cmGeneratorTarget: Cache GetAllConfigCompileLanguages

Source/cmGeneratorTarget.cxx

@@ -533,6 +533,7 @@ cmValue cmGeneratorTarget::GetFileSuffixInternal(
 void cmGeneratorTarget::ClearSourcesCache()
 {
   this->AllConfigSources.clear();
+  this->AllConfigCompileLanguages.clear();
   this->KindedSourcesMap.clear();
   this->SourcesAreContextDependent = Tribool::Indeterminate;
   this->Objects.clear();

Source/cmGeneratorTarget.h

@@ -1326,6 +1326,9 @@ private:
   mutable std::vector<AllConfigSource> AllConfigSources;
   void ComputeAllConfigSources() const;
 
+  mutable std::set<std::string> AllConfigCompileLanguages;
+  void ComputeAllConfigCompileLanguages() const;
+
   mutable std::unordered_map<std::string, bool> MaybeInterfacePropertyExists;
   bool MaybeHaveInterfaceProperty(std::string const& prop,
                                   cm::GenEx::Evaluation* eval,

Source/cmGeneratorTarget_Sources.cxx

@@ -511,7 +511,7 @@ cmGeneratorTarget::GetAllConfigSources(SourceKind kind) const
   return result;
 }
 
-std::set<std::string> cmGeneratorTarget::GetAllConfigCompileLanguages() const
+void cmGeneratorTarget::ComputeAllConfigCompileLanguages() const
 {
   std::set<std::string> languages;
   std::vector<AllConfigSource> const& sources = this->GetAllConfigSources();
@@ -521,5 +521,13 @@ std::set<std::string> cmGeneratorTarget::GetAllConfigCompileLanguages() const
       languages.emplace(lang);
     }
   }
-  return languages;
+  this->AllConfigCompileLanguages = languages;
+}
+
+std::set<std::string> cmGeneratorTarget::GetAllConfigCompileLanguages() const
+{
+  if (this->AllConfigCompileLanguages.empty()) {
+    this->ComputeAllConfigCompileLanguages();
+  }
+  return this->AllConfigCompileLanguages;
 }