[clang][deps] Initialize build session timestamp properly

Author: jansvoboda11

clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h

@@ -12,6 +12,7 @@
 #include "clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h"
 #include "clang/Tooling/DependencyScanning/InProcessModuleCache.h"
 #include "llvm/ADT/BitmaskEnum.h"
+#include "llvm/Support/Chrono.h"
 
 namespace clang {
 namespace tooling {
@@ -84,7 +85,9 @@ class DependencyScanningService {
   DependencyScanningService(
       ScanningMode Mode, ScanningOutputFormat Format,
       ScanningOptimizations OptimizeArgs = ScanningOptimizations::Default,
-      bool EagerLoadModules = false, bool TraceVFS = false);
+      bool EagerLoadModules = false, bool TraceVFS = false,
+      std::time_t BuildSessionTimestamp =
+          llvm::sys::toTimeT(std::chrono::system_clock::now()));
 
   ScanningMode getMode() const { return Mode; }
 
@@ -102,6 +105,8 @@ class DependencyScanningService {
 
   ModuleCacheEntries &getModuleCacheEntries() { return ModCacheEntries; }
 
+  std::time_t getBuildSessionTimestamp() const { return BuildSessionTimestamp; }
+
 private:
   const ScanningMode Mode;
   const ScanningOutputFormat Format;
@@ -115,6 +120,8 @@ class DependencyScanningService {
   DependencyScanningFilesystemSharedCache SharedCache;
   /// The global module cache entries.
   ModuleCacheEntries ModCacheEntries;
+  /// The build session timestamp.
+  std::time_t BuildSessionTimestamp;
 };
 
 } // end namespace dependencies

clang/lib/Serialization/ASTReader.cpp

@@ -3102,9 +3102,6 @@ ASTReader::ReadControlBlock(ModuleFile &F,
         // files.
 
         unsigned N = ValidateSystemInputs ? NumInputs : NumUserInputs;
-        // FIXME: F.InputFilesValidationTimestamp comes from std::chrono, but
-        // HSOpts.BuildSessionTimestamp comes from the FS. They may not be
-        // comparable.
         if (HSOpts.ModulesValidateOncePerBuildSession &&
             F.InputFilesValidationTimestamp > HSOpts.BuildSessionTimestamp &&
             F.Kind == MK_ImplicitModule)
@@ -4935,9 +4932,6 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName, ModuleKind Type,
     // timestamp files are up-to-date in this build session.
     for (unsigned I = 0, N = Loaded.size(); I != N; ++I) {
       ImportedModule &M = Loaded[I];
-      // FIXME: F.InputFilesValidationTimestamp comes from std::chrono, but
-      // HSOpts.BuildSessionTimestamp comes from the FS. They may not be
-      // comparable.
       if (M.Mod->Kind == MK_ImplicitModule &&
           M.Mod->InputFilesValidationTimestamp < HSOpts.BuildSessionTimestamp)
         getModuleManager().getModuleCache().updateModuleTimestamp(

clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp

@@ -14,6 +14,8 @@ using namespace dependencies;
 
 DependencyScanningService::DependencyScanningService(
     ScanningMode Mode, ScanningOutputFormat Format,
-    ScanningOptimizations OptimizeArgs, bool EagerLoadModules, bool TraceVFS)
+    ScanningOptimizations OptimizeArgs, bool EagerLoadModules, bool TraceVFS,
+    std::time_t BuildSessionTimestamp)
     : Mode(Mode), Format(Format), OptimizeArgs(OptimizeArgs),
-      EagerLoadModules(EagerLoadModules), TraceVFS(TraceVFS) {}
+      EagerLoadModules(EagerLoadModules), TraceVFS(TraceVFS),
+      BuildSessionTimestamp(BuildSessionTimestamp) {}

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

@@ -428,6 +428,10 @@ class DependencyScanningAction : public tooling::ToolAction {
     ScanInstance.getPreprocessorOpts().AllowPCHWithDifferentModulesCachePath =
         true;
 
+    if (ScanInstance.getHeaderSearchOpts().ModulesValidateOncePerBuildSession)
+      ScanInstance.getHeaderSearchOpts().BuildSessionTimestamp =
+          Service.getBuildSessionTimestamp();
+
     ScanInstance.getFrontendOpts().GenerateGlobalModuleIndex = false;
     ScanInstance.getFrontendOpts().UseGlobalModuleIndex = false;
     // This will prevent us compiling individual modules asynchronously since