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llvm-for-llvmta/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp

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//===-- AArch64AsmBackend.cpp - AArch64 Assembler Backend -----------------===//
//
// 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 "MCTargetDesc/AArch64FixupKinds.h"
#include "MCTargetDesc/AArch64MCExpr.h"
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "Utils/AArch64BaseInfo.h"
#include "llvm/ADT/Triple.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;
namespace {
class AArch64AsmBackend : public MCAsmBackend {
static const unsigned PCRelFlagVal =
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits | MCFixupKindInfo::FKF_IsPCRel;
protected:
Triple TheTriple;
public:
AArch64AsmBackend(const Target &T, const Triple &TT, bool IsLittleEndian)
: MCAsmBackend(IsLittleEndian ? support::little : support::big),
TheTriple(TT) {}
unsigned getNumFixupKinds() const override {
return AArch64::NumTargetFixupKinds;
}
Optional<MCFixupKind> getFixupKind(StringRef Name) const override;
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}};
// Fixup kinds from .reloc directive are like R_AARCH64_NONE. They do not
// require any extra processing.
if (Kind >= FirstLiteralRelocationKind)
return MCAsmBackend::getFixupKindInfo(FK_NONE);
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
const MCValue &Target, MutableArrayRef<char> Data,
uint64_t Value, bool IsResolved,
const MCSubtargetInfo *STI) const override;
bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const override;
void relaxInstruction(MCInst &Inst,
const MCSubtargetInfo &STI) const override;
bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
void HandleAssemblerFlag(MCAssemblerFlag Flag) {}
unsigned getPointerSize() const { return 8; }
unsigned getFixupKindContainereSizeInBytes(unsigned Kind) const;
bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
const MCValue &Target) override;
};
} // end anonymous namespace
/// The number of bytes the fixup may change.
static unsigned getFixupKindNumBytes(unsigned Kind) {
switch (Kind) {
default:
llvm_unreachable("Unknown fixup kind!");
case AArch64::fixup_aarch64_tlsdesc_call:
return 0;
case FK_Data_1:
return 1;
case FK_Data_2:
case FK_SecRel_2:
return 2;
case AArch64::fixup_aarch64_movw:
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:
case FK_SecRel_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(const MCFixup &Fixup, const MCValue &Target,
uint64_t Value, MCContext &Ctx,
const Triple &TheTriple, bool IsResolved) {
int64_t SignedValue = static_cast<int64_t>(Value);
switch (Fixup.getTargetKind()) {
default:
llvm_unreachable("Unknown fixup kind!");
case AArch64::fixup_aarch64_pcrel_adr_imm21:
if (SignedValue > 2097151 || SignedValue < -2097152)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
return AdrImmBits(Value & 0x1fffffULL);
case AArch64::fixup_aarch64_pcrel_adrp_imm21:
assert(!IsResolved);
if (TheTriple.isOSBinFormatCOFF())
return AdrImmBits(Value & 0x1fffffULL);
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)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0x3)
Ctx.reportError(Fixup.getLoc(), "fixup not sufficiently aligned");
// Low two bits are not encoded.
