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c6c7bfc4d2bc37f55f57504c19d47deb7645dd76
clang-p2996/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
Peter Smith 57f661bd7d [MC] Pass MCSubtargetInfo to fixupNeedsRelaxation and applyFixup 
On targets like Arm some relaxations may only be performed when certain
architectural features are available. As functions can be compiled with
differing levels of architectural support we must make a judgement on
whether we can relax based on the MCSubtargetInfo for the function. This
change passes through the MCSubtargetInfo for the function to
fixupNeedsRelaxation so that the decision on whether to relax can be made
per function. In this patch, only the ARM backend makes use of this
information. We must also pass the MCSubtargetInfo to applyFixup because
some fixups skip error checking on the assumption that relaxation has
occurred, to prevent code-generation errors applyFixup must see the same
MCSubtargetInfo as fixupNeedsRelaxation.

Differential Revision: https://reviews.llvm.org/D44928

llvm-svn: 334078
2018-06-06 09:40:06 +00:00

896 lines
30 KiB
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//===-- X86AsmBackend.cpp - X86 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/X86BaseInfo.h"
#include "MCTargetDesc/X86FixupKinds.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCMachObjectWriter.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
static unsigned getFixupKindLog2Size(unsigned Kind) {
switch (Kind) {
default:
llvm_unreachable("invalid fixup kind!");
case FK_PCRel_1:
case FK_SecRel_1:
case FK_Data_1:
return 0;
case FK_PCRel_2:
case FK_SecRel_2:
case FK_Data_2:
return 1;
case FK_PCRel_4:
case X86::reloc_riprel_4byte:
case X86::reloc_riprel_4byte_relax:
case X86::reloc_riprel_4byte_relax_rex:
case X86::reloc_riprel_4byte_movq_load:
case X86::reloc_signed_4byte:
case X86::reloc_signed_4byte_relax:
case X86::reloc_global_offset_table:
case X86::reloc_branch_4byte_pcrel:
case FK_SecRel_4:
case FK_Data_4:
return 2;
case FK_PCRel_8:
case FK_SecRel_8:
case FK_Data_8:
case X86::reloc_global_offset_table8:
return 3;
}
}
namespace {
class X86ELFObjectWriter : public MCELFObjectTargetWriter {
public:
X86ELFObjectWriter(bool is64Bit, uint8_t OSABI, uint16_t EMachine,
bool HasRelocationAddend, bool foobar)
: MCELFObjectTargetWriter(is64Bit, OSABI, EMachine, HasRelocationAddend) {}
};
class X86AsmBackend : public MCAsmBackend {
const MCSubtargetInfo &STI;
public:
X86AsmBackend(const Target &T, const MCSubtargetInfo &STI)
: MCAsmBackend(support::little), STI(STI) {}
unsigned getNumFixupKinds() const override {
return X86::NumTargetFixupKinds;
}
const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
const static MCFixupKindInfo Infos[X86::NumTargetFixupKinds] = {
{"reloc_riprel_4byte", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"reloc_riprel_4byte_movq_load", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"reloc_riprel_4byte_relax", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"reloc_riprel_4byte_relax_rex", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
{"reloc_signed_4byte", 0, 32, 0},
{"reloc_signed_4byte_relax", 0, 32, 0},
{"reloc_global_offset_table", 0, 32, 0},
{"reloc_global_offset_table8", 0, 64, 0},
{"reloc_branch_4byte_pcrel", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
};
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
assert(Infos[Kind - FirstTargetFixupKind].Name && "Empty fixup name!");
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 {
unsigned Size = 1 << getFixupKindLog2Size(Fixup.getKind());
assert(Fixup.getOffset() + Size <= Data.size() && "Invalid fixup offset!");
// Check that uppper bits are either all zeros or all ones.
