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llvm-project/llvm/lib/Target/ARM/ARMAsmBackend.cpp

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//===-- ARMAsmBackend.cpp - ARM Assembler Backend -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMAddressingModes.h"
#include "ARMFixupKinds.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCMachObjectWriter.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Object/MachOFormat.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetAsmBackend.h"
#include "llvm/Target/TargetRegistry.h"
using namespace llvm;
namespace {
class ARMMachObjectWriter : public MCMachObjectTargetWriter {
public:
ARMMachObjectWriter(bool Is64Bit, uint32_t CPUType,
uint32_t CPUSubtype)
: MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype,
/*UseAggressiveSymbolFolding=*/true) {}
};
class ARMELFObjectWriter : public MCELFObjectTargetWriter {
public:
ARMELFObjectWriter(Triple::OSType OSType)
: MCELFObjectTargetWriter(/*Is64Bit*/ false, OSType, ELF::EM_ARM,
/*HasRelocationAddend*/ false) {}
};
class ARMAsmBackend : public TargetAsmBackend {
bool isThumbMode; // Currently emitting Thumb code.
public:
ARMAsmBackend(const Target &T) : TargetAsmBackend(), isThumbMode(false) {}
unsigned getNumFixupKinds() const { return ARM::NumTargetFixupKinds; }
const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
const static MCFixupKindInfo Infos[ARM::NumTargetFixupKinds] = {
// This table *must* be in the order that the fixup_* kinds are defined in
// ARMFixupKinds.h.
//
// Name Offset (bits) Size (bits) Flags
{ "fixup_arm_ldst_pcrel_12", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_ldst_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{ "fixup_arm_pcrel_10", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_pcrel_10", 0, 32, MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{ "fixup_thumb_adr_pcrel_10",0, 8, MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{ "fixup_arm_adr_pcrel_12", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_adr_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{ "fixup_arm_branch", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_condbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_uncondbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_br", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_blx", 7, 21, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_cb", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_cp", 1, 8, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_bcc", 1, 8, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_movt_hi16", 0, 16, 0 },
{ "fixup_arm_movw_lo16", 0, 16, 0 },
};
if (Kind < FirstTargetFixupKind)
return TargetAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
bool MayNeedRelaxation(const MCInst &Inst) const;
void RelaxInstruction(const MCInst &Inst, MCInst &Res) const;
bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const;
void HandleAssemblerFlag(MCAssemblerFlag Flag) {
switch (Flag) {
default: break;
case MCAF_Code16:
setIsThumb(true);
break;
case MCAF_Code32:
setIsThumb(false);
break;
}
}
unsigned getPointerSize() const { return 4; }
bool isThumb() const { return isThumbMode; }
void setIsThumb(bool it) { isThumbMode = it; }
};
} // end anonymous namespace
bool ARMAsmBackend::MayNeedRelaxation(const MCInst &Inst) const {
// FIXME: Thumb targets, different move constant targets..
return false;
}
void ARMAsmBackend::RelaxInstruction(const MCInst &Inst, MCInst &Res) const {
assert(0 && "ARMAsmBackend::RelaxInstruction() unimplemented");
return;
}
bool ARMAsmBackend::WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
if (isThumb()) {
// FIXME: 0xbf00 is the ARMv7 value. For v6 and before, we'll need to
// use 0x46c0 (which is a 'mov r8, r8' insn).
