Index: llvm/lib/Transforms/IPO/HotColdSplitting.cpp
===================================================================
--- llvm/lib/Transforms/IPO/HotColdSplitting.cpp
+++ llvm/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -117,8 +117,12 @@
   if (blockEndsInUnreachable(BB)) {
     if (auto *CI =
             dyn_cast_or_null<CallInst>(BB.getTerminator()->getPrevNode()))
-      if (CI->hasFnAttr(Attribute::NoReturn))
-        return false;
+      if (CI->hasFnAttr(Attribute::NoReturn)) {
+        if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI))
+          return II->getIntrinsicID() != Intrinsic::longjmp;
+        CallSite CS(CI);
+        return !CS.getCalledFunction()->getName().startswith("longjmp");
+      }
     return true;
   }
 
Index: llvm/test/Transforms/HotColdSplit/noreturn.ll
===================================================================
--- llvm/test/Transforms/HotColdSplit/noreturn.ll
+++ llvm/test/Transforms/HotColdSplit/noreturn.ll
@@ -59,6 +59,24 @@
   ret void
 }
 
+; Outline noreturn calls which are explicitly marked noreturn unless they are longjmp.
+
+; CHECK-LABEL: define {{.*}}@gap(
+; CHECK: gap.cold.1
+define void @gap(i32, %struct.__jmp_buf_tag*) {
+  %3 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %3, label %5, label %4
+
+; <label>:4:                                      ; preds = %2
+  tail call void @_assert_noreturn(%struct.__jmp_buf_tag* %1, i32 0)
+  unreachable
+
+; <label>:5:                                      ; preds = %2
+  ret void
+}
+
+
 ; CHECK-LABEL: define {{.*}}@bar.cold.1(
 ; CHECK: call {{.*}}@llvm.trap(
 
@@ -69,3 +87,4 @@
 declare void @_Z10sideeffectv()
 
 declare void @longjmp(%struct.__jmp_buf_tag*, i32) noreturn nounwind
+declare void @_assert_noreturn(%struct.__jmp_buf_tag*, i32) noreturn nounwind