[Driver] Pass -f[no-]emulated-tls and set up ExplicitEmulatedTLS

[chh]

Summary

Since LLVM r326341, default EmulatedTLS mode is decided in backend according to target triple. Any front-end should pass -f[no]-emulated-tls to backend and set up ExplicitEmulatedTLS only when the flags are used.

[chh]

I will upload a different fix soon.
We should set ExplicitEmulatedTLS only when -f[no-]emulated-tls flag is found at command line.
Any front-end should only pass the flag and let backend decide the default based on target.

[mstorsjo]

Ok, thanks. Yes, this should probably only set it if some of those flags are set here.

FWIW, clang also has got a list of targets where emulated TLS is enabled by default - could this be omitted somehow, now that LLVM can handle that on its own?

[mstorsjo]

LGTM (although I didn't test run it).

[chh]

Martin, thanks for finding this problem.
Please review/accept my new change if it passes your tests.
After this and D42999, the default emulated TLS mode should only be decided in
llvm/trunk/include/llvm/ADT/Triple.h hasDefaultEmulatedTLS().

[mstorsjo]

Tested on the case that was broken before, and seems to work fine. Thanks!

include/clang/Driver/Options.td

 def fno_elide_type : Flag<["-"], "fno-elide-type">, Group<f_Group>,
     Flags<[CC1Option]>,
     HelpText<"Do not elide types when printing diagnostics">;
 def feliminate_unused_debug_symbols : Flag<["-"], "feliminate-unused-debug-symbols">, Group<f_Group>;
 def femit_all_decls : Flag<["-"], "femit-all-decls">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Emit all declarations, even if unused">;
 def femulated_tls : Flag<["-"], "femulated-tls">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Use emutls functions to access thread_local variables">;
-def fno_emulated_tls : Flag<["-"], "fno-emulated-tls">, Group<f_Group>;
+def fno_emulated_tls : Flag<["-"], "fno-emulated-tls">, Group<f_Group>, Flags<[CC1Option]>;
 def fencoding_EQ : Joined<["-"], "fencoding=">, Group<f_Group>;
 def ferror_limit_EQ : Joined<["-"], "ferror-limit=">, Group<f_Group>, Flags<[CoreOption]>;
 def fexceptions : Flag<["-"], "fexceptions">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Enable support for exception handling">;
 def fdwarf_exceptions : Flag<["-"], "fdwarf-exceptions">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Use DWARF style exceptions">;
 def fsjlj_exceptions : Flag<["-"], "fsjlj-exceptions">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Use SjLj style exceptions">;

include/clang/Frontend/CodeGenOptions.def

 CODEGENOPT(DisableTailCalls  , 1, 0) ///< Do not emit tail calls.
 CODEGENOPT(EmitDeclMetadata  , 1, 0) ///< Emit special metadata indicating what
                                      ///< Decl* various IR entities came from.
                                      ///< Only useful when running CodeGen as a
                                      ///< subroutine.
 CODEGENOPT(EmitGcovArcs      , 1, 0) ///< Emit coverage data files, aka. GCDA.
 CODEGENOPT(EmitGcovNotes     , 1, 0) ///< Emit coverage "notes" files, aka GCNO.
 CODEGENOPT(EmitOpenCLArgMetadata , 1, 0) ///< Emit OpenCL kernel arg metadata.
-CODEGENOPT(EmulatedTLS       , 1, 0) ///< Set when -femulated-tls is enabled.
+CODEGENOPT(EmulatedTLS       , 1, 0) ///< Set by default or -f[no-]emulated-tls.
+CODEGENOPT(ExplicitEmulatedTLS , 1, 0) ///< Set if -f[no-]emulated-tls is used.
 /// \brief Embed Bitcode mode (off/all/bitcode/marker).
 ENUM_CODEGENOPT(EmbedBitcode, EmbedBitcodeKind, 2, Embed_Off)
 CODEGENOPT(ForbidGuardVariables , 1, 0) ///< Issue errors if C++ guard variables
                                         ///< are required.
 CODEGENOPT(FunctionSections  , 1, 0) ///< Set when -ffunction-sections is enabled.
 CODEGENOPT(InstrumentFunctions , 1, 0) ///< Set when -finstrument-functions is
                                        ///< enabled.
 CODEGENOPT(InstrumentFunctionsAfterInlining , 1, 0) ///< Set when

lib/CodeGen/BackendUtil.cpp

static void initTargetOptions(llvm::TargetOptions &Options,
   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
   Options.FunctionSections = CodeGenOpts.FunctionSections;
   Options.DataSections = CodeGenOpts.DataSections;
   Options.UniqueSectionNames = CodeGenOpts.UniqueSectionNames;
   Options.EmulatedTLS = CodeGenOpts.EmulatedTLS;
+  Options.ExplicitEmulatedTLS = CodeGenOpts.ExplicitEmulatedTLS;
   Options.DebuggerTuning = CodeGenOpts.getDebuggerTuning();
   Options.EmitStackSizeSection = CodeGenOpts.StackSizeSection;
 
   if (CodeGenOpts.EnableSplitDwarf)
     Options.MCOptions.SplitDwarfFile = CodeGenOpts.SplitDwarfFile;
   Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;

lib/Driver/ToolChains/Clang.cpp

#endif
   Args.AddLastArg(CmdArgs, options::OPT_fvisibility_inlines_hidden);
 
   Args.AddLastArg(CmdArgs, options::OPT_ftlsmodel_EQ);
 
