[lld-macho] Implement -S

[thevinster]

Summary

There are a couple internal builds that require the use of this flag.

[int3]

Thanks!

lld/MachO/InputFiles.cpp

839–840

When we implement https://bugs.llvm.org/show_bug.cgi?id=49282, we'll want to parse debug info regardless

lld/test/MachO/stabs.s

64

we're not testing -oso_prefix here, so there's no need to do the cd %t

[thevinster]

lld/MachO/InputFiles.cpp

839–840

Removed it. I added it originally to avoid the extra computation work if it's going to be skipped but performing this doesn't seem like a huge impact (plus the need to parse it down the road regardless)

[thevinster]

nit feedback

lld/MachO/Config.h

struct Configuration {
   bool adhocCodesign = false;
   bool emitFunctionStarts = false;
   bool emitBitcodeBundle = false;
   bool emitDataInCodeInfo = false;
   bool emitEncryptionInfo = false;
   bool timeTraceEnabled = false;
   bool dataConst = false;
   bool dedupLiterals = true;
+  bool omitDebugInfo = false;
   uint32_t headerPad;
   uint32_t dylibCompatibilityVersion = 0;
   uint32_t dylibCurrentVersion = 0;
   uint32_t timeTraceGranularity = 500;
   unsigned optimize;
   std::string progName;
 
   // For `clang -arch arm64 -arch x86_64`, clang will:

lld/MachO/Driver.cpp

bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
   config->astPaths = args.getAllArgValues(OPT_add_ast_path);
   config->headerPad = args::getHex(args, OPT_headerpad, /*Default=*/32);
   config->headerPadMaxInstallNames =
       args.hasArg(OPT_headerpad_max_install_names);
   config->printDylibSearch =
       args.hasArg(OPT_print_dylib_search) || getenv("RC_TRACE_DYLIB_SEARCHING");
   config->printEachFile = args.hasArg(OPT_t);
   config->printWhyLoad = args.hasArg(OPT_why_load);
+  config->omitDebugInfo = args.hasArg(OPT_S);
   config->outputType = getOutputType(args);
   if (const Arg *arg = args.getLastArg(OPT_bundle_loader)) {
     if (config->outputType != MH_BUNDLE)
       error("-bundle_loader can only be used with MachO bundle output");
     addFile(arg->getValue(), /*forceLoadArchive=*/false, /*isExplicit=*/false,
             /*isBundleLoader=*/true);
   }
   if (const Arg *arg = args.getLastArg(OPT_umbrella)) {

lld/MachO/InputFiles.cpp

template <class LP> void ObjFile::parse() {
 
   parseDebugInfo();
   if (config->emitDataInCodeInfo)
     parseDataInCode();
   registerCompactUnwind();
 }
 
 void ObjFile::parseDebugInfo() {
+  if (config->omitDebugInfo)
+    return;
+
   std::unique_ptr<DwarfObject> dObj = DwarfObject::create(this);
   if (!dObj)
     return;
 
   auto *ctx = make<DWARFContext>(
       std::move(dObj), "",
       [&](Error err) {
         warn(toString(this) + ": " + toString(std::move(err)));

lld/MachO/Options.td

 def save_temps : Flag<["-"], "save-temps">,
     HelpText<"Save intermediate LTO compilation results">,
     Group<grp_introspect>;
 
 def grp_symtab : OptionGroup<"symtab">, HelpText<"SYMBOL TABLE">;
 
 def S : Flag<["-"], "S">,
     HelpText<"Strip debug information (STABS or DWARF) from the output">,
-    Flags<[HelpHidden]>,
     Group<grp_symtab>;
 def x : Flag<["-"], "x">,
     HelpText<"Exclude non-global symbols from the output symbol table">,
     Flags<[HelpHidden]>,
     Group<grp_symtab>;
 def non_global_symbols_strip_list : Separate<["-"], "non_global_symbols_strip_list">,
     MetaVarName<"<path>">,
     HelpText<"Specify in <path> the non-global symbols that should be removed from the output symbol table">,

lld/MachO/SyntheticSections.cpp

 
 void SymtabSection::emitEndFunStab(Defined *defined) {
   StabsEntry stab(N_FUN);
   stab.value = defined->size;
   stabs.emplace_back(std::move(stab));
 }
 
 void SymtabSection::emitStabs() {
+  if (config->omitDebugInfo)
+    return;
+
   for (const std::string &s : config->astPaths) {
     StabsEntry astStab(N_AST);
     astStab.strx = stringTableSection.addString(s);
     stabs.emplace_back(std::move(astStab));
   }
 
   std::vector<Defined *> symbolsNeedingStabs;
   for (const SymtabEntry &entry :

lld/test/MachO/stabs.s

 # RUN: cd %t && %lld -lSystem test.o foo.o no-debug.o -o test
 # RUN: (llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | \
 # RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o \
 # RUN:       -D#TEST_TIME=0x10 -D#FOO_TIME=0x20
 
