[clang] [llvm] [SystemZ][z/OS] Refactor AutoConvert.h to remove large MVS guard (PR #143174)

[Sean Perry via llvm-commits]

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@@ -5199,13 +5199,13 @@ static void flush_atexit(void) {
 int main(int argc, const char **argv) {
   thread_info client_data;
 
-#ifdef __MVS__
+  // On z/OS we need to enable auto conversion
   if (enablezOSAutoConversion(fileno(stdout)) == -1)
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perry-ca wrote:

I suggest defining `enableAutoConversion()` as an inline function in AutoConvert.h that always returns true for non z/OS platforms and for z/OS it calls this function.  That will allow us to:
- not add unneeded function calls in the final code.
- keep the AutoConvert.cpp strictly for z/OS.
This would go for all functions in AutoConvert.h.

https://github.com/llvm/llvm-project/pull/143174