MCSectionELF: Remove classof

The object file format specific derived classes are used in context like
MCStreamer and MCObjectTargetWriter where the type is statically known.
We don't use isa/dyn_cast and we want to eliminate
MCSection::SectionVariant in the base class.

Author: MaskRay

llvm/include/llvm/MC/MCSectionELF.h

@@ -100,10 +100,6 @@ class MCSectionELF final : public MCSection {
   std::pair<uint64_t, uint64_t> getOffsets() const {
     return std::make_pair(StartOffset, EndOffset);
   }
-
-  static bool classof(const MCSection *S) {
-    return S->getVariant() == SV_ELF;
-  }
 };
 
 } // end namespace llvm

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -995,7 +995,7 @@ MCSection *TargetLoweringObjectFileELF::getSectionForLSDA(
   if (!LSDASection || (!F.hasComdat() && !TM.getFunctionSections()))
     return LSDASection;
 
-  const auto *LSDA = cast<MCSectionELF>(LSDASection);
+  const auto *LSDA = static_cast<const MCSectionELF *>(LSDASection);
   unsigned Flags = LSDA->getFlags();
   const MCSymbolELF *LinkedToSym = nullptr;
   StringRef Group;

llvm/lib/MC/ELFObjectWriter.cpp

@@ -1087,7 +1087,8 @@ uint64_t ELFWriter::writeObject() {
       // Remember the offset into the file for this section.
       const uint64_t SecStart = align(RelSection->getAlign());
 
-      writeRelocations(cast<MCSectionELF>(*RelSection->getLinkedToSection()));
+      writeRelocations(
+          static_cast<const MCSectionELF &>(*RelSection->getLinkedToSection()));
 
       uint64_t SecEnd = W.OS.tell();
       RelSection->setOffsets(SecStart, SecEnd);
@@ -1260,7 +1261,7 @@ bool ELFObjectWriter::useSectionSymbol(const MCValue &Val,
   // that it pointed to another string and subtracting 42 at runtime will
   // produce the wrong value.
   if (Sym->isInSection()) {
-    auto &Sec = cast<MCSectionELF>(Sym->getSection());
+    auto &Sec = static_cast<const MCSectionELF &>(Sym->getSection());
     unsigned Flags = Sec.getFlags();
     if (Flags & ELF::SHF_MERGE) {
       if (C != 0)
@@ -1312,13 +1313,14 @@ bool ELFObjectWriter::checkRelocation(SMLoc Loc, const MCSectionELF *From,
 void ELFObjectWriter::recordRelocation(const MCFragment &F,
                                        const MCFixup &Fixup, MCValue Target,
                                        uint64_t &FixedValue) {
-  const MCSectionELF &Section = cast<MCSectionELF>(*F.getParent());
+  auto &Section = static_cast<const MCSectionELF &>(*F.getParent());
   MCContext &Ctx = getContext();
 
   const auto *SymA = cast_or_null<MCSymbolELF>(Target.getAddSym());
-  const MCSectionELF *SecA = (SymA && SymA->isInSection())
-                                 ? cast<MCSectionELF>(&SymA->getSection())
-                                 : nullptr;
+  const MCSectionELF *SecA =
+      (SymA && SymA->isInSection())
+          ? static_cast<const MCSectionELF *>(&SymA->getSection())
+          : nullptr;
   if (DwoOS && !checkRelocation(Fixup.getLoc(), &Section, SecA))
     return;
 

llvm/lib/MC/MCParser/ELFAsmParser.cpp

@@ -644,8 +644,8 @@ bool ELFAsmParser::parseSectionArguments(bool IsPush, SMLoc loc) {
   }
 
   if (UseLastGroup) {
-    if (const MCSectionELF *Section =
-            cast_or_null<MCSectionELF>(getStreamer().getCurrentSectionOnly()))
+    if (auto *Section = static_cast<const MCSectionELF *>(
+            getStreamer().getCurrentSectionOnly()))
       if (const MCSymbol *Group = Section->getGroup()) {
         GroupName = Group->getName();
         IsComdat = Section->isComdat();

