Unity build: Add support for Ninja and Makefile generators

Source/cmLocalGenerator.cxx

@@ -38,6 +38,7 @@
 
 #include <algorithm>
 #include <assert.h>
+#include <cstdlib>
 #include <functional>
 #include <initializer_list>
 #include <iterator>
@@ -2202,6 +2203,90 @@ void cmLocalGenerator::AddPchDependencies(cmGeneratorTarget* target,
   }
 }
 
+void cmLocalGenerator::AddUnityBuild(cmGeneratorTarget* target,
+                                     const std::string& config)
+{
+  if (!target->GetPropertyAsBool("UNITY_BUILD")) {
+    return;
+  }
+
+  const std::string buildType = cmSystemTools::UpperCase(config);
+
+  std::string filename_base =
+    cmStrCat(this->GetCurrentBinaryDirectory(), "/CMakeFiles/",
+             target->GetName(), ".dir/Unity/");
+
+  std::vector<cmSourceFile*> sources;
+  target->GetSourceFiles(sources, buildType);
+
+  auto batchSizeString = target->GetProperty("UNITY_BUILD_BATCH_SIZE");
+  const size_t unityBatchSize =
+    static_cast<size_t>(std::atoi(batchSizeString));
+
+  auto beforeInclude = target->GetProperty("UNITY_BUILD_CODE_BEFORE_INCLUDE");
+  auto afterInclude = target->GetProperty("UNITY_BUILD_CODE_AFTER_INCLUDE");
+
+  for (std::string lang : { "C", "CXX" }) {
+    std::vector<cmSourceFile*> filtered_sources;
+    std::copy_if(sources.begin(), sources.end(),
+                 std::back_inserter(filtered_sources), [&](cmSourceFile* sf) {
+                   return sf->GetLanguage() == lang &&
+                     !sf->GetPropertyAsBool("SKIP_UNITY_BUILD_INCLUSION") &&
+                     !sf->GetPropertyAsBool("GENERATED") &&
+                     !sf->GetProperty("COMPILE_OPTIONS") &&
+                     !sf->GetProperty("COMPILE_DEFINITIONS") &&
+                     !sf->GetProperty("COMPILE_FLAGS") &&
+                     !sf->GetProperty("INCLUDE_DIRECTORIES");
+                 });
+
+    size_t batchSize = unityBatchSize;
+    if (unityBatchSize == 0) {
+      batchSize = filtered_sources.size();
+    }
+
+    for (size_t itemsLeft = filtered_sources.size(), chunk = batchSize,
+                batch = 0;
+         itemsLeft > 0; itemsLeft -= chunk, ++batch) {
+
+      chunk = std::min(itemsLeft, batchSize);
+
+      std::string filename = cmStrCat(filename_base, "unity_", batch,
+                                      (lang == "C") ? ".c" : ".cxx");
+
+      const std::string filename_tmp = cmStrCat(filename, ".tmp");
+      {
+        size_t begin = batch * batchSize;
+        size_t end = begin + chunk;
+
+        cmGeneratedFileStream file(
+          filename_tmp, false,
+          this->GetGlobalGenerator()->GetMakefileEncoding());
+        file << "/* generated by CMake */\n\n";
+
+        for (; begin != end; ++begin) {
+          cmSourceFile* sf = filtered_sources[begin];
+
+          sf->SetProperty("HEADER_FILE_ONLY", "ON");
+
+          if (beforeInclude) {
+            file << beforeInclude << "\n";
+          }
+
+          file << "#include \"" << sf->GetFullPath() << "\"\n";
+
+          if (afterInclude) {
+            file << afterInclude << "\n";
+          }
+        }
+      }
+      cmSystemTools::CopyFileIfDifferent(filename_tmp, filename);
+      cmSystemTools::RemoveFile(filename_tmp);
+
+      target->AddSource(filename, true);
+    }
+  }
+}
+
 void cmLocalGenerator::AppendIPOLinkerFlags(std::string& flags,
                                             cmGeneratorTarget* target,
                                             const std::string& config,

Source/cmLocalGenerator.h

@@ -126,6 +126,7 @@ public:
                                 const std::string& rawFlag) const;
   void AddPchDependencies(cmGeneratorTarget* target,
                           const std::string& config);
+  void AddUnityBuild(cmGeneratorTarget* target, const std::string& config);
   void AppendIPOLinkerFlags(std::string& flags, cmGeneratorTarget* target,
                             const std::string& config,
                             const std::string& lang);

Source/cmMakefileExecutableTargetGenerator.cxx

@@ -41,6 +41,7 @@ cmMakefileExecutableTargetGenerator::cmMakefileExecutableTargetGenerator(
     cm::make_unique<cmOSXBundleGenerator>(target, this->ConfigName);
   this->OSXBundleGenerator->SetMacContentFolders(&this->MacContentFolders);
 
+  this->LocalGenerator->AddUnityBuild(target, this->ConfigName);
   this->LocalGenerator->AddPchDependencies(target, this->ConfigName);
 }
 

Source/cmMakefileLibraryTargetGenerator.cxx

@@ -43,6 +43,7 @@ cmMakefileLibraryTargetGenerator::cmMakefileLibraryTargetGenerator(
     cm::make_unique<cmOSXBundleGenerator>(target, this->ConfigName);
   this->OSXBundleGenerator->SetMacContentFolders(&this->MacContentFolders);
 
+  this->LocalGenerator->AddUnityBuild(target, this->ConfigName);
   this->LocalGenerator->AddPchDependencies(target, this->ConfigName);
 }
 

Source/cmMakefileUtilityTargetGenerator.cxx

@@ -26,6 +26,7 @@ cmMakefileUtilityTargetGenerator::cmMakefileUtilityTargetGenerator(
     cm::make_unique<cmOSXBundleGenerator>(target, this->ConfigName);
   this->OSXBundleGenerator->SetMacContentFolders(&this->MacContentFolders);
 
+  this->LocalGenerator->AddUnityBuild(target, this->ConfigName);
   this->LocalGenerator->AddPchDependencies(target, this->ConfigName);
 }
 

Source/cmNinjaNormalTargetGenerator.cxx

@@ -60,6 +60,7 @@ cmNinjaNormalTargetGenerator::cmNinjaNormalTargetGenerator(
     cm::make_unique<cmOSXBundleGenerator>(target, this->GetConfigName());
   this->OSXBundleGenerator->SetMacContentFolders(&this->MacContentFolders);
 
+  GetLocalGenerator()->AddUnityBuild(target, this->GetConfigName());
   GetLocalGenerator()->AddPchDependencies(target, this->GetConfigName());
 }
 

Source/cmTarget.cxx

@@ -352,6 +352,8 @@ cmTarget::cmTarget(std::string const& name, cmStateEnums::TargetType type,
     initProp("Swift_MODULE_DIRECTORY");
     initProp("VS_JUST_MY_CODE_DEBUGGING");
     initProp("DISABLE_PRECOMPILE_HEADERS");
+    initProp("UNITY_BUILD");
+    initPropValue("UNITY_BUILD_BATCH_SIZE", "8");
 #ifdef __APPLE__
     if (this->GetGlobalGenerator()->IsXcode()) {
       initProp("XCODE_GENERATE_SCHEME");