[Support] Prevent loss of file type flags when creating temporary (#167939)

Non-binary output files from the compiler need the `OF_Text` flag set
for encoding conversion to be performed correctly on z/OS.

---------

Co-authored-by: Tony Tao <[email protected]>

Author: tltao

clang/test/CodeGen/SystemZ/encoding.c

@@ -0,0 +1,9 @@
+// Checks encoding of output file
+// This is only required for z/OS.
+//
+// REQUIRES: system-zos, systemz-registered-target
+// RUN: %clang_cc1 -triple s390x-ibm-zos -S %s -o %t.s
+// RUN: ls -T %t.s | FileCheck %s
+
+// CHECK: t IBM-1047    T=on
+void foo() { return; }

llvm/lib/Support/VirtualOutputBackends.cpp

@@ -254,6 +254,20 @@ static Error createDirectoriesOnDemand(StringRef OutputPath,
   });
 }
 
+static sys::fs::OpenFlags generateFlagsFromConfig(OutputConfig Config) {
+  sys::fs::OpenFlags OF = sys::fs::OF_None;
+  if (Config.getTextWithCRLF())
+    OF |= sys::fs::OF_TextWithCRLF;
+  else if (Config.getText())
+    OF |= sys::fs::OF_Text;
+  // Don't pass OF_Append if writting to temporary since OF_Append is
+  // not Atomic Append
+  if (Config.getAppend() && !Config.getAtomicWrite())
+    OF |= sys::fs::OF_Append;
+
+  return OF;
+}
+
 Error OnDiskOutputFile::tryToCreateTemporary(std::optional<int> &FD) {
   // Create a temporary file.
   // Insert -%%%%%%%% before the extension (if any), and because some tools
@@ -269,8 +283,9 @@ Error OnDiskOutputFile::tryToCreateTemporary(std::optional<int> &FD) {
   return createDirectoriesOnDemand(OutputPath, Config, [&]() -> Error {
     int NewFD;
     SmallString<128> UniquePath;
+    sys::fs::OpenFlags OF = generateFlagsFromConfig(Config);
     if (std::error_code EC =
-            sys::fs::createUniqueFile(ModelPath, NewFD, UniquePath))
+            sys::fs::createUniqueFile(ModelPath, NewFD, UniquePath, OF))
       return make_error<TempFileOutputError>(ModelPath, OutputPath, EC);
 
     if (Config.getDiscardOnSignal())
@@ -312,13 +327,7 @@ Error OnDiskOutputFile::initializeFile(std::optional<int> &FD) {
   // Not using a temporary file. Open the final output file.
   return createDirectoriesOnDemand(OutputPath, Config, [&]() -> Error {
     int NewFD;
-    sys::fs::OpenFlags OF = sys::fs::OF_None;
-    if (Config.getTextWithCRLF())
-      OF |= sys::fs::OF_TextWithCRLF;
-    else if (Config.getText())
-      OF |= sys::fs::OF_Text;
-    if (Config.getAppend())
-      OF |= sys::fs::OF_Append;
+    sys::fs::OpenFlags OF = generateFlagsFromConfig(Config);
     if (std::error_code EC = sys::fs::openFileForWrite(
             OutputPath, NewFD, sys::fs::CD_CreateAlways, OF))
       return convertToOutputError(OutputPath, EC);