[lld-macho] Implement -ignore_auto_link

[keith]

Summary

This option is really only useful for things like debugging
https://github.com/llvm/llvm-project/issues/56939, but there are some
actual uses of it in Swift's build system as well.

[int3]

lgtm

lld/MachO/Config.h

171

nit: would prefer to have this mirror the option name exactly, i.e. ignoreAutoLink

[keith]

Rename var to match option

lld/MachO/Config.h

struct Configuration {
   llvm::StringRef umbrella;
   uint32_t ltoo = 2;
   llvm::CachePruningPolicy thinLTOCachePolicy;
   llvm::StringRef thinLTOCacheDir;
   bool deadStripDylibs = false;
   bool demangle = false;
   bool deadStrip = false;
   bool errorForArchMismatch = false;
+  bool ignoreAutoLink = false;
   PlatformInfo platformInfo;
   llvm::Optional<PlatformInfo> secondaryPlatformInfo;
   NamespaceKind namespaceKind = NamespaceKind::twolevel;
   UndefinedSymbolTreatment undefinedSymbolTreatment =
       UndefinedSymbolTreatment::error;
   ICFLevel icfLevel = ICFLevel::none;
   ObjCStubsMode objcStubsMode = ObjCStubsMode::fast;
   llvm::MachO::HeaderFileType outputType;

lld/MachO/Driver.cpp

static void addFramework(StringRef name, bool isNeeded, bool isWeak,
   }
   error("framework not found for -framework " + name);
 }
 
 // Parses LC_LINKER_OPTION contents, which can add additional command line
 // flags. This directly parses the flags instead of using the standard argument
 // parser to improve performance.
 void macho::parseLCLinkerOption(InputFile *f, unsigned argc, StringRef data) {
+  if (config->ignoreAutoLink)
+    return;
+
   SmallVector<StringRef, 4> argv;
   size_t offset = 0;
   for (unsigned i = 0; i < argc && offset < data.size(); ++i) {
     argv.push_back(data.data() + offset);
     offset += strlen(data.data() + offset) + 1;
   }
   if (argv.size() != argc || offset > data.size())
     fatal(toString(f) + ": invalid LC_LINKER_OPTION");
config->warnDylibInstallName = args.hasFlag(
       OPT_warn_dylib_install_name, OPT_no_warn_dylib_install_name, false);
   config->ignoreOptimizationHints = args.hasArg(OPT_ignore_optimization_hints);
   config->callGraphProfileSort = args.hasFlag(
       OPT_call_graph_profile_sort, OPT_no_call_graph_profile_sort, true);
   config->printSymbolOrder = args.getLastArgValue(OPT_print_symbol_order_eq);
   config->forceExactCpuSubtypeMatch =
       getenv("LD_DYLIB_CPU_SUBTYPES_MUST_MATCH");
   config->objcStubsMode = getObjCStubsMode(args);
+  config->ignoreAutoLink = args.hasArg(OPT_ignore_auto_link);
 
   for (const Arg *arg : args.filtered(OPT_alias)) {
     config->aliasedSymbols.push_back(
         std::make_pair(arg->getValue(0), arg->getValue(1)));
   }
 
   // FIXME: Add a commandline flag for this too.
   config->zeroModTime = getenv("ZERO_AR_DATE");

lld/MachO/Options.td

def objc_stubs_fast : Flag<["-"], "objc_stubs_fast">,
     Group<grp_rare>;
 def objc_stubs_small : Flag<["-"], "objc_stubs_small">,
     HelpText<"Produce smaller stubs for Objective-C method calls with more jumps.">,
     Group<grp_rare>;
 def dyld_env : Separate<["-"], "dyld_env">,
     MetaVarName<"<dyld_env_var>">,
     HelpText<"Specifies a LC_DYLD_ENVIRONMENT variable value pair.">,
     Group<grp_rare>;
+def ignore_auto_link : Flag<["-"], "ignore_auto_link">,
+    HelpText<"Ignore LC_LINKER_OPTIONs">,
+    Group<grp_rare>;
 
 def grp_deprecated : OptionGroup<"deprecated">, HelpText<"DEPRECATED">;
 
 def lazy_framework : Separate<["-"], "lazy_framework">,
     MetaVarName<"<name>">,
     HelpText<"This option is deprecated and is now an alias for -framework.">,
     Flags<[HelpHidden]>,
     Group<grp_deprecated>;
def force_symbol_weak : Flag<["-"], "force_symbol_weak">,
     Group<grp_undocumented>;
 def function_starts : Flag<["-"], "function_starts">,
     HelpText<"Create table of function start addresses (default)">,
     Group<grp_undocumented>;
 def i : Flag<["-"], "i">,
     HelpText<"This option is undocumented in ld64">,
     Flags<[HelpHidden]>,
     Group<grp_undocumented>;
-def ignore_auto_link : Flag<["-"], "ignore_auto_link">,
-    HelpText<"This option is undocumented in ld64">,
-    Flags<[HelpHidden]>,
-    Group<grp_undocumented>;
 def ignore_optimization_hints : Flag<["-"], "ignore_optimization_hints">,
     HelpText<"Ignore Linker Optimization Hints">,
     Group<grp_undocumented>;
 def init_offsets : Flag<["-"], "init_offsets">,
     HelpText<"Store __TEXT segment offsets of static initializers">,
     Group<grp_undocumented>;
 def keep_dwarf_unwind : Flag<["-"], "keep_dwarf_unwind">,
     HelpText<"This option is undocumented in ld64">,

lld/test/MachO/lc-linker-option.ll

 ; REQUIRES: x86
 ; RUN: rm -rf %t; split-file %s %t
 
 ; RUN: llvm-as %t/framework.ll -o %t/framework.o
 ; RUN: %lld -lSystem %t/framework.o -o %t/frame
 ; RUN: llvm-otool -l %t/frame | FileCheck --check-prefix=FRAME %s \
 ; RUN:  --implicit-check-not LC_LOAD_DYLIB
 ; FRAME:          cmd LC_LOAD_DYLIB
 ; FRAME-NEXT: cmdsize
 ; FRAME-NEXT:    name /usr/lib/libSystem.dylib
 ; FRAME:          cmd LC_LOAD_DYLIB
 ; FRAME-NEXT: cmdsize
 ; FRAME-NEXT:    name /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
 
+; RUN: not %lld %t/framework.o -o %t/frame_no_autolink -ignore_auto_link 2>&1 | FileCheck --check-prefix=NO_AUTOLINK %s
+; NO_AUTOLINK: error: undefined symbol: __CFBigNumGetInt128
+
 ; RUN: llvm-as %t/l.ll -o %t/l.o
 ;; The dynamic call to _CFBigNumGetInt128 uses dyld_stub_binder,
 ;; which needs -lSystem from LC_LINKER_OPTION to get resolved.
 ;; The reference to __cxa_allocate_exception will require -lc++ from
 ;; LC_LINKER_OPTION to get resolved.
 ; RUN: %no-lsystem-lld %t/l.o -o %t/l -framework CoreFoundation
 ; RUN: llvm-otool -l %t/l | FileCheck --check-prefix=LIB %s \
 ; RUN:  --implicit-check-not LC_LOAD_DYLIB