[clang][ThinLTO] Promote cc1 -fthin_link_bitcode to driver -fthinlto_link_bitcode

[ychen]

Summary

A necessary step to let build system caching work for its output.
I renamed it to match existing driver options for ThinLTO. Let me know if you
prefer keeping the name.

[tejohnson]

Thanks. Prefer the old name since it is already in use and since this is for the "thin link" phase.

[ychen]

Address reviewer's comments.

[steven_wu]

LGTM.

clang/include/clang/Driver/CC1Options.td

def fprofile_instrument_use_path_EQ :
     Joined<["-"], "fprofile-instrument-use-path=">,
     HelpText<"Specify the profile path in PGO use compilation">;
 def flto_visibility_public_std:
     Flag<["-"], "flto-visibility-public-std">,
     HelpText<"Use public LTO visibility for classes in std and stdext namespaces">;
 def flto_unit: Flag<["-"], "flto-unit">,
     HelpText<"Emit IR to support LTO unit features (CFI, whole program vtable opt)">;
 def fno_lto_unit: Flag<["-"], "fno-lto-unit">;
-def fthin_link_bitcode_EQ : Joined<["-"], "fthin-link-bitcode=">,
-    HelpText<"Write minimized bitcode to <file> for the ThinLTO thin link only">;
 def femit_debug_entry_values : Flag<["-"], "femit-debug-entry-values">,
     HelpText<"Enables debug info about call site parameter's entry values">;
 def fdebug_pass_manager : Flag<["-"], "fdebug-pass-manager">,
     HelpText<"Prints debug information for the new pass manager">;
 def fno_debug_pass_manager : Flag<["-"], "fno-debug-pass-manager">,
     HelpText<"Disables debug printing for the new pass manager">;
 // The driver option takes the key as a parameter to the -msign-return-address=
 // and -mbranch-protection= options, but CC1 has a separate option so we

clang/include/clang/Driver/Options.td

 def flto_jobs_EQ : Joined<["-"], "flto-jobs=">,
   Flags<[CC1Option]>, Group<f_Group>,
   HelpText<"Controls the backend parallelism of -flto=thin (default "
            "of 0 means the number of threads will be derived from "
            "the number of CPUs detected)">;
 def fthinlto_index_EQ : Joined<["-"], "fthinlto-index=">,
   Flags<[CoreOption, CC1Option]>, Group<f_Group>,
   HelpText<"Perform ThinLTO importing using provided function summary index">;
+def fthin_link_bitcode_EQ : Joined<["-"], "fthin-link-bitcode=">,
+  Flags<[CoreOption, CC1Option]>, Group<f_Group>,
+  HelpText<"Write minimized bitcode to <file> for the ThinLTO thin link only">;
 def fmacro_backtrace_limit_EQ : Joined<["-"], "fmacro-backtrace-limit=">,
                                 Group<f_Group>, Flags<[DriverOption, CoreOption]>;
 def fmerge_all_constants : Flag<["-"], "fmerge-all-constants">, Group<f_Group>,
   Flags<[CC1Option, CoreOption]>, HelpText<"Allow merging of constants">;
 def fmessage_length_EQ : Joined<["-"], "fmessage-length=">, Group<f_Group>;
 def fms_extensions : Flag<["-"], "fms-extensions">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,
   HelpText<"Accept some non-standard constructs supported by the Microsoft compiler">;
 def fms_compatibility : Flag<["-"], "fms-compatibility">, Group<f_Group>, Flags<[CC1Option, CoreOption]>,

clang/lib/Driver/ToolChains/Clang.cpp

void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   }
 
   if (const Arg *A = Args.getLastArg(options::OPT_fthinlto_index_EQ)) {
     if (!types::isLLVMIR(Input.getType()))
       D.Diag(diag::err_drv_arg_requires_bitcode_input) << A->getAsString(Args);
     Args.AddLastArg(CmdArgs, options::OPT_fthinlto_index_EQ);
   }
 
+  if (Args.getLastArg(options::OPT_fthin_link_bitcode_EQ))
+    Args.AddLastArg(CmdArgs, options::OPT_fthin_link_bitcode_EQ);
+
   if (Args.getLastArg(options::OPT_save_temps_EQ))
     Args.AddLastArg(CmdArgs, options::OPT_save_temps_EQ);
 
   // Embed-bitcode option.
   // Only white-listed flags below are allowed to be embedded.
   if (C.getDriver().embedBitcodeInObject() && !C.getDriver().isUsingLTO() &&
       (isa<BackendJobAction>(JA) || isa<AssembleJobAction>(JA))) {
     // Add flags implied by -fembed-bitcode.

clang/test/CodeGen/thin_link_bitcode.c

 // REQUIRES: x86-registered-target
 //
+// RUN: %clang -flto=thin -fthin-link-bitcode=%t.bc -target x86_64-unknown-linux-gnu -### %s 2>&1 | FileCheck %s --check-prefix=LINKBC
+//
 // RUN: %clang_cc1 -o %t -flto=thin -fthin-link-bitcode=%t.nodebug -triple x86_64-unknown-linux-gnu -emit-llvm-bc -debug-info-kind=limited %s
 // RUN: llvm-bcanalyzer -dump %t | FileCheck %s
 // RUN: llvm-bcanalyzer -dump %t.nodebug | FileCheck %s --check-prefix=NO_DEBUG
 // RUN: %clang_cc1 -o %t.newpm -flto=thin -fexperimental-new-pass-manager -fthin-link-bitcode=%t.newpm.nodebug -triple x86_64-unknown-linux-gnu -emit-llvm-bc -debug-info-kind=limited  %s
 // RUN: llvm-bcanalyzer -dump %t.newpm | FileCheck %s
 // RUN: llvm-bcanalyzer -dump %t.newpm.nodebug | FileCheck %s --check-prefix=NO_DEBUG
 int main (void) {
   return 0;
 }
 
+// LINKBC: -fthin-link-bitcode=
+
 // CHECK: COMPILE_UNIT
 // NO_DEBUG-NOT: COMPILE_UNIT