Move alignment from MCSectionData to MCSection.

This starts merging MCSection and MCSectionData.

There are a few issues with the current split between MCSection and
MCSectionData.

* It optimizes the the not as important case. We want the production
of .o files to be really fast, but the split puts the information used
for .o emission in a separate data structure.

* The ELF/COFF/MachO hierarchy is not represented in MCSectionData,
leading to some ad-hoc ways to represent the various flags.

* It makes it harder to remember where each item is.

The attached patch starts merging the two by moving the alignment from
MCSectionData to MCSection.

Most of the patch is actually just dropping 'const', since
MCSectionData is mutable, but MCSection was not.

llvm-svn: 237936

1 files changed, 16 insertions, 18 deletions

diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index c36da56..ff1c2a9 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -133,8 +133,8 @@ class ELFObjectWriter : public MCObjectWriter {
     unsigned ShstrtabIndex;
 
     // Sections in the order they are to be output in the section table.
-    std::vector<const MCSectionELF *> SectionTable;
-    unsigned addToSectionTable(const MCSectionELF *Sec);
+    std::vector<MCSectionELF *> SectionTable;
+    unsigned addToSectionTable(MCSectionELF *Sec);
 
     // TargetObjectWriter wrappers.
     bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
@@ -221,8 +221,8 @@ class ELFObjectWriter : public MCObjectWriter {
                             const SectionIndexMapTy &SectionIndexMap,
                             const RevGroupMapTy &RevGroupMap);
 
-    const MCSectionELF *createRelocationSection(MCAssembler &Asm,
-                                                const MCSectionELF &Sec);
+    MCSectionELF *createRelocationSection(MCAssembler &Asm,
+                                          const MCSectionELF &Sec);
 
     const MCSectionELF *createSectionHeaderStringTable();
     const MCSectionELF *createStringTable(MCContext &Ctx);
@@ -261,7 +261,7 @@ class ELFObjectWriter : public MCObjectWriter {
   };
 }
 
-unsigned ELFObjectWriter::addToSectionTable(const MCSectionELF *Sec) {
+unsigned ELFObjectWriter::addToSectionTable(MCSectionELF *Sec) {
   SectionTable.push_back(Sec);
   ShStrTabBuilder.add(Sec->getSectionName());
   return SectionTable.size();
@@ -549,7 +549,7 @@ void ELFObjectWriter::WriteSymbolTable(MCAssembler &Asm,
   unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
 
   // Symbol table
-  const MCSectionELF *SymtabSection =
+  MCSectionELF *SymtabSection =
       Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
   MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
   SymtabSD.setAlignment(is64Bit() ? 8 : 4);
@@ -608,7 +608,7 @@ void ELFObjectWriter::WriteSymbolTable(MCAssembler &Asm,
     return;
 
   SecStart = OS.tell();
-  const MCSectionELF *SymtabShndxSection =
+  MCSectionELF *SymtabShndxSection =
       Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
   addToSectionTable(SymtabShndxSection);
   MCSectionData *SymtabShndxSD =
@@ -1064,7 +1064,7 @@ void ELFObjectWriter::computeSymbolTable(
     UndefinedSymbolData[i].Symbol->getData().setIndex(Index++);
 }
 
-const MCSectionELF *
+MCSectionELF *
 ELFObjectWriter::createRelocationSection(MCAssembler &Asm,
                                          const MCSectionELF &Sec) {
   if (Relocations[&Sec].empty())
@@ -1085,7 +1085,7 @@ ELFObjectWriter::createRelocationSection(MCAssembler &Asm,
   if (Sec.getFlags() & ELF::SHF_GROUP)
     Flags = ELF::SHF_GROUP;
 
-  const MCSectionELF *RelaSection = Ctx.createELFRelSection(
+  MCSectionELF *RelaSection = Ctx.createELFRelSection(
       RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
       Flags, EntrySize, Sec.getGroup(), &Sec);
   MCSectionData &RelSD = Asm.getOrCreateSectionData(*RelaSection);
@@ -1141,8 +1141,7 @@ prependCompressionHeader(uint64_t Size,
 void ELFObjectWriter::writeSectionData(const MCAssembler &Asm,
                                        const MCSectionData &SD,
                                        const MCAsmLayout &Layout) {
-  const MCSectionELF &Section =
-      static_cast<const MCSectionELF &>(SD.getSection());
+  MCSectionELF &Section = static_cast<MCSectionELF &>(SD.getSection());
   StringRef SectionName = Section.getSectionName();
 
   // Compressing debug_frame requires handling alignment fragments which is
@@ -1245,7 +1244,7 @@ const MCSectionELF *ELFObjectWriter::createSectionHeaderStringTable() {
 }
 
 const MCSectionELF *ELFObjectWriter::createStringTable(MCContext &Ctx) {
-  const MCSectionELF *StrtabSection =
+  MCSectionELF *StrtabSection =
       Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
   StringTableIndex = addToSectionTable(StrtabSection);
   OS << StrTabBuilder.data();
@@ -1315,7 +1314,7 @@ void ELFObjectWriter::writeSectionHeader(
       (NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
   WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
 
-  for (const MCSectionELF *Section : SectionTable) {
+  for (MCSectionELF *Section : SectionTable) {
     const MCSectionData &SD = Asm.getOrCreateSectionData(*Section);
     uint32_t GroupSymbolIndex;
     unsigned Type = Section->getType();
@@ -1337,7 +1336,7 @@ void ELFObjectWriter::writeSectionHeader(
 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
                                   const MCAsmLayout &Layout) {
   MCContext &Ctx = Asm.getContext();
-  const MCSectionELF *ShstrtabSection =
+  MCSectionELF *ShstrtabSection =
       Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0);
   ShstrtabIndex = addToSectionTable(ShstrtabSection);
 
@@ -1353,8 +1352,7 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
   SectionOffsetsTy SectionOffsets;
   bool ComputedSymtab = false;
   for (const MCSectionData &SD : Asm) {
-    const MCSectionELF &Section =
-        static_cast<const MCSectionELF &>(SD.getSection());
+    MCSectionELF &Section = static_cast<MCSectionELF &>(SD.getSection());
 
     uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
     WriteZeros(Padding);
@@ -1388,13 +1386,13 @@ void ELFObjectWriter::WriteObject(MCAssembler &Asm,
     if (Type == ELF::SHT_GROUP || Type == ELF::SHT_REL || Type == ELF::SHT_RELA)
       continue;
 
-    const MCSectionELF *RelSection = createRelocationSection(Asm, Section);
+    MCSectionELF *RelSection = createRelocationSection(Asm, Section);
 
     if (SignatureSymbol) {
       Asm.getOrCreateSymbolData(*SignatureSymbol);
       unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
       if (!GroupIdx) {
-        const MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
+        MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
         GroupIdx = addToSectionTable(Group);
         MCSectionData *GroupD = &Asm.getOrCreateSectionData(*Group);
         GroupD->setAlignment(4);