text: //===- ARM64.cpp ----------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  #include "Arch/ARM64Common.h"
  #include "InputFiles.h"
  #include "Symbols.h"
  #include "SyntheticSections.h"
  #include "Target.h"
  
  #include "lld/Common/ErrorHandler.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/BinaryFormat/MachO.h"
  #include "llvm/Support/Endian.h"
  #include "llvm/Support/MathExtras.h"
  
  using namespace llvm;
  using namespace llvm::MachO;
  using namespace llvm::support::endian;
  using namespace lld;
  using namespace lld::macho;
  
  namespace {
  
  struct ARM64 : ARM64Common {
    ARM64();
    void writeStub(uint8_t *buf, const Symbol &) const override;
    void writeStubHelperHeader(uint8_t *buf) const override;
    void writeStubHelperEntry(uint8_t *buf, const Symbol &,
                              uint64_t entryAddr) const override;
    const RelocAttrs &getRelocAttrs(uint8_t type) const override;
    void populateThunk(InputSection *thunk, Symbol *funcSym) override;
  };
  
  } // namespace
  
  // Random notes on reloc types:
  // ADDEND always pairs with BRANCH26, PAGE21, or PAGEOFF12
  // 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(BYTE4) | B(BYTE8)},
        {"SUBTRACTOR", B(SUBTRAHEND) | B(EXTERN) | 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)},
        {"TLVP_LOAD_PAGE21", B(PCREL) | B(EXTERN) | B(TLV) | B(BYTE4)},
        {"TLVP_LOAD_PAGEOFF12",
         B(ABSOLUTE) | B(EXTERN) | B(TLV) | B(LOAD) | B(BYTE4)},
        {"ADDEND", B(ADDEND)},
  #undef B
    }};
    assert(type < relocAttrsArray.size() && "invalid relocation type");
    if (type >= relocAttrsArray.size())
      return invalidRelocAttrs;
    return relocAttrsArray[type];
  }
  
  static constexpr uint32_t stubCode[] = {
      0x90000010, // 00: adrp  x16, __la_symbol_ptr@page
      0xf9400210, // 04: ldr   x16, [x16, __la_symbol_ptr@pageoff]
      0xd61f0200, // 08: br    x16
  };
  
  void ARM64::writeStub(uint8_t *buf8, const Symbol &sym) const {
    ::writeStub<LP64>(buf8, stubCode, sym);
  }
  
  static constexpr uint32_t stubHelperHeaderCode[] = {
      0x90000011, // 00: adrp  x17, _dyld_private@page
      0x91000231, // 04: add   x17, x17, _dyld_private@pageoff
      0xa9bf47f0, // 08: stp   x16/x17, [sp, #-16]!
      0x90000010, // 0c: adrp  x16, dyld_stub_binder@page
      0xf9400210, // 10: ldr   x16, [x16, dyld_stub_binder@pageoff]
      0xd61f0200, // 14: br    x16
  };
  
  void ARM64::writeStubHelperHeader(uint8_t *buf8) const {
    ::writeStubHelperHeader<LP64>(buf8, stubHelperHeaderCode);
  }
  
  static constexpr uint32_t stubHelperEntryCode[] = {
      0x18000050, // 00: ldr  w16, l0
      0x14000000, // 04: b    stubHelperHeader
      0x00000000, // 08: l0: .long 0
  };
  
  void ARM64::writeStubHelperEntry(uint8_t *buf8, const Symbol &sym,
                                   uint64_t entryVA) const {
    ::writeStubHelperEntry(buf8, stubHelperEntryCode, sym, entryVA);
  }
  
  // A thunk is the relaxed variation of stubCode. We don't need the
  // extra indirection through a lazy pointer because the target address
  // is known at link time.
  static constexpr uint32_t thunkCode[] = {
      0x90000010, // 00: adrp  x16, <thunk.ptr>@page
      0x91000210, // 04: add   x16, [x16,<thunk.ptr>@pageoff]
      0xd61f0200, // 08: br    x16
  };
  
  void ARM64::populateThunk(InputSection *thunk, Symbol *funcSym) {
    thunk->align = 4;
    thunk->data = {reinterpret_cast<const uint8_t *>(thunkCode),
                   sizeof(thunkCode)};
    thunk->relocs.push_back({/*type=*/ARM64_RELOC_PAGEOFF12,
                             /*pcrel=*/false, /*length=*/2,
                             /*offset=*/4, /*addend=*/0,
                             /*referent=*/funcSym});
    thunk->relocs.push_back({/*type=*/ARM64_RELOC_PAGE21,
                             /*pcrel=*/true, /*length=*/2,
                             /*offset=*/0, /*addend=*/0,
                             /*referent=*/funcSym});
  }
  
  ARM64::ARM64() : ARM64Common(LP64()) {
    cpuType = CPU_TYPE_ARM64;
    cpuSubtype = CPU_SUBTYPE_ARM64_ALL;
  
    stubSize = sizeof(stubCode);
    thunkSize = sizeof(thunkCode);
  
    // Branch immediate is two's complement 26 bits, which is implicitly
    // multiplied by 4 (since all functions are 4-aligned: The branch range
    // is -4*(2**(26-1))..4*(2**(26-1) - 1).
    backwardBranchRange = 128 * 1024 * 1024;
    forwardBranchRange = backwardBranchRange - 4;
  
    stubHelperHeaderSize = sizeof(stubHelperHeaderCode);
    stubHelperEntrySize = sizeof(stubHelperEntryCode);
  }
  
  TargetInfo *macho::createARM64TargetInfo() {
    static ARM64 t;
    return &t;
  }
  