AArch64/ARM64: move ARM64 into AArch64's place

This commit starts with a "git mv ARM64 AArch64" and continues out
from there, renaming the C++ classes, intrinsics, and other
target-local objects for consistency.

"ARM64" test directories are also moved, and tests that began their
life in ARM64 use an arm64 triple, those from AArch64 use an aarch64
triple. Both should be equivalent though.

This finishes the AArch64 merge, and everyone should feel free to
continue committing as normal now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209577 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 566 insertions, 0 deletions

diff --git a/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
new file mode 100644
index 0000000000..d8900d4fce
--- /dev/null
+++ b/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -0,0 +1,566 @@
+//===-- AArch64AsmBackend.cpp - AArch64 Assembler Backend -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AArch64.h"
+#include "AArch64RegisterInfo.h"
+#include "MCTargetDesc/AArch64FixupKinds.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCDirectives.h"
+#include "llvm/MC/MCFixupKindInfo.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCSectionELF.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MachO.h"
+using namespace llvm;
+
+namespace {
+
+class AArch64AsmBackend : public MCAsmBackend {
+  static const unsigned PCRelFlagVal =
+      MCFixupKindInfo::FKF_IsAlignedDownTo32Bits | MCFixupKindInfo::FKF_IsPCRel;
+
+public:
+  AArch64AsmBackend(const Target &T) : MCAsmBackend() {}
+
+  unsigned getNumFixupKinds() const override {
+    return AArch64::NumTargetFixupKinds;
+  }
+
+  const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
+    const static MCFixupKindInfo Infos[AArch64::NumTargetFixupKinds] = {
+      // This table *must* be in the order that the fixup_* kinds are defined in
+      // AArch64FixupKinds.h.
+      //
+      // Name                           Offset (bits) Size (bits)     Flags
+      { "fixup_aarch64_pcrel_adr_imm21", 0, 32, PCRelFlagVal },
+      { "fixup_aarch64_pcrel_adrp_imm21", 0, 32, PCRelFlagVal },
+      { "fixup_aarch64_add_imm12", 10, 12, 0 },
+      { "fixup_aarch64_ldst_imm12_scale1", 10, 12, 0 },
+      { "fixup_aarch64_ldst_imm12_scale2", 10, 12, 0 },
+      { "fixup_aarch64_ldst_imm12_scale4", 10, 12, 0 },
+      { "fixup_aarch64_ldst_imm12_scale8", 10, 12, 0 },
+      { "fixup_aarch64_ldst_imm12_scale16", 10, 12, 0 },
+      { "fixup_aarch64_ldr_pcrel_imm19", 5, 19, PCRelFlagVal },
+      { "fixup_aarch64_movw", 5, 16, 0 },
+      { "fixup_aarch64_pcrel_branch14", 5, 14, PCRelFlagVal },
+      { "fixup_aarch64_pcrel_branch19", 5, 19, PCRelFlagVal },
+      { "fixup_aarch64_pcrel_branch26", 0, 26, PCRelFlagVal },
+      { "fixup_aarch64_pcrel_call26", 0, 26, PCRelFlagVal },
+      { "fixup_aarch64_tlsdesc_call", 0, 0, 0 }
+    };
+
+    if (Kind < FirstTargetFixupKind)
+      return MCAsmBackend::getFixupKindInfo(Kind);
+
+    assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
+           "Invalid kind!");
+    return Infos[Kind - FirstTargetFixupKind];
+  }
+
+  void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
+                  uint64_t Value, bool IsPCRel) const override;
+
+  bool mayNeedRelaxation(const MCInst &Inst) const override;
+  bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
+                            const MCRelaxableFragment *DF,
+                            const MCAsmLayout &Layout) const override;
+  void relaxInstruction(const MCInst &Inst, MCInst &Res) const override;
+  bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
+
+  void HandleAssemblerFlag(MCAssemblerFlag Flag) {}
+
+  unsigned getPointerSize() const { return 8; }
+};
+
+} // end anonymous namespace
+
+/// \brief The number of bytes the fixup may change.
