[ClangModuleManager] Extend the ext4 file system workaround

Extend the ext4 file system workaround so it covers `lookupByFileName`.
This doesn't fix all the problems from the workaround, but it allows
correct lookup of the previously added module/PCH files.

rdar://119269472

Author: cachemeifyoucan

clang/lib/Basic/FileManager.cpp

@@ -483,7 +483,7 @@ OptionalFileEntryRef FileManager::getBypassFile(FileEntryRef VF) {
 
   // If we've already bypassed just use the existing one.
   auto Insertion = SeenBypassFileEntries->insert(
-      {VF.getName(), std::errc::no_such_file_or_directory});
+      {VF.getNameAsRequested(), std::errc::no_such_file_or_directory});
   if (!Insertion.second)
     return FileEntryRef(*Insertion.first);
 

clang/lib/Frontend/CompilerInstance.cpp

@@ -1980,9 +1980,16 @@ ModuleLoadResult CompilerInstance::findOrCompileModuleAndReadAST(
 
     // Check whether M refers to the file in the prebuilt module path.
     if (M && M->getASTFile())
-      if (auto ModuleFile = FileMgr->getFile(ModuleFilename))
+      if (auto ModuleFile = FileMgr->getOptionalFileRef(ModuleFilename)) {
         if (*ModuleFile == M->getASTFile())
           return M;
+#if !defined(__APPLE__)
+        // Workaround for ext4 file system. Also check bypass file if exists.
+        if (auto Bypass = FileMgr->getBypassFile(*ModuleFile))
+          if (*Bypass == M->getASTFile())
+            return M;
+#endif
+      }
 
     getDiagnostics().Report(ModuleNameLoc, diag::err_module_prebuilt)
         << ModuleName;

clang/lib/Frontend/Rewrite/FrontendActions.cpp

@@ -213,9 +213,15 @@ class RewriteIncludesAction::RewriteImportsListener : public ASTReaderListener {
 
   void visitModuleFile(StringRef Filename,
                        serialization::ModuleKind Kind) override {
-    auto File = CI.getFileManager().getFile(Filename);
+    auto File = CI.getFileManager().getOptionalFileRef(Filename);
     assert(File && "missing file for loaded module?");
 
+#if !defined(__APPLE__)
+    // Workaround for ext4 file system.
+    if (auto Bypass = CI.getFileManager().getBypassFile(*File))
+      File = *Bypass;
+#endif
+
     // Only rewrite each module file once.
     if (!Rewritten.insert(*File).second)
       return;

clang/lib/Serialization/ModuleManager.cpp

@@ -42,8 +42,18 @@ using namespace clang;
 using namespace serialization;
 
 ModuleFile *ModuleManager::lookupByFileName(StringRef Name) const {
-  auto Entry = FileMgr.getFile(Name, /*OpenFile=*/false,
-                               /*CacheFailure=*/false);
+  auto Entry = FileMgr.getOptionalFileRef(Name, /*OpenFile=*/false,
+                                          /*CacheFailure=*/false);
+#if !defined(__APPLE__)
+  if (Entry) {
+    // On Linux ext4 FileManager's inode caching system does not
+    // provide us correct behaviour for ModuleCache directories.
+    // inode can be reused after PCM delete resulting in cache misleading.
+    if (auto BypassFile = FileMgr.getBypassFile(*Entry))
+      Entry = *BypassFile;
+  }
+#endif
+
   if (Entry)
     return lookup(*Entry);
 
@@ -449,7 +459,10 @@ bool ModuleManager::lookupModuleFile(StringRef FileName, off_t ExpectedSize,
     // On Linux ext4 FileManager's inode caching system does not
     // provide us correct behaviour for ModuleCache directories.
     // inode can be reused after PCM delete resulting in cache misleading.
-    File = FileMgr.getBypassFile(*File);
+    // Only use the bypass file if bypass succeed in case the underlying file
+    // system doesn't support bypass (thus there is no need for the workaround).
+    if (auto Bypass = FileMgr.getBypassFile(*File))
+      File = *Bypass;
   }
 #endif
 

clang/test/Modules/explicit-build-relpath.cpp

@@ -1,3 +1,6 @@
+/// Due to module bypass workaround in https://reviews.llvm.org/D97850 for ext4 FS, relative and absolute path do not match after bypass.
+// REQUIRES: system-darwin
+
 // RUN: rm -rf %t
 // RUN: mkdir %t
 // RUN: cd %t