Merge branch 'unity-after-compile-features' into restore-pch-with-unity

Replace commit 76b5383123 (cmGlobalGenerator: add unity sources after
computing target compile features, 2024-01-01, v3.28.2~17^2~1) with an
alternative change.  This merge commit resolves conflicts such that
future `git blame` calls will follow the second parent for the relevant
lines and pretend the replaced commit never existed.

Fixes: #25650

Source/cmGlobalGenerator.cxx

@@ -1543,10 +1543,7 @@ bool cmGlobalGenerator::Compute()
   // so create the map from project name to vector of local generators
   this->FillProjectMap();
 
-  // Add automatically generated sources (e.g. unity build).
-  if (!this->AddAutomaticSources()) {
-    return false;
-  }
+  this->CreateFileGenerateOutputs();
 
   // Iterate through all targets and add verification targets for header sets
   if (!this->AddHeaderSetVerification()) {
@@ -1587,10 +1584,11 @@ bool cmGlobalGenerator::Compute()
     }
   }
 
+  // Add automatically generated sources (e.g. unity build).
   // Add unity sources after computing compile features.  Unity sources do
   // not change the set of languages or features, but we need to know them
   // to filter out sources that are scanned for C++ module dependencies.
-  if (!this->AddUnitySources()) {
+  if (!this->AddAutomaticSources()) {
     return false;
   }
 
@@ -1860,16 +1858,21 @@ bool cmGlobalGenerator::AddHeaderSetVerification()
   return true;
 }
 
-bool cmGlobalGenerator::AddAutomaticSources()
+void cmGlobalGenerator::CreateFileGenerateOutputs()
 {
   for (const auto& lg : this->LocalGenerators) {
     lg->CreateEvaluationFileOutputs();
   }
+}
+
+bool cmGlobalGenerator::AddAutomaticSources()
+{
   for (const auto& lg : this->LocalGenerators) {
     for (const auto& gt : lg->GetGeneratorTargets()) {
       if (!gt->CanCompileSources()) {
         continue;
       }
+      lg->AddUnityBuild(gt.get());
       lg->AddISPCDependencies(gt.get());
       // Targets that reuse a PCH are handled below.
       if (!gt->GetProperty("PRECOMPILE_HEADERS_REUSE_FROM")) {
@@ -1901,28 +1904,6 @@ bool cmGlobalGenerator::AddAutomaticSources()
   return true;
 }
 
-bool cmGlobalGenerator::AddUnitySources()
-{
-  for (const auto& lg : this->LocalGenerators) {
-    for (const auto& gt : lg->GetGeneratorTargets()) {
-      if (!gt->CanCompileSources()) {
-        continue;
-      }
-      lg->AddUnityBuild(gt.get());
-    }
-  }
-  // The above transformation may have changed the classification of sources.
-  // Clear the source list and classification cache (KindedSources) of all
-  // targets so that it will be recomputed correctly by the generators later
-  // now that the above transformations are done for all targets.
-  for (const auto& lg : this->LocalGenerators) {
-    for (const auto& gt : lg->GetGeneratorTargets()) {
-      gt->ClearSourcesCache();
-    }
-  }
-  return true;
-}
-
 std::unique_ptr<cmLinkLineComputer> cmGlobalGenerator::CreateLinkLineComputer(
   cmOutputConverter* outputConverter, cmStateDirectory const& stateDir) const
 {

Source/cmGlobalGenerator.h

@@ -676,8 +676,8 @@ protected:
 
   bool AddHeaderSetVerification();
 
+  void CreateFileGenerateOutputs();
   bool AddAutomaticSources();
-  bool AddUnitySources();
 
   std::string SelectMakeProgram(const std::string& makeProgram,
                                 const std::string& makeDefault = "") const;

Tests/RunCMake/PrecompileHeaders/PchInterfaceUnity-check.cmake

@@ -0,0 +1 @@
+include(${CMAKE_CURRENT_LIST_DIR}/PchInterface-check.cmake)

Tests/RunCMake/PrecompileHeaders/PchInterfaceUnity.cmake

@@ -0,0 +1,2 @@
+set(CMAKE_UNITY_BUILD 1)
+include(PchInterface.cmake)

Tests/RunCMake/PrecompileHeaders/RunCMakeTest.cmake

@@ -12,6 +12,7 @@ endfunction()
 run_cmake(DisabledPch)
 run_cmake(PchDebugGenex)
 run_test(PchInterface)
+run_test(PchInterfaceUnity)
 run_cmake(PchPrologueEpilogue)
 run_test(SkipPrecompileHeaders)
 run_test(CXXnotC)