MCSectionCOFF: Avoid cast

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/MCMachObjectWriter.h

@@ -16,7 +16,7 @@
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCLinkerOptimizationHint.h"
 #include "llvm/MC/MCObjectWriter.h"
-#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/EndianStream.h"
@@ -276,7 +276,7 @@ class LLVM_ABI MachObjectWriter final : public MCObjectWriter {
                                uint64_t SectionDataSize, uint32_t MaxProt,
                                uint32_t InitProt);
 
-  void writeSection(const MCAssembler &Asm, const MCSection &Sec,
+  void writeSection(const MCAssembler &Asm, const MCSectionMachO &Sec,
                     uint64_t VMAddr, uint64_t FileOffset, unsigned Flags,
                     uint64_t RelocationsStart, unsigned NumRelocations);
 

llvm/lib/MC/MCFragment.cpp

@@ -35,7 +35,7 @@ MCFragment::MCFragment(FragmentType Kind, bool HasInstructions)
 }
 
 const MCSymbol *MCFragment::getAtom() const {
-  return cast<MCSectionMachO>(Parent)->getAtom(LayoutOrder);
+  return static_cast<const MCSectionMachO *>(Parent)->getAtom(LayoutOrder);
 }
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)

llvm/lib/MC/MCMachOStreamer.cpp

@@ -443,13 +443,13 @@ void MCMachOStreamer::finishImpl() {
   // Set the fragment atom associations by tracking the last seen atom defining
   // symbol.
   for (MCSection &Sec : getAssembler()) {
-    cast<MCSectionMachO>(Sec).allocAtoms();
+    static_cast<MCSectionMachO &>(Sec).allocAtoms();
     const MCSymbol *CurrentAtom = nullptr;
     size_t I = 0;
     for (MCFragment &Frag : Sec) {
       if (const MCSymbol *Symbol = DefiningSymbolMap.lookup(&Frag))
         CurrentAtom = Symbol;
-      cast<MCSectionMachO>(Sec).setAtom(I++, CurrentAtom);
+      static_cast<MCSectionMachO &>(Sec).setAtom(I++, CurrentAtom);
     }
   }
 

llvm/lib/MC/MachObjectWriter.cpp

@@ -126,7 +126,8 @@ uint64_t MachObjectWriter::getSymbolAddress(const MCSymbol &S) const {
 uint64_t MachObjectWriter::getPaddingSize(const MCAssembler &Asm,
                                           const MCSection *Sec) const {
   uint64_t EndAddr = getSectionAddress(Sec) + Asm.getSectionAddressSize(*Sec);
-  unsigned Next = cast<MCSectionMachO>(Sec)->getLayoutOrder() + 1;
+  unsigned Next =
+      static_cast<const MCSectionMachO *>(Sec)->getLayoutOrder() + 1;
   if (Next >= SectionOrder.size())
     return 0;
 
@@ -259,27 +260,24 @@ void MachObjectWriter::writeSegmentLoadCommand(
 }
 
 void MachObjectWriter::writeSection(const MCAssembler &Asm,
-                                    const MCSection &Sec, uint64_t VMAddr,
+                                    const MCSectionMachO &Sec, uint64_t VMAddr,
                                     uint64_t FileOffset, unsigned Flags,
                                     uint64_t RelocationsStart,
                                     unsigned NumRelocations) {
-  uint64_t SectionSize = Asm.getSectionAddressSize(Sec);
-  const MCSectionMachO &Section = cast<MCSectionMachO>(Sec);
-
   // The offset is unused for virtual sections.
-  if (Section.isBssSection()) {
+  if (Sec.isBssSection()) {
     assert(Asm.getSectionFileSize(Sec) == 0 && "Invalid file size!");
     FileOffset = 0;
   }
 
   // struct section (68 bytes) or
   // struct section_64 (80 bytes)
 
+  uint64_t SectionSize = Asm.getSectionAddressSize(Sec);
   uint64_t Start = W.OS.tell();
   (void) Start;
-
-  writeWithPadding(Section.getName(), 16);
-  writeWithPadding(Section.getSegmentName(), 16);
+  writeWithPadding(Sec.getName(), 16);
+  writeWithPadding(Sec.getSegmentName(), 16);
   if (is64Bit()) {
     W.write<uint64_t>(VMAddr);      // address
     W.write<uint64_t>(SectionSize); // size
@@ -290,14 +288,14 @@ void MachObjectWriter::writeSection(const MCAssembler &Asm,
   assert(isUInt<32>(FileOffset) && "Cannot encode offset of section");
   W.write<uint32_t>(FileOffset);
 