// Specifically ignore overflow/underflow as long as the leakage is
// limited to the lower bits. This is to remain compatible with
// other assemblers.
assert(isIntN(Size * 8 + 1, Value) &&
"Value does not fit in the Fixup field");
for (unsigned i = 0; i != Size; ++i)
Data[Fixup.getOffset() + i] = uint8_t(Value >> (i * 8));
}
bool mayNeedRelaxation(const MCInst &Inst,
const MCSubtargetInfo &STI) const override;
bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const override;
void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
MCInst &Res) const override;
bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
};
} // end anonymous namespace
static unsigned getRelaxedOpcodeBranch(const MCInst &Inst, bool is16BitMode) {
unsigned Op = Inst.getOpcode();
switch (Op) {
default:
return Op;
case X86::JAE_1:
return (is16BitMode) ? X86::JAE_2 : X86::JAE_4;
case X86::JA_1:
return (is16BitMode) ? X86::JA_2 : X86::JA_4;
case X86::JBE_1:
return (is16BitMode) ? X86::JBE_2 : X86::JBE_4;
case X86::JB_1:
return (is16BitMode) ? X86::JB_2 : X86::JB_4;
case X86::JE_1:
return (is16BitMode) ? X86::JE_2 : X86::JE_4;
case X86::JGE_1:
return (is16BitMode) ? X86::JGE_2 : X86::JGE_4;
case X86::JG_1:
return (is16BitMode) ? X86::JG_2 : X86::JG_4;
case X86::JLE_1:
return (is16BitMode) ? X86::JLE_2 : X86::JLE_4;
case X86::JL_1:
return (is16BitMode) ? X86::JL_2 : X86::JL_4;
case X86::JMP_1:
return (is16BitMode) ? X86::JMP_2 : X86::JMP_4;
case X86::JNE_1:
return (is16BitMode) ? X86::JNE_2 : X86::JNE_4;
case X86::JNO_1:
return (is16BitMode) ? X86::JNO_2 : X86::JNO_4;
case X86::JNP_1:
return (is16BitMode) ? X86::JNP_2 : X86::JNP_4;
case X86::JNS_1:
return (is16BitMode) ? X86::JNS_2 : X86::JNS_4;
case X86::JO_1:
return (is16BitMode) ? X86::JO_2 : X86::JO_4;
case X86::JP_1:
return (is16BitMode) ? X86::JP_2 : X86::JP_4;
case X86::JS_1:
return (is16BitMode) ? X86::JS_2 : X86::JS_4;
}
}
static unsigned getRelaxedOpcodeArith(const MCInst &Inst) {
unsigned Op = Inst.getOpcode();
switch (Op) {
default:
return Op;
// IMUL
case X86::IMUL16rri8: return X86::IMUL16rri;
case X86::IMUL16rmi8: return X86::IMUL16rmi;
case X86::IMUL32rri8: return X86::IMUL32rri;
case X86::IMUL32rmi8: return X86::IMUL32rmi;
case X86::IMUL64rri8: return X86::IMUL64rri32;
case X86::IMUL64rmi8: return X86::IMUL64rmi32;
// AND
case X86::AND16ri8: return X86::AND16ri;
case X86::AND16mi8: return X86::AND16mi;
case X86::AND32ri8: return X86::AND32ri;
case X86::AND32mi8: return X86::AND32mi;
case X86::AND64ri8: return X86::AND64ri32;
case X86::AND64mi8: return X86::AND64mi32;
// OR
case X86::OR16ri8: return X86::OR16ri;
case X86::OR16mi8: return X86::OR16mi;
case X86::OR32ri8: return X86::OR32ri;
case X86::OR32mi8: return X86::OR32mi;
case X86::OR64ri8: return X86::OR64ri32;
case X86::OR64mi8: return X86::OR64mi32;
// XOR
case X86::XOR16ri8: return X86::XOR16ri;
case X86::XOR16mi8: return X86::XOR16mi;
case X86::XOR32ri8: return X86::XOR32ri;
case X86::XOR32mi8: return X86::XOR32mi;
case X86::XOR64ri8: return X86::XOR64ri32;