uint64_t NumNops = Count / 2;
for (uint64_t i = 0; i != NumNops; ++i)
OW->Write16(0xbf00);
if (Count & 1)
OW->Write8(0);
return true;
}
// ARM mode
uint64_t NumNops = Count / 4;
for (uint64_t i = 0; i != NumNops; ++i)
OW->Write32(0xe1a00000);
switch (Count % 4) {
default: break; // No leftover bytes to write
case 1: OW->Write8(0); break;
case 2: OW->Write16(0); break;
case 3: OW->Write16(0); OW->Write8(0xa0); break;
}
return true;
}
static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
switch (Kind) {
default:
llvm_unreachable("Unknown fixup kind!");
case FK_Data_1:
case FK_Data_2:
case FK_Data_4:
return Value;
case ARM::fixup_arm_movt_hi16:
case ARM::fixup_arm_movw_lo16: {
unsigned Hi4 = (Value & 0xF000) >> 12;
unsigned Lo12 = Value & 0x0FFF;
// inst{19-16} = Hi4;
// inst{11-0} = Lo12;
Value = (Hi4 << 16) | (Lo12);
return Value;
}
case ARM::fixup_arm_ldst_pcrel_12:
// ARM PC-relative values are offset by 8.
Value -= 4;
// FALLTHROUGH
case ARM::fixup_t2_ldst_pcrel_12: {
// Offset by 4, adjusted by two due to the half-word ordering of thumb.
Value -= 4;
bool isAdd = true;
if ((int64_t)Value < 0) {
Value = -Value;
isAdd = false;
}
assert ((Value < 4096) && "Out of range pc-relative fixup value!");
Value |= isAdd << 23;
// Same addressing mode as fixup_arm_pcrel_10,
// but with 16-bit halfwords swapped.
if (Kind == ARM::fixup_t2_ldst_pcrel_12) {
uint64_t swapped = (Value & 0xFFFF0000) >> 16;
swapped |= (Value & 0x0000FFFF) << 16;
return swapped;
}
return Value;
}
case ARM::fixup_thumb_adr_pcrel_10:
return ((Value - 4) >> 2) & 0xff;
case ARM::fixup_arm_adr_pcrel_12: {
// ARM PC-relative values are offset by 8.
Value -= 8;
unsigned opc = 4; // bits {24-21}. Default to add: 0b0100
if ((int64_t)Value < 0) {
Value = -Value;
opc = 2; // 0b0010
}
assert(ARM_AM::getSOImmVal(Value) != -1 &&
"Out of range pc-relative fixup value!");
// Encode the immediate and shift the opcode into place.
return ARM_AM::getSOImmVal(Value) | (opc << 21);
}
case ARM::fixup_t2_adr_pcrel_12: {
Value -= 4;
unsigned opc = 0;
if ((int64_t)Value < 0) {
Value = -Value;
opc = 5;
}
uint32_t out = (opc << 21);
out |= (Value & 0x800) << 14;
out |= (Value & 0x700) << 4;
out |= (Value & 0x0FF);
uint64_t swapped = (out & 0xFFFF0000) >> 16;
swapped |= (out & 0x0000FFFF) << 16;
return swapped;
}
case ARM::fixup_arm_branch:
// These values don't encode the low two bits since they're always zero.
// Offset by 8 just as above.
return 0xffffff & ((Value - 8) >> 2);
case ARM::fixup_t2_uncondbranch: {
Value = Value - 4;
Value >>= 1; // Low bit is not encoded.
uint32_t out = 0;
bool I = Value & 0x800000;
bool J1 = Value & 0x400000;
bool J2 = Value & 0x200000;
J1 ^= I;
J2 ^= I;
out |= I << 26; // S bit
out |= !J1 << 13; // J1 bit
out |= !J2 << 11; // J2 bit
out |= (Value & 0x1FF800) << 5; // imm6 field
out |= (Value & 0x0007FF); // imm11 field
uint64_t swapped = (out & 0xFFFF0000) >> 16;
swapped |= (out & 0x0000FFFF) << 16;
return swapped;
}
case ARM::fixup_t2_condbranch: {
Value = Value - 4;
Value >>= 1; // Low bit is not encoded.