+static unsigned getFixupKindNumBytes(unsigned Kind) {
+  switch (Kind) {
+  default:
+    assert(0 && "Unknown fixup kind!");
+
+  case AArch64::fixup_aarch64_tlsdesc_call:
+    return 0;
+
+  case FK_Data_1:
+    return 1;
+
+  case FK_Data_2:
+  case AArch64::fixup_aarch64_movw:
+    return 2;
+
+  case AArch64::fixup_aarch64_pcrel_branch14:
+  case AArch64::fixup_aarch64_add_imm12:
+  case AArch64::fixup_aarch64_ldst_imm12_scale1:
+  case AArch64::fixup_aarch64_ldst_imm12_scale2:
+  case AArch64::fixup_aarch64_ldst_imm12_scale4:
+  case AArch64::fixup_aarch64_ldst_imm12_scale8:
+  case AArch64::fixup_aarch64_ldst_imm12_scale16:
+  case AArch64::fixup_aarch64_ldr_pcrel_imm19:
+  case AArch64::fixup_aarch64_pcrel_branch19:
+    return 3;
+
+  case AArch64::fixup_aarch64_pcrel_adr_imm21:
+  case AArch64::fixup_aarch64_pcrel_adrp_imm21:
+  case AArch64::fixup_aarch64_pcrel_branch26:
+  case AArch64::fixup_aarch64_pcrel_call26:
+  case FK_Data_4:
+    return 4;
+
+  case FK_Data_8:
+    return 8;
+  }
+}
+
+static unsigned AdrImmBits(unsigned Value) {
+  unsigned lo2 = Value & 0x3;
+  unsigned hi19 = (Value & 0x1ffffc) >> 2;
+  return (hi19 << 5) | (lo2 << 29);
+}
+
+static uint64_t adjustFixupValue(unsigned Kind, uint64_t Value) {
+  int64_t SignedValue = static_cast<int64_t>(Value);
+  switch (Kind) {
+  default:
+    assert(false && "Unknown fixup kind!");
+  case AArch64::fixup_aarch64_pcrel_adr_imm21:
+    if (SignedValue > 2097151 || SignedValue < -2097152)
+      report_fatal_error("fixup value out of range");
+    return AdrImmBits(Value & 0x1fffffULL);
+  case AArch64::fixup_aarch64_pcrel_adrp_imm21:
+    return AdrImmBits((Value & 0x1fffff000ULL) >> 12);
+  case AArch64::fixup_aarch64_ldr_pcrel_imm19:
+  case AArch64::fixup_aarch64_pcrel_branch19:
+    // Signed 21-bit immediate
+    if (SignedValue > 2097151 || SignedValue < -2097152)
+      report_fatal_error("fixup value out of range");
+    // Low two bits are not encoded.
+    return (Value >> 2) & 0x7ffff;
+  case AArch64::fixup_aarch64_add_imm12:
+  case AArch64::fixup_aarch64_ldst_imm12_scale1:
+    // Unsigned 12-bit immediate
+    if (Value >= 0x1000)
+      report_fatal_error("invalid imm12 fixup value");
+    return Value;
+  case AArch64::fixup_aarch64_ldst_imm12_scale2:
+    // Unsigned 12-bit immediate which gets multiplied by 2
+    if (Value & 1 || Value >= 0x2000)
+      report_fatal_error("invalid imm12 fixup value");
+    return Value >> 1;
+  case AArch64::fixup_aarch64_ldst_imm12_scale4:
+    // Unsigned 12-bit immediate which gets multiplied by 4
+    if (Value & 3 || Value >= 0x4000)
+      report_fatal_error("invalid imm12 fixup value");
+    return Value >> 2;
+  case AArch64::fixup_aarch64_ldst_imm12_scale8:
+    // Unsigned 12-bit immediate which gets multiplied by 8
+    if (Value & 7 || Value >= 0x8000)
+      report_fatal_error("invalid imm12 fixup value");
+    return Value >> 3;
+  case AArch64::fixup_aarch64_ldst_imm12_scale16:
+    // Unsigned 12-bit immediate which gets multiplied by 16
+    if (Value & 15 || Value >= 0x10000)
+      report_fatal_error("invalid imm12 fixup value");
+    return Value >> 4;
+  case AArch64::fixup_aarch64_movw:
+    report_fatal_error("no resolvable MOVZ/MOVK fixups supported yet");
+    return Value;
+  case AArch64::fixup_aarch64_pcrel_branch14:
+    // Signed 16-bit immediate
+    if (SignedValue > 32767 || SignedValue < -32768)
+      report_fatal_error("fixup value out of range");
+    // Low two bits are not encoded (4-byte alignment assumed).
