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llvm-project/llvm/lib/Target/ARM/MCTargetDesc/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 "MCTargetDesc/ARMMCTargetDesc.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "MCTargetDesc/ARMAsmBackend.h"
#include "MCTargetDesc/ARMAsmBackendDarwin.h"
#include "MCTargetDesc/ARMAsmBackendELF.h"
#include "MCTargetDesc/ARMAsmBackendWinCOFF.h"
#include "MCTargetDesc/ARMBaseInfo.h"
#include "MCTargetDesc/ARMFixupKinds.h"
#include "llvm/ADT/StringSwitch.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/MCExpr.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCMachObjectWriter.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MachO.h"
#include "llvm/Support/TargetParser.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
class ARMELFObjectWriter : public MCELFObjectTargetWriter {
public:
ARMELFObjectWriter(uint8_t OSABI)
: MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI, ELF::EM_ARM,
/*HasRelocationAddend*/ false) {}
};
const MCFixupKindInfo &ARMAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
const static MCFixupKindInfo InfosLE[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", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_t2_ldst_pcrel_12", 0, 32,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_pcrel_10_unscaled", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_pcrel_10", 0, 32, 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", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_t2_adr_pcrel_12", 0, 32,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_condbranch", 0, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_uncondbranch", 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_uncondbl", 0, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_condbl", 0, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_blx", 0, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_blx", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_cb", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_cp", 0, 8,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_thumb_bcc", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
// movw / movt: 16-bits immediate but scattered into two chunks 0 - 12, 16
// - 19.
{"fixup_arm_movt_hi16", 0, 20, 0},
{"fixup_arm_movw_lo16", 0, 20, 0},
{"fixup_t2_movt_hi16", 0, 20, 0},
{"fixup_t2_movw_lo16", 0, 20, 0},
};
const static MCFixupKindInfo InfosBE[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", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_t2_ldst_pcrel_12", 0, 32,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_pcrel_10_unscaled", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_pcrel_10", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_t2_pcrel_10", 0, 32,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_thumb_adr_pcrel_10", 8, 8,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_adr_pcrel_12", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_t2_adr_pcrel_12", 0, 32,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_condbranch", 8, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_uncondbranch", 8, 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_uncondbl", 8, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_condbl", 8, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_blx", 8, 24, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_blx", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_cb", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
{"fixup_arm_thumb_cp", 8, 8,
MCFixupKindInfo::FKF_IsPCRel |
MCFixupKindInfo::FKF_IsAlignedDownTo32Bits},
{"fixup_arm_thumb_bcc", 8, 8, MCFixupKindInfo::FKF_IsPCRel},
// movw / movt: 16-bits immediate but scattered into two chunks 0 - 12, 16
// - 19.
{"fixup_arm_movt_hi16", 12, 20, 0},
{"fixup_arm_movw_lo16", 12, 20, 0},
{"fixup_t2_movt_hi16", 12, 20, 0},
{"fixup_t2_movw_lo16", 12, 20, 0},
};
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
return (IsLittleEndian ? InfosLE : InfosBE)[Kind - FirstTargetFixupKind];
}
void ARMAsmBackend::handleAssemblerFlag(MCAssemblerFlag Flag) {
switch (Flag) {
default:
break;
case MCAF_Code16:
setIsThumb(true);
break;
case MCAF_Code32:
setIsThumb(false);
break;
}
}
} // end anonymous namespace
unsigned ARMAsmBackend::getRelaxedOpcode(unsigned Op) const {
bool HasThumb2 = STI->getFeatureBits()[ARM::FeatureThumb2];
bool HasV8MBaselineOps = STI->getFeatureBits()[ARM::HasV8MBaselineOps];
switch (Op) {
default:
return Op;
case ARM::tBcc:
return HasThumb2 ? (unsigned)ARM::t2Bcc : Op;
case ARM::tLDRpci:
return HasThumb2 ? (unsigned)ARM::t2LDRpci : Op;
case ARM::tADR:
return HasThumb2 ? (unsigned)ARM::t2ADR : Op;
case ARM::tB:
return HasV8MBaselineOps ? (unsigned)ARM::t2B : Op;
case ARM::tCBZ:
return ARM::tHINT;
case ARM::tCBNZ:
return ARM::tHINT;
}
}
bool ARMAsmBackend::mayNeedRelaxation(const MCInst &Inst) const {
if (getRelaxedOpcode(Inst.getOpcode()) != Inst.getOpcode())
return true;
return false;
}
const char *ARMAsmBackend::reasonForFixupRelaxation(const MCFixup &Fixup,
uint64_t Value) const {
switch ((unsigned)Fixup.getKind()) {
case ARM::fixup_arm_thumb_br: {
// Relaxing tB to t2B. tB has a signed 12-bit displacement with the
// low bit being an implied zero. There's an implied +4 offset for the
// branch, so we adjust the other way here to determine what's
// encodable.
