[llvm] [SystemZ][z/OS] Preserve filetag when rewriting files (PR #181733)

[Abhina Sree via llvm-commits]

https://github.com/abhina-sree updated https://github.com/llvm/llvm-project/pull/181733

>From 992ebb61b05fd3721fc8cfa4e6243dbe591a9dea Mon Sep 17 00:00:00 2001
From: Abhina Sreeskantharajan <Abhina.Sreeskantharajan at ibm.com>
Date: Mon, 16 Feb 2026 10:47:14 -0500
Subject: [PATCH 1/3] copy file tag attributes on z/OS

---
 llvm/include/llvm/Support/AutoConvert.h | 10 ++++++++++
 llvm/lib/Support/AutoConvert.cpp        | 10 ++++++++++
 llvm/lib/Support/raw_ostream.cpp        |  8 ++++++++
 3 files changed, 28 insertions(+)

diff --git a/llvm/include/llvm/Support/AutoConvert.h b/llvm/include/llvm/Support/AutoConvert.h
index 15f1ec8af6c57..70b617178cb05 100644
--- a/llvm/include/llvm/Support/AutoConvert.h
+++ b/llvm/include/llvm/Support/AutoConvert.h
@@ -55,6 +55,16 @@ ErrorOr<__ccsid_t> getzOSFileTag(const Twine &FileName, const int FD = -1);
  */
 ErrorOr<bool> needzOSConversion(const Twine &FileName, const int FD = -1);
 
+/** Copy the tag attributes from \a source to \a destination.
+ *
+ * @param Source The name of the source file.
+ * @param Destination The file descriptor of the destination file.
+ * @returns errc::success if the tag attributes were copied successfully,
+ *          otherwise returns a specific error_code.
+ */
+std::error_code copyFileTagAttributes(const std::string &Source,
+                                      const int Destination);
+
 #endif /* __MVS__*/
 
 inline std::error_code disableAutoConversion(int FD) {
diff --git a/llvm/lib/Support/AutoConvert.cpp b/llvm/lib/Support/AutoConvert.cpp
index 741bb7bd2c5b0..03517815be3a3 100644
--- a/llvm/lib/Support/AutoConvert.cpp
+++ b/llvm/lib/Support/AutoConvert.cpp
@@ -132,4 +132,14 @@ ErrorOr<bool> llvm::needzOSConversion(const Twine &FileName, const int FD) {
   }
 }
 
+std::error_code llvm::copyFileTagAttributes(const std::string &Source,
+                                            const int Destination) {
+  struct stat SourceAttributes;
+  if (stat(Source.c_str(), &SourceAttributes) == -1)
+    return std::error_code(errno, std::generic_category());
+
+  return setzOSFileTag(Destination, SourceAttributes.st_tag.ft_ccsid,
+                       SourceAttributes.st_tag.ft_txtflag);
+}
+
 #endif //__MVS__
diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index fe07aed335f7e..2b856383e50fc 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -1025,6 +1025,14 @@ Error llvm::writeToOutput(StringRef OutputFileName,
 
   raw_fd_ostream Out(Temp->FD, false);
 
+#if defined(__MVS__)
+  if (auto EC = llvm::copyFileTagAttributes(OutputFileName.str(), Temp->FD)) {
+    if (EC != std::errc::no_such_file_or_directory)
+      llvm::errs() << "Failed to preserve file tag attributes for "
+                   << OutputFileName << "\n";
+  }
+#endif
+
   if (Error E = Write(Out)) {
     if (Error DiscardError = Temp->discard())
       return joinErrors(std::move(E), std::move(DiscardError));

>From aeeb290173e3c6fd502403f366a4282b18e42c92 Mon Sep 17 00:00:00 2001
From: Abhina Sreeskantharajan <Abhina.Sreeskantharajan at ibm.com>
Date: Wed, 18 Feb 2026 14:04:46 -0500
Subject: [PATCH 2/3] address comments