case X86::XOR64mi8: return X86::XOR64mi32;
// ADD
case X86::ADD16ri8: return X86::ADD16ri;
case X86::ADD16mi8: return X86::ADD16mi;
case X86::ADD32ri8: return X86::ADD32ri;
case X86::ADD32mi8: return X86::ADD32mi;
case X86::ADD64ri8: return X86::ADD64ri32;
case X86::ADD64mi8: return X86::ADD64mi32;
// ADC
case X86::ADC16ri8: return X86::ADC16ri;
case X86::ADC16mi8: return X86::ADC16mi;
case X86::ADC32ri8: return X86::ADC32ri;
case X86::ADC32mi8: return X86::ADC32mi;
case X86::ADC64ri8: return X86::ADC64ri32;
case X86::ADC64mi8: return X86::ADC64mi32;
// SUB
case X86::SUB16ri8: return X86::SUB16ri;
case X86::SUB16mi8: return X86::SUB16mi;
case X86::SUB32ri8: return X86::SUB32ri;
case X86::SUB32mi8: return X86::SUB32mi;
case X86::SUB64ri8: return X86::SUB64ri32;
case X86::SUB64mi8: return X86::SUB64mi32;
// SBB
case X86::SBB16ri8: return X86::SBB16ri;
case X86::SBB16mi8: return X86::SBB16mi;
case X86::SBB32ri8: return X86::SBB32ri;
case X86::SBB32mi8: return X86::SBB32mi;
case X86::SBB64ri8: return X86::SBB64ri32;
case X86::SBB64mi8: return X86::SBB64mi32;
// CMP
case X86::CMP16ri8: return X86::CMP16ri;
case X86::CMP16mi8: return X86::CMP16mi;
case X86::CMP32ri8: return X86::CMP32ri;
case X86::CMP32mi8: return X86::CMP32mi;
case X86::CMP64ri8: return X86::CMP64ri32;
case X86::CMP64mi8: return X86::CMP64mi32;
// PUSH
case X86::PUSH32i8: return X86::PUSHi32;
case X86::PUSH16i8: return X86::PUSHi16;
case X86::PUSH64i8: return X86::PUSH64i32;
}
}
static unsigned getRelaxedOpcode(const MCInst &Inst, bool is16BitMode) {
unsigned R = getRelaxedOpcodeArith(Inst);
if (R != Inst.getOpcode())
return R;
return getRelaxedOpcodeBranch(Inst, is16BitMode);
}
bool X86AsmBackend::mayNeedRelaxation(const MCInst &Inst,
const MCSubtargetInfo &STI) const {
// Branches can always be relaxed in either mode.
if (getRelaxedOpcodeBranch(Inst, false) != Inst.getOpcode())
return true;
// Check if this instruction is ever relaxable.
if (getRelaxedOpcodeArith(Inst) == Inst.getOpcode())
return false;
// Check if the relaxable operand has an expression. For the current set of
// relaxable instructions, the relaxable operand is always the last operand.
unsigned RelaxableOp = Inst.getNumOperands() - 1;
if (Inst.getOperand(RelaxableOp).isExpr())
return true;
return false;
}
bool X86AsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const {
// Relax if the value is too big for a (signed) i8.
return int64_t(Value) != int64_t(int8_t(Value));
}
// FIXME: Can tblgen help at all here to verify there aren't other instructions
// we can relax?
void X86AsmBackend::relaxInstruction(const MCInst &Inst,
const MCSubtargetInfo &STI,
MCInst &Res) const {
// The only relaxations X86 does is from a 1byte pcrel to a 4byte pcrel.
bool is16BitMode = STI.getFeatureBits()[X86::Mode16Bit];
unsigned RelaxedOp = getRelaxedOpcode(Inst, is16BitMode);
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());
}
Res = Inst;
Res.setOpcode(RelaxedOp);
}
/// Write a sequence of optimal nops to the output, covering \p Count
/// bytes.