uint64_t out = 0;
out |= (Value & 0x80000) << 7; // S bit
out |= (Value & 0x40000) >> 7; // J2 bit
out |= (Value & 0x20000) >> 4; // J1 bit
out |= (Value & 0x1F800) << 5; // imm6 field
out |= (Value & 0x007FF); // imm11 field
uint32_t swapped = (out & 0xFFFF0000) >> 16;
swapped |= (out & 0x0000FFFF) << 16;
return swapped;
}
case ARM::fixup_arm_thumb_bl: {
// The value doesn't encode the low bit (always zero) and is offset by
// four. The value is encoded into disjoint bit positions in the destination
// opcode. x = unchanged, I = immediate value bit, S = sign extension bit
//
// BL: xxxxxSIIIIIIIIII xxxxxIIIIIIIIIII
//
// Note that the halfwords are stored high first, low second; so we need
// to transpose the fixup value here to map properly.
unsigned isNeg = (int64_t(Value) < 0) ? 1 : 0;
uint32_t Binary = 0;
Value = 0x3fffff & ((Value - 4) >> 1);
Binary = (Value & 0x7ff) << 16; // Low imm11 value.
Binary |= (Value & 0x1ffc00) >> 11; // High imm10 value.
Binary |= isNeg << 10; // Sign bit.
return Binary;
}
case ARM::fixup_arm_thumb_blx: {
// The value doesn't encode the low two bits (always zero) and is offset by
// four (see fixup_arm_thumb_cp). The value is encoded into disjoint bit
// positions in the destination opcode. x = unchanged, I = immediate value
// bit, S = sign extension bit, 0 = zero.
//
// BLX: xxxxxSIIIIIIIIII xxxxxIIIIIIIIII0
//
// Note that the halfwords are stored high first, low second; so we need
// to transpose the fixup value here to map properly.
unsigned isNeg = (int64_t(Value) < 0) ? 1 : 0;
uint32_t Binary = 0;
Value = 0xfffff & ((Value - 2) >> 2);
Binary = (Value & 0x3ff) << 17; // Low imm10L value.
Binary |= (Value & 0xffc00) >> 10; // High imm10H value.
Binary |= isNeg << 10; // Sign bit.
return Binary;
}
case ARM::fixup_arm_thumb_cp:
// Offset by 4, and don't encode the low two bits. Two bytes of that
// 'off by 4' is implicitly handled by the half-word ordering of the
// Thumb encoding, so we only need to adjust by 2 here.
return ((Value - 2) >> 2) & 0xff;
case ARM::fixup_arm_thumb_cb: {
// Offset by 4 and don't encode the lower bit, which is always 0.
uint32_t Binary = (Value - 4) >> 1;
return ((Binary & 0x20) << 4) | ((Binary & 0x1f) << 3);
}
case ARM::fixup_arm_thumb_br:
// Offset by 4 and don't encode the lower bit, which is always 0.
return ((Value - 4) >> 1) & 0x7ff;
case ARM::fixup_arm_thumb_bcc:
// Offset by 4 and don't encode the lower bit, which is always 0.
return ((Value - 4) >> 1) & 0xff;
case ARM::fixup_arm_pcrel_10:
Value = Value - 4; // ARM fixups offset by an additional word and don't
// need to adjust for the half-word ordering.
// Fall through.
case ARM::fixup_t2_pcrel_10: {
// Offset by 4, adjusted by two due to the half-word ordering of thumb.
Value = Value - 4;
bool isAdd = true;
if ((int64_t)Value < 0) {
Value = -Value;
isAdd = false;
}
// These values don't encode the low two bits since they're always zero.
Value >>= 2;
assert ((Value < 256) && "Out of range pc-relative fixup value!");
Value |= isAdd << 23;
// Same addressing mode as fixup_arm_pcrel_10,
// but with 16-bit halfwords swapped.
if (Kind == ARM::fixup_t2_pcrel_10) {
uint32_t swapped = (Value & 0xFFFF0000) >> 16;
swapped |= (Value & 0x0000FFFF) << 16;
return swapped;
}
return Value;
}
}
}
namespace {
// FIXME: This should be in a separate file.