+    if (Value & 0x3)
+      report_fatal_error("fixup not sufficiently aligned");
+    return (Value >> 2) & 0x3fff;
+  case AArch64::fixup_aarch64_pcrel_branch26:
+  case AArch64::fixup_aarch64_pcrel_call26:
+    // Signed 28-bit immediate
+    if (SignedValue > 134217727 || SignedValue < -134217728)
+      report_fatal_error("fixup value out of range");
+    // Low two bits are not encoded (4-byte alignment assumed).
+    if (Value & 0x3)
+      report_fatal_error("fixup not sufficiently aligned");
+    return (Value >> 2) & 0x3ffffff;
+  case FK_Data_1:
+  case FK_Data_2:
+  case FK_Data_4:
+  case FK_Data_8:
+    return Value;
+  }
+}
+
+void AArch64AsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
+                                   unsigned DataSize, uint64_t Value,
+                                   bool IsPCRel) const {
+  unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
+  if (!Value)
+    return; // Doesn't change encoding.
+  MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
+  // Apply any target-specific value adjustments.
+  Value = adjustFixupValue(Fixup.getKind(), Value);
+
+  // Shift the value into position.
+  Value <<= Info.TargetOffset;
+
+  unsigned Offset = Fixup.getOffset();
+  assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!");
+
+  // For each byte of the fragment that the fixup touches, mask in the
+  // bits from the fixup value.
+  for (unsigned i = 0; i != NumBytes; ++i)
+    Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
+}
+
+bool AArch64AsmBackend::mayNeedRelaxation(const MCInst &Inst) const {
+  return false;
+}
+
+bool AArch64AsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
+                                             uint64_t Value,
+                                             const MCRelaxableFragment *DF,
+                                             const MCAsmLayout &Layout) const {
+  // FIXME:  This isn't correct for AArch64. Just moving the "generic" logic
+  // into the targets for now.
+  //
+  // Relax if the value is too big for a (signed) i8.
+  return int64_t(Value) != int64_t(int8_t(Value));
+}
+
+void AArch64AsmBackend::relaxInstruction(const MCInst &Inst,
+                                         MCInst &Res) const {
+  assert(false && "AArch64AsmBackend::relaxInstruction() unimplemented");
+}
+
+bool AArch64AsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
+  // If the count is not 4-byte aligned, we must be writing data into the text
+  // section (otherwise we have unaligned instructions, and thus have far
+  // bigger problems), so just write zeros instead.
+  if ((Count & 3) != 0) {
+    for (uint64_t i = 0, e = (Count & 3); i != e; ++i)
+      OW->Write8(0);
+  }
+
+  // We are properly aligned, so write NOPs as requested.
+  Count /= 4;
+  for (uint64_t i = 0; i != Count; ++i)
+    OW->Write32(0xd503201f);
+  return true;
+}
+
+namespace {
+
+namespace CU {
+
+/// \brief Compact unwind encoding values.
+enum CompactUnwindEncodings {
+  /// \brief A "frameless" leaf function, where no non-volatile registers are
+  /// saved. The return remains in LR throughout the function.
+  UNWIND_AArch64_MODE_FRAMELESS = 0x02000000,
+
+  /// \brief No compact unwind encoding available. Instead the low 23-bits of
+  /// the compact unwind encoding is the offset of the DWARF FDE in the
+  /// __eh_frame section. This mode is never used in object files. It is only
+  /// generated by the linker in final linked images, which have only DWARF info
+  /// for a function.
+  UNWIND_AArch64_MODE_DWARF = 0x03000000,
+
+  /// \brief This is a standard arm64 prologue where FP/LR are immediately
+  /// pushed on the stack, then SP is copied to FP. If there are any
+  /// non-volatile register saved, they are copied into the stack fame in pairs
+  /// in a contiguous ranger right below the saved FP/LR pair. Any subset of the
+  /// five X pairs and four D pairs can be saved, but the memory layout must be
+  /// in register number order.
+  UNWIND_AArch64_MODE_FRAME = 0x04000000,
+
+  /// \brief Frame register pair encodings.
+  UNWIND_AArch64_FRAME_X19_X20_PAIR = 0x00000001,
+  UNWIND_AArch64_FRAME_X21_X22_PAIR = 0x00000002,
+  UNWIND_AArch64_FRAME_X23_X24_PAIR = 0x00000004,
+  UNWIND_AArch64_FRAME_X25_X26_PAIR = 0x00000008,
+  UNWIND_AArch64_FRAME_X27_X28_PAIR = 0x00000010,
+  UNWIND_AArch64_FRAME_D8_D9_PAIR = 0x00000100,
+  UNWIND_AArch64_FRAME_D10_D11_PAIR = 0x00000200,
+  UNWIND_AArch64_FRAME_D12_D13_PAIR = 0x00000400,
+  UNWIND_AArch64_FRAME_D14_D15_PAIR = 0x00000800
+};
+
+} // end CU namespace
+
+// FIXME: This should be in a separate file.