---
 llvm/include/llvm/Support/AutoConvert.h | 2 +-
 llvm/lib/Support/AutoConvert.cpp        | 4 ++--
 llvm/lib/Support/raw_ostream.cpp        | 3 +--
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/llvm/include/llvm/Support/AutoConvert.h b/llvm/include/llvm/Support/AutoConvert.h
index 70b617178cb05..d68b0e8b515e0 100644
--- a/llvm/include/llvm/Support/AutoConvert.h
+++ b/llvm/include/llvm/Support/AutoConvert.h
@@ -63,7 +63,7 @@ ErrorOr<bool> needzOSConversion(const Twine &FileName, const int FD = -1);
  *          otherwise returns a specific error_code.
  */
 std::error_code copyFileTagAttributes(const std::string &Source,
-                                      const int Destination);
+                                      const int DestinationFD);
 
 #endif /* __MVS__*/
 
diff --git a/llvm/lib/Support/AutoConvert.cpp b/llvm/lib/Support/AutoConvert.cpp
index 03517815be3a3..d7b33b1c36d04 100644
--- a/llvm/lib/Support/AutoConvert.cpp
+++ b/llvm/lib/Support/AutoConvert.cpp
@@ -133,12 +133,12 @@ ErrorOr<bool> llvm::needzOSConversion(const Twine &FileName, const int FD) {
 }
 
 std::error_code llvm::copyFileTagAttributes(const std::string &Source,
-                                            const int Destination) {
+                                            const int DestinationFD) {
   struct stat SourceAttributes;
   if (stat(Source.c_str(), &SourceAttributes) == -1)
     return std::error_code(errno, std::generic_category());
 
-  return setzOSFileTag(Destination, SourceAttributes.st_tag.ft_ccsid,
+  return setzOSFileTag(DestinationFD, SourceAttributes.st_tag.ft_ccsid,
                        SourceAttributes.st_tag.ft_txtflag);
 }
 
diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index 2b856383e50fc..9b590dbc2ae27 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -1028,8 +1028,7 @@ Error llvm::writeToOutput(StringRef OutputFileName,
 #if defined(__MVS__)
   if (auto EC = llvm::copyFileTagAttributes(OutputFileName.str(), Temp->FD)) {
     if (EC != std::errc::no_such_file_or_directory)
-      llvm::errs() << "Failed to preserve file tag attributes for "
-                   << OutputFileName << "\n";
+      return createFileError(OutputFileName, EC);
   }
 #endif
 

>From c4abaf7c3c2ee89147a77707dd7ee779c4312f4d Mon Sep 17 00:00:00 2001
From: Abhina Sreeskantharajan <Abhina.Sreeskantharajan at ibm.com>
Date: Thu, 19 Feb 2026 14:12:59 -0500
Subject: [PATCH 3/3] add workaround for file systems that do not support
 tagging

---
 llvm/lib/Support/AutoConvert.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Support/AutoConvert.cpp b/llvm/lib/Support/AutoConvert.cpp
index d7b33b1c36d04..852d16aa181fb 100644
--- a/llvm/lib/Support/AutoConvert.cpp
+++ b/llvm/lib/Support/AutoConvert.cpp
@@ -91,8 +91,14 @@ std::error_code llvm::setzOSFileTag(int FD, int CCSID, bool Text) {
   Tag.ft_deferred = 0;
   Tag.ft_rsvflags = 0;
 
-  if (fcntl(FD, F_SETTAG, &Tag) == -1)
-    return errnoAsErrorCode();
+  if (fcntl(FD, F_SETTAG, &Tag) == -1) {
+    if (errno == ENOSYS)
+      // This is a workaround for file systems that do not support filetags.
+      // Ignore ENOSYS error to allow compilation.
+      errno = 0;
+    else
+      return errnoAsErrorCode();
+  }
   return std::error_code();
 }