 ## Check that we emit relative path to object files in OSO entries
 ## when -oso_prefix <path> is used.
 # RUN: cd %t && %lld -lSystem test.o foo.o no-debug.o -oso_prefix "%t" -o %t/test-rel
-# RUN: dsymutil -s  %t/test-rel | grep 'N_OSO' | FileCheck %s  -D#TEST_TIME=0x10 -D#FOO_TIME=0x20 --check-prefix=REL-PATH 
+# RUN: dsymutil -s  %t/test-rel | grep 'N_OSO' | FileCheck %s  -D#TEST_TIME=0x10 -D#FOO_TIME=0x20 --check-prefix=REL-PATH
 # RUN: cd %t && %lld -lSystem test.o foo.o no-debug.o -oso_prefix "." -o %t/test-rel-dot
-# RUN: dsymutil -s  %t/test-rel-dot | grep 'N_OSO' | FileCheck %s  -D#TEST_TIME=0x10 -D#FOO_TIME=0x20 --check-prefix=REL-DOT 
+# RUN: dsymutil -s  %t/test-rel-dot | grep 'N_OSO' | FileCheck %s  -D#TEST_TIME=0x10 -D#FOO_TIME=0x20 --check-prefix=REL-DOT
 ## Set HOME to %t (for ~ to expand to)
 # RUN: cd %t && env HOME=%t %lld -lSystem test.o foo.o no-debug.o -oso_prefix "~" -o %t/test-rel-tilde
 # RUN: dsymutil -s  %t/test-rel-tilde | grep 'N_OSO' | FileCheck %s  -D#TEST_TIME=0x10 -D#FOO_TIME=0x20 --check-prefix=REL-PATH
 
+## Check that we don't emit DWARF or stabs when -S is used
+# RUN: cd %t && %lld -lSystem test.o foo.o no-debug.o -S -o %t/test-no-debug
+## grep returns an exit code of 1 if it cannot match the intended pattern. We
+## expect to not find any entries which requires the exit code to be negated.
+# RUN: llvm-nm -ap %t/test-no-debug | not grep -e ' - '
 
 # RUN: cd %t && %lld -lSystem test.o foo.a no-debug.o -o %t/test
 # RUN: (llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | \
 # RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\) \
 # RUN:       -D#TEST_TIME=0x10 -D#FOO_TIME=0x20
 
 # CHECK:       Sections:
 # CHECK-NEXT:  Idx                Name
 # CHECK-NEXT:  [[#TEXT_ID:]]      __text
 # CHECK-NEXT:  [[#DATA_ID:]]      __data
 # CHECK-NEXT:  [[#MORE_DATA_ID:]] more_data
 # CHECK-NEXT:  [[#COMM_ID:]]      __common
 # CHECK-NEXT:  [[#MORE_TEXT_ID:]] more_text
 
 # CHECK:      (N_SO         ) 00                         0000   0000000000000000   '/tmp/test.cpp'
 # CHECK-NEXT: (N_OSO        ) 03                         0001   [[#%.16x,TEST_TIME]] '[[DIR]]/test.o'
 # REL-PATH:   (N_OSO        ) 03                         0001   [[#%.16x,TEST_TIME]] '/test.o'
-# REL-DOT:    (N_OSO        ) 03                         0001   [[#%.16x,TEST_TIME]] 'test.o'        
+# REL-DOT:    (N_OSO        ) 03                         0001   [[#%.16x,TEST_TIME]] 'test.o'
 # CHECK-NEXT: (N_STSYM      ) [[#%.2d,MORE_DATA_ID + 1]] 0000   [[#%.16x,STATIC:]] '_static_var'
 # CHECK-NEXT: (N_FUN        ) [[#%.2d,TEXT_ID + 1]]      0000   [[#%.16x,MAIN:]]   '_main'
 # CHECK-NEXT: (N_FUN        ) 00                         0000   0000000000000006{{$}}
 # CHECK-NEXT: (N_FUN        ) [[#%.2d,TEXT_ID + 1]]      0000   [[#%.16x,BAR:]]    '_bar'
 # CHECK-NEXT: (N_FUN        ) 00                         0000   0000000000000000{{$}}
 # CHECK-NEXT: (N_FUN        ) [[#%.2d,TEXT_ID + 1]]      0000   [[#%.16x,BAR2:]]   '_bar2'
 # CHECK-NEXT: (N_FUN        ) 00                         0000   0000000000000001{{$}}
 # CHECK-NEXT: (N_FUN        ) [[#%.2d,TEXT_ID + 1]]      0000   [[#%.16x,BAZ:]]    '_baz'