Reland "[clang][modules] Timestamp-less validation API (#139987)"

This reverts commit 18b885f66babff3a10451bc811ffc077d61ed8ee, effectively reapplying #139987. This commit fixes unit tests (for example ASTUnitTest.SaveLoadPreservesLangOptionsInPrintingPolicy) where the `ASTUnit::ModCache` pointer dereferenced within `ASTUnit::serialize()` was null. This commit makes sure each factory function does initialize `ASTUnit::ModCache`.

1 files changed, 14 insertions, 6 deletions

diff --git a/clang/lib/Serialization/ModuleCache.cpp b/clang/lib/Serialization/ModuleCache.cpp
index 4ae49c4..43f8ff8 100644
--- a/clang/lib/Serialization/ModuleCache.cpp
+++ b/clang/lib/Serialization/ModuleCache.cpp
@@ -20,7 +20,12 @@ namespace {
 class CrossProcessModuleCache : public ModuleCache {
   InMemoryModuleCache InMemory;
 
+  std::time_t BuildSessionTimestamp;
+
 public:
+  explicit CrossProcessModuleCache(std::time_t BuildSessionTimestamp)
+      : BuildSessionTimestamp(BuildSessionTimestamp) {}
+
   void prepareForGetLock(StringRef ModuleFilename) override {
     // FIXME: Do this in LockFileManager and only if the directory doesn't
     // exist.
@@ -33,16 +38,17 @@ public:
     return std::make_unique<llvm::LockFileManager>(ModuleFilename);
   }
 
-  std::time_t getModuleTimestamp(StringRef ModuleFilename) override {
+  bool isMarkedUpToDate(StringRef ModuleFilename) override {
     std::string TimestampFilename =
         serialization::ModuleFile::getTimestampFilename(ModuleFilename);
     llvm::sys::fs::file_status Status;
     if (llvm::sys::fs::status(ModuleFilename, Status) != std::error_code{})
-      return 0;
-    return llvm::sys::toTimeT(Status.getLastModificationTime());
+      return false;
+    return llvm::sys::toTimeT(Status.getLastModificationTime()) >
+           BuildSessionTimestamp;
   }
 
-  void updateModuleTimestamp(StringRef ModuleFilename) override {
+  void markUpToDate(StringRef ModuleFilename) override {
     // Overwrite the timestamp file contents so that file's mtime changes.
     std::error_code EC;
     llvm::raw_fd_ostream OS(
@@ -62,6 +68,8 @@ public:
 };
 } // namespace
 
-IntrusiveRefCntPtr<ModuleCache> clang::createCrossProcessModuleCache() {
-  return llvm::makeIntrusiveRefCnt<CrossProcessModuleCache>();
+IntrusiveRefCntPtr<ModuleCache>
+clang::createCrossProcessModuleCache(std::time_t BuildSessionTimestamp) {
+  return llvm::makeIntrusiveRefCnt<CrossProcessModuleCache>(
+      BuildSessionTimestamp);
 }