[NFC] Optimize vector usage in lld

[gAlfonso-bit]

Summary

By using emplace_back, as well as converting some loops to for-each, we can do more efficient vectorization.

Make copy constructor for TemporaryFile noexcept.

[gAlfonso-bit]

Fix formatting

[int3]

lld/COFF/Writer.cpp

521

codebase convention is to use explicit type instead of auto as long as it's not too ugly

lld/ELF/InputFiles.cpp

1709–1711

c seems like a better name for a char

also there's no need to take this by reference

lld/ELF/MapFile.cpp

248

let's keep this, seems like it was intentionally done to help readability

[int3]

clearing queue

[gAlfonso-bit]

Addressed! @MaskRay

[int3]

Thanks!

lld/COFF/DriverUtils.cpp

350

maybe add a remark about this noexcept to the commit message

[andrewng]

lld/ELF/InputFiles.cpp

1711

Just saw this in passing, I think c needs to be a reference as the intention is to change the character in s.

[gAlfonso-bit]

Done!

[gAlfonso-bit]

@int3 I do not have permission to merge this. Could you?

[int3]

Done :)

[int3]

Just noticed I'd messed up the author attribution in the commit. Sorry ):

lld/COFF/Chunks.cpp

     }
     // sizeInBits is used to initialize the Flags field; currently no
     // other flags are defined.
-    res.emplace_back(
-        RuntimePseudoReloc(target, this, rel.VirtualAddress, sizeInBits));
+    res.emplace_back(target, this, rel.VirtualAddress, sizeInBits);
   }
 }
 

lld/COFF/Driver.cpp

   }
 
   // Construct search path list.
-  searchPaths.push_back("");
+  searchPaths.emplace_back("");
   for (auto *arg : args.filtered(OPT_libpath))
     searchPaths.push_back(arg->getValue());
   detectWinSysRoot(args);

lld/COFF/DriverUtils.cpp

     }
   }
 
-  TemporaryFile(TemporaryFile &&obj) {
-    std::swap(path, obj.path);
+  TemporaryFile(TemporaryFile &&obj) { 
+    std::swap(path, obj.path); 
   }
 
   ~TemporaryFile() {

   config->argv = {argv[0]};
   for (opt::Arg *arg : args) {
     if (arg->getOption().getKind() != opt::Option::InputClass) {
-      config->argv.push_back(args.getArgString(arg->getIndex()));
+      config->argv.emplace_back(args.getArgString(arg->getIndex()));
     }
   }
 

lld/COFF/MinGW.cpp

   // Update pointers in input files.
   parallelForEach(ctx.objFileInstances, [&](ObjFile *file) {
     MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
-    for (size_t i = 0, e = syms.size(); i != e; ++i)
-      if (Symbol *s = map.lookup(syms[i]))
-        syms[i] = s;
+    for (auto &sym : syms)
+      if (Symbol *s = map.lookup(sym))
+        sym = s;
   });
 }

lld/COFF/Writer.cpp

       uint32_t &thunkSymbolIndex = insertion.first->second;
       if (insertion.second)
         thunkSymbolIndex = file->addRangeThunkSymbol(thunk);
-      relocReplacements.push_back({j, thunkSymbolIndex});
+      relocReplacements.emplace_back(j, thunkSymbolIndex);
     }
 
     // Get a writable copy of this section's relocations so they can be

       continue;
 
     ArrayRef<coff_relocation> relocs = sc->getRelocs();
-    for (size_t j = 0, e = relocs.size(); j < e; ++j) {
-      const coff_relocation &rel = relocs[j];
+    for (const auto &rel : relocs) {
       Symbol *relocTarget = sc->file->getSymbol(rel.SymbolTableIndex);
 
       Defined *sym = dyn_cast_or_null<Defined>(relocTarget);