/// \return - true on success, false on failure
bool X86AsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
static const char Nops[10][11] = {
// nop
"\x90",
// xchg %ax,%ax
"\x66\x90",
// nopl (%[re]ax)
"\x0f\x1f\x00",
// nopl 0(%[re]ax)
"\x0f\x1f\x40\x00",
// nopl 0(%[re]ax,%[re]ax,1)
"\x0f\x1f\x44\x00\x00",
// nopw 0(%[re]ax,%[re]ax,1)
"\x66\x0f\x1f\x44\x00\x00",
// nopl 0L(%[re]ax)
"\x0f\x1f\x80\x00\x00\x00\x00",
// nopl 0L(%[re]ax,%[re]ax,1)
"\x0f\x1f\x84\x00\x00\x00\x00\x00",
// nopw 0L(%[re]ax,%[re]ax,1)
"\x66\x0f\x1f\x84\x00\x00\x00\x00\x00",
// nopw %cs:0L(%[re]ax,%[re]ax,1)
"\x66\x2e\x0f\x1f\x84\x00\x00\x00\x00\x00",
};
// This CPU doesn't support long nops. If needed add more.
// FIXME: We could generated something better than plain 0x90.
if (!STI.getFeatureBits()[X86::FeatureNOPL]) {
for (uint64_t i = 0; i < Count; ++i)
OS << '\x90';
return true;
}
// 15-bytes is the longest single NOP instruction, but 10-bytes is
// commonly the longest that can be efficiently decoded.
uint64_t MaxNopLength = 10;
if (STI.getFeatureBits()[X86::ProcIntelSLM])
MaxNopLength = 7;
else if (STI.getFeatureBits()[X86::FeatureFast15ByteNOP])
MaxNopLength = 15;
else if (STI.getFeatureBits()[X86::FeatureFast11ByteNOP])
MaxNopLength = 11;
// Emit as many MaxNopLength NOPs as needed, then emit a NOP of the remaining
// length.
do {
const uint8_t ThisNopLength = (uint8_t) std::min(Count, MaxNopLength);
const uint8_t Prefixes = ThisNopLength <= 10 ? 0 : ThisNopLength - 10;
for (uint8_t i = 0; i < Prefixes; i++)
OS << '\x66';
const uint8_t Rest = ThisNopLength - Prefixes;
if (Rest != 0)
OS.write(Nops[Rest - 1], Rest);
Count -= ThisNopLength;
} while (Count != 0);
return true;
}
/* *** */
namespace {
class ELFX86AsmBackend : public X86AsmBackend {
public:
uint8_t OSABI;
ELFX86AsmBackend(const Target &T, uint8_t OSABI, const MCSubtargetInfo &STI)
: X86AsmBackend(T, STI), OSABI(OSABI) {}
};
class ELFX86_32AsmBackend : public ELFX86AsmBackend {
public:
ELFX86_32AsmBackend(const Target &T, uint8_t OSABI,
const MCSubtargetInfo &STI)
: ELFX86AsmBackend(T, OSABI, STI) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86ELFObjectWriter(/*IsELF64*/ false, OSABI, ELF::EM_386);
}
};
class ELFX86_X32AsmBackend : public ELFX86AsmBackend {
public:
ELFX86_X32AsmBackend(const Target &T, uint8_t OSABI,
const MCSubtargetInfo &STI)
: ELFX86AsmBackend(T, OSABI, STI) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86ELFObjectWriter(/*IsELF64*/ false, OSABI,
ELF::EM_X86_64);
}
};
class ELFX86_IAMCUAsmBackend : public ELFX86AsmBackend {
public:
ELFX86_IAMCUAsmBackend(const Target &T, uint8_t OSABI,
const MCSubtargetInfo &STI)
: ELFX86AsmBackend(T, OSABI, STI) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86ELFObjectWriter(/*IsELF64*/ false, OSABI,
ELF::EM_IAMCU);
}
};
class ELFX86_64AsmBackend : public ELFX86AsmBackend {
public:
ELFX86_64AsmBackend(const Target &T, uint8_t OSABI,
const MCSubtargetInfo &STI)
: ELFX86AsmBackend(T, OSABI, STI) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86ELFObjectWriter(/*IsELF64*/ true, OSABI, ELF::EM_X86_64);
}
};
class WindowsX86AsmBackend : public X86AsmBackend {
bool Is64Bit;
public:
WindowsX86AsmBackend(const Target &T, bool is64Bit,
const MCSubtargetInfo &STI)
: X86AsmBackend(T, STI)
, Is64Bit(is64Bit) {
}
Optional<MCFixupKind> getFixupKind(StringRef Name) const override {
return StringSwitch<Optional<MCFixupKind>>(Name)
.Case("dir32", FK_Data_4)
.Case("secrel32", FK_SecRel_4)
.Case("secidx", FK_SecRel_2)
.Default(MCAsmBackend::getFixupKind(Name));
}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86WinCOFFObjectWriter(Is64Bit);
}
};
namespace CU {
/// Compact unwind encoding values.