return (Value >> 2) & 0x7ffff;
case AArch64::fixup_aarch64_add_imm12:
case AArch64::fixup_aarch64_ldst_imm12_scale1:
if (TheTriple.isOSBinFormatCOFF() && !IsResolved)
Value &= 0xfff;
// Unsigned 12-bit immediate
if (Value >= 0x1000)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
return Value;
case AArch64::fixup_aarch64_ldst_imm12_scale2:
if (TheTriple.isOSBinFormatCOFF() && !IsResolved)
Value &= 0xfff;
// Unsigned 12-bit immediate which gets multiplied by 2
if (Value >= 0x2000)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0x1)
Ctx.reportError(Fixup.getLoc(), "fixup must be 2-byte aligned");
return Value >> 1;
case AArch64::fixup_aarch64_ldst_imm12_scale4:
if (TheTriple.isOSBinFormatCOFF() && !IsResolved)
Value &= 0xfff;
// Unsigned 12-bit immediate which gets multiplied by 4
if (Value >= 0x4000)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0x3)
Ctx.reportError(Fixup.getLoc(), "fixup must be 4-byte aligned");
return Value >> 2;
case AArch64::fixup_aarch64_ldst_imm12_scale8:
if (TheTriple.isOSBinFormatCOFF() && !IsResolved)
Value &= 0xfff;
// Unsigned 12-bit immediate which gets multiplied by 8
if (Value >= 0x8000)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0x7)
Ctx.reportError(Fixup.getLoc(), "fixup must be 8-byte aligned");
return Value >> 3;
case AArch64::fixup_aarch64_ldst_imm12_scale16:
if (TheTriple.isOSBinFormatCOFF() && !IsResolved)
Value &= 0xfff;
// Unsigned 12-bit immediate which gets multiplied by 16
if (Value >= 0x10000)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0xf)
Ctx.reportError(Fixup.getLoc(), "fixup must be 16-byte aligned");
return Value >> 4;
case AArch64::fixup_aarch64_movw: {
AArch64MCExpr::VariantKind RefKind =
static_cast<AArch64MCExpr::VariantKind>(Target.getRefKind());
if (AArch64MCExpr::getSymbolLoc(RefKind) != AArch64MCExpr::VK_ABS &&
AArch64MCExpr::getSymbolLoc(RefKind) != AArch64MCExpr::VK_SABS) {
if (!RefKind) {
// The fixup is an expression
if (SignedValue > 0xFFFF || SignedValue < -0xFFFF)
Ctx.reportError(Fixup.getLoc(),
"fixup value out of range [-0xFFFF, 0xFFFF]");
// Invert the negative immediate because it will feed into a MOVN.
if (SignedValue < 0)
SignedValue = ~SignedValue;
Value = static_cast<uint64_t>(SignedValue);
} else
// VK_GOTTPREL, VK_TPREL, VK_DTPREL are movw fixups, but they can't
// ever be resolved in the assembler.
Ctx.reportError(Fixup.getLoc(),
"relocation for a thread-local variable points to an "
"absolute symbol");
return Value;
}
if (!IsResolved) {
// FIXME: Figure out when this can actually happen, and verify our
// behavior.
Ctx.reportError(Fixup.getLoc(), "unresolved movw fixup not yet "
"implemented");
return Value;
}
if (AArch64MCExpr::getSymbolLoc(RefKind) == AArch64MCExpr::VK_SABS) {
switch (AArch64MCExpr::getAddressFrag(RefKind)) {
case AArch64MCExpr::VK_G0:
break;
case AArch64MCExpr::VK_G1:
SignedValue = SignedValue >> 16;
break;
case AArch64MCExpr::VK_G2:
SignedValue = SignedValue >> 32;
break;
case AArch64MCExpr::VK_G3:
SignedValue = SignedValue >> 48;
break;
default:
llvm_unreachable("Variant kind doesn't correspond to fixup");
}
} else {
switch (AArch64MCExpr::getAddressFrag(RefKind)) {
case AArch64MCExpr::VK_G0:
break;
case AArch64MCExpr::VK_G1:
Value = Value >> 16;
break;
case AArch64MCExpr::VK_G2:
Value = Value >> 32;
break;
case AArch64MCExpr::VK_G3:
Value = Value >> 48;
break;
default:
llvm_unreachable("Variant kind doesn't correspond to fixup");
}
}
if (RefKind & AArch64MCExpr::VK_NC) {
Value &= 0xFFFF;
}
else if (AArch64MCExpr::getSymbolLoc(RefKind) == AArch64MCExpr::VK_SABS) {
if (SignedValue > 0xFFFF || SignedValue < -0xFFFF)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
// Invert the negative immediate because it will feed into a MOVN.
if (SignedValue < 0)
SignedValue = ~SignedValue;
Value = static_cast<uint64_t>(SignedValue);
}
else if (Value > 0xFFFF) {
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
}
return Value;
}
case AArch64::fixup_aarch64_pcrel_branch14:
// Signed 16-bit immediate
if (SignedValue > 32767 || SignedValue < -32768)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
// Low two bits are not encoded (4-byte alignment assumed).
if (Value & 0x3)
Ctx.reportError(Fixup.getLoc(), "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)
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
// Low two bits are not encoded (4-byte alignment assumed).
