[NFC][XCOFF] Replace structs FileHeader32/SectionHeader32 with constants.

[Esme]

Summary

Some structs like FileHeader32/SectionHeader32 defined in llvm/include/llvm/BinaryFormat/XCOFF.h seem unnecessary, because we only need their size. So this patch removes them and defines size constants directly.

[sfertile]

One comment but otherwise LGTM.

llvm/include/llvm/BinaryFormat/XCOFF.h

30

The constants for the 64-bit XCOFF headers/relocs aren't used yet so they shouldn't be added in this patch. You can add them in the yaml changes that use them.

[Higuoxing]

LGTM, once @sfertile 's comments are addressed. Thanks!

[Esme]

Addressed comments.

llvm/include/llvm/BinaryFormat/XCOFF.h

 template <unsigned> class SmallString;
 
 namespace XCOFF {
 
 // Constants used in the XCOFF definition.
 
 constexpr size_t FileNamePadSize = 6;
 constexpr size_t NameSize = 8;
+constexpr size_t FileHeaderSize32 = 20;
+constexpr size_t SectionHeaderSize32 = 40;
 constexpr size_t SymbolTableEntrySize = 18;
 constexpr size_t RelocationSerializationSize32 = 10;
 constexpr uint16_t RelocOverflow = 65535;
 constexpr uint8_t AllocRegNo = 31;
 
 enum ReservedSectionNum : int16_t { N_DEBUG = -2, N_ABS = -1, N_UNDEF = 0 };
 
 enum MagicNumber : uint16_t { XCOFF32 = 0x01DF, XCOFF64 = 0x01F7 };
enum RelocationType : uint8_t {
   R_TLSML = 0x25, ///< Module reference to the local TLS storage.
 
   R_TOCU = 0x30, ///< Relative to TOC upper. Specifies the high-order 16 bits of
                  ///< a large code model TOC-relative relocation.
   R_TOCL = 0x31 ///< Relative to TOC lower. Specifies the low-order 16 bits of a
                 ///< large code model TOC-relative relocation.
 };
 
-struct FileHeader32 {
-  uint16_t Magic;
-  uint16_t NumberOfSections;
-  int32_t TimeStamp;
-  uint32_t SymbolTableFileOffset;
-  int32_t NumberOfSymbolTableEntries;
-  uint16_t AuxiliaryHeaderSize;
-  uint16_t Flags;
-};
-
-struct SectionHeader32 {
-  char Name[XCOFF::NameSize];
-  uint32_t PhysicalAddress;
-  uint32_t VirtualAddress;
-  uint32_t Size;
-  uint32_t FileOffsetToData;
-  uint32_t FileOffsetToRelocations;
-  uint32_t FileOffsetToLineNumbers;
-  uint16_t NumberOfRelocations;
-  uint16_t NumberOfLineNumbers;
-  int32_t Flags;
-};
-
 enum CFileStringType : uint8_t {
   XFT_FN = 0,  ///< Specifies the source-file name.
   XFT_CT = 1,  ///< Specifies the compiler time stamp.
   XFT_CV = 2,  ///< Specifies the compiler version number.
   XFT_CD = 128 ///< Specifies compiler-defined information.
 };
 
 enum CFileLangId : uint8_t {

llvm/lib/MC/XCOFFObjectWriter.cpp

for (auto *Section : Sections) {
     // DefaultSectionAlign.
     Address = alignTo(Address, DefaultSectionAlign);
     Section->Size = Address - Section->Address;
   }
 
   SymbolTableEntryCount = SymbolTableIndex;
 
   // Calculate the RawPointer value for each section.
-  uint64_t RawPointer = sizeof(XCOFF::FileHeader32) + auxiliaryHeaderSize() +
-                        SectionCount * sizeof(XCOFF::SectionHeader32);
+  uint64_t RawPointer = XCOFF::FileHeaderSize32 + auxiliaryHeaderSize() +
+                        SectionCount * XCOFF::SectionHeaderSize32;
   for (auto *Sec : Sections) {
     if (Sec->Index == Section::UninitializedIndex || Sec->IsVirtual)
       continue;
 
     Sec->FileOffsetToData = RawPointer;
     RawPointer += Sec->Size;
     if (RawPointer > UINT32_MAX)
       report_fatal_error("Section raw data overflowed this object file.");

llvm/lib/ObjectYAML/XCOFFEmitter.cpp

if (InitFileHdr.NumberOfSymTableEntries) {
     }
   }
   // TODO: Calculate FileOffsetToLineNumbers when line number supported.
   return true;
 }
 
 bool XCOFFWriter::assignAddressesAndIndices() {
   uint64_t CurrentOffset =
-      sizeof(XCOFF::FileHeader32) /* TODO: + auxiliaryHeaderSize() */ +
-      InitSections.size() * sizeof(XCOFF::SectionHeader32);
+      XCOFF::FileHeaderSize32 /* TODO: + auxiliaryHeaderSize() */ +
+      InitSections.size() * XCOFF::SectionHeaderSize32;
 
   // Calculate section header info.
   if (!initSectionHeader(CurrentOffset))
     return false;
   // Calculate file header info.
   return initFileHeader(CurrentOffset);
 }