[lld-macho] Support -no_function_starts

[int3]

Summary

Pretty simple code-wise. Also threw in some refactoring:

• Put the functionStartSection under Writer instead of InStruct, since it doesn't need to be accessed outside of Writer
• Adjusted the test to put all files under the temp dir instead of at the top-level
• Added some CHECK-LABELs to make it clearer where the function starts data is

lld/MachO/Config.h

struct Configuration {
   bool headerPadMaxInstallNames = false;
   bool ltoNewPassManager = LLVM_ENABLE_NEW_PASS_MANAGER;
   bool markDeadStrippableDylib = false;
   bool printEachFile = false;
   bool printWhyLoad = false;
   bool searchDylibsFirst = false;
   bool saveTemps = false;
   bool adhocCodesign = false;
+  bool emitFunctionStarts = false;
   bool timeTraceEnabled = false;
   uint32_t headerPad;
   uint32_t dylibCompatibilityVersion = 0;
   uint32_t dylibCurrentVersion = 0;
   uint32_t timeTraceGranularity = 0;
   std::string progName;
   llvm::StringRef installName;
   llvm::StringRef mapFile;

lld/MachO/Driver.cpp

bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
   config->ltoNewPassManager =
       args.hasFlag(OPT_no_lto_legacy_pass_manager, OPT_lto_legacy_pass_manager,
                    LLVM_ENABLE_NEW_PASS_MANAGER);
   config->runtimePaths = args::getStrings(args, OPT_rpath);
   config->allLoad = args.hasArg(OPT_all_load);
   config->forceLoadObjC = args.hasArg(OPT_ObjC);
   config->demangle = args.hasArg(OPT_demangle);
   config->implicitDylibs = !args.hasArg(OPT_no_implicit_dylibs);
+  config->emitFunctionStarts = !args.hasArg(OPT_no_function_starts);
 
   if (const Arg *arg = args.getLastArg(OPT_install_name)) {
     if (config->outputType != MH_DYLIB)
       warn(arg->getAsString(args) + ": ignored, only has effect with -dylib");
     else
       config->installName = arg->getValue();
   } else if (config->outputType == MH_DYLIB) {
     config->installName = config->outputFile;

lld/MachO/Options.td

def read_only_stubs : Flag<["-"], "read_only_stubs">,
     Flags<[HelpHidden]>,
     Group<grp_rare>;
 def interposable_list : Separate<["-"], "interposable_list">,
     MetaVarName<"<path>">,
     HelpText<"Access global symbols listed in <path> indirectly">,
     Flags<[HelpHidden]>,
     Group<grp_rare>;
 def no_function_starts : Flag<["-"], "no_function_starts">,
-    HelpText<"Do not creates a compressed table of function start addresses">,
-    Flags<[HelpHidden]>,
+    HelpText<"Do not create a table of function start addresses">,
     Group<grp_rare>;
 def no_objc_category_merging : Flag<["-"], "no_objc_category_merging">,
     HelpText<"Do not merge Objective-C categories into their classes">,
     Flags<[HelpHidden]>,
     Group<grp_rare>;
 def object_path_lto : Separate<["-"], "object_path_lto">,
     MetaVarName<"<path>">,
     HelpText<"Retain any temporary mach-o file in <path> that would otherwise be deleted during LTO">,

lld/MachO/SyntheticSections.h

 
 struct InStruct {
   MachHeaderSection *header = nullptr;
   RebaseSection *rebase = nullptr;
   BindingSection *binding = nullptr;
   WeakBindingSection *weakBinding = nullptr;
   LazyBindingSection *lazyBinding = nullptr;
   ExportSection *exports = nullptr;
-  FunctionStartsSection *functionStarts = nullptr;
   GotSection *got = nullptr;
   TlvPointerSection *tlvPointers = nullptr;
   LazyPointerSection *lazyPointers = nullptr;
   StubsSection *stubs = nullptr;
   StubHelperSection *stubHelper = nullptr;
   ImageLoaderCacheSection *imageLoaderCache = nullptr;
 };
 

lld/MachO/Writer.cpp

public:
   uint64_t addr = 0;
   uint64_t fileOff = 0;
   MachHeaderSection *header = nullptr;
   StringTableSection *stringTableSection = nullptr;
   SymtabSection *symtabSection = nullptr;
   IndirectSymtabSection *indirectSymtabSection = nullptr;
   CodeSignatureSection *codeSignatureSection = nullptr;
   UnwindInfoSection *unwindInfoSection = nullptr;
+  FunctionStartsSection *functionStartsSection = nullptr;
+
   LCUuid *uuidCommand = nullptr;
   OutputSegment *linkEditSegment = nullptr;
 };
 