enum CompactUnwindEncodings {
/// [RE]BP based frame where [RE]BP is pused on the stack immediately after
/// the return address, then [RE]SP is moved to [RE]BP.
UNWIND_MODE_BP_FRAME = 0x01000000,
/// A frameless function with a small constant stack size.
UNWIND_MODE_STACK_IMMD = 0x02000000,
/// A frameless function with a large constant stack size.
UNWIND_MODE_STACK_IND = 0x03000000,
/// No compact unwind encoding is available.
UNWIND_MODE_DWARF = 0x04000000,
/// Mask for encoding the frame registers.
UNWIND_BP_FRAME_REGISTERS = 0x00007FFF,
/// Mask for encoding the frameless registers.
UNWIND_FRAMELESS_STACK_REG_PERMUTATION = 0x000003FF
};
} // end CU namespace
class DarwinX86AsmBackend : public X86AsmBackend {
const MCRegisterInfo &MRI;
/// Number of registers that can be saved in a compact unwind encoding.
enum { CU_NUM_SAVED_REGS = 6 };
mutable unsigned SavedRegs[CU_NUM_SAVED_REGS];
bool Is64Bit;
unsigned OffsetSize; ///< Offset of a "push" instruction.
unsigned MoveInstrSize; ///< Size of a "move" instruction.
unsigned StackDivide; ///< Amount to adjust stack size by.
protected:
/// Size of a "push" instruction for the given register.
unsigned PushInstrSize(unsigned Reg) const {
switch (Reg) {
case X86::EBX:
case X86::ECX:
case X86::EDX:
case X86::EDI:
case X86::ESI:
case X86::EBP:
case X86::RBX:
case X86::RBP:
return 1;
case X86::R12:
case X86::R13:
case X86::R14:
case X86::R15:
return 2;
}
return 1;
}
/// Implementation of algorithm to generate the compact unwind encoding
/// for the CFI instructions.
uint32_t
generateCompactUnwindEncodingImpl(ArrayRef<MCCFIInstruction> Instrs) const {
if (Instrs.empty()) return 0;
// Reset the saved registers.
unsigned SavedRegIdx = 0;
memset(SavedRegs, 0, sizeof(SavedRegs));
bool HasFP = false;
// Encode that we are using EBP/RBP as the frame pointer.
uint32_t CompactUnwindEncoding = 0;
unsigned SubtractInstrIdx = Is64Bit ? 3 : 2;
unsigned InstrOffset = 0;
unsigned StackAdjust = 0;
unsigned StackSize = 0;
unsigned PrevStackSize = 0;
unsigned NumDefCFAOffsets = 0;
for (unsigned i = 0, e = Instrs.size(); i != e; ++i) {
const MCCFIInstruction &Inst = Instrs[i];
switch (Inst.getOperation()) {
default:
// Any other CFI directives indicate a frame that we aren't prepared
// to represent via compact unwind, so just bail out.
return 0;
case MCCFIInstruction::OpDefCfaRegister: {
// Defines a frame pointer. E.g.
