[AIX] Revert #pragma mc_func check (#102919)

#99888 added a specific
diagnostic for `#pragma mc_func` on AIX. There are some disagreements
on:

1. If the check should be on by default. Leaving the check off by
default is dangerous, since it is difficult to be aware of such a check.
Turning it on by default at the moment causes build failures on AIX. See
#101336 for more details.
2. If the check can be made more general. See
#101336 (comment).

This PR reverts this check from `main` so we can flush out these
disagreements.

Author: qiongsiwu

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1260,9 +1260,6 @@ def warn_pragma_intrinsic_builtin : Warning<
 def warn_pragma_unused_expected_var : Warning<
   "expected '#pragma unused' argument to be a variable name">,
   InGroup<IgnoredPragmas>;
-// - #pragma mc_func
-def err_pragma_mc_func_not_supported :
-   Error<"#pragma mc_func is not supported">;
 // - #pragma init_seg
 def warn_pragma_init_seg_unsupported_target : Warning<
   "'#pragma init_seg' is only supported when targeting a "

clang/include/clang/Driver/Options.td

@@ -8114,13 +8114,6 @@ def source_date_epoch : Separate<["-"], "source-date-epoch">,
 
 } // let Visibility = [CC1Option]
 
-defm err_pragma_mc_func_aix : BoolFOption<"err-pragma-mc-func-aix",
-  PreprocessorOpts<"ErrorOnPragmaMcfuncOnAIX">, DefaultFalse,
-  PosFlag<SetTrue, [], [ClangOption, CC1Option],
-          "Treat uses of #pragma mc_func as errors">,
-  NegFlag<SetFalse,[], [ClangOption, CC1Option],
-          "Ignore uses of #pragma mc_func">>;
-
 //===----------------------------------------------------------------------===//
 // CUDA Options
 //===----------------------------------------------------------------------===//

clang/include/clang/Lex/PreprocessorOptions.h

@@ -211,10 +211,6 @@ class PreprocessorOptions {
   /// If set, the UNIX timestamp specified by SOURCE_DATE_EPOCH.
   std::optional<uint64_t> SourceDateEpoch;
 
-  /// If set, the preprocessor reports an error when processing #pragma mc_func
-  /// on AIX.
-  bool ErrorOnPragmaMcfuncOnAIX = false;
-
 public:
   PreprocessorOptions() : PrecompiledPreambleBytes(0, false) {}
 
@@ -252,7 +248,6 @@ class PreprocessorOptions {
     PrecompiledPreambleBytes.first = 0;
     PrecompiledPreambleBytes.second = false;
     RetainExcludedConditionalBlocks = false;
-    ErrorOnPragmaMcfuncOnAIX = false;
   }
 };
 

clang/include/clang/Parse/Parser.h

@@ -221,7 +221,6 @@ class Parser : public CodeCompletionHandler {
   std::unique_ptr<PragmaHandler> MaxTokensHerePragmaHandler;
   std::unique_ptr<PragmaHandler> MaxTokensTotalPragmaHandler;
   std::unique_ptr<PragmaHandler> RISCVPragmaHandler;
-  std::unique_ptr<PragmaHandler> MCFuncPragmaHandler;
 
   std::unique_ptr<CommentHandler> CommentSemaHandler;
 

clang/lib/Driver/ToolChains/AIX.cpp

@@ -560,12 +560,6 @@ void AIX::addClangTargetOptions(
   if (!Args.getLastArgNoClaim(options::OPT_fsized_deallocation,
                               options::OPT_fno_sized_deallocation))
     CC1Args.push_back("-fno-sized-deallocation");
-
-  if (Args.hasFlag(options::OPT_ferr_pragma_mc_func_aix,
-                   options::OPT_fno_err_pragma_mc_func_aix, false))
-    CC1Args.push_back("-ferr-pragma-mc-func-aix");
-  else
-    CC1Args.push_back("-fno-err-pragma-mc-func-aix");
 }
 
 void AIX::addProfileRTLibs(const llvm::opt::ArgList &Args,

clang/lib/Parse/ParsePragma.cpp

@@ -14,7 +14,6 @@
 #include "clang/Basic/PragmaKinds.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Lex/Preprocessor.h"
-#include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Lex/Token.h"
 #include "clang/Parse/LoopHint.h"
 #include "clang/Parse/ParseDiagnostic.h"
@@ -412,19 +411,6 @@ struct PragmaRISCVHandler : public PragmaHandler {
   Sema &Actions;
 };
 
-struct PragmaMCFuncHandler : public PragmaHandler {
-  PragmaMCFuncHandler(bool ReportError)
-      : PragmaHandler("mc_func"), ReportError(ReportError) {}
-  void HandlePragma(Preprocessor &PP, PragmaIntroducer Introducer,
-                    Token &Tok) override {
-    if (ReportError)
-      PP.Diag(Tok, diag::err_pragma_mc_func_not_supported);
-  }
-
-private:
-  bool ReportError = false;
-};
-
 void markAsReinjectedForRelexing(llvm::MutableArrayRef<clang::Token> Toks) {
   for (auto &T : Toks)
     T.setFlag(clang::Token::IsReinjected);
@@ -582,12 +568,6 @@ void Parser::initializePragmaHandlers() {
     RISCVPragmaHandler = std::make_unique<PragmaRISCVHandler>(Actions);
     PP.AddPragmaHandler("clang", RISCVPragmaHandler.get());
   }
-
-  if (getTargetInfo().getTriple().isOSAIX()) {
-    MCFuncPragmaHandler = std::make_unique<PragmaMCFuncHandler>(
-        PP.getPreprocessorOpts().ErrorOnPragmaMcfuncOnAIX);
-    PP.AddPragmaHandler(MCFuncPragmaHandler.get());
-  }
 }
 
 void Parser::resetPragmaHandlers() {
@@ -722,11 +702,6 @@ void Parser::resetPragmaHandlers() {
     PP.RemovePragmaHandler("clang", RISCVPragmaHandler.get());
     RISCVPragmaHandler.reset();
   }
-
-  if (getTargetInfo().getTriple().isOSAIX()) {
-    PP.RemovePragmaHandler(MCFuncPragmaHandler.get());
-    MCFuncPragmaHandler.reset();
-  }
 }
 
 /// Handle the annotation token produced for #pragma unused(...)