//
// Relax if the value is too big for a (signed) i8.
int64_t Offset = int64_t(Value) - 4;
if (Offset > 2046 || Offset < -2048)
return "out of range pc-relative fixup value";
break;
}
case ARM::fixup_arm_thumb_bcc: {
// Relaxing tBcc to t2Bcc. tBcc has a signed 9-bit displacement with the
// low bit being an implied zero. There's an implied +4 offset for the
// branch, so we adjust the other way here to determine what's
// encodable.
//
// Relax if the value is too big for a (signed) i8.
int64_t Offset = int64_t(Value) - 4;
if (Offset > 254 || Offset < -256)
return "out of range pc-relative fixup value";
break;
}
case ARM::fixup_thumb_adr_pcrel_10:
case ARM::fixup_arm_thumb_cp: {
// If the immediate is negative, greater than 1020, or not a multiple
// of four, the wide version of the instruction must be used.
int64_t Offset = int64_t(Value) - 4;
if (Offset & 3)
return "misaligned pc-relative fixup value";
else if (Offset > 1020 || Offset < 0)
return "out of range pc-relative fixup value";
break;
}
case ARM::fixup_arm_thumb_cb: {
// If we have a Thumb CBZ or CBNZ instruction and its target is the next
// instruction it is is actually out of range for the instruction.
// It will be changed to a NOP.
int64_t Offset = (Value & ~1);
if (Offset == 2)
return "will be converted to nop";
break;
}
default:
llvm_unreachable("Unexpected fixup kind in reasonForFixupRelaxation()!");
}
return nullptr;
}
bool ARMAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const {
return reasonForFixupRelaxation(Fixup, Value);
}
void ARMAsmBackend::relaxInstruction(const MCInst &Inst, MCInst &Res) const {
unsigned RelaxedOp = getRelaxedOpcode(Inst.getOpcode());
// Sanity check w/ diagnostic if we get here w/ a bogus instruction.
if (RelaxedOp == Inst.getOpcode()) {
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
Inst.dump_pretty(OS);
OS << "\n";
report_fatal_error("unexpected instruction to relax: " + OS.str());
}
// If we are changing Thumb CBZ or CBNZ instruction to a NOP, aka tHINT, we
// have to change the operands too.
if ((Inst.getOpcode() == ARM::tCBZ || Inst.getOpcode() == ARM::tCBNZ) &&
RelaxedOp == ARM::tHINT) {
Res.setOpcode(RelaxedOp);
Res.addOperand(MCOperand::createImm(0));
Res.addOperand(MCOperand::createImm(14));
Res.addOperand(MCOperand::createReg(0));
return;
}
// The rest of instructions we're relaxing have the same operands.
// We just need to update to the proper opcode.
Res = Inst;
Res.setOpcode(RelaxedOp);
}
bool ARMAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
const uint16_t Thumb1_16bitNopEncoding = 0x46c0; // using MOV r8,r8
const uint16_t Thumb2_16bitNopEncoding = 0xbf00; // NOP
const uint32_t ARMv4_NopEncoding = 0xe1a00000; // using MOV r0,r0
const uint32_t ARMv6T2_NopEncoding = 0xe320f000; // NOP
if (isThumb()) {
const uint16_t nopEncoding =
hasNOP() ? Thumb2_16bitNopEncoding : Thumb1_16bitNopEncoding;
uint64_t NumNops = Count / 2;
for (uint64_t i = 0; i != NumNops; ++i)
OW->write16(nopEncoding);
if (Count & 1)
OW->write8(0);
return true;
}
// ARM mode
const uint32_t nopEncoding =
hasNOP() ? ARMv6T2_NopEncoding : ARMv4_NopEncoding;
uint64_t NumNops = Count / 4;
for (uint64_t i = 0; i != NumNops; ++i)
OW->write32(nopEncoding);
// FIXME: should this function return false when unable to write exactly
// 'Count' bytes with NOP encodings?