+class DarwinAArch64AsmBackend : public AArch64AsmBackend {
+  const MCRegisterInfo &MRI;
+
+  /// \brief Encode compact unwind stack adjustment for frameless functions.
+  /// See UNWIND_AArch64_FRAMELESS_STACK_SIZE_MASK in compact_unwind_encoding.h.
+  /// The stack size always needs to be 16 byte aligned.
+  uint32_t encodeStackAdjustment(uint32_t StackSize) const {
+    return (StackSize / 16) << 12;
+  }
+
+public:
+  DarwinAArch64AsmBackend(const Target &T, const MCRegisterInfo &MRI)
+      : AArch64AsmBackend(T), MRI(MRI) {}
+
+  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+    return createAArch64MachObjectWriter(OS, MachO::CPU_TYPE_ARM64,
+                                         MachO::CPU_SUBTYPE_ARM64_ALL);
+  }
+
+  bool doesSectionRequireSymbols(const MCSection &Section) const override {
+    // Any section for which the linker breaks things into atoms needs to
+    // preserve symbols, including assembler local symbols, to identify
+    // those atoms. These sections are:
+    // Sections of type:
+    //
+    //    S_CSTRING_LITERALS  (e.g. __cstring)
+    //    S_LITERAL_POINTERS  (e.g.  objc selector pointers)
+    //    S_16BYTE_LITERALS, S_8BYTE_LITERALS, S_4BYTE_LITERALS
+    //
+    // Sections named:
+    //
+    //    __TEXT,__eh_frame
+    //    __TEXT,__ustring
+    //    __DATA,__cfstring
+    //    __DATA,__objc_classrefs
+    //    __DATA,__objc_catlist
+    //
+    // FIXME: It would be better if the compiler used actual linker local
+    // symbols for each of these sections rather than preserving what
+    // are ostensibly assembler local symbols.
+    const MCSectionMachO &SMO = static_cast<const MCSectionMachO &>(Section);
+    return (SMO.getType() == MachO::S_CSTRING_LITERALS ||
+            SMO.getType() == MachO::S_4BYTE_LITERALS ||
+            SMO.getType() == MachO::S_8BYTE_LITERALS ||
+            SMO.getType() == MachO::S_16BYTE_LITERALS ||
+            SMO.getType() == MachO::S_LITERAL_POINTERS ||
+            (SMO.getSegmentName() == "__TEXT" &&
+             (SMO.getSectionName() == "__eh_frame" ||
+              SMO.getSectionName() == "__ustring")) ||
+            (SMO.getSegmentName() == "__DATA" &&
+             (SMO.getSectionName() == "__cfstring" ||
+              SMO.getSectionName() == "__objc_classrefs" ||
+              SMO.getSectionName() == "__objc_catlist")));
+  }
+
+  /// \brief Generate the compact unwind encoding from the CFI directives.
+  uint32_t generateCompactUnwindEncoding(
+                             ArrayRef<MCCFIInstruction> Instrs) const override {
+    if (Instrs.empty())
+      return CU::UNWIND_AArch64_MODE_FRAMELESS;
+
+    bool HasFP = false;
+    unsigned StackSize = 0;
+
+    uint32_t CompactUnwindEncoding = 0;
+    for (size_t i = 0, e = Instrs.size(); i != e; ++i) {
+      const MCCFIInstruction &Inst = Instrs[i];
+
+      switch (Inst.getOperation()) {
+      default:
+        // Cannot handle this directive:  bail out.
+        return CU::UNWIND_AArch64_MODE_DWARF;
+      case MCCFIInstruction::OpDefCfa: {
+        // Defines a frame pointer.
+        assert(getXRegFromWReg(MRI.getLLVMRegNum(Inst.getRegister(), true)) ==
+                   AArch64::FP &&
+               "Invalid frame pointer!");
+        assert(i + 2 < e && "Insufficient CFI instructions to define a frame!");
+
+        const MCCFIInstruction &LRPush = Instrs[++i];
+        assert(LRPush.getOperation() == MCCFIInstruction::OpOffset &&
+               "Link register not pushed!");
+        const MCCFIInstruction &FPPush = Instrs[++i];
+        assert(FPPush.getOperation() == MCCFIInstruction::OpOffset &&
+               "Frame pointer not pushed!");
+
+        unsigned LRReg = MRI.getLLVMRegNum(LRPush.getRegister(), true);
+        unsigned FPReg = MRI.getLLVMRegNum(FPPush.getRegister(), true);
+
+        LRReg = getXRegFromWReg(LRReg);
+        FPReg = getXRegFromWReg(FPReg);
+
+        assert(LRReg == AArch64::LR && FPReg == AArch64::FP &&
+               "Pushing invalid registers for frame!");
+
+        // Indicate that the function has a frame.
+        CompactUnwindEncoding |= CU::UNWIND_AArch64_MODE_FRAME;
+        HasFP = true;
+        break;
+      }
+      case MCCFIInstruction::OpDefCfaOffset: {
+        assert(StackSize == 0 && "We already have the CFA offset!");
+        StackSize = std::abs(Inst.getOffset());
+        break;
+      }
+      case MCCFIInstruction::OpOffset: {
+        // Registers are saved in pairs. We expect there to be two consecutive
+        // `.cfi_offset' instructions with the appropriate registers specified.
+        unsigned Reg1 = MRI.getLLVMRegNum(Inst.getRegister(), true);
+        if (i + 1 == e)
+          return CU::UNWIND_AArch64_MODE_DWARF;
+
+        const MCCFIInstruction &Inst2 = Instrs[++i];
+        if (Inst2.getOperation() != MCCFIInstruction::OpOffset)
+          return CU::UNWIND_AArch64_MODE_DWARF;
+        unsigned Reg2 = MRI.getLLVMRegNum(Inst2.getRegister(), true);
+
+        // N.B. The encodings must be in register number order, and the X
+        // registers before the D registers.
+
+        // X19/X20 pair = 0x00000001,
+        // X21/X22 pair = 0x00000002,
+        // X23/X24 pair = 0x00000004,
+        // X25/X26 pair = 0x00000008,
+        // X27/X28 pair = 0x00000010
+        Reg1 = getXRegFromWReg(Reg1);
+        Reg2 = getXRegFromWReg(Reg2);
+
+        if (Reg1 == AArch64::X19 && Reg2 == AArch64::X20 &&
+            (CompactUnwindEncoding & 0xF1E) == 0)
+          CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X19_X20_PAIR;
+        else if (Reg1 == AArch64::X21 && Reg2 == AArch64::X22 &&
+                 (CompactUnwindEncoding & 0xF1C) == 0)
+          CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X21_X22_PAIR;
+        else if (Reg1 == AArch64::X23 && Reg2 == AArch64::X24 &&
+                 (CompactUnwindEncoding & 0xF18) == 0)
+          CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X23_X24_PAIR;
+        else if (Reg1 == AArch64::X25 && Reg2 == AArch64::X26 &&
+                 (CompactUnwindEncoding & 0xF10) == 0)
+          CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X25_X26_PAIR;
+        else if (Reg1 == AArch64::X27 && Reg2 == AArch64::X28 &&
+                 (CompactUnwindEncoding & 0xF00) == 0)
+          CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_X27_X28_PAIR;
+        else {
+          Reg1 = getDRegFromBReg(Reg1);
+          Reg2 = getDRegFromBReg(Reg2);
+
+          // D8/D9 pair   = 0x00000100,
+          // D10/D11 pair = 0x00000200,
+          // D12/D13 pair = 0x00000400,
+          // D14/D15 pair = 0x00000800
+          if (Reg1 == AArch64::D8 && Reg2 == AArch64::D9 &&
+              (CompactUnwindEncoding & 0xE00) == 0)
+            CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D8_D9_PAIR;
+          else if (Reg1 == AArch64::D10 && Reg2 == AArch64::D11 &&
+                   (CompactUnwindEncoding & 0xC00) == 0)
+            CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D10_D11_PAIR;
+          else if (Reg1 == AArch64::D12 && Reg2 == AArch64::D13 &&
+                   (CompactUnwindEncoding & 0x800) == 0)
+            CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D12_D13_PAIR;
+          else if (Reg1 == AArch64::D14 && Reg2 == AArch64::D15)
+            CompactUnwindEncoding |= CU::UNWIND_AArch64_FRAME_D14_D15_PAIR;
+          else
+            // A pair was pushed which we cannot handle.
