[clang][driver] Emit error when enabling emulated tls on unsupported architectures

[paulkirth]

Summary

LLVM does not support Emulated TLS for some architectures, like RISCV.
This patch issues an error during options parsing to avoid potential
problems during codegen.

Bug: https://github.com/llvm/llvm-project/issues/59500

Depends on D143619

[MaskRay]

clang/lib/Driver/ToolChains/Clang.cpp

6169

Use render and remove the previous Args.AddLastArg(CmdArgs, options::OPT_femulated_tls, options::OPT_fno_emulated_tls);

clang/test/Driver/emulated-tls.cpp

32

--target= for new tests

49

delete trailing blank line

[paulkirth]

Address comments.

• use render and remove redundant/incorrect call to AddLastArg.
• add test to make sure we don't issue an error when emulated TLS is disabled on unsupported platforms

[hiraditya]

LGTM, thanks for putting this patch.

[paulkirth]

Rebase on parent revision

[MaskRay]

With nits

clang/test/Driver/emulated-tls.cpp

49

Prepend error:

For the NOT pattern, use RISCV-NOT: error: or change FileCheck to FileCheck --implicit-check-not=error:

[paulkirth]

Address comments.

• improve FileCheck directive in test

[paulkirth]

Based on discussion at the LLVM RISC-V community call, we're going to support emulated TLS in RISC-V, so we can abandon this patch.

clang/lib/Driver/ToolChains/Clang.cpp

   if (Args.hasFlag(options::OPT_fno_operator_names,
                    options::OPT_foperator_names, false))
     CmdArgs.push_back("-fno-operator-names");
 
   // 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_fdigraphs, options::OPT_fno_digraphs);
-  Args.AddLastArg(CmdArgs, options::OPT_femulated_tls,
-                  options::OPT_fno_emulated_tls);
+
+  if (Arg *A = Args.getLastArg(options::OPT_femulated_tls,
+                               options::OPT_fno_emulated_tls)) {
+    // LLVM does not support Emulated TLS for some architectures, like RISCV
+    // So issue an error to avoid subtle problems in codegen if the flags are
+    // incompatible. see https://github.com/llvm/llvm-project/issues/59500
+    if (!Triple.supportsEmulatedTLS() &&
+        A->getOption().getID() == options::OPT_femulated_tls)
+      D.Diag(diag::err_drv_unsupported_opt_for_target)
+          << A->getAsString(Args) << TripleStr;
+    A->render(Args, CmdArgs);
+  }
+
   Args.AddLastArg(CmdArgs, options::OPT_fzero_call_used_regs_EQ);
 
   if (Arg *A = Args.getLastArg(options::OPT_fzero_call_used_regs_EQ)) {
     // FIXME: There's no reason for this to be restricted to X86. The backend
     // code needs to be changed to include the appropriate function calls
     // automatically.
     if (!Triple.isX86() && !Triple.isAArch64())
       D.Diag(diag::err_drv_unsupported_opt_for_target)

clang/test/Driver/emulated-tls.cpp

 // 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
 
+// RUN: %clang -### --target=riscv64-linux-android %s -fno-emulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=RISCV %s
+// RUN: %clang -### --target=riscv64-linux-android %s -fno-emulated-tls -femulated-tls 2>&1 \
+// RUN: | FileCheck -check-prefix=RISCV-ERROR %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"
+
+// RISCV-NOT: error: unsupported option '-fno-emulated-tls' for target 'riscv64-unknown-linux-android'
+// RISCV-ERROR: error: unsupported option '-femulated-tls' for target 'riscv64-unknown-linux-android'