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 uint32_t swapHalfWords(uint32_t Value, bool IsLittleEndian) {
if (IsLittleEndian) {
// Note that the halfwords are stored high first and low second in thumb;
// so we need to swap the fixup value here to map properly.
uint32_t Swapped = (Value & 0xFFFF0000) >> 16;
Swapped |= (Value & 0x0000FFFF) << 16;
return Swapped;
} else
return Value;
}
static uint32_t joinHalfWords(uint32_t FirstHalf, uint32_t SecondHalf,
bool IsLittleEndian) {
uint32_t Value;
if (IsLittleEndian) {
Value = (SecondHalf & 0xFFFF) << 16;
Value |= (FirstHalf & 0xFFFF);
} else {
Value = (SecondHalf & 0xFFFF);
Value |= (FirstHalf & 0xFFFF) << 16;
}
return Value;
}
unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
bool IsPCRel, MCContext *Ctx,
bool IsLittleEndian,
bool IsResolved) const {
unsigned Kind = Fixup.getKind();
switch (Kind) {
default:
llvm_unreachable("Unknown fixup kind!");
case FK_Data_1:
case FK_Data_2:
case FK_Data_4:
return Value;
case FK_SecRel_2:
return Value;
case FK_SecRel_4:
return Value;
case ARM::fixup_arm_movt_hi16:
if (!IsPCRel)
Value >>= 16;
// Fallthrough
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_t2_movt_hi16:
if (!IsPCRel)
Value >>= 16;
// Fallthrough
case ARM::fixup_t2_movw_lo16: {
unsigned Hi4 = (Value & 0xF000) >> 12;
unsigned i = (Value & 0x800) >> 11;
unsigned Mid3 = (Value & 0x700) >> 8;
unsigned Lo8 = Value & 0x0FF;
// inst{19-16} = Hi4;
// inst{26} = i;
// inst{14-12} = Mid3;
// inst{7-0} = Lo8;
Value = (Hi4 << 16) | (i << 26) | (Mid3 << 12) | (Lo8);
return swapHalfWords(Value, IsLittleEndian);
}
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;
}
if (Ctx && Value >= 4096) {
Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
return 0;
}
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)
return swapHalfWords(Value, IsLittleEndian);
return Value;
}
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
}
if (Ctx && ARM_AM::getSOImmVal(Value) == -1) {
Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
return 0;
}
// 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) << 15;
out |= (Value & 0x700) << 4;
out |= (Value & 0x0FF);
return swapHalfWords(out, IsLittleEndian);
}
case ARM::fixup_arm_condbranch:
case ARM::fixup_arm_uncondbranch:
case ARM::fixup_arm_uncondbl:
case ARM::fixup_arm_condbl:
case ARM::fixup_arm_blx:
// These values don't encode the low two bits since they're always zero.
// Offset by 8 just as above.
if (const MCSymbolRefExpr *SRE =
dyn_cast<MCSymbolRefExpr>(Fixup.getValue()))
if (SRE->getKind() == MCSymbolRefExpr::VK_ARM_TLSCALL)
return 0;
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
return swapHalfWords(out, IsLittleEndian);
}
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
return swapHalfWords(out, IsLittleEndian);
}
case ARM::fixup_arm_thumb_bl: {
// The value doesn't encode the low bit (always zero) and is offset by
// four. The 32-bit immediate value is encoded as
// imm32 = SignExtend(S:I1:I2:imm10:imm11:0)
// where I1 = NOT(J1 ^ S) and I2 = NOT(J2 ^ S).
// The value is encoded into disjoint bit positions in the destination
// opcode. x = unchanged, I = immediate value bit, S = sign extension bit,
// J = either J1 or J2 bit
//
// BL: xxxxxSIIIIIIIIII xxJxJIIIIIIIIIII
//
// Note that the halfwords are stored high first, low second; so we need
// to transpose the fixup value here to map properly.
