COFF: Rename Chunk::getPermissions to getOutputCharacteristics.

[pcc]

Summary

In an upcoming change I will need to make a distinction between section
type (code, data, bss) and permissions. The term that I use for both
of these things is "output characteristics".

[ruiu]

LGTM

lld/COFF/Chunks.h

public:
   void setRVA(uint64_t V) { RVA = V; }
 
   // Returns true if this has non-zero data. BSS chunks return
   // false. If false is returned, the space occupied by this chunk
   // will be filled with zeros.
   virtual bool hasData() const { return true; }
 
   // Returns readable/writable/executable bits.
-  virtual uint32_t getPermissions() const { return 0; }
+  virtual uint32_t getOutputCharacteristics() const { return 0; }
 
   // Returns the section name if this is a section chunk.
   // It is illegal to call this function on non-section chunks.
   virtual StringRef getSectionName() const {
     llvm_unreachable("unimplemented getSectionName");
   }
 
   // An output section has pointers to chunks in the section, and each
public:
   };
 
   SectionChunk(ObjFile *File, const coff_section *Header);
   static bool classof(const Chunk *C) { return C->kind() == SectionKind; }
   size_t getSize() const override { return Header->SizeOfRawData; }
   ArrayRef<uint8_t> getContents() const;
   void writeTo(uint8_t *Buf) const override;
   bool hasData() const override;
-  uint32_t getPermissions() const override;
+  uint32_t getOutputCharacteristics() const override;
   StringRef getSectionName() const override { return SectionName; }
   void getBaserels(std::vector<Baserel> *Res) override;
   bool isCOMDAT() const;
   void applyRelX64(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
                    uint64_t P) const;
   void applyRelX86(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
                    uint64_t P) const;
   void applyRelARM(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,

 // class and assigns RVAs and section offsets to each of the member chunks based
 // on the offsets assigned by the StringTableBuilder.
 class MergeChunk : public Chunk {
 public:
   MergeChunk(uint32_t Alignment);
   static void addSection(SectionChunk *C);
   void finalizeContents() override;
 
-  uint32_t getPermissions() const override;
+  uint32_t getOutputCharacteristics() const override;
   StringRef getSectionName() const override { return ".rdata"; }
   size_t getSize() const override;
   void writeTo(uint8_t *Buf) const override;
 
   static std::map<uint32_t, MergeChunk *> Instances;
   std::vector<SectionChunk *> Sections;
 
 private:
   llvm::StringTableBuilder Builder;
 };
 
 // A chunk for common symbols. Common chunks don't have actual data.
 class CommonChunk : public Chunk {
 public:
   CommonChunk(const COFFSymbolRef Sym);
   size_t getSize() const override { return Sym.getValue(); }
   bool hasData() const override { return false; }
-  uint32_t getPermissions() const override;
+  uint32_t getOutputCharacteristics() const override;
   StringRef getSectionName() const override { return ".bss"; }
 
 private:
   const COFFSymbolRef Sym;
 };
 
 // A chunk for linker-created strings.
 class StringChunk : public Chunk {

lld/COFF/Chunks.cpp

for (const coff_relocation &Rel : Relocs) {
     Res->emplace_back(RVA + Rel.VirtualAddress, Ty);
   }
 }
 
 bool SectionChunk::hasData() const {
   return !(Header->Characteristics & IMAGE_SCN_CNT_UNINITIALIZED_DATA);
 }
 
-uint32_t SectionChunk::getPermissions() const {
+uint32_t SectionChunk::getOutputCharacteristics() const {
   return Header->Characteristics & PermMask;
 }
 
 bool SectionChunk::isCOMDAT() const {
   return Header->Characteristics & IMAGE_SCN_LNK_COMDAT;
 }
 
 void SectionChunk::printDiscardedMessage() const {

 }
 
 CommonChunk::CommonChunk(const COFFSymbolRef S) : Sym(S) {
   // Common symbols are aligned on natural boundaries up to 32 bytes.
   // This is what MSVC link.exe does.
   Alignment = std::min(uint64_t(32), PowerOf2Ceil(Sym.getValue()));
 }
 
-uint32_t CommonChunk::getPermissions() const {
+uint32_t CommonChunk::getOutputCharacteristics() const {
   return IMAGE_SCN_CNT_UNINITIALIZED_DATA | IMAGE_SCN_MEM_READ |
          IMAGE_SCN_MEM_WRITE;
 }
 
 void StringChunk::writeTo(uint8_t *Buf) const {
   memcpy(Buf + OutputSectionOff, Str.data(), Str.size());
 }
 
if (!C->isLive())
       continue;
     size_t Off = Builder.getOffset(toStringRef(C->getContents()));
     C->setOutputSection(Out);
     C->setRVA(RVA + Off);
     C->OutputSectionOff = OutputSectionOff + Off;
   }
 }
 
-uint32_t MergeChunk::getPermissions() const {
+uint32_t MergeChunk::getOutputCharacteristics() const {
   return IMAGE_SCN_MEM_READ | IMAGE_SCN_CNT_INITIALIZED_DATA;
 }
 
 size_t MergeChunk::getSize() const {
   return Builder.getSize();
 }
 
 void MergeChunk::writeTo(uint8_t *Buf) const {
   Builder.write(Buf + OutputSectionOff);
 }
 
 } // namespace coff
 } // namespace lld

lld/COFF/Driver.cpp

if (Config->DLL && ((Config->MinGW && Config->Exports.empty()) ||
     Symtab->forEachSymbol([=](Symbol *S) {
       auto *Def = dyn_cast<Defined>(S);
       if (!Exporter.shouldExport(Def))
         return;
       Export E;
       E.Name = Def->getName();
       E.Sym = Def;
       if (Def->getChunk() &&
-          !(Def->getChunk()->getPermissions() & IMAGE_SCN_MEM_EXECUTE))
+          !(Def->getChunk()->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE))
         E.Data = true;
       Config->Exports.push_back(E);
     });
   }
 
   // Windows specific -- when we are creating a .dll file, we also
   // need to create a .lib file.
   if (!Config->Exports.empty() || Config->DLL) {

lld/COFF/ICF.cpp

private:
 
   std::vector<SectionChunk *> Chunks;
   int Cnt = 0;
   std::atomic<bool> Repeat = {false};
 };
 
 // Returns a hash value for S.
 uint32_t ICF::getHash(SectionChunk *C) {
-  return hash_combine(C->getPermissions(), C->SectionName, C->Relocs.size(),
+  return hash_combine(C->getOutputCharacteristics(), C->SectionName, C->Relocs.size(),
                       C->Alignment, uint32_t(C->Header->SizeOfRawData),
                       C->Checksum, C->getContents());
 }
 
 // Returns true if section S is subject of ICF.
 //
 // Microsoft's documentation
 // (https://msdn.microsoft.com/en-us/library/bxwfs976.aspx; visited April
 // 2017) says that /opt:icf folds both functions and read-only data.
 // Despite that, the MSVC linker folds only functions. We found
 // a few instances of programs that are not safe for data merging.
 // Therefore, we merge only functions just like the MSVC tool. However, we merge
 // identical .xdata sections, because the address of unwind information is
 // insignificant to the user program and the Visual C++ linker does this.
 bool ICF::isEligible(SectionChunk *C) {
   // Non-comdat chunks, dead chunks, and writable chunks are not elegible.
-  bool Writable = C->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_WRITE;
+  bool Writable = C->getOutputCharacteristics() & llvm::COFF::IMAGE_SCN_MEM_WRITE;
   if (!C->isCOMDAT() || !C->isLive() || Writable)
     return false;
 
   // Code sections are eligible.
-  if (C->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_EXECUTE)
+  if (C->getOutputCharacteristics() & llvm::COFF::IMAGE_SCN_MEM_EXECUTE)
     return true;
 
   // .xdata unwind info sections are eligble.
   return C->getSectionName().split('$').first == ".xdata";
 }
 
 // Split an equivalence class into smaller classes.
 void ICF::segregate(size_t Begin, size_t End, bool Constant) {
if (auto *D1 = dyn_cast<DefinedRegular>(B1))
         return D1->getValue() == D2->getValue() &&
                D1->getChunk()->Class[Cnt % 2] == D2->getChunk()->Class[Cnt % 2];
     return false;
   };
   if (!std::equal(A->Relocs.begin(), A->Relocs.end(), B->Relocs.begin(), Eq))
     return false;
 
   // Compare section attributes and contents.
-  return A->getPermissions() == B->getPermissions() &&
+  return A->getOutputCharacteristics() == B->getOutputCharacteristics() &&
          A->SectionName == B->SectionName && A->Alignment == B->Alignment &&
          A->Header->SizeOfRawData == B->Header->SizeOfRawData &&
          A->Checksum == B->Checksum && A->getContents() == B->getContents();
 }
 
 // Compare "moving" part of two sections, namely relocation targets.
 bool ICF::equalsVariable(const SectionChunk *A, const SectionChunk *B) {
   // Compare relocations.

lld/COFF/MinGW.cpp

if (EC)
     fatal("cannot open " + Name + ": " + EC.message());
 
   OS << "EXPORTS\n";
   for (Export &E : Config->Exports) {
     OS << "    " << E.ExportName << " "
        << "@" << E.Ordinal;
     if (auto *Def = dyn_cast_or_null<Defined>(E.Sym)) {
       if (Def && Def->getChunk() &&
-          !(Def->getChunk()->getPermissions() & IMAGE_SCN_MEM_EXECUTE))
+          !(Def->getChunk()->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE))
         OS << " DATA";
     }
     OS << "\n";
   }
 }

lld/COFF/Writer.cpp

if (Name == ".pdata") {
       if (!FirstPdata)
         FirstPdata = Pair.second.front();
       LastPdata = Pair.second.back();
     }
     OutputSection *Sec = CreateSection(Name, 0);
     std::vector<Chunk *> &Chunks = Pair.second;
     for (Chunk *C : Chunks) {
       Sec->addChunk(C);
-      Sec->addPermissions(C->getPermissions());
+      Sec->addPermissions(C->getOutputCharacteristics());
     }
   }
 
   // Finally, move some output sections to the end.
   auto SectionOrder = [&](OutputSection *S) {
     // .reloc should come last of all since it refers to RVAs of data in the
     // previous sections.
     if (S == RelocSec)