[lld-macho][nfc] Remove DYSYM8 reloc attribute

[int3]

Summary

It's likely redundant, per discussion with @gkm. The BYTE8
attribute covers the bit width requirement already.

[gkm]

LGTM

lld/MachO/Arch/ARM64.cpp

 // POINTER_TO_GOT: ld64 supports a 4-byte pc-relative form as well as an 8-byte
 // absolute version of this relocation. The semantics of the absolute relocation
 // are weird -- it results in the value of the GOT slot being written, instead
 // of the address. Let's not support it unless we find a real-world use case.
 
 const RelocAttrs &ARM64::getRelocAttrs(uint8_t type) const {
   static const std::array<RelocAttrs, 11> relocAttrsArray{{
 #define B(x) RelocAttrBits::x
-      {"UNSIGNED", B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) |
-                       B(DYSYM8) | B(BYTE4) | B(BYTE8)},
+      {"UNSIGNED",
+       B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) | B(BYTE4) | B(BYTE8)},
       {"SUBTRACTOR", B(SUBTRAHEND) | B(BYTE4) | B(BYTE8)},
       {"BRANCH26", B(PCREL) | B(EXTERN) | B(BRANCH) | B(BYTE4)},
       {"PAGE21", B(PCREL) | B(EXTERN) | B(BYTE4)},
       {"PAGEOFF12", B(ABSOLUTE) | B(EXTERN) | B(BYTE4)},
       {"GOT_LOAD_PAGE21", B(PCREL) | B(EXTERN) | B(GOT) | B(BYTE4)},
       {"GOT_LOAD_PAGEOFF12",
        B(ABSOLUTE) | B(EXTERN) | B(GOT) | B(LOAD) | B(BYTE4)},
       {"POINTER_TO_GOT", B(PCREL) | B(EXTERN) | B(GOT) | B(POINTER) | B(BYTE4)},

lld/MachO/Arch/X86_64.cpp

struct X86_64 : TargetInfo {
   uint64_t getPageSize() const override { return 4 * 1024; }
 };
 
 } // namespace
 
 const RelocAttrs &X86_64::getRelocAttrs(uint8_t type) const {
   static const std::array<RelocAttrs, 10> relocAttrsArray{{
 #define B(x) RelocAttrBits::x
-      {"UNSIGNED", B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) |
-                       B(DYSYM8) | B(BYTE4) | B(BYTE8)},
+      {"UNSIGNED",
+       B(UNSIGNED) | B(ABSOLUTE) | B(EXTERN) | B(LOCAL) | B(BYTE4) | B(BYTE8)},
       {"SIGNED", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
       {"BRANCH", B(PCREL) | B(EXTERN) | B(BRANCH) | B(BYTE4)},
       {"GOT_LOAD", B(PCREL) | B(EXTERN) | B(GOT) | B(LOAD) | B(BYTE4)},
       {"GOT", B(PCREL) | B(EXTERN) | B(GOT) | B(POINTER) | B(BYTE4)},
       {"SUBTRACTOR", B(SUBTRAHEND) | B(BYTE4) | B(BYTE8)},
       {"SIGNED_1", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
       {"SIGNED_2", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},
       {"SIGNED_4", B(PCREL) | B(EXTERN) | B(LOCAL) | B(BYTE4)},

lld/MachO/Relocations.h

enum class RelocAttrBits {
   BYTE8 = 1 << 3,      // 8 byte datum
   EXTERN = 1 << 4,     // Can have an external symbol
   LOCAL = 1 << 5,      // Can have a local symbol
   ADDEND = 1 << 6,     // *_ADDEND paired prefix reloc
   SUBTRAHEND = 1 << 7, // *_SUBTRACTOR paired prefix reloc
   BRANCH = 1 << 8,     // Value is branch target
   GOT = 1 << 9,        // References a symbol in the Global Offset Table
   TLV = 1 << 10,       // References a thread-local symbol
-  DYSYM8 = 1 << 11,    // Requires DySym width to be 8 bytes
-  LOAD = 1 << 12,      // Relaxable indirect load
-  POINTER = 1 << 13,   // Non-relaxable indirect load (pointer is taken)
-  UNSIGNED = 1 << 14,  // *_UNSIGNED relocs
-  LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue*/ (1 << 15) - 1),
+  LOAD = 1 << 11,      // Relaxable indirect load
+  POINTER = 1 << 12,   // Non-relaxable indirect load (pointer is taken)
+  UNSIGNED = 1 << 13,  // *_UNSIGNED relocs
+  LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue*/ (1 << 14) - 1),
 };
 // Note: SUBTRACTOR always pairs with UNSIGNED (a delta between two symbols).
 
 struct RelocAttrs {
   llvm::StringRef name;
   RelocAttrBits bits;
   bool hasAttr(RelocAttrBits b) const { return (bits & b) == b; }
 };

lld/MachO/Relocations.cpp

auto message = [relocAttrs, sym, isec, &valid](const Twine &diagnostic) {
     return (relocAttrs.name + " relocation " + diagnostic + " for `" +
             sym->getName() + "' in " + toString(isec))
         .str();
   };
 
   if (relocAttrs.hasAttr(RelocAttrBits::TLV) != sym->isTlv())
     error(message(Twine("requires that variable ") +
                   (sym->isTlv() ? "not " : "") + "be thread-local"));
-  if (relocAttrs.hasAttr(RelocAttrBits::DYSYM8) && isa<DylibSymbol>(sym) &&
-      r.length != 3)
-    error(message("has width " + std::to_string(1 << r.length) +
-                  " bytes, but must be 8 bytes"));
 
   return valid;
 }
 
 void macho::reportRangeError(const Reloc &r, const Twine &v, uint8_t bits,
                              int64_t min, uint64_t max) {
   std::string hint;
   if (auto *sym = r.referent.dyn_cast<Symbol *>())