llvm/lib/Target/AArch64/AArch64TargetObjectFile.cpp

@@ -36,7 +36,7 @@ void AArch64_ELFTargetObjectFile::Initialize(MCContext &Ctx,
   // SHF_AARCH64_PURECODE flag set if the "+execute-only" target feature is
   // present.
   if (TM.getMCSubtargetInfo()->hasFeature(AArch64::FeatureExecuteOnly)) {
-    auto *Text = cast<MCSectionELF>(TextSection);
+    auto *Text = static_cast<MCSectionELF *>(TextSection);
     Text->setFlags(Text->getFlags() | ELF::SHF_AARCH64_PURECODE);
   }
 }

llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp

@@ -523,7 +523,8 @@ void AArch64TargetELFStreamer::finish() {
   // mark it execute-only if it is empty and there is at least one
   // execute-only section in the object.
   if (any_of(Asm, [](const MCSection &Sec) {
-        return cast<MCSectionELF>(Sec).getFlags() & ELF::SHF_AARCH64_PURECODE;
+        return static_cast<const MCSectionELF &>(Sec).getFlags() &
+               ELF::SHF_AARCH64_PURECODE;
       })) {
     auto *Text =
         static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());

llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

@@ -1138,7 +1138,8 @@ void ARMTargetELFStreamer::finish() {
   MCContext &Ctx = getContext();
   auto &Asm = getStreamer().getAssembler();
   if (any_of(Asm, [](const MCSection &Sec) {
-        return cast<MCSectionELF>(Sec).getFlags() & ELF::SHF_ARM_PURECODE;
+        return static_cast<const MCSectionELF &>(Sec).getFlags() &
+               ELF::SHF_ARM_PURECODE;
       })) {
     auto *Text =
         static_cast<MCSectionELF *>(Ctx.getObjectFileInfo()->getTextSection());

llvm/lib/Target/AVR/AVRAsmPrinter.cpp

@@ -260,7 +260,7 @@ bool AVRAsmPrinter::doFinalization(Module &M) {
       continue;
     }
 
-    auto *Section = cast<MCSectionELF>(TLOF.SectionForGlobal(&GO, TM));
+    auto *Section = static_cast<MCSectionELF *>(TLOF.SectionForGlobal(&GO, TM));
     if (Section->getName().starts_with(".data"))
       NeedsCopyData = true;
     else if (Section->getName().starts_with(".rodata") && SubTM->hasLPM())

llvm/lib/Target/BPF/BTFDebug.cpp

@@ -1255,10 +1255,8 @@ void BTFDebug::beginFunctionImpl(const MachineFunction *MF) {
   FuncInfo.Label = FuncLabel;
   FuncInfo.TypeId = FuncTypeId;
   if (FuncLabel->isInSection()) {
-    MCSection &Section = FuncLabel->getSection();
-    const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
-    assert(SectionELF && "Null section for Function Label");
-    SecNameOff = addString(SectionELF->getName());
+    auto &Sec = static_cast<const MCSectionELF &>(FuncLabel->getSection());
+    SecNameOff = addString(Sec.getName());
   } else {
     SecNameOff = addString(".text");
   }

llvm/lib/Target/BPF/MCTargetDesc/BPFELFObjectWriter.cpp

@@ -54,11 +54,8 @@ unsigned BPFELFObjectWriter::getRelocType(const MCFixup &Fixup,
       const MCSymbol &Sym = *A;
 
       if (Sym.isDefined()) {
-        MCSection &Section = Sym.getSection();
-        const MCSectionELF *SectionELF = dyn_cast<MCSectionELF>(&Section);
-        assert(SectionELF && "Null section for reloc symbol");
-
-        unsigned Flags = SectionELF->getFlags();
+        auto &Section = static_cast<const MCSectionELF &>(Sym.getSection());
+        unsigned Flags = Section.getFlags();
 
         if (Sym.isTemporary()) {
           // .BTF.ext generates FK_Data_4 relocations for