+            return CU::UNWIND_AArch64_MODE_DWARF;
+        }
+
+        break;
+      }
+      }
+    }
+
+    if (!HasFP) {
+      // With compact unwind info we can only represent stack adjustments of up
+      // to 65520 bytes.
+      if (StackSize > 65520)
+        return CU::UNWIND_AArch64_MODE_DWARF;
+
+      CompactUnwindEncoding |= CU::UNWIND_AArch64_MODE_FRAMELESS;
+      CompactUnwindEncoding |= encodeStackAdjustment(StackSize);
+    }
+
+    return CompactUnwindEncoding;
+  }
+};
+
+} // end anonymous namespace
+
+namespace {
+
+class ELFAArch64AsmBackend : public AArch64AsmBackend {
+public:
+  uint8_t OSABI;
+  bool IsLittleEndian;
+
+  ELFAArch64AsmBackend(const Target &T, uint8_t OSABI, bool IsLittleEndian)
+    : AArch64AsmBackend(T), OSABI(OSABI), IsLittleEndian(IsLittleEndian) {}
+
+  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+    return createAArch64ELFObjectWriter(OS, OSABI, IsLittleEndian);
+  }
+
+  void processFixupValue(const MCAssembler &Asm, const MCAsmLayout &Layout,
+                         const MCFixup &Fixup, const MCFragment *DF,
+                         const MCValue &Target, uint64_t &Value,
+                         bool &IsResolved) override;
+
+  void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
+                  uint64_t Value, bool IsPCRel) const override;
+};
+
+void ELFAArch64AsmBackend::processFixupValue(
+    const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFixup &Fixup,
+    const MCFragment *DF, const MCValue &Target, uint64_t &Value,
+    bool &IsResolved) {
+  // The ADRP instruction adds some multiple of 0x1000 to the current PC &
+  // ~0xfff. This means that the required offset to reach a symbol can vary by
+  // up to one step depending on where the ADRP is in memory. For example:
+  //
+  //     ADRP x0, there
+  //  there:
+  //
+  // If the ADRP occurs at address 0xffc then "there" will be at 0x1000 and
+  // we'll need that as an offset. At any other address "there" will be in the
+  // same page as the ADRP and the instruction should encode 0x0. Assuming the
+  // section isn't 0x1000-aligned, we therefore need to delegate this decision
+  // to the linker -- a relocation!
+  if ((uint32_t)Fixup.getKind() == AArch64::fixup_aarch64_pcrel_adrp_imm21)
+    IsResolved = false;
+}
+
+void ELFAArch64AsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
+                                      unsigned DataSize, uint64_t Value,
+                                      bool IsPCRel) const {
+  // store fixups in .eh_frame section in big endian order
+  if (!IsLittleEndian && Fixup.getKind() == FK_Data_4) {
+    const MCSection *Sec = Fixup.getValue()->FindAssociatedSection();
+    const MCSectionELF *SecELF = static_cast<const MCSectionELF *>(Sec);
+    if (SecELF->getSectionName() == ".eh_frame")
+      Value = ByteSwap_32(unsigned(Value));
+  }
+  AArch64AsmBackend::applyFixup (Fixup, Data, DataSize, Value, IsPCRel);
+}
+}
+
+MCAsmBackend *llvm::createAArch64leAsmBackend(const Target &T,
+                                            const MCRegisterInfo &MRI,
+                                            StringRef TT, StringRef CPU) {
+  Triple TheTriple(TT);
+
+  if (TheTriple.isOSDarwin())
+    return new DarwinAArch64AsmBackend(T, MRI);
+
+  assert(TheTriple.isOSBinFormatELF() && "Expect either MachO or ELF target");
+  return new ELFAArch64AsmBackend(T, TheTriple.getOS(), /*IsLittleEndian=*/true);
+}
+
+MCAsmBackend *llvm::createAArch64beAsmBackend(const Target &T,
+                                            const MCRegisterInfo &MRI,
+                                            StringRef TT, StringRef CPU) {
+  Triple TheTriple(TT);
+
+  assert(TheTriple.isOSBinFormatELF() &&
+         "Big endian is only supported for ELF targets!");
+  return new ELFAArch64AsmBackend(T, TheTriple.getOS(),
+                                  /*IsLittleEndian=*/false);
+}