[lld/mac] Change load command order to be more like ld64

[thakis]

Summary

No meaningful behavior change. Makes diffing otool -l output a bit easier.

[int3]

lld/MachO/Writer.cpp

721–722

:/ seems kind of awkward that this isn't part of the switch statement above. maybe add a comment about why?

lld/MachO/Writer.cpp

template <class LP> void Writer::createLoadCommands() {
 
   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));
   if (!config->umbrella.empty())
     in.header->addLoadCommand(make<LCSubFramework>(config->umbrella));
-  if (functionStartsSection)
-    in.header->addLoadCommand(make<LCFunctionStarts>(functionStartsSection));
-  if (dataInCodeSection)
-    in.header->addLoadCommand(make<LCDataInCode>(dataInCodeSection));
   if (config->emitEncryptionInfo)
     in.header->addLoadCommand(make<LCEncryptionInfo<LP>>());
   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;
   case MH_DYLIB:
     in.header->addLoadCommand(make<LCDylib>(LC_ID_DYLIB, config->installName,
                                             config->dylibCompatibilityVersion,
                                             config->dylibCurrentVersion));
     break;
   case MH_BUNDLE:
     break;
   default:
     llvm_unreachable("unhandled output file type");
   }
 
   uuidCommand = make<LCUuid>();
   in.header->addLoadCommand(uuidCommand);
 
   if (useLCBuildVersion(config->platformInfo))
     in.header->addLoadCommand(make<LCBuildVersion>(config->platformInfo));
   else
     in.header->addLoadCommand(make<LCMinVersion>(config->platformInfo));
 
+  // This is down here to match ld64's load command order.
+  if (config->outputType == MH_EXECUTE)
+    in.header->addLoadCommand(make<LCMain>());
+
   int64_t dylibOrdinal = 1;
   DenseMap<StringRef, int64_t> ordinalForInstallName;
   for (InputFile *file : inputFiles) {
     if (auto *dylibFile = dyn_cast<DylibFile>(file)) {
       if (dylibFile->isBundleLoader) {
         dylibFile->ordinal = BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE;
         // Shortcut since bundle-loader does not re-export the symbols.
 
if (auto *dylibFile = dyn_cast<DylibFile>(file)) {
                                               dylibFile->currentVersion));
 
       if (dylibFile->reexport)
         in.header->addLoadCommand(
             make<LCDylib>(LC_REEXPORT_DYLIB, dylibFile->installName));
     }
   }
 
+  if (functionStartsSection)
+    in.header->addLoadCommand(make<LCFunctionStarts>(functionStartsSection));
+  if (dataInCodeSection)
+    in.header->addLoadCommand(make<LCDataInCode>(dataInCodeSection));
   if (codeSignatureSection)
     in.header->addLoadCommand(make<LCCodeSignature>(codeSignatureSection));
 
   const uint32_t MACOS_MAXPATHLEN = 1024;
   config->headerPad = std::max(
       config->headerPad, (config->headerPadMaxInstallNames
                               ? LCDylib::getInstanceCount() * MACOS_MAXPATHLEN
                               : 0));

lld/test/MachO/load-command-sequence.s

 # COMMON: segname __DATA
 # COMMON: cmd LC_SEGMENT_64
 # COMMON: segname __LINKEDIT
 # COMMON: cmd LC_DYLD_INFO_ONLY
 # COMMON: cmd LC_SYMTAB
 # COMMON: cmd LC_DYSYMTAB
 
 # EXEC: cmd LC_LOAD_DYLINKER
-# EXEC: cmd LC_MAIN
 # DYLIB: cmd LC_ID_DYLIB
 
 # COMMON: cmd LC_UUID
 # COMMON: cmd LC_BUILD_VERSION
+
+# EXEC: cmd LC_MAIN
+
 # COMMON: cmd LC_LOAD_DYLIB
 
 .section __TEXT,__cstring
 _str:
   .asciz "Help me! I'm trapped in a test!\n"
 
 .globl _mutable
 .section __DATA,__data