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

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.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D103901

Author: EsmeYi

llvm/include/llvm/BinaryFormat/XCOFF.h

@@ -26,6 +26,8 @@ namespace XCOFF {
 
 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;
@@ -255,29 +257,6 @@ enum RelocationType : uint8_t {
                 ///< 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.

llvm/lib/MC/XCOFFObjectWriter.cpp

@@ -922,8 +922,8 @@ void XCOFFObjectWriter::assignAddressesAndIndices(const MCAsmLayout &Layout) {
   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;

llvm/lib/ObjectYAML/XCOFFEmitter.cpp

@@ -158,8 +158,8 @@ bool XCOFFWriter::initFileHeader(uint64_t CurrentOffset) {
 
 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))