uint32_t offset = (Value - 4) >> 1;
uint32_t signBit = (offset & 0x800000) >> 23;
uint32_t I1Bit = (offset & 0x400000) >> 22;
uint32_t J1Bit = (I1Bit ^ 0x1) ^ signBit;
uint32_t I2Bit = (offset & 0x200000) >> 21;
uint32_t J2Bit = (I2Bit ^ 0x1) ^ signBit;
uint32_t imm10Bits = (offset & 0x1FF800) >> 11;
uint32_t imm11Bits = (offset & 0x000007FF);
uint32_t FirstHalf = (((uint16_t)signBit << 10) | (uint16_t)imm10Bits);
uint32_t SecondHalf = (((uint16_t)J1Bit << 13) | ((uint16_t)J2Bit << 11) |
(uint16_t)imm11Bits);
return joinHalfWords(FirstHalf, SecondHalf, IsLittleEndian);
}
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 32-bit immediate value is encoded as
// imm32 = SignExtend(S:I1:I2:imm10H:imm10L:00)
// where I1 = NOT(J1 ^ S) and I2 = NOT(J2 ^ S).
// The value is encoded into disjoint bit positions in the destination
// opcode. x = unchanged, I = immediate value bit, S = sign extension bit,
// J = either J1 or J2 bit, 0 = zero.
//
// BLX: xxxxxSIIIIIIIIII xxJxJIIIIIIIIII0
//
// Note that the halfwords are stored high first, low second; so we need
// to transpose the fixup value here to map properly.
uint32_t offset = (Value - 2) >> 2;
if (const MCSymbolRefExpr *SRE =
dyn_cast<MCSymbolRefExpr>(Fixup.getValue()))
if (SRE->getKind() == MCSymbolRefExpr::VK_ARM_TLSCALL)
offset = 0;
uint32_t signBit = (offset & 0x400000) >> 22;
uint32_t I1Bit = (offset & 0x200000) >> 21;
uint32_t J1Bit = (I1Bit ^ 0x1) ^ signBit;
uint32_t I2Bit = (offset & 0x100000) >> 20;
uint32_t J2Bit = (I2Bit ^ 0x1) ^ signBit;
uint32_t imm10HBits = (offset & 0xFFC00) >> 10;
uint32_t imm10LBits = (offset & 0x3FF);
uint32_t FirstHalf = (((uint16_t)signBit << 10) | (uint16_t)imm10HBits);
uint32_t SecondHalf = (((uint16_t)J1Bit << 13) | ((uint16_t)J2Bit << 11) |
((uint16_t)imm10LBits) << 1);
return joinHalfWords(FirstHalf, SecondHalf, IsLittleEndian);
}
case ARM::fixup_thumb_adr_pcrel_10:
case ARM::fixup_arm_thumb_cp:
// On CPUs supporting Thumb2, this will be relaxed to an ldr.w, otherwise we
// could have an error on our hands.
if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2] && IsResolved) {
const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
if (FixupDiagnostic) {
Ctx->reportError(Fixup.getLoc(), FixupDiagnostic);
return 0;
}
}
// Offset by 4, and don't encode the low two bits.
return ((Value - 4) >> 2) & 0xff;
case ARM::fixup_arm_thumb_cb: {
// Offset by 4 and don't encode the lower bit, which is always 0.
// FIXME: diagnose if no Thumb2
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.
if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2] &&
!STI->getFeatureBits()[ARM::HasV8MBaselineOps]) {
const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
if (FixupDiagnostic) {
Ctx->reportError(Fixup.getLoc(), FixupDiagnostic);
return 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.
if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2]) {
const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
if (FixupDiagnostic) {
Ctx->reportError(Fixup.getLoc(), FixupDiagnostic);
return 0;
}
}
return ((Value - 4) >> 1) & 0xff;
case ARM::fixup_arm_pcrel_10_unscaled: {
Value = Value - 8; // ARM fixups offset by an additional word and don't
// need to adjust for the half-word ordering.
bool isAdd = true;
if ((int64_t)Value < 0) {
Value = -Value;
isAdd = false;
}
// The value has the low 4 bits encoded in [3:0] and the high 4 in [11:8].
if (Ctx && Value >= 256) {
Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
return 0;
}
Value = (Value & 0xf) | ((Value & 0xf0) << 4);
return Value | (isAdd << 23);
}
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;
if (Ctx && Value >= 256) {
Ctx->reportError(Fixup.getLoc(), "out of range pc-relative fixup value");
return 0;
}
Value |= isAdd << 23;
// Same addressing mode as fixup_arm_pcrel_10, but with 16-bit halfwords
// swapped.