 // LC_DYLD_INFO_ONLY stores the offsets of symbol import/export information.
 class LCDyldInfo : public LoadCommand {
 public:
   LCDyldInfo(RebaseSection *rebaseSection, BindingSection *bindingSection,
public:
   BindingSection *bindingSection;
   WeakBindingSection *weakBindingSection;
   LazyBindingSection *lazyBindingSection;
   ExportSection *exportSection;
 };
 
 class LCFunctionStarts : public LoadCommand {
 public:
-  explicit LCFunctionStarts(FunctionStartsSection *functionStarts)
-      : functionStarts(functionStarts) {}
+  explicit LCFunctionStarts(FunctionStartsSection *functionStartsSection)
+      : functionStartsSection(functionStartsSection) {}
 
   uint32_t getSize() const override { return sizeof(linkedit_data_command); }
 
   void writeTo(uint8_t *buf) const override {
     auto *c = reinterpret_cast<linkedit_data_command *>(buf);
     c->cmd = LC_FUNCTION_STARTS;
     c->cmdsize = getSize();
-    c->dataoff = functionStarts->fileOff;
-    c->datasize = functionStarts->getFileSize();
+    c->dataoff = functionStartsSection->fileOff;
+    c->datasize = functionStartsSection->getFileSize();
   }
 
 private:
-  FunctionStartsSection *functionStarts;
+  FunctionStartsSection *functionStartsSection;
 };
 
 class LCDysymtab : public LoadCommand {
 public:
   LCDysymtab(SymtabSection *symtabSection,
              IndirectSymtabSection *indirectSymtabSection)
       : symtabSection(symtabSection),
         indirectSymtabSection(indirectSymtabSection) {}
for (OutputSegment *seg : outputSegments) {
     seg->index = segIndex++;
   }
 
   in.header->addLoadCommand(make<LCDyldInfo>(
       in.rebase, in.binding, in.weakBinding, in.lazyBinding, in.exports));
   in.header->addLoadCommand(make<LCSymtab>(symtabSection, stringTableSection));
   in.header->addLoadCommand(
       make<LCDysymtab>(symtabSection, indirectSymtabSection));
-  in.header->addLoadCommand(make<LCFunctionStarts>(in.functionStarts));
+  if (functionStartsSection)
+    in.header->addLoadCommand(make<LCFunctionStarts>(functionStartsSection));
   for (StringRef path : config->runtimePaths)
     in.header->addLoadCommand(make<LCRPath>(path));
 
   switch (config->outputType) {
   case MH_EXECUTE:
     in.header->addLoadCommand(make<LCLoadDylinker>());
     in.header->addLoadCommand(make<LCMain>());
     break;
void Writer::createOutputSections() {
   TimeTraceScope timeScope("Create output sections");
   // First, create hidden sections
   stringTableSection = make<StringTableSection>();
   unwindInfoSection = make<UnwindInfoSection>(); // TODO(gkm): only when no -r
   symtabSection = make<SymtabSection>(*stringTableSection);
   indirectSymtabSection = make<IndirectSymtabSection>();
   if (config->adhocCodesign)
     codeSignatureSection = make<CodeSignatureSection>();
+  if (config->emitFunctionStarts)
+    functionStartsSection = make<FunctionStartsSection>();
 
   switch (config->outputType) {
   case MH_EXECUTE:
     make<PageZeroSection>();
     break;
   case MH_DYLIB:
   case MH_BUNDLE:
     break;

 void Writer::finalizeLinkEditSegment() {
   TimeTraceScope timeScope("Finalize __LINKEDIT segment");
   // Fill __LINKEDIT contents.
   in.rebase->finalizeContents();
   in.binding->finalizeContents();
   in.weakBinding->finalizeContents();
   in.lazyBinding->finalizeContents();
   in.exports->finalizeContents();
-  in.functionStarts->finalizeContents();
   symtabSection->finalizeContents();
   indirectSymtabSection->finalizeContents();
 
+  if (functionStartsSection)
+    functionStartsSection->finalizeContents();
+
   // Now that __LINKEDIT is filled out, do a proper calculation of its
   // addresses and offsets.
   assignAddresses(linkEditSegment);
 }
 
 void Writer::assignAddresses(OutputSegment *seg) {
   uint64_t pageSize = target->getPageSize();
   addr = alignTo(addr, pageSize);

 
 void macho::createSyntheticSections() {
   in.header = make<MachHeaderSection>();
   in.rebase = make<RebaseSection>();
   in.binding = make<BindingSection>();
   in.weakBinding = make<WeakBindingSection>();
   in.lazyBinding = make<LazyBindingSection>();
   in.exports = make<ExportSection>();
-  in.functionStarts = make<FunctionStartsSection>();
   in.got = make<GotSection>();
   in.tlvPointers = make<TlvPointerSection>();
   in.lazyPointers = make<LazyPointerSection>();
   in.stubs = make<StubsSection>();
   in.stubHelper = make<StubHelperSection>();
   in.imageLoaderCache = make<ImageLoaderCacheSection>();
 }
 