     // allowing a debugger to match a PDB and an executable.  So we need it even
     // if we're ultimately not going to write CodeView data to the PDB.
     buildId = make<CVDebugRecordChunk>();
-    debugRecords.push_back({COFF::IMAGE_DEBUG_TYPE_CODEVIEW, buildId});
+    debugRecords.emplace_back(COFF::IMAGE_DEBUG_TYPE_CODEVIEW, buildId);
   }
 
   if (config->cetCompat) {
-    debugRecords.push_back({COFF::IMAGE_DEBUG_TYPE_EX_DLLCHARACTERISTICS,
+    debugRecords.emplace_back(COFF::IMAGE_DEBUG_TYPE_EX_DLLCHARACTERISTICS,
                               make<ExtendedDllCharacteristicsChunk>(
-                                IMAGE_DLL_CHARACTERISTICS_EX_CET_COMPAT)});
+                                  IMAGE_DLL_CHARACTERISTICS_EX_CET_COMPAT));
   }
 
   // Align and add each chunk referenced by the debug data directory.

lld/ELF/InputFiles.cpp

   // user programs can access blobs by name. Non-alphanumeric
   // characters in a filename are replaced with underscore.
   std::string s = "_binary_" + mb.getBufferIdentifier().str();
-  for (size_t i = 0; i < s.size(); ++i)
-    if (!isAlnum(s[i]))
-      s[i] = '_';
+  for (char &i : s)
+    if (!isAlnum(i))
+      i = '_';
 
   llvm::StringSaver &saver = lld::saver();
 

lld/ELF/MapFile.cpp

   os << right_justify("VMA", w) << ' ' << right_justify("LMA", w)
      << "     Size Align Out     In      Symbol\n";
 
-  OutputSection* osec = nullptr;
+  OutputSection *osec = nullptr;
   for (SectionCommand *cmd : script->sectionCommands) {
     if (auto *assign = dyn_cast<SymbolAssignment>(cmd)) {
       if (assign->provide && !assign->sym)

   print("Symbol", "File");
 
   // Print out a table.
-  for (auto kv : map) {
+  for (const auto &kv : map) {
     Symbol *sym = kv.first;
     SetVector<InputFile *> &files = kv.second;
 

lld/ELF/OutputSections.cpp

                         llvm::function_ref<int(InputSectionBase *s)> order) {
   std::vector<std::pair<int, InputSection *>> v;
   for (InputSection *s : in)
-    v.push_back({order(s), s});
+    v.emplace_back(order(s), s);
   llvm::stable_sort(v, less_first());
 
   for (size_t i = 0; i < v.size(); ++i)

lld/MachO/Arch/ARM64.cpp

   thunk->align = 4;
   thunk->data = {reinterpret_cast<const uint8_t *>(thunkCode),
                  sizeof(thunkCode)};
-  thunk->relocs.push_back({/*type=*/ARM64_RELOC_PAGEOFF12,
+  thunk->relocs.emplace_back(/*type=*/ARM64_RELOC_PAGEOFF12,
                              /*pcrel=*/false, /*length=*/2,
                              /*offset=*/4, /*addend=*/0,
-                           /*referent=*/funcSym});
-  thunk->relocs.push_back({/*type=*/ARM64_RELOC_PAGE21,
+                             /*referent=*/funcSym);
+  thunk->relocs.emplace_back(/*type=*/ARM64_RELOC_PAGE21,
                              /*pcrel=*/true, /*length=*/2,
                              /*offset=*/0, /*addend=*/0,
-                           /*referent=*/funcSym});
+                             /*referent=*/funcSym);
 }
 
 ARM64::ARM64() : ARM64Common(LP64()) {

lld/MachO/SyntheticSections.h

 
   void addEntry(const InputSection *isec, uint64_t offset) {
     if (config->isPic)
-      locations.push_back({isec, offset});
+      locations.emplace_back(isec, offset);
   }
 
 private:

   int64_t addend;
   Location target;
   BindingEntry(int64_t addend, Location target)
-      : addend(addend), target(std::move(target)) {}
+      : addend(addend), target(target) {}
 };
 
 template <class Sym>