diff --git a/src/libs/clangsupport/generatedfiles.cpp b/src/libs/clangsupport/generatedfiles.cpp
index f4863baba5d..644137886ba 100644
--- a/src/libs/clangsupport/generatedfiles.cpp
+++ b/src/libs/clangsupport/generatedfiles.cpp
@@ -25,6 +25,8 @@
 
 #include "generatedfiles.h"
 
+#include <utils/algorithm.h>
+
 namespace ClangBackEnd {
 
 void GeneratedFiles::update(V2::FileContainers &&fileContainers)
@@ -32,16 +34,16 @@ void GeneratedFiles::update(V2::FileContainers &&fileContainers)
     V2::FileContainers unionFileContainers;
     unionFileContainers.reserve(m_fileContainers.size() + fileContainers.size());
 
-    auto compare = [] (const V2::FileContainer &first, const V2::FileContainer &second) {
+    auto compare = [](const V2::FileContainer &first, const V2::FileContainer &second) {
         return first.filePath < second.filePath;
     };
 
-    std::set_union(std::make_move_iterator(fileContainers.begin()),
-                   std::make_move_iterator(fileContainers.end()),
-                   std::make_move_iterator(m_fileContainers.begin()),
-                   std::make_move_iterator(m_fileContainers.end()),
-                   std::back_inserter(unionFileContainers),
-                   compare);
+    Utils::set_union(std::make_move_iterator(fileContainers.begin()),
+                     std::make_move_iterator(fileContainers.end()),
+                     std::make_move_iterator(m_fileContainers.begin()),
+                     std::make_move_iterator(m_fileContainers.end()),
+                     std::back_inserter(unionFileContainers),
+                     compare);
 
     m_fileContainers = std::move(unionFileContainers);
 }
@@ -55,12 +57,12 @@ void GeneratedFiles::update(const V2::FileContainers &fileContainers)
         return first.filePath < second.filePath;
     };
 
-    std::set_union(fileContainers.begin(),
-                   fileContainers.end(),
-                   std::make_move_iterator(m_fileContainers.begin()),
-                   std::make_move_iterator(m_fileContainers.end()),
-                   std::back_inserter(unionFileContainers),
-                   compare);
+    Utils::set_union(fileContainers.begin(),
+                     fileContainers.end(),
+                     std::make_move_iterator(m_fileContainers.begin()),
+                     std::make_move_iterator(m_fileContainers.end()),
+                     std::back_inserter(unionFileContainers),
+                     compare);
 
     m_fileContainers = std::move(unionFileContainers);
 }
diff --git a/src/libs/utils/algorithm.h b/src/libs/utils/algorithm.h
index bae78aacdac..766f9419b84 100644
--- a/src/libs/utils/algorithm.h
+++ b/src/libs/utils/algorithm.h
@@ -862,4 +862,70 @@ std::make_signed_t<typename Container::size_type> ssize(Container container)
 {
     return static_cast<std::make_signed_t<typename Container::size_type>>(container.size());
 }
+
+template<typename Compare>
+struct CompareIter
+{
+    Compare compare;
+
+    explicit constexpr CompareIter(Compare compare)
+        : compare(std::move(compare))
+    {}
+
+    template<typename Iterator1, typename Iterator2>
+    constexpr bool operator()(Iterator1 it1, Iterator2 it2)
+    {
+        return bool(compare(*it1, *it2));
+    }
+};
+
+template<typename InputIterator1, typename InputIterator2, typename OutputIterator, typename Compare>
+OutputIterator set_union_impl(InputIterator1 first1,
+                              InputIterator1 last1,
+                              InputIterator2 first2,
+                              InputIterator2 last2,
+                              OutputIterator result,
+                              Compare comp)
+{
+    auto compare = CompareIter<Compare>(comp);
+
+    while (first1 != last1 && first2 != last2) {
+        if (compare(first1, first2)) {
+            *result = *first1;
+            ++first1;
+        } else if (compare(first2, first1)) {
+            *result = *first2;
+            ++first2;
+        } else {
+            *result = *first1;
+            ++first1;
+            ++first2;
+        }
+        ++result;
+    }
+
+    return std::copy(first2, last2, std::copy(first1, last1, result));
+}
+
+template<typename InputIterator1, typename InputIterator2, typename OutputIterator, typename Compare>
+OutputIterator set_union(InputIterator1 first1,
+                         InputIterator1 last1,
+                         InputIterator2 first2,
+                         InputIterator2 last2,
+                         OutputIterator result,
+                         Compare comp)
+{
+    return Utils::set_union_impl(first1, last1, first2, last2, result, comp);
+}
+
+template<typename InputIterator1, typename InputIterator2, typename OutputIterator>
+OutputIterator set_union(InputIterator1 first1,
+                         InputIterator1 last1,
+                         InputIterator2 first2,
+                         InputIterator2 last2,
+                         OutputIterator result)
+{
+    return Utils::set_union_impl(
+        first1, last1, first2, last2, result, std::less<typename InputIterator1::value_type>{});
+}
 } // namespace Utils
diff --git a/src/tools/clangpchmanagerbackend/source/pchtaskqueue.cpp b/src/tools/clangpchmanagerbackend/source/pchtaskqueue.cpp
index 2abe3fa3946..1bf21712fd8 100644
--- a/src/tools/clangpchmanagerbackend/source/pchtaskqueue.cpp
+++ b/src/tools/clangpchmanagerbackend/source/pchtaskqueue.cpp
@@ -30,6 +30,8 @@
 #include <progresscounter.h>
 #include <sqlitetransaction.h>
 