// ELF is an ELF of course...
class ELFARMAsmBackend : public ARMAsmBackend {
public:
Triple::OSType OSType;
ELFARMAsmBackend(const Target &T, Triple::OSType _OSType)
: ARMAsmBackend(T), OSType(_OSType) { }
void ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
uint64_t Value) const;
MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
return createELFObjectWriter(new ARMELFObjectWriter(OSType), OS,
/*IsLittleEndian*/ true);
}
};
// FIXME: Raise this to share code between Darwin and ELF.
void ELFARMAsmBackend::ApplyFixup(const MCFixup &Fixup, char *Data,
unsigned DataSize, uint64_t Value) const {
unsigned NumBytes = 4; // FIXME: 2 for Thumb
Value = adjustFixupValue(Fixup.getKind(), Value);
if (!Value) return; // Doesn't change encoding.
unsigned Offset = Fixup.getOffset();
assert(Offset % NumBytes == 0 && "Offset mod NumBytes is nonzero!");
// For each byte of the fragment that the fixup touches, mask in the bits from
// the fixup value. The Value has been "split up" into the appropriate
// bitfields above.
for (unsigned i = 0; i != NumBytes; ++i)
Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
}
// FIXME: This should be in a separate file.
class DarwinARMAsmBackend : public ARMAsmBackend {
public:
DarwinARMAsmBackend(const Target &T) : ARMAsmBackend(T) { }
void ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
uint64_t Value) const;
MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
// FIXME: Subtarget info should be derived. Force v7 for now.
return createMachObjectWriter(new ARMMachObjectWriter(
/*Is64Bit=*/false,
object::mach::CTM_ARM,
object::mach::CSARM_V7),
OS,
/*IsLittleEndian=*/true);
}
virtual bool doesSectionRequireSymbols(const MCSection &Section) const {
return false;
}
};
/// getFixupKindNumBytes - The number of bytes the fixup may change.
static unsigned getFixupKindNumBytes(unsigned Kind) {
switch (Kind) {
default:
llvm_unreachable("Unknown fixup kind!");
case FK_Data_1:
case ARM::fixup_arm_thumb_bcc:
case ARM::fixup_arm_thumb_cp:
case ARM::fixup_thumb_adr_pcrel_10:
return 1;
case FK_Data_2:
case ARM::fixup_arm_thumb_br:
case ARM::fixup_arm_thumb_cb:
return 2;
case ARM::fixup_arm_ldst_pcrel_12:
case ARM::fixup_arm_pcrel_10:
case ARM::fixup_arm_adr_pcrel_12:
case ARM::fixup_arm_branch:
return 3;
case FK_Data_4:
case ARM::fixup_t2_ldst_pcrel_12:
case ARM::fixup_t2_condbranch:
case ARM::fixup_t2_uncondbranch:
case ARM::fixup_t2_pcrel_10:
case ARM::fixup_t2_adr_pcrel_12:
case ARM::fixup_arm_thumb_bl:
case ARM::fixup_arm_thumb_blx:
return 4;
}
}
void DarwinARMAsmBackend::ApplyFixup(const MCFixup &Fixup, char *Data,
unsigned DataSize, uint64_t Value) const {
unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
Value = adjustFixupValue(Fixup.getKind(), Value);
if (!Value) return; // Doesn't change encoding.
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);
}
} // end anonymous namespace
TargetAsmBackend *llvm::createARMAsmBackend(const Target &T,
const std::string &TT) {
switch (Triple(TT).getOS()) {
case Triple::Darwin:
return new DarwinARMAsmBackend(T);
case Triple::MinGW32:
case Triple::Cygwin:
case Triple::Win32:
assert(0 && "Windows not supported on ARM");
default:
return new ELFARMAsmBackend(T, Triple(TT).getOS());
}
}
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