @llvm.lifetime.end.p0(ptr %alloca)
+  ret void
+}
+
+declare void @dummy()
+
+attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }