[Alignment] Use Align for ObjectFile::getSectionAlignment

[gchatelet]

• Add documentation and refactor alignment log decode

llvm/include/llvm/Object/COFF.h

struct coff_section {
 
   // Returns true if the actual number of relocations is stored in
   // VirtualAddress field of the first relocation table entry.
   bool hasExtendedRelocations() const {
     return (Characteristics & COFF::IMAGE_SCN_LNK_NRELOC_OVFL) &&
            NumberOfRelocations == UINT16_MAX;
   }
 
-  uint32_t getAlignment() const {
+  Align getAlignment() const {
     // The IMAGE_SCN_TYPE_NO_PAD bit is a legacy way of getting to
     // IMAGE_SCN_ALIGN_1BYTES.
     if (Characteristics & COFF::IMAGE_SCN_TYPE_NO_PAD)
-      return 1;
+      return Align(1);
 
     // Bit [20:24] contains section alignment. 0 means use a default alignment
     // of 16.
-    uint32_t Shift = (Characteristics >> 20) & 0xF;
-    if (Shift > 0)
-      return 1U << (Shift - 1);
-    return 16;
+    uint32_t EncodedLogValue = (Characteristics >> 20) & 0xF;
+    return decodeMaybeAlign(EncodedLogValue).value_or(Align(16));
   }
 };
 
 struct coff_relocation {
   support::ulittle32_t VirtualAddress;
   support::ulittle32_t SymbolTableIndex;
   support::ulittle16_t Type;
 };
protected:
   Expected<section_iterator> getSymbolSection(DataRefImpl Symb) const override;
   void moveSectionNext(DataRefImpl &Sec) const override;
   Expected<StringRef> getSectionName(DataRefImpl Sec) const override;
   uint64_t getSectionAddress(DataRefImpl Sec) const override;
   uint64_t getSectionIndex(DataRefImpl Sec) const override;
   uint64_t getSectionSize(DataRefImpl Sec) const override;
   Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const override;
-  uint64_t getSectionAlignment(DataRefImpl Sec) const override;
+  Align getSectionAlignment(DataRefImpl Sec) const override;
   bool isSectionCompressed(DataRefImpl Sec) const override;
   bool isSectionText(DataRefImpl Sec) const override;
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
   bool isDebugSection(DataRefImpl Sec) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;
   relocation_iterator section_rel_end(DataRefImpl Sec) const override;

llvm/include/llvm/Object/ELFObjectFile.h

protected:
 
   void moveSectionNext(DataRefImpl &Sec) const override;
   Expected<StringRef> getSectionName(DataRefImpl Sec) const override;
   uint64_t getSectionAddress(DataRefImpl Sec) const override;
   uint64_t getSectionIndex(DataRefImpl Sec) const override;
   uint64_t getSectionSize(DataRefImpl Sec) const override;
   Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const override;
-  uint64_t getSectionAlignment(DataRefImpl Sec) const override;
+  Align getSectionAlignment(DataRefImpl Sec) const override;
   bool isSectionCompressed(DataRefImpl Sec) const override;
   bool isSectionText(DataRefImpl Sec) const override;
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
   bool isBerkeleyText(DataRefImpl Sec) const override;
   bool isBerkeleyData(DataRefImpl Sec) const override;
   bool isDebugSection(DataRefImpl Sec) const override;
if (Error E =
           checkOffset(getMemoryBufferRef(),
                       (uintptr_t)base() + EShdr->sh_offset, EShdr->sh_size))
     return std::move(E);
   return makeArrayRef((const uint8_t *)base() + EShdr->sh_offset,
                       EShdr->sh_size);
 }
 
 template <class ELFT>
-uint64_t ELFObjectFile<ELFT>::getSectionAlignment(DataRefImpl Sec) const {
-  return getSection(Sec)->sh_addralign;
+Align ELFObjectFile<ELFT>::getSectionAlignment(DataRefImpl Sec) const {
+  // The value 0 or 1 means that the section has no alignment constraints.
+  // https://man7.org/linux/man-pages/man5/elf.5.html
+  return MaybeAlign(getSection(Sec)->sh_addralign).valueOrOne();
 }
 
 template <class ELFT>
 bool ELFObjectFile<ELFT>::isSectionCompressed(DataRefImpl Sec) const {
   return getSection(Sec)->sh_flags & ELF::SHF_COMPRESSED;
 }
 
 template <class ELFT>

llvm/include/llvm/Object/MachO.h

public:
   void moveSectionNext(DataRefImpl &Sec) const override;
   Expected<StringRef> getSectionName(DataRefImpl Sec) const override;
   uint64_t getSectionAddress(DataRefImpl Sec) const override;
   uint64_t getSectionIndex(DataRefImpl Sec) const override;
   uint64_t getSectionSize(DataRefImpl Sec) const override;
   ArrayRef<uint8_t> getSectionContents(uint32_t Offset, uint64_t Size) const;
   Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const override;
-  uint64_t getSectionAlignment(DataRefImpl Sec) const override;
+  Align getSectionAlignment(DataRefImpl Sec) const override;
   Expected<SectionRef> getSection(unsigned SectionIndex) const;
   Expected<SectionRef> getSection(StringRef SectionName) const;
   bool isSectionCompressed(DataRefImpl Sec) const override;
   bool isSectionText(DataRefImpl Sec) const override;
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
   bool isSectionBitcode(DataRefImpl Sec) const override;

llvm/include/llvm/Object/ObjectFile.h

protected:
 
   virtual void moveSectionNext(DataRefImpl &Sec) const = 0;
   virtual Expected<StringRef> getSectionName(DataRefImpl Sec) const = 0;
   virtual uint64_t getSectionAddress(DataRefImpl Sec) const = 0;
   virtual uint64_t getSectionIndex(DataRefImpl Sec) const = 0;
   virtual uint64_t getSectionSize(DataRefImpl Sec) const = 0;
   virtual Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const = 0;
-  virtual uint64_t getSectionAlignment(DataRefImpl Sec) const = 0;
+  virtual Align getSectionAlignment(DataRefImpl Sec) const = 0;
   virtual bool isSectionCompressed(DataRefImpl Sec) const = 0;
   virtual bool isSectionText(DataRefImpl Sec) const = 0;
   virtual bool isSectionData(DataRefImpl Sec) const = 0;
   virtual bool isSectionBSS(DataRefImpl Sec) const = 0;
   // A section is 'virtual' if its contents aren't present in the object image.
   virtual bool isSectionVirtual(DataRefImpl Sec) const = 0;
   virtual bool isSectionBitcode(DataRefImpl Sec) const;
   virtual bool isSectionStripped(DataRefImpl Sec) const;
inline Expected<StringRef> SectionRef::getContents() const {
   Expected<ArrayRef<uint8_t>> Res =
       OwningObject->getSectionContents(SectionPimpl);
   if (!Res)
     return Res.takeError();
   return StringRef(reinterpret_cast<const char *>(Res->data()), Res->size());
 }
 
 inline uint64_t SectionRef::getAlignment() const {
-  return OwningObject->getSectionAlignment(SectionPimpl);
+  return OwningObject->getSectionAlignment(SectionPimpl).value();
 }
 
 inline bool SectionRef::isCompressed() const {
   return OwningObject->isSectionCompressed(SectionPimpl);
 }
 
 inline bool SectionRef::isText() const {
   return OwningObject->isSectionText(SectionPimpl);

llvm/include/llvm/Object/Wasm.h

public:
   // Overrides from SectionRef.
   void moveSectionNext(DataRefImpl &Sec) const override;
   Expected<StringRef> getSectionName(DataRefImpl Sec) const override;
   uint64_t getSectionAddress(DataRefImpl Sec) const override;
   uint64_t getSectionIndex(DataRefImpl Sec) const override;
   uint64_t getSectionSize(DataRefImpl Sec) const override;
   Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const override;
-  uint64_t getSectionAlignment(DataRefImpl Sec) const override;
+  Align getSectionAlignment(DataRefImpl Sec) const override;
   bool isSectionCompressed(DataRefImpl Sec) const override;
   bool isSectionText(DataRefImpl Sec) const override;
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;
   relocation_iterator section_rel_end(DataRefImpl Sec) const override;
 

llvm/include/llvm/Object/XCOFFObjectFile.h

public:
 
   void moveSectionNext(DataRefImpl &Sec) const override;
   Expected<StringRef> getSectionName(DataRefImpl Sec) const override;
   uint64_t getSectionAddress(DataRefImpl Sec) const override;
   uint64_t getSectionIndex(DataRefImpl Sec) const override;
   uint64_t getSectionSize(DataRefImpl Sec) const override;
   Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const override;
-  uint64_t getSectionAlignment(DataRefImpl Sec) const override;
+  Align getSectionAlignment(DataRefImpl Sec) const override;
   bool isSectionCompressed(DataRefImpl Sec) const override;
   bool isSectionText(DataRefImpl Sec) const override;
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isDebugSection(DataRefImpl Sec) const override;
 
   bool isSectionVirtual(DataRefImpl Sec) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;

llvm/lib/ExecutionEngine/JITLink/COFFLinkGraphBuilder.cpp

for (COFFSectionIndex SecIndex = 1;
     if (GraphSec->getMemProt() != Prot)
       return make_error<JITLinkError>("MemProt should match");
 
     Block *B = nullptr;
     if ((*Sec)->Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA)
       B = &G->createZeroFillBlock(
           *GraphSec, getSectionSize(Obj, *Sec),
           orc::ExecutorAddr(getSectionAddress(Obj, *Sec)),
-          (*Sec)->getAlignment(), 0);
+          (*Sec)->getAlignment().value(), 0);
     else {
       ArrayRef<uint8_t> Data;
       if (auto Err = Obj.getSectionContents(*Sec, Data))
         return Err;
 
       auto CharData = ArrayRef<char>(
           reinterpret_cast<const char *>(Data.data()), Data.size());
 
       if (SectionName == getDirectiveSectionName())
         if (auto Err = handleDirectiveSection(
                 StringRef(CharData.data(), CharData.size())))
           return Err;
 
       B = &G->createContentBlock(
           *GraphSec, CharData, orc::ExecutorAddr(getSectionAddress(Obj, *Sec)),
-          (*Sec)->getAlignment(), 0);
+          (*Sec)->getAlignment().value(), 0);
     }
 
     setGraphBlock(SecIndex, B);
   }
 
   return Error::success();
 }
 

llvm/lib/Object/COFFObjectFile.cpp

 COFFObjectFile::getSectionContents(DataRefImpl Ref) const {
   const coff_section *Sec = toSec(Ref);
   ArrayRef<uint8_t> Res;
   if (Error E = getSectionContents(Sec, Res))
     return std::move(E);
   return Res;
 }
 
-uint64_t COFFObjectFile::getSectionAlignment(DataRefImpl Ref) const {
+Align COFFObjectFile::getSectionAlignment(DataRefImpl Ref) const {
   const coff_section *Sec = toSec(Ref);
-  return Sec->getAlignment();
+  return Align(Sec->getAlignment());
 }
 
 bool COFFObjectFile::isSectionCompressed(DataRefImpl Sec) const {
   return false;
 }
 
 bool COFFObjectFile::isSectionText(DataRefImpl Ref) const {
   const coff_section *Sec = toSec(Ref);

llvm/lib/Object/MachOObjectFile.cpp

if (is64Bit()) {
     MachO::section Sect = getSection(Sec);
     Offset = Sect.offset;
     Size = Sect.size;
   }
 
   return getSectionContents(Offset, Size);
 }
 
-uint64_t MachOObjectFile::getSectionAlignment(DataRefImpl Sec) const {
-  uint32_t Align;
-  if (is64Bit()) {
-    MachO::section_64 Sect = getSection64(Sec);
-    Align = Sect.align;
-  } else {
-    MachO::section Sect = getSection(Sec);
-    Align = Sect.align;
-  }
+Align MachOObjectFile::getSectionAlignment(DataRefImpl Sec) const {
 
-  return uint64_t(1) << Align;
+  return is64Bit() ? Align(1ULL << getSection64(Sec).align)
+                   : Align(1ULL << getSection(Sec).align);
 }
 
 Expected<SectionRef> MachOObjectFile::getSection(unsigned SectionIndex) const {
   if (SectionIndex < 1 || SectionIndex > Sections.size())
     return malformedError("bad section index: " + Twine((int)SectionIndex));
 
   DataRefImpl DRI;
   DRI.d.a = SectionIndex - 1;

llvm/lib/Object/WasmObjectFile.cpp

 Expected<ArrayRef<uint8_t>>
 WasmObjectFile::getSectionContents(DataRefImpl Sec) const {
   const WasmSection &S = Sections[Sec.d.a];
   // This will never fail since wasm sections can never be empty (user-sections
   // must have a name and non-user sections each have a defined structure).
   return S.Content;
 }
 
-uint64_t WasmObjectFile::getSectionAlignment(DataRefImpl Sec) const {
-  return 1;
+Align WasmObjectFile::getSectionAlignment(DataRefImpl Sec) const {
+  return Align(1);
 }
 
 bool WasmObjectFile::isSectionCompressed(DataRefImpl Sec) const {
   return false;
 }
 
 bool WasmObjectFile::isSectionText(DataRefImpl Sec) const {
   return getWasmSection(Sec).Type == wasm::WASM_SEC_CODE;

llvm/lib/Object/XCOFFObjectFile.cpp

if (Error E = Binary::checkOffset(
     return createError(
         toString(std::move(E)) + ": section data with offset 0x" +
         Twine::utohexstr(OffsetToRaw) + " and size 0x" +
         Twine::utohexstr(SectionSize) + " goes past the end of the file");
 
   return makeArrayRef(ContentStart,SectionSize);
 }
 
-uint64_t XCOFFObjectFile::getSectionAlignment(DataRefImpl Sec) const {
-  uint64_t Result = 0;
+Align XCOFFObjectFile::getSectionAlignment(DataRefImpl Sec) const {
   llvm_unreachable("Not yet implemented!");
-  return Result;
+  return {};
 }
 
 uint64_t XCOFFObjectFile::getSectionFileOffsetToRawData(DataRefImpl Sec) const {
   if (is64Bit())
     return toSection64(Sec)->FileOffsetToRawData;
 
   return toSection32(Sec)->FileOffsetToRawData;
 }