if (Value & 0x3)
Ctx.reportError(Fixup.getLoc(), "fixup not sufficiently aligned");
return (Value >> 2) & 0x3ffffff;
case FK_Data_1:
case FK_Data_2:
case FK_Data_4:
case FK_Data_8:
case FK_SecRel_2:
case FK_SecRel_4:
return Value;
}
}
Optional<MCFixupKind> AArch64AsmBackend::getFixupKind(StringRef Name) const {
if (!TheTriple.isOSBinFormatELF())
return None;
unsigned Type = llvm::StringSwitch<unsigned>(Name)
#define ELF_RELOC(X, Y) .Case(#X, Y)
#include "llvm/BinaryFormat/ELFRelocs/AArch64.def"
#undef ELF_RELOC
.Default(-1u);
if (Type == -1u)
return None;
return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type);
}
/// getFixupKindContainereSizeInBytes - The number of bytes of the
/// container involved in big endian or 0 if the item is little endian
unsigned AArch64AsmBackend::getFixupKindContainereSizeInBytes(unsigned Kind) const {
if (Endian == support::little)
return 0;
switch (Kind) {
default:
llvm_unreachable("Unknown fixup kind!");
case FK_Data_1:
return 1;
case FK_Data_2:
return 2;
case FK_Data_4:
return 4;
case FK_Data_8:
return 8;
case AArch64::fixup_aarch64_tlsdesc_call:
case AArch64::fixup_aarch64_movw:
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:
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:
// Instructions are always little endian
return 0;
}
}
void AArch64AsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
const MCValue &Target,
MutableArrayRef<char> Data, uint64_t Value,
bool IsResolved,
const MCSubtargetInfo *STI) const {
if (!Value)
return; // Doesn't change encoding.
unsigned Kind = Fixup.getKind();
if (Kind >= FirstLiteralRelocationKind)
return;
unsigned NumBytes = getFixupKindNumBytes(Kind);
MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
MCContext &Ctx = Asm.getContext();
int64_t SignedValue = static_cast<int64_t>(Value);
// Apply any target-specific value adjustments.
Value = adjustFixupValue(Fixup, Target, Value, Ctx, TheTriple, IsResolved);
// Shift the value into position.
Value <<= Info.TargetOffset;
unsigned Offset = Fixup.getOffset();
assert(Offset + NumBytes <= Data.size() && "Invalid fixup offset!");
// Used to point to big endian bytes.
unsigned FulleSizeInBytes = getFixupKindContainereSizeInBytes(Fixup.getKind());
// For each byte of the fragment that the fixup touches, mask in the
// bits from the fixup value.
if (FulleSizeInBytes == 0) {
// Handle as little-endian
for (unsigned i = 0; i != NumBytes; ++i) {
Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
}
} else {
// Handle as big-endian
assert((Offset + FulleSizeInBytes) <= Data.size() && "Invalid fixup size!");
assert(NumBytes <= FulleSizeInBytes && "Invalid fixup size!");
for (unsigned i = 0; i != NumBytes; ++i) {
unsigned Idx = FulleSizeInBytes - 1 - i;
Data[Offset + Idx] |= uint8_t((Value >> (i * 8)) & 0xff);
}
}
// FIXME: getFixupKindInfo() and getFixupKindNumBytes() could be fixed to
// handle this more cleanly. This may affect the output of -show-mc-encoding.
AArch64MCExpr::VariantKind RefKind =
static_cast<AArch64MCExpr::VariantKind>(Target.getRefKind());
if (AArch64MCExpr::getSymbolLoc(RefKind) == AArch64MCExpr::VK_SABS ||
(!RefKind && Fixup.getTargetKind() == AArch64::fixup_aarch64_movw)) {
// If the immediate is negative, generate MOVN else MOVZ.
// (Bit 30 = 0) ==> MOVN, (Bit 30 = 1) ==> MOVZ.
if (SignedValue < 0)
Data[Offset + 3] &= ~(1 << 6);
else
Data[Offset + 3] |= (1 << 6);
}
}
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(MCInst &Inst,
const MCSubtargetInfo &STI) const {
llvm_unreachable("AArch64AsmBackend::relaxInstruction() unimplemented");
}
bool AArch64AsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) 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.
OS.write_zeros(Count % 4);
// We are properly aligned, so write NOPs as requested.