-  W.write<uint32_t>(Log2(Section.getAlign()));
+  W.write<uint32_t>(Log2(Sec.getAlign()));
   assert((!NumRelocations || isUInt<32>(RelocationsStart)) &&
          "Cannot encode offset of relocations");
   W.write<uint32_t>(NumRelocations ? RelocationsStart : 0);
   W.write<uint32_t>(NumRelocations);
   W.write<uint32_t>(Flags);
   W.write<uint32_t>(IndirectSymBase.lookup(&Sec)); // reserved1
-  W.write<uint32_t>(Section.getStubSize()); // reserved2
+  W.write<uint32_t>(Sec.getStubSize());            // reserved2
   if (is64Bit())
     W.write<uint32_t>(0); // reserved3
 
@@ -531,7 +529,7 @@ void MachObjectWriter::bindIndirectSymbols(MCAssembler &Asm) {
   // Report errors for use of .indirect_symbol not in a symbol pointer section
   // or stub section.
   for (IndirectSymbolData &ISD : IndirectSymbols) {
-    const MCSectionMachO &Section = cast<MCSectionMachO>(*ISD.Section);
+    const MCSectionMachO &Section = static_cast<MCSectionMachO &>(*ISD.Section);
 
     if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS &&
         Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
@@ -545,7 +543,7 @@ void MachObjectWriter::bindIndirectSymbols(MCAssembler &Asm) {
 
   // Bind non-lazy symbol pointers first.
   for (auto [IndirectIndex, ISD] : enumerate(IndirectSymbols)) {
-    const auto &Section = cast<MCSectionMachO>(*ISD.Section);
+    const auto &Section = static_cast<MCSectionMachO &>(*ISD.Section);
 
     if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS &&
         Section.getType() !=  MachO::S_THREAD_LOCAL_VARIABLE_POINTERS)
@@ -559,7 +557,7 @@ void MachObjectWriter::bindIndirectSymbols(MCAssembler &Asm) {
 
   // Then lazy symbol pointers and symbol stubs.
   for (auto [IndirectIndex, ISD] : enumerate(IndirectSymbols)) {
-    const auto &Section = cast<MCSectionMachO>(*ISD.Section);
+    const auto &Section = static_cast<MCSectionMachO &>(*ISD.Section);
 
     if (Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS &&
         Section.getType() != MachO::S_SYMBOL_STUBS)
@@ -684,13 +682,13 @@ void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm) {
   for (MCSection &Sec : Asm) {
     if (!Sec.isBssSection()) {
       SectionOrder.push_back(&Sec);
-      cast<MCSectionMachO>(Sec).setLayoutOrder(i++);
+      static_cast<MCSectionMachO &>(Sec).setLayoutOrder(i++);
     }
   }
   for (MCSection &Sec : Asm) {
     if (Sec.isBssSection()) {
       SectionOrder.push_back(&Sec);
-      cast<MCSectionMachO>(Sec).setLayoutOrder(i++);
+      static_cast<MCSectionMachO &>(Sec).setLayoutOrder(i++);
     }
   }
 
@@ -907,7 +905,7 @@ uint64_t MachObjectWriter::writeObject() {
   // ... and then the section headers.
   uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
   for (const MCSection &Section : Asm) {
-    const auto &Sec = cast<MCSectionMachO>(Section);
+    const auto &Sec = static_cast<const MCSectionMachO &>(Section);
     std::vector<RelAndSymbol> &Relocs = Relocations[&Sec];
     unsigned NumRelocs = Relocs.size();
     uint64_t SectionStart = SectionDataStart + getSectionAddress(&Sec);

llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp

@@ -132,7 +132,8 @@ static bool canUseLocalRelocation(const MCSectionMachO &Section,
   // But only if they don't point to a few forbidden sections.
   if (!Symbol.isInSection())
     return true;
-  const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
+  const MCSectionMachO &RefSec =
+      static_cast<MCSectionMachO &>(Symbol.getSection());
   if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
     return false;
 

llvm/tools/dsymutil/MachOUtils.cpp

@@ -331,7 +331,7 @@ static bool createDwarfSegment(const MCAssembler& Asm,uint64_t VMAddr, uint64_t
                                  /* InitProt =*/3);
 
   for (unsigned int i = 0, n = Writer.getSectionOrder().size(); i != n; ++i) {
-    MCSection *Sec = Writer.getSectionOrder()[i];
+    auto *Sec = static_cast<MCSectionMachO *>(Writer.getSectionOrder()[i]);
     if (!Asm.getSectionFileSize(*Sec))
       continue;