   // Forward -f (flag) options which we can pass directly.
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);
   Args.AddLastArg(CmdArgs, options::OPT_fno_operator_names);
-  // Emulated TLS is enabled by default on Android and OpenBSD, and can be enabled
-  // manually with -femulated-tls.
-  bool EmulatedTLSDefault = Triple.isAndroid() || Triple.isOSOpenBSD() ||
-                            Triple.isWindowsCygwinEnvironment();
-  if (Args.hasFlag(options::OPT_femulated_tls, options::OPT_fno_emulated_tls,
-                   EmulatedTLSDefault))
-    CmdArgs.push_back("-femulated-tls");
+  Args.AddLastArg(CmdArgs, options::OPT_femulated_tls,
+                  options::OPT_fno_emulated_tls);
+
   // AltiVec-like language extensions aren't relevant for assembling.
   if (!isa<PreprocessJobAction>(JA) || Output.getType() != types::TY_PP_Asm)
     Args.AddLastArg(CmdArgs, options::OPT_fzvector);
 
   Args.AddLastArg(CmdArgs, options::OPT_fdiagnostics_show_template_tree);
   Args.AddLastArg(CmdArgs, options::OPT_fno_elide_type);
 
   // Forward flags for OpenMP. We don't do this if the current action is an

lib/Frontend/CompilerInvocation.cpp

if (Method == ~0U) {
       Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Name;
       Success = false;
     } else {
       Opts.setObjCDispatchMethod(
         static_cast<CodeGenOptions::ObjCDispatchMethodKind>(Method));
     }
   }
 
+  if (Args.getLastArg(OPT_femulated_tls) ||
+      Args.getLastArg(OPT_fno_emulated_tls)) {
+    Opts.ExplicitEmulatedTLS = true;
     Opts.EmulatedTLS =
         Args.hasFlag(OPT_femulated_tls, OPT_fno_emulated_tls, false);
+  }
 
   if (Arg *A = Args.getLastArg(OPT_ftlsmodel_EQ)) {
     StringRef Name = A->getValue();
     unsigned Model = llvm::StringSwitch<unsigned>(Name)
         .Case("global-dynamic", CodeGenOptions::GeneralDynamicTLSModel)
         .Case("local-dynamic", CodeGenOptions::LocalDynamicTLSModel)
         .Case("initial-exec", CodeGenOptions::InitialExecTLSModel)
         .Case("local-exec", CodeGenOptions::LocalExecTLSModel)

test/Driver/emulated-tls.cpp

-// Cygwin and OpenBSD use emutls. Clang should pass -femulated-tls to cc1
-// and cc1 should pass EmulatedTLS to LLVM CodeGen.
-// FIXME: Add more targets here to use emutls.
-// RUN: %clang -### -std=c++11 -target i686-pc-cygwin %s 2>&1 | FileCheck %s
-// RUN: %clang -### -std=c++11 -target i686-pc-openbsd %s 2>&1 | FileCheck %s
+// Android, Cygwin and OpenBSD use emutls by default.
+// Clang should pass -femulated-tls or -fno-emulated-tls to cc1 if they are used,
+// and cc1 should set up EmulatedTLS and ExplicitEmulatedTLS to LLVM CodeGen.
+//
+// RUN: %clang -### -target arm-linux-androideabi %s 2>&1 \
+// RUN: | FileCheck -check-prefix=DEFAULT %s
+// RUN: %clang -### -target arm-linux-gnu %s 2>&1 \
+// RUN: | FileCheck -check-prefix=DEFAULT %s
+// RUN: %clang -### -target i686-pc-cygwin %s 2>&1 \
+// RUN: | FileCheck -check-prefix=DEFAULT %s
+// RUN: %clang -### -target i686-pc-openbsd %s 2>&1 \
+// RUN: | FileCheck -check-prefix=DEFAULT %s
 
-// CHECK: "-cc1" {{.*}}"-femulated-tls"
+// RUN: %clang -### -target arm-linux-androideabi -fno-emulated-tls -femulated-tls %s 2>&1 \
+// RUN: | FileCheck -check-prefix=EMU %s
+// RUN: %clang -### -target arm-linux-gnu %s -fno-emulated-tls -femulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=EMU %s
+// RUN: %clang -### -target i686-pc-cygwin %s -fno-emulated-tls -femulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=EMU %s
+// RUN: %clang -### -target i686-pc-openbsd %s -fno-emulated-tls -femulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=EMU %s
+
+// RUN: %clang -### -target arm-linux-androideabi -femulated-tls -fno-emulated-tls %s 2>&1 \
+// RUN: | FileCheck -check-prefix=NOEMU %s
+// RUN: %clang -### -target arm-linux-gnu %s -femulated-tls -fno-emulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=NOEMU %s
+// RUN: %clang -### -target i686-pc-cygwin %s -femulated-tls -fno-emulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=NOEMU %s
+// RUN: %clang -### -target i686-pc-openbsd %s -femulated-tls -fno-emulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=NOEMU %s
+
+
+// Default without -f[no-]emulated-tls, will be decided by the target triple.
+// DEFAULT-NOT: "-cc1" {{.*}}"-femulated-tls"
+// DEFAULT-NOT: "-cc1" {{.*}}"-fno-emulated-tls"
+
+// Explicit and last -f[no-]emulated-tls flag will be passed to cc1.
+// EMU: "-cc1" {{.*}}"-femulated-tls"
+// EMU-NOT: "-cc1" {{.*}}"-fno-emulated-tls"
+
+// NOEMU: "-cc1" {{.*}}"-fno-emulated-tls"
+// NOEMU-NOT: "-cc1" {{.*}}"-femulated-tls"