if (Kind == ARM::fixup_t2_pcrel_10)
return swapHalfWords(Value, IsLittleEndian);
return Value;
}
}
}
void ARMAsmBackend::processFixupValue(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFixup &Fixup,
const MCFragment *DF,
const MCValue &Target, uint64_t &Value,
bool &IsResolved) {
const MCSymbolRefExpr *A = Target.getSymA();
const MCSymbol *Sym = A ? &A->getSymbol() : nullptr;
// Some fixups to thumb function symbols need the low bit (thumb bit)
// twiddled.
if ((unsigned)Fixup.getKind() != ARM::fixup_arm_ldst_pcrel_12 &&
(unsigned)Fixup.getKind() != ARM::fixup_t2_ldst_pcrel_12 &&
(unsigned)Fixup.getKind() != ARM::fixup_arm_adr_pcrel_12 &&
(unsigned)Fixup.getKind() != ARM::fixup_thumb_adr_pcrel_10 &&
(unsigned)Fixup.getKind() != ARM::fixup_t2_adr_pcrel_12 &&
(unsigned)Fixup.getKind() != ARM::fixup_arm_thumb_cp) {
if (Sym) {
if (Asm.isThumbFunc(Sym))
Value |= 1;
}
}
if (IsResolved && (unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_bl) {
assert(Sym && "How did we resolve this?");
// If the symbol is external the linker will handle it.
// FIXME: Should we handle it as an optimization?
// If the symbol is out of range, produce a relocation and hope the
// linker can handle it. GNU AS produces an error in this case.
if (Sym->isExternal() || Value >= 0x400004)
IsResolved = false;
}
// We must always generate a relocation for BL/BLX instructions if we have
// a symbol to reference, as the linker relies on knowing the destination
// symbol's thumb-ness to get interworking right.
if (A && ((unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_blx ||
(unsigned)Fixup.getKind() == ARM::fixup_arm_blx ||
(unsigned)Fixup.getKind() == ARM::fixup_arm_uncondbl ||
(unsigned)Fixup.getKind() == ARM::fixup_arm_condbl))
IsResolved = false;
// Try to get the encoded value for the fixup as-if we're mapping it into
// the instruction. This allows adjustFixupValue() to issue a diagnostic
// if the value aren't invalid.
(void)adjustFixupValue(Fixup, Value, false, &Asm.getContext(),
IsLittleEndian, IsResolved);
}
/// 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_pcrel_10_unscaled:
case ARM::fixup_arm_ldst_pcrel_12:
case ARM::fixup_arm_pcrel_10:
case ARM::fixup_arm_adr_pcrel_12:
case ARM::fixup_arm_uncondbl:
case ARM::fixup_arm_condbl:
case ARM::fixup_arm_blx:
case ARM::fixup_arm_condbranch:
case ARM::fixup_arm_uncondbranch:
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:
case ARM::fixup_arm_movt_hi16:
case ARM::fixup_arm_movw_lo16:
case ARM::fixup_t2_movt_hi16:
case ARM::fixup_t2_movw_lo16:
return 4;
case FK_SecRel_2:
return 2;
case FK_SecRel_4:
return 4;
}
}
/// getFixupKindContainerSizeBytes - The number of bytes of the
/// container involved in big endian.
static unsigned getFixupKindContainerSizeBytes(unsigned Kind) {
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 ARM::fixup_arm_thumb_bcc:
case ARM::fixup_arm_thumb_cp:
case ARM::fixup_thumb_adr_pcrel_10:
case ARM::fixup_arm_thumb_br:
case ARM::fixup_arm_thumb_cb:
// Instruction size is 2 bytes.
return 2;
case ARM::fixup_arm_pcrel_10_unscaled:
case ARM::fixup_arm_ldst_pcrel_12:
case ARM::fixup_arm_pcrel_10:
case ARM::fixup_arm_adr_pcrel_12:
case ARM::fixup_arm_uncondbl:
case ARM::fixup_arm_condbl:
case ARM::fixup_arm_blx:
case ARM::fixup_arm_condbranch:
case ARM::fixup_arm_uncondbranch:
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:
case ARM::fixup_arm_movt_hi16:
case ARM::fixup_arm_movw_lo16:
case ARM::fixup_t2_movt_hi16:
case ARM::fixup_t2_movw_lo16:
// Instruction size is 4 bytes.
return 4;
}
}
void ARMAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
unsigned DataSize, uint64_t Value,
bool IsPCRel) const {
unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
Value =
adjustFixupValue(Fixup, Value, IsPCRel, nullptr, IsLittleEndian, true);
if (!Value)
return; // Doesn't change encoding.
unsigned Offset = Fixup.getOffset();
assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!");
// Used to point to big endian bytes.
unsigned FullSizeBytes;
if (!IsLittleEndian) {
FullSizeBytes = getFixupKindContainerSizeBytes(Fixup.getKind());
assert((Offset + FullSizeBytes) <= DataSize && "Invalid fixup size!");
assert(NumBytes <= FullSizeBytes && "Invalid fixup size!");
}
// 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) {
unsigned Idx = IsLittleEndian ? i : (FullSizeBytes - 1 - i);
Data[Offset + Idx] |= uint8_t((Value >> (i * 8)) & 0xff);
}
}
namespace CU {
/// \brief Compact unwind encoding values.
enum CompactUnwindEncodings {
UNWIND_ARM_MODE_MASK = 0x0F000000,
UNWIND_ARM_MODE_FRAME = 0x01000000,
UNWIND_ARM_MODE_FRAME_D = 0x02000000,
UNWIND_ARM_MODE_DWARF = 0x04000000,
UNWIND_ARM_FRAME_STACK_ADJUST_MASK = 0x00C00000,
UNWIND_ARM_FRAME_FIRST_PUSH_R4 = 0x00000001,
UNWIND_ARM_FRAME_FIRST_PUSH_R5 = 0x00000002,
UNWIND_ARM_FRAME_FIRST_PUSH_R6 = 0x00000004,
UNWIND_ARM_FRAME_SECOND_PUSH_R8 = 0x00000008,
UNWIND_ARM_FRAME_SECOND_PUSH_R9 = 0x00000010,
UNWIND_ARM_FRAME_SECOND_PUSH_R10 = 0x00000020,
UNWIND_ARM_FRAME_SECOND_PUSH_R11 = 0x00000040,
UNWIND_ARM_FRAME_SECOND_PUSH_R12 = 0x00000080,
UNWIND_ARM_FRAME_D_REG_COUNT_MASK = 0x00000F00,
UNWIND_ARM_DWARF_SECTION_OFFSET = 0x00FFFFFF
};
} // end CU namespace
/// Generate compact unwind encoding for the function based on the CFI
/// instructions. If the CFI instructions describe a frame that cannot be
/// encoded in compact unwind, the method returns UNWIND_ARM_MODE_DWARF which
/// tells the runtime to fallback and unwind using dwarf.
uint32_t ARMAsmBackendDarwin::generateCompactUnwindEncoding(
ArrayRef<MCCFIInstruction> Instrs) const {
DEBUG_WITH_TYPE("compact-unwind", llvm::dbgs() << "generateCU()\n");
// Only armv7k uses CFI based unwinding.
if (Subtype != MachO::CPU_SUBTYPE_ARM_V7K)
return 0;
// No .cfi directives means no frame.
if (Instrs.empty())
return 0;
// Start off assuming CFA is at SP+0.
int CFARegister = ARM::SP;
int CFARegisterOffset = 0;
// Mark savable registers as initially unsaved
DenseMap<unsigned, int> RegOffsets;
int FloatRegCount = 0;
// Process each .cfi directive and build up compact unwind info.
for (size_t i = 0, e = Instrs.size(); i != e; ++i) {
int Reg;
const MCCFIInstruction &Inst = Instrs[i];
switch (Inst.getOperation()) {
case MCCFIInstruction::OpDefCfa: // DW_CFA_def_cfa
CFARegisterOffset = -Inst.getOffset();
CFARegister = MRI.getLLVMRegNum(Inst.getRegister(), true);
break;
case MCCFIInstruction::OpDefCfaOffset: // DW_CFA_def_cfa_offset
CFARegisterOffset = -Inst.getOffset();
break;
case MCCFIInstruction::OpDefCfaRegister: // DW_CFA_def_cfa_register
CFARegister = MRI.getLLVMRegNum(Inst.getRegister(), true);
break;
case MCCFIInstruction::OpOffset: // DW_CFA_offset
Reg = MRI.getLLVMRegNum(Inst.getRegister(), true);
if (ARMMCRegisterClasses[ARM::GPRRegClassID].contains(Reg))
RegOffsets[Reg] = Inst.getOffset();
else if (ARMMCRegisterClasses[ARM::DPRRegClassID].contains(Reg)) {
RegOffsets[Reg] = Inst.getOffset();
++FloatRegCount;
} else {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs() << ".cfi_offset on unknown register="
<< Inst.getRegister() << "\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
break;
case MCCFIInstruction::OpRelOffset: // DW_CFA_advance_loc
// Ignore
break;
default:
// Directive not convertable to compact unwind, bail out.
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs()
<< "CFI directive not compatiable with comact "
"unwind encoding, opcode=" << Inst.getOperation()
<< "\n");
return CU::UNWIND_ARM_MODE_DWARF;
break;
}
}
// If no frame set up, return no unwind info.
if ((CFARegister == ARM::SP) && (CFARegisterOffset == 0))
return 0;
// Verify standard frame (lr/r7) was used.
if (CFARegister != ARM::R7) {
DEBUG_WITH_TYPE("compact-unwind", llvm::dbgs() << "frame register is "
<< CFARegister
<< " instead of r7\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
int StackAdjust = CFARegisterOffset - 8;
if (RegOffsets.lookup(ARM::LR) != (-4 - StackAdjust)) {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs()
<< "LR not saved as standard frame, StackAdjust="
<< StackAdjust
<< ", CFARegisterOffset=" << CFARegisterOffset
<< ", lr save at offset=" << RegOffsets[14] << "\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
if (RegOffsets.lookup(ARM::R7) != (-8 - StackAdjust)) {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs() << "r7 not saved as standard frame\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
uint32_t CompactUnwindEncoding = CU::UNWIND_ARM_MODE_FRAME;
// If var-args are used, there may be a stack adjust required.
switch (StackAdjust) {
case 0:
break;
case 4:
CompactUnwindEncoding |= 0x00400000;
break;
case 8:
CompactUnwindEncoding |= 0x00800000;
break;
case 12:
CompactUnwindEncoding |= 0x00C00000;
break;
default:
DEBUG_WITH_TYPE("compact-unwind", llvm::dbgs()
<< ".cfi_def_cfa stack adjust ("
<< StackAdjust << ") out of range\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
// If r6 is saved, it must be right below r7.
static struct {
unsigned Reg;
unsigned Encoding;
} GPRCSRegs[] = {{ARM::R6, CU::UNWIND_ARM_FRAME_FIRST_PUSH_R6},
{ARM::R5, CU::UNWIND_ARM_FRAME_FIRST_PUSH_R5},
{ARM::R4, CU::UNWIND_ARM_FRAME_FIRST_PUSH_R4},
{ARM::R12, CU::UNWIND_ARM_FRAME_SECOND_PUSH_R12},
{ARM::R11, CU::UNWIND_ARM_FRAME_SECOND_PUSH_R11},
{ARM::R10, CU::UNWIND_ARM_FRAME_SECOND_PUSH_R10},
{ARM::R9, CU::UNWIND_ARM_FRAME_SECOND_PUSH_R9},
{ARM::R8, CU::UNWIND_ARM_FRAME_SECOND_PUSH_R8}};
int CurOffset = -8 - StackAdjust;
for (auto CSReg : GPRCSRegs) {
auto Offset = RegOffsets.find(CSReg.Reg);
if (Offset == RegOffsets.end())
continue;
int RegOffset = Offset->second;
if (RegOffset != CurOffset - 4) {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs() << MRI.getName(CSReg.Reg) << " saved at "
<< RegOffset << " but only supported at "
<< CurOffset << "\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
CompactUnwindEncoding |= CSReg.Encoding;
CurOffset -= 4;
}
// If no floats saved, we are done.
if (FloatRegCount == 0)
return CompactUnwindEncoding;
// Switch mode to include D register saving.
