use vector to store cstring sections

Author: ellishg

lld/MachO/Driver.cpp

@@ -1520,9 +1520,8 @@ static void foldIdenticalLiterals() {
   // We always create a cStringSection, regardless of whether dedupLiterals is
   // true. If it isn't, we simply create a non-deduplicating CStringSection.
   // Either way, we must unconditionally finalize it here.
-  for (auto &[name, sec] : in.cStringSectionMap)
+  for (auto *sec : in.cStringSections)
     sec->finalizeContents();
-  in.objcMethnameSection->finalizeContents();
   in.wordLiteralSection->finalizeContents();
 }
 

lld/MachO/InputSection.cpp

@@ -63,18 +63,13 @@ void lld::macho::addInputSection(InputSection *inputSection) {
     isec->parent = osec;
     inputSections.push_back(isec);
   } else if (auto *isec = dyn_cast<CStringInputSection>(inputSection)) {
-    if (isec->getName() == section_names::objcMethname) {
-      if (in.objcMethnameSection->inputOrder == UnspecifiedInputOrder)
-        in.objcMethnameSection->inputOrder = inputSectionsOrder++;
-      in.objcMethnameSection->addInput(isec);
-    } else {
-      auto *osec = in.getOrCreateCStringSection(
-          config->separateCstringLiteralSections ? isec->getName()
-                                                 : section_names::cString);
-      if (osec->inputOrder == UnspecifiedInputOrder)
-        osec->inputOrder = inputSectionsOrder++;
-      osec->addInput(isec);
-    }
+    bool useSectionName = config->separateCstringLiteralSections ||
+                          isec->getName() == section_names::objcMethname;
+    auto *osec = in.getOrCreateCStringSection(
+        useSectionName ? isec->getName() : section_names::cString);
+    if (osec->inputOrder == UnspecifiedInputOrder)
+      osec->inputOrder = inputSectionsOrder++;
+    osec->addInput(isec);
   } else if (auto *isec = dyn_cast<WordLiteralInputSection>(inputSection)) {
     if (in.wordLiteralSection->inputOrder == UnspecifiedInputOrder)
       in.wordLiteralSection->inputOrder = inputSectionsOrder++;

lld/MachO/MapFile.cpp

@@ -239,9 +239,7 @@ void macho::writeMapFile() {
         printIsecArrSyms(textOsec->inputs, textOsec->getThunks());
       } else if (auto *concatOsec = dyn_cast<ConcatOutputSection>(osec)) {
         printIsecArrSyms(concatOsec->inputs);
-      } else if (any_of(in.cStringSectionMap,
-                        [&](auto &it) { return osec == it.getValue(); }) ||
-                 osec == in.objcMethnameSection) {
+      } else if (is_contained(in.cStringSections, osec)) {
         const auto &liveCStrings = info.liveCStringsForSection.lookup(osec);
         uint64_t lastAddr = 0; // strings will never start at address 0, so this
                                // is a sentinel value

lld/MachO/ObjC.cpp

@@ -1057,7 +1057,7 @@ Defined *ObjcCategoryMerger::emitCategoryName(const std::string &name,
   newStringSec->splitIntoPieces();
   newStringSec->pieces[0].live = true;
   newStringSec->parent = infoCategoryWriter.catNameInfo.outputSection;
-  in.getOrCreateCStringSection(section_names::cString)->addInput(newStringSec);
+  in.cStringSection->addInput(newStringSec);
   assert(newStringSec->pieces.size() == 1);
 
   Defined *catNameSym = make<Defined>(

lld/MachO/SyntheticSections.h

@@ -843,7 +843,8 @@ void writeChainedFixup(uint8_t *buf, const Symbol *sym, int64_t addend);
 struct InStruct {
   const uint8_t *bufferStart = nullptr;
   MachHeaderSection *header = nullptr;
-  llvm::StringMap<CStringSection *> cStringSectionMap;
+  llvm::SmallVector<CStringSection *> cStringSections;
+  CStringSection *cStringSection = nullptr;
   DeduplicatedCStringSection *objcMethnameSection = nullptr;
   WordLiteralSection *wordLiteralSection = nullptr;
   RebaseSection *rebase = nullptr;
@@ -864,20 +865,25 @@ struct InStruct {
   ObjCMethListSection *objcMethList = nullptr;
   ChainedFixupsSection *chainedFixups = nullptr;
 
-  CStringSection *getOrCreateCStringSection(StringRef name) {
-    auto it = cStringSectionMap.find(name);
-    if (it != cStringSectionMap.end())
-      return it->getValue();
+  CStringSection *getOrCreateCStringSection(StringRef name,
+                                            bool forceDedupStrings = false) {
+    auto [it, didEmplace] =
+        cStringSectionMap.try_emplace(name, cStringSections.size());
+    if (!didEmplace)
+      return cStringSections[it->getValue()];
 
     std::string &nameData = *make<std::string>(name);
     CStringSection *sec;
-    if (config->dedupStrings)
+    if (config->dedupStrings || forceDedupStrings)
       sec = make<DeduplicatedCStringSection>(nameData.c_str());
     else
       sec = make<CStringSection>(nameData.c_str());
-    cStringSectionMap[name] = sec;
+    cStringSections.push_back(sec);
     return sec;
   }
+
+private:
+  llvm::StringMap<unsigned> cStringSectionMap;
 };
 
 extern InStruct in;

lld/MachO/Writer.cpp

@@ -1377,10 +1377,11 @@ void macho::resetWriter() { LCDylib::resetInstanceCount(); }
 
 void macho::createSyntheticSections() {
   in.header = make<MachHeaderSection>();
-  // Materialize the cstring section
-  in.getOrCreateCStringSection(section_names::cString);
-  in.objcMethnameSection =
-      make<DeduplicatedCStringSection>(section_names::objcMethname);
+  // Materialize cstring and objcMethname sections
+  in.cStringSection = in.getOrCreateCStringSection(section_names::cString);
+  in.objcMethnameSection = cast<DeduplicatedCStringSection>(
+      in.getOrCreateCStringSection(section_names::objcMethname,
+                                   /*forceDedupStrings=*/true));
   in.wordLiteralSection = make<WordLiteralSection>();
   if (config->emitChainedFixups) {
     in.chainedFixups = make<ChainedFixupsSection>();