 OutputSection *macho::firstTLVDataSection = nullptr;

lld/test/MachO/function-starts.s

 # REQUIRES: x86
 
-# RUN: split-file %s %t
+# RUN: rm -rf %t; split-file %s %t
 
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/basic.s -o %t.basic.o
-# RUN: %lld %t.basic.o -o %t.basic
-# RUN: llvm-objdump --syms %t.basic > %t.objdump
-# RUN: llvm-objdump --macho --function-starts %t.basic >> %t.objdump
-# RUN: FileCheck %s --check-prefix=BASIC < %t.objdump
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/basic.s -o %t/basic.o
+# RUN: %lld %t/basic.o -o %t/basic
+# RUN: llvm-objdump --syms %t/basic > %t/objdump
+# RUN: llvm-objdump --macho --function-starts %t/basic >> %t/objdump
+# RUN: FileCheck %s --check-prefix=BASIC < %t/objdump
 
-# BASIC:      SYMBOL TABLE:
-# BASIC-NEXT: [[#%x,MAIN:]] g F __TEXT,__text _main
-# BASIC-NEXT: [[#%x,F1:]] g F __TEXT,__text _f1
-# BASIC-NEXT: [[#%x,F2:]] g F __TEXT,__text _f2
-# BASIC:      [[#MAIN]]
-# BASIC:      [[#F1]]
-# BASIC:      [[#F2]]
+# BASIC-LABEL: SYMBOL TABLE:
+# BASIC-NEXT:  [[#%x,MAIN:]] g F __TEXT,__text _main
+# BASIC-NEXT:  [[#%x,F1:]] g F __TEXT,__text _f1
+# BASIC-NEXT:  [[#%x,F2:]] g F __TEXT,__text _f2
+# BASIC-LABEL: basic:
+# BASIC:       [[#MAIN]]
+# BASIC:       [[#F1]]
+# BASIC:       [[#F2]]
 
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/alias.s -o %t.alias.o
-# RUN: %lld %t.alias.o -o %t.alias
-# RUN: llvm-objdump --syms  %t.alias > %t.objdump
-# RUN: llvm-objdump --macho --function-starts %t.alias >> %t.objdump
-# RUN: FileCheck %s --check-prefix=ALIAS < %t.objdump
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/alias.s -o %t/alias.o
+# RUN: %lld %t/alias.o -o %t/alias
+# RUN: llvm-objdump --syms  %t/alias > %t/objdump
+# RUN: llvm-objdump --macho --function-starts %t/alias >> %t/objdump
+# RUN: FileCheck %s --check-prefix=ALIAS < %t/objdump
 
-# ALIAS:      SYMBOL TABLE:
-# ALIAS-NEXT: [[#%x,F2:]] l F __TEXT,__text _f2
-# ALIAS-NEXT: [[#%x,MAIN:]] g F __TEXT,__text _main
-# ALIAS-NEXT: [[#%x,F1:]] g F __TEXT,__text _f1
-# ALIAS:      [[#MAIN]]
-# ALIAS:      [[#F1]]
+# ALIAS-LABEL: SYMBOL TABLE:
+# ALIAS-NEXT:  [[#%x,F2:]] l F __TEXT,__text _f2
+# ALIAS-NEXT:  [[#%x,MAIN:]] g F __TEXT,__text _main
+# ALIAS-NEXT:  [[#%x,F1:]] g F __TEXT,__text _f1
+# ALIAS-LABEL: alias:
+# ALIAS:       [[#MAIN]]
+# ALIAS:       [[#F1]]
 
+# RUN: %lld %t/basic.o -no_function_starts -o %t/basic-no-function-starts
+# RUN: llvm-objdump --macho --function-starts %t/basic-no-function-starts | FileCheck %s --check-prefix=NO-FUNCTION-STARTS
+# NO-FUNCTION-STARTS: basic-no-function-starts:
+# NO-FUNCTION-STARTS-EMPTY:
+
 #--- basic.s
 .section  __TEXT,__text,regular,pure_instructions
 .globl  _f1
 .globl  _f2
 .globl  _main
 _f1:
   retq
 _f2: