Reapply "[clang][modules] Timestamp PCM files when writing (#9483)"

This reverts commit 89d4029.

Author: jansvoboda11

clang/include/clang/Serialization/ModuleFile.h

@@ -15,6 +15,7 @@
 #define LLVM_CLANG_SERIALIZATION_MODULEFILE_H
 
 #include "clang/Basic/FileManager.h"
+#include "clang/Basic/LLVM.h"
 #include "clang/Basic/Module.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Serialization/ASTBitCodes.h"
@@ -155,8 +156,8 @@ class ModuleFile {
   /// The base directory of the module.
   std::string BaseDirectory;
 
-  std::string getTimestampFilename() const {
-    return FileName + ".timestamp";
+  static std::string getTimestampFilename(StringRef FileName) {
+    return (FileName + ".timestamp").str();
   }
 
   /// The original source file name that was used to build the

clang/lib/Serialization/ASTCommon.cpp

@@ -15,7 +15,10 @@
 #include "clang/AST/DeclObjC.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Serialization/ASTDeserializationListener.h"
+#include "clang/Serialization/ModuleFile.h"
 #include "llvm/Support/DJB.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace clang;
 
@@ -498,3 +501,15 @@ bool serialization::needsAnonymousDeclarationNumber(const NamedDecl *D) {
     return false;
   return isa<TagDecl, FieldDecl>(D);
 }
+
+void serialization::updateModuleTimestamp(StringRef ModuleFilename) {
+  // Overwrite the timestamp file contents so that file's mtime changes.
+  std::error_code EC;
+  llvm::raw_fd_ostream OS(ModuleFile::getTimestampFilename(ModuleFilename), EC,
+                          llvm::sys::fs::OF_TextWithCRLF);
+  if (EC)
+    return;
+  OS << "Timestamp file\n";
+  OS.close();
+  OS.clear_error(); // Avoid triggering a fatal error.
+}

clang/lib/Serialization/ASTCommon.h

@@ -15,6 +15,7 @@
 
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclFriend.h"
+#include "clang/Basic/LLVM.h"
 #include "clang/Serialization/ASTBitCodes.h"
 
 namespace clang {
@@ -100,6 +101,8 @@ inline bool isPartOfPerModuleInitializer(const Decl *D) {
   return false;
 }
 
+void updateModuleTimestamp(StringRef ModuleFilename);
+
 } // namespace serialization
 
 } // namespace clang

clang/lib/Serialization/ASTReader.cpp

@@ -4408,19 +4408,6 @@ bool ASTReader::isGlobalIndexUnavailable() const {
          !hasGlobalIndex() && TriedLoadingGlobalIndex;
 }
 
-static void updateModuleTimestamp(ModuleFile &MF) {
-  // Overwrite the timestamp file contents so that file's mtime changes.
-  std::string TimestampFilename = MF.getTimestampFilename();
-  std::error_code EC;
-  llvm::raw_fd_ostream OS(TimestampFilename, EC,
-                          llvm::sys::fs::OF_TextWithCRLF);
-  if (EC)
-    return;
-  OS << "Timestamp file\n";
-  OS.close();
-  OS.clear_error(); // Avoid triggering a fatal error.
-}
-
 /// Given a cursor at the start of an AST file, scan ahead and drop the
 /// cursor into the start of the given block ID, returning false on success and
 /// true on failure.
@@ -4699,7 +4686,7 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName, ModuleKind Type,
       ImportedModule &M = Loaded[I];
       if (M.Mod->Kind == MK_ImplicitModule &&
           M.Mod->InputFilesValidationTimestamp < HSOpts.BuildSessionTimestamp)
-        updateModuleTimestamp(*M.Mod);
+        updateModuleTimestamp(M.Mod->FileName);
     }
   }
 

clang/lib/Serialization/ASTWriter.cpp

@@ -4892,6 +4892,12 @@ ASTFileSignature ASTWriter::WriteAST(Sema &SemaRef, StringRef OutputFile,
   this->BaseDirectory.clear();
 
   WritingAST = false;
+
+  if (WritingModule && SemaRef.PP.getHeaderSearchInfo()
+                           .getHeaderSearchOpts()
+                           .ModulesValidateOncePerBuildSession)
+    updateModuleTimestamp(OutputFile);
+
   if (ShouldCacheASTInMemory) {
     // Construct MemoryBuffer and update buffer manager.
     ModuleCache.addBuiltPCM(OutputFile,

clang/lib/Serialization/ModuleManager.cpp

@@ -180,7 +180,8 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
   NewModule->InputFilesValidationTimestamp = 0;
 
   if (NewModule->Kind == MK_ImplicitModule) {
-    std::string TimestampFilename = NewModule->getTimestampFilename();
+    std::string TimestampFilename =
+        ModuleFile::getTimestampFilename(NewModule->FileName);
     llvm::vfs::Status Status;
     // A cached stat value would be fine as well.
     if (!FileMgr.getNoncachedStatValue(TimestampFilename, Status))