CompactUnwindEncoding &= ~CU::UNWIND_ARM_MODE_MASK;
CompactUnwindEncoding |= CU::UNWIND_ARM_MODE_FRAME_D;
// FIXME: supporting more than 4 saved D-registers compactly would be trivial,
// but needs coordination with the linker and libunwind.
if (FloatRegCount > 4) {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs() << "unsupported number of D registers saved ("
<< FloatRegCount << ")\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
// Floating point registers must either be saved sequentially, or we defer to
// DWARF. No gaps allowed here so check that each saved d-register is
// precisely where it should be.
static unsigned FPRCSRegs[] = { ARM::D8, ARM::D10, ARM::D12, ARM::D14 };
for (int Idx = FloatRegCount - 1; Idx >= 0; --Idx) {
auto Offset = RegOffsets.find(FPRCSRegs[Idx]);
if (Offset == RegOffsets.end()) {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs() << FloatRegCount << " D-regs saved, but "
<< MRI.getName(FPRCSRegs[Idx])
<< " not saved\n");
return CU::UNWIND_ARM_MODE_DWARF;
} else if (Offset->second != CurOffset - 8) {
DEBUG_WITH_TYPE("compact-unwind",
llvm::dbgs() << FloatRegCount << " D-regs saved, but "
<< MRI.getName(FPRCSRegs[Idx])
<< " saved at " << Offset->second
<< ", expected at " << CurOffset - 8
<< "\n");
return CU::UNWIND_ARM_MODE_DWARF;
}
CurOffset -= 8;
}
return CompactUnwindEncoding | ((FloatRegCount - 1) << 8);
}
static MachO::CPUSubTypeARM getMachOSubTypeFromArch(StringRef Arch) {
unsigned AK = ARM::parseArch(Arch);
switch (AK) {
default:
return MachO::CPU_SUBTYPE_ARM_V7;
case ARM::AK_ARMV4T:
return MachO::CPU_SUBTYPE_ARM_V4T;
case ARM::AK_ARMV5T:
case ARM::AK_ARMV5TE:
case ARM::AK_ARMV5TEJ:
return MachO::CPU_SUBTYPE_ARM_V5;
case ARM::AK_ARMV6:
case ARM::AK_ARMV6K:
return MachO::CPU_SUBTYPE_ARM_V6;
case ARM::AK_ARMV7A:
return MachO::CPU_SUBTYPE_ARM_V7;
case ARM::AK_ARMV7S:
return MachO::CPU_SUBTYPE_ARM_V7S;
case ARM::AK_ARMV7K:
return MachO::CPU_SUBTYPE_ARM_V7K;
case ARM::AK_ARMV6M:
return MachO::CPU_SUBTYPE_ARM_V6M;
case ARM::AK_ARMV7M:
return MachO::CPU_SUBTYPE_ARM_V7M;
case ARM::AK_ARMV7EM:
return MachO::CPU_SUBTYPE_ARM_V7EM;
}
}
MCAsmBackend *llvm::createARMAsmBackend(const Target &T,
const MCRegisterInfo &MRI,
const Triple &TheTriple, StringRef CPU,
bool isLittle) {
switch (TheTriple.getObjectFormat()) {
default:
llvm_unreachable("unsupported object format");
case Triple::MachO: {
MachO::CPUSubTypeARM CS = getMachOSubTypeFromArch(TheTriple.getArchName());
return new ARMAsmBackendDarwin(T, TheTriple, MRI, CS);
}
case Triple::COFF:
assert(TheTriple.isOSWindows() && "non-Windows ARM COFF is not supported");
return new ARMAsmBackendWinCOFF(T, TheTriple);
case Triple::ELF:
assert(TheTriple.isOSBinFormatELF() && "using ELF for non-ELF target");
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
return new ARMAsmBackendELF(T, TheTriple, OSABI, isLittle);
}
}
MCAsmBackend *llvm::createARMLEAsmBackend(const Target &T,
const MCRegisterInfo &MRI,
const Triple &TT, StringRef CPU) {
return createARMAsmBackend(T, MRI, TT, CPU, true);
}
MCAsmBackend *llvm::createARMBEAsmBackend(const Target &T,
const MCRegisterInfo &MRI,
const Triple &TT, StringRef CPU) {
return createARMAsmBackend(T, MRI, TT, CPU, false);
}
MCAsmBackend *llvm::createThumbLEAsmBackend(const Target &T,
const MCRegisterInfo &MRI,
const Triple &TT, StringRef CPU) {
return createARMAsmBackend(T, MRI, TT, CPU, true);
}
MCAsmBackend *llvm::createThumbBEAsmBackend(const Target &T,
const MCRegisterInfo &MRI,
const Triple &TT, StringRef CPU) {
return createARMAsmBackend(T, MRI, TT, CPU, false);
}
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