Count /= 4;
for (uint64_t i = 0; i != Count; ++i)
support::endian::write<uint32_t>(OS, 0xd503201f, Endian);
return true;
}
bool AArch64AsmBackend::shouldForceRelocation(const MCAssembler &Asm,
const MCFixup &Fixup,
const MCValue &Target) {
unsigned Kind = Fixup.getKind();
if (Kind >= FirstLiteralRelocationKind)
return true;
// 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 (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
return true;
AArch64MCExpr::VariantKind RefKind =
static_cast<AArch64MCExpr::VariantKind>(Target.getRefKind());
AArch64MCExpr::VariantKind SymLoc = AArch64MCExpr::getSymbolLoc(RefKind);
// LDR GOT relocations need a relocation
if (Kind == AArch64::fixup_aarch64_ldr_pcrel_imm19 &&
SymLoc == AArch64MCExpr::VK_GOT)
return true;
return false;
}
namespace {
namespace CU {
/// Compact unwind encoding values.
enum CompactUnwindEncodings {
/// A "frameless" leaf function, where no non-volatile registers are
/// saved. The return remains in LR throughout the function.
UNWIND_ARM64_MODE_FRAMELESS = 0x02000000,
/// 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_ARM64_MODE_DWARF = 0x03000000,
/// 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_ARM64_MODE_FRAME = 0x04000000,
/// Frame register pair encodings.
UNWIND_ARM64_FRAME_X19_X20_PAIR = 0x00000001,
UNWIND_ARM64_FRAME_X21_X22_PAIR = 0x00000002,
UNWIND_ARM64_FRAME_X23_X24_PAIR = 0x00000004,
UNWIND_ARM64_FRAME_X25_X26_PAIR = 0x00000008,
UNWIND_ARM64_FRAME_X27_X28_PAIR = 0x00000010,
UNWIND_ARM64_FRAME_D8_D9_PAIR = 0x00000100,
UNWIND_ARM64_FRAME_D10_D11_PAIR = 0x00000200,
UNWIND_ARM64_FRAME_D12_D13_PAIR = 0x00000400,
UNWIND_ARM64_FRAME_D14_D15_PAIR = 0x00000800
};
} // end CU namespace
// FIXME: This should be in a separate file.
class DarwinAArch64AsmBackend : public AArch64AsmBackend {
const MCRegisterInfo &MRI;
/// Encode compact unwind stack adjustment for frameless functions.
/// See UNWIND_ARM64_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 Triple &TT,
const MCRegisterInfo &MRI)
: AArch64AsmBackend(T, TT, /*IsLittleEndian*/ true), MRI(MRI) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
uint32_t CPUType = cantFail(MachO::getCPUType(TheTriple));
uint32_t CPUSubType = cantFail(MachO::getCPUSubType(TheTriple));
return createAArch64MachObjectWriter(CPUType, CPUSubType,
TheTriple.isArch32Bit());
}
/// Generate the compact unwind encoding from the CFI directives.
uint32_t generateCompactUnwindEncoding(
ArrayRef<MCCFIInstruction> Instrs) const override {
if (Instrs.empty())
return CU::UNWIND_ARM64_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_ARM64_MODE_DWARF;
case MCCFIInstruction::OpDefCfa: {
// Defines a frame pointer.
unsigned XReg =
getXRegFromWReg(*MRI.getLLVMRegNum(Inst.getRegister(), true));
// Other CFA registers than FP are not supported by compact unwind.
// Fallback on DWARF.
// FIXME: When opt-remarks are supported in MC, add a remark to notify
// the user.