+#include <utils/algorithm.h>
+
 namespace ClangBackEnd {
 
 void PchTaskQueue::addPchTasks(PchTasks &&newPchTasks, PchTasks &destination)
@@ -42,12 +44,12 @@ void PchTaskQueue::addPchTasks(PchTasks &&newPchTasks, PchTasks &destination)
 
     PchTasks mergedPchTasks;
     mergedPchTasks.reserve(destination.size() + newPchTasks.size());
-    std::set_union(std::make_move_iterator(newPchTasks.begin()),
-                   std::make_move_iterator(newPchTasks.end()),
-                   std::make_move_iterator(destination.begin()),
-                   std::make_move_iterator(destination.end()),
-                   std::back_inserter(mergedPchTasks),
-                   compare);
+    Utils::set_union(std::make_move_iterator(newPchTasks.begin()),
+                     std::make_move_iterator(newPchTasks.end()),
+                     std::make_move_iterator(destination.begin()),
+                     std::make_move_iterator(destination.end()),
+                     std::back_inserter(mergedPchTasks),
+                     compare);
 
     destination = std::move(mergedPchTasks);
 
diff --git a/src/tools/clangpchmanagerbackend/source/pchtasksmerger.cpp b/src/tools/clangpchmanagerbackend/source/pchtasksmerger.cpp
index 7e850b8947e..68a8e4a6427 100644
--- a/src/tools/clangpchmanagerbackend/source/pchtasksmerger.cpp
+++ b/src/tools/clangpchmanagerbackend/source/pchtasksmerger.cpp
@@ -27,6 +27,8 @@
 
 #include "pchtaskqueueinterface.h"
 
+#include <utils/algorithm.h>
+
 namespace ClangBackEnd {
 
 void PchTasksMerger::mergeTasks(PchTaskSets &&taskSets,
@@ -48,11 +50,11 @@ Result merge(Container &&first, Container &&second)
     Result result;
     result.reserve(first.size() + second.size());
 
-    std::set_union(std::make_move_iterator(first.begin()),
-                   std::make_move_iterator(first.end()),
-                   std::make_move_iterator(second.begin()),
-                   std::make_move_iterator(second.end()),
-                   std::back_inserter(result));
+    Utils::set_union(std::make_move_iterator(first.begin()),
+                     std::make_move_iterator(first.end()),
+                     std::make_move_iterator(second.begin()),
+                     std::make_move_iterator(second.end()),
+                     std::back_inserter(result));
 
     return result;
 }
diff --git a/src/tools/clangpchmanagerbackend/source/toolchainargumentscache.h b/src/tools/clangpchmanagerbackend/source/toolchainargumentscache.h
index ed5ab3b1fd1..d4d8a6479fb 100644
--- a/src/tools/clangpchmanagerbackend/source/toolchainargumentscache.h
+++ b/src/tools/clangpchmanagerbackend/source/toolchainargumentscache.h
@@ -27,6 +27,8 @@
 
 #include <projectpartcontainer.h>
 
+#include <utils/algorithm.h>
+
 #include <functional>
 
 namespace ClangBackEnd {
@@ -48,11 +50,11 @@ struct ArgumentsEntry
         ProjectPartIds mergedIds;
         mergedIds.reserve(ids.size() + newIds.size());
 
-        std::set_union(std::make_move_iterator(ids.begin()),
-                       std::make_move_iterator(ids.end()),
-                       std::make_move_iterator(newIds.begin()),
-                       std::make_move_iterator(newIds.end()),
-                       std::back_inserter(mergedIds));
+        Utils::set_union(std::make_move_iterator(ids.begin()),
+                         std::make_move_iterator(ids.end()),
+                         std::make_move_iterator(newIds.begin()),
+                         std::make_move_iterator(newIds.end()),
+                         std::back_inserter(mergedIds));
 
         ids = std::move(mergedIds);
     }