[clang] [llvm] [SystemZ][z/OS] Update autoconversion functions to improve support for UTF-8 (PR #98652)

[Abhina Sree via cfe-commits]

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@@ -617,6 +625,23 @@ FileID SourceManager::createFileIDImpl(ContentCache &File, StringRef Filename,
     return FileID::get(LoadedID);
   }
   unsigned FileSize = File.getSize();
+#ifdef __MVS__
+  llvm::ErrorOr<bool> NeedConversion =
+      llvm::needzOSConversion(Filename.str().c_str());
+  if (NeedConversion && *NeedConversion) {
+    // Buffer size may increase due to potential z/OS EBCDIC to UTF-8
+    // conversion.
+    if (std::optional<llvm::MemoryBufferRef> Buffer =
+            File.getBufferOrNone(Diag, getFileManager())) {
+      unsigned BufSize = Buffer->getBufferSize();
+      if (BufSize > FileSize) {
+        if (File.ContentsEntry.has_value())
+          File.ContentsEntry->getFileEntry().setSize(BufSize);
+        FileSize = BufSize;
+      }
+    }
+  }
+#endif
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abhina-sree wrote:

I did a small bit of refactoring based on Sean's comments to reduce the number of ifdefs now, thanks!

https://github.com/llvm/llvm-project/pull/98652