if (XReg != AArch64::FP)
return CU::UNWIND_ARM64_MODE_DWARF;
assert(XReg == 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_ARM64_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_ARM64_MODE_DWARF;
const MCCFIInstruction &Inst2 = Instrs[++i];
if (Inst2.getOperation() != MCCFIInstruction::OpOffset)
return CU::UNWIND_ARM64_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_ARM64_FRAME_X19_X20_PAIR;
else if (Reg1 == AArch64::X21 && Reg2 == AArch64::X22 &&
(CompactUnwindEncoding & 0xF1C) == 0)
CompactUnwindEncoding |= CU::UNWIND_ARM64_FRAME_X21_X22_PAIR;
else if (Reg1 == AArch64::X23 && Reg2 == AArch64::X24 &&
(CompactUnwindEncoding & 0xF18) == 0)
CompactUnwindEncoding |= CU::UNWIND_ARM64_FRAME_X23_X24_PAIR;
else if (Reg1 == AArch64::X25 && Reg2 == AArch64::X26 &&
(CompactUnwindEncoding & 0xF10) == 0)
CompactUnwindEncoding |= CU::UNWIND_ARM64_FRAME_X25_X26_PAIR;
else if (Reg1 == AArch64::X27 && Reg2 == AArch64::X28 &&
(CompactUnwindEncoding & 0xF00) == 0)
CompactUnwindEncoding |= CU::UNWIND_ARM64_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_ARM64_FRAME_D8_D9_PAIR;
else if (Reg1 == AArch64::D10 && Reg2 == AArch64::D11 &&
(CompactUnwindEncoding & 0xC00) == 0)
CompactUnwindEncoding |= CU::UNWIND_ARM64_FRAME_D10_D11_PAIR;
else if (Reg1 == AArch64::D12 && Reg2 == AArch64::D13 &&
(CompactUnwindEncoding & 0x800) == 0)
CompactUnwindEncoding |= CU::UNWIND_ARM64_FRAME_D12_D13_PAIR;
else if (Reg1 == AArch64::D14 && Reg2 == AArch64::D15)
CompactUnwindEncoding |= CU::UNWIND_ARM64_FRAME_D14_D15_PAIR;
else
// A pair was pushed which we cannot handle.
return CU::UNWIND_ARM64_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_ARM64_MODE_DWARF;
CompactUnwindEncoding |= CU::UNWIND_ARM64_MODE_FRAMELESS;
CompactUnwindEncoding |= encodeStackAdjustment(StackSize);
}
return CompactUnwindEncoding;
}
};
} // end anonymous namespace
namespace {
class ELFAArch64AsmBackend : public AArch64AsmBackend {
public:
uint8_t OSABI;
bool IsILP32;
ELFAArch64AsmBackend(const Target &T, const Triple &TT, uint8_t OSABI,
bool IsLittleEndian, bool IsILP32)
: AArch64AsmBackend(T, TT, IsLittleEndian), OSABI(OSABI),
IsILP32(IsILP32) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createAArch64ELFObjectWriter(OSABI, IsILP32);
}
};
}
namespace {
class COFFAArch64AsmBackend : public AArch64AsmBackend {
public:
COFFAArch64AsmBackend(const Target &T, const Triple &TheTriple)
: AArch64AsmBackend(T, TheTriple, /*IsLittleEndian*/ true) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createAArch64WinCOFFObjectWriter();
}
};
}
MCAsmBackend *llvm::createAArch64leAsmBackend(const Target &T,
const MCSubtargetInfo &STI,
const MCRegisterInfo &MRI,
const MCTargetOptions &Options) {
const Triple &TheTriple = STI.getTargetTriple();
if (TheTriple.isOSBinFormatMachO()) {
return new DarwinAArch64AsmBackend(T, TheTriple, MRI);
}
if (TheTriple.isOSBinFormatCOFF())
return new COFFAArch64AsmBackend(T, TheTriple);
assert(TheTriple.isOSBinFormatELF() && "Invalid target");
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
bool IsILP32 = STI.getTargetTriple().getEnvironment() == Triple::GNUILP32;
return new ELFAArch64AsmBackend(T, TheTriple, OSABI, /*IsLittleEndian=*/true,
IsILP32);
}
MCAsmBackend *llvm::createAArch64beAsmBackend(const Target &T,
const MCSubtargetInfo &STI,
const MCRegisterInfo &MRI,
const MCTargetOptions &Options) {
const Triple &TheTriple = STI.getTargetTriple();
assert(TheTriple.isOSBinFormatELF() &&
"Big endian is only supported for ELF targets!");
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
bool IsILP32 = STI.getTargetTriple().getEnvironment() == Triple::GNUILP32;
return new ELFAArch64AsmBackend(T, TheTriple, OSABI, /*IsLittleEndian=*/false,
IsILP32);
}
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