[lld-macho][nfc][cleanup] Fix a few code style lints and clang-tidy f…

…indings

- Use .empty() instead of `size() == 0` when possible.
- Use const-ref to avoid copying

Differential Revision: https://reviews.llvm.org/D112978

lld/MachO/ConcatOutputSection.cpp

@@ -353,7 +353,7 @@ void ConcatOutputSection::writeTo(uint8_t *buf) const {
   size_t i = 0, ie = inputs.size();
   size_t t = 0, te = thunks.size();
   while (i < ie || t < te) {
-    while (i < ie && (t == te || inputs[i]->getSize() == 0 ||
+    while (i < ie && (t == te || inputs[i]->empty() ||
                       inputs[i]->outSecOff < thunks[t]->outSecOff)) {
       inputs[i]->writeTo(buf + inputs[i]->outSecOff);
       ++i;

lld/MachO/Driver.cpp

@@ -174,7 +174,7 @@ static std::vector<StringRef> getSystemLibraryRoots(InputArgList &args) {
   for (const Arg *arg : args.filtered(OPT_syslibroot))
     roots.push_back(arg->getValue());
   // NOTE: the final `-syslibroot` being `/` will ignore all roots
-  if (roots.size() && roots.back() == "/")
+  if (!roots.empty() && roots.back() == "/")
     roots.clear();
   // NOTE: roots can never be empty - add an empty root to simplify the library
   // and framework search path computation.
@@ -206,7 +206,9 @@ static llvm::CachePruningPolicy getLTOCachePolicy(InputArgList &args) {
        args.filtered(OPT_thinlto_cache_policy, OPT_prune_interval_lto,
                      OPT_prune_after_lto, OPT_max_relative_cache_size_lto)) {
     switch (arg->getOption().getID()) {
-    case OPT_thinlto_cache_policy: add(arg->getValue()); break;
+    case OPT_thinlto_cache_policy:
+      add(arg->getValue());
+      break;
     case OPT_prune_interval_lto:
       if (!strcmp("-1", arg->getValue()))
         add("prune_interval=87600h"); // 10 years

lld/MachO/InputFiles.cpp

@@ -269,7 +269,7 @@ void ObjFile::parseSections(ArrayRef<Section> sections) {
 
     auto splitRecords = [&](int recordSize) -> void {
       subsections.push_back({});
-      if (data.size() == 0)
+      if (data.empty())
         return;
 
       SubsectionMap &subsecMap = subsections.back();
@@ -619,8 +619,7 @@ macho::Symbol *ObjFile::parseNonSectionSymbol(const NList &sym,
   }
 }
 
-template <class NList>
-static bool isUndef(const NList &sym) {
+template <class NList> static bool isUndef(const NList &sym) {
   return (sym.n_type & N_TYPE) == N_UNDF && sym.n_value == 0;
 }
 
@@ -1211,7 +1210,7 @@ DylibFile::DylibFile(const InterfaceFile &interface, DylibFile *umbrella,
 void DylibFile::parseReexports(const InterfaceFile &interface) {
   const InterfaceFile *topLevel =
       interface.getParent() == nullptr ? &interface : interface.getParent();
-  for (InterfaceFileRef intfRef : interface.reexportedLibraries()) {
+  for (const InterfaceFileRef &intfRef : interface.reexportedLibraries()) {
     InterfaceFile::const_target_range targets = intfRef.targets();
     if (is_contained(skipPlatformChecks, intfRef.getInstallName()) ||
         is_contained(targets, config->platformInfo.target))

lld/MachO/InputSection.cpp

@@ -110,7 +110,7 @@ void ConcatInputSection::foldIdentical(ConcatInputSection *copy) {
   copy->symbols.clear();
 
   // Remove duplicate compact unwind info for symbols at the same address.
-  if (symbols.size() == 0)
+  if (symbols.empty())
     return;
   it = symbols.begin();
   uint64_t v = (*it)->value;

lld/MachO/InputSection.h

@@ -38,6 +38,7 @@ class InputSection {
   Kind kind() const { return shared->sectionKind; }
   virtual ~InputSection() = default;
   virtual uint64_t getSize() const { return data.size(); }
+  virtual bool empty() const { return data.empty(); }
   InputFile *getFile() const { return shared->file; }
   StringRef getName() const { return shared->name; }
   StringRef getSegName() const { return shared->segname; }
@@ -115,7 +116,7 @@ class ConcatInputSection final : public InputSection {
   // ConcatInputSections are entirely live or dead, so the offset is irrelevant.
   bool isLive(uint64_t off) const override { return live; }
   void markLive(uint64_t off) override { live = true; }
-  bool isCoalescedWeak() const { return wasCoalesced && symbols.size() == 0; }
+  bool isCoalescedWeak() const { return wasCoalesced && symbols.empty(); }
   bool shouldOmitFromOutput() const { return !live || isCoalescedWeak(); }
   bool isHashableForICF() const;
   void hashForICF();

lld/MachO/UnwindInfoSection.cpp

@@ -602,7 +602,7 @@ void UnwindInfoSectionImpl<Ptr>::writeTo(uint8_t *buf) const {
         *ep++ = (it->second << COMPRESSED_ENTRY_FUNC_OFFSET_BITS) |
                 (cuep->functionAddress - functionAddressBase);
       }
-      if (page.localEncodings.size() != 0)
+      if (!page.localEncodings.empty())
         memcpy(ep, page.localEncodings.data(),
                page.localEncodings.size() * sizeof(uint32_t));
     } else {