[clang] Explicitly set the EmulatedTLS codegen option. NFC.

Set the EmulatedTLS option based on `Triple::hasDefaultEmulatedTLS()`
if the user didn't specify it; set `ExplicitEmulatedTLS` to true
in `llvm::TargetOptions` and set `EmulatedTLS` to Clang's
opinion of what the default or preference is.

This avoids any risk of deviance between the two.

This affects one check of `getCodeGenOpts().EmulatedTLS` in
`shouldAssumeDSOLocal` in CodeGenModule, but as that check only
is done for `TT.isWindowsGNUEnvironment()`, and
`hasDefaultEmulatedTLS()` returns false for such environments
it doesn't make any current testable difference - thus NFC.

Some mingw distributions carry a downstream patch, that enables
emulated TLS by default for mingw targets in `hasDefaultEmulatedTLS()`
- and for such cases, this patch does make a difference and fixes the
detection of emulated TLS, if it is implicitly enabled.

Differential Revision: https://reviews.llvm.org/D132916

3 files changed, 6 insertions, 12 deletions

diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index ca2aa0d..9c1a23c 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -88,7 +88,6 @@ 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 by default or -f[no-]emulated-tls.
-CODEGENOPT(ExplicitEmulatedTLS , 1, 0) ///< Set if -f[no-]emulated-tls is used.
 /// Embed Bitcode mode (off/all/bitcode/marker).
 ENUM_CODEGENOPT(EmbedBitcode, EmbedBitcodeKind, 2, Embed_Off)
 /// Inline asm dialect, -masm=(att|intel)
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index f4a4f1c..aff277f 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -440,7 +440,7 @@ static bool initTargetOptions(DiagnosticsEngine &Diags,
       CodeGenOpts.UniqueBasicBlockSectionNames;
   Options.TLSSize = CodeGenOpts.TLSSize;
   Options.EmulatedTLS = CodeGenOpts.EmulatedTLS;
-  Options.ExplicitEmulatedTLS = CodeGenOpts.ExplicitEmulatedTLS;
+  Options.ExplicitEmulatedTLS = true;
   Options.DebuggerTuning = CodeGenOpts.getDebuggerTuning();
   Options.EmitStackSizeSection = CodeGenOpts.StackSizeSection;
   Options.StackUsageOutput = CodeGenOpts.StackUsageOutput;
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 9ac522a..201b996 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1492,13 +1492,8 @@ void CompilerInvocation::GenerateCodeGenArgs(
                 F.Filename, SA);
   }
 
-  // TODO: Consider removing marshalling annotations from f[no_]emulated_tls.
-  //  That would make it easy to generate the option only **once** if it was
-  //  explicitly set to non-default value.
-  if (Opts.ExplicitEmulatedTLS) {
-    GenerateArg(
-        Args, Opts.EmulatedTLS ? OPT_femulated_tls : OPT_fno_emulated_tls, SA);
-  }
+  GenerateArg(
+      Args, Opts.EmulatedTLS ? OPT_femulated_tls : OPT_fno_emulated_tls, SA);
 
   if (Opts.FPDenormalMode != llvm::DenormalMode::getIEEE())
     GenerateArg(Args, OPT_fdenormal_fp_math_EQ, Opts.FPDenormalMode.str(), SA);
@@ -1862,9 +1857,9 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
     Opts.LinkBitcodeFiles.push_back(F);
   }
 
-  if (Args.getLastArg(OPT_femulated_tls) ||
-      Args.getLastArg(OPT_fno_emulated_tls)) {
-    Opts.ExplicitEmulatedTLS = true;
+  if (!Args.getLastArg(OPT_femulated_tls) &&
+      !Args.getLastArg(OPT_fno_emulated_tls)) {
+    Opts.EmulatedTLS = T.hasDefaultEmulatedTLS();
   }
 
   if (Arg *A = Args.getLastArg(OPT_ftlsmodel_EQ)) {