//
// movq %rsp, %rbp
// L0:
// .cfi_def_cfa_register %rbp
//
HasFP = true;
// If the frame pointer is other than esp/rsp, we do not have a way to
// generate a compact unwinding representation, so bail out.
if (MRI.getLLVMRegNum(Inst.getRegister(), true) !=
(Is64Bit ? X86::RBP : X86::EBP))
return 0;
// Reset the counts.
memset(SavedRegs, 0, sizeof(SavedRegs));
StackAdjust = 0;
SavedRegIdx = 0;
InstrOffset += MoveInstrSize;
break;
}
case MCCFIInstruction::OpDefCfaOffset: {
// Defines a new offset for the CFA. E.g.
//
// With frame:
//
// pushq %rbp
// L0:
// .cfi_def_cfa_offset 16
//
// Without frame:
//
// subq $72, %rsp
// L0:
// .cfi_def_cfa_offset 80
//
PrevStackSize = StackSize;
StackSize = std::abs(Inst.getOffset()) / StackDivide;
++NumDefCFAOffsets;
break;
}
case MCCFIInstruction::OpOffset: {
// Defines a "push" of a callee-saved register. E.g.
//
// pushq %r15
// pushq %r14
// pushq %rbx
// L0:
// subq $120, %rsp
// L1:
// .cfi_offset %rbx, -40
// .cfi_offset %r14, -32
// .cfi_offset %r15, -24
//
if (SavedRegIdx == CU_NUM_SAVED_REGS)
// If there are too many saved registers, we cannot use a compact
// unwind encoding.
return CU::UNWIND_MODE_DWARF;
unsigned Reg = MRI.getLLVMRegNum(Inst.getRegister(), true);
SavedRegs[SavedRegIdx++] = Reg;
StackAdjust += OffsetSize;
InstrOffset += PushInstrSize(Reg);
break;
}
}
}
StackAdjust /= StackDivide;
if (HasFP) {
if ((StackAdjust & 0xFF) != StackAdjust)
// Offset was too big for a compact unwind encoding.
return CU::UNWIND_MODE_DWARF;
// Get the encoding of the saved registers when we have a frame pointer.
uint32_t RegEnc = encodeCompactUnwindRegistersWithFrame();
if (RegEnc == ~0U) return CU::UNWIND_MODE_DWARF;
CompactUnwindEncoding |= CU::UNWIND_MODE_BP_FRAME;
CompactUnwindEncoding |= (StackAdjust & 0xFF) << 16;
CompactUnwindEncoding |= RegEnc & CU::UNWIND_BP_FRAME_REGISTERS;
} else {
// If the amount of the stack allocation is the size of a register, then
// we "push" the RAX/EAX register onto the stack instead of adjusting the
// stack pointer with a SUB instruction. We don't support the push of the
// RAX/EAX register with compact unwind. So we check for that situation
// here.
if ((NumDefCFAOffsets == SavedRegIdx + 1 &&
StackSize - PrevStackSize == 1) ||
(Instrs.size() == 1 && NumDefCFAOffsets == 1 && StackSize == 2))
return CU::UNWIND_MODE_DWARF;
SubtractInstrIdx += InstrOffset;
++StackAdjust;
if ((StackSize & 0xFF) == StackSize) {
// Frameless stack with a small stack size.
CompactUnwindEncoding |= CU::UNWIND_MODE_STACK_IMMD;
// Encode the stack size.
CompactUnwindEncoding |= (StackSize & 0xFF) << 16;
} else {
if ((StackAdjust & 0x7) != StackAdjust)
// The extra stack adjustments are too big for us to handle.
return CU::UNWIND_MODE_DWARF;
// Frameless stack with an offset too large for us to encode compactly.
CompactUnwindEncoding |= CU::UNWIND_MODE_STACK_IND;
// Encode the offset to the nnnnnn value in the 'subl $nnnnnn, ESP'
// instruction.
CompactUnwindEncoding |= (SubtractInstrIdx & 0xFF) << 16;
// Encode any extra stack adjustments (done via push instructions).
CompactUnwindEncoding |= (StackAdjust & 0x7) << 13;
}
// Encode the number of registers saved. (Reverse the list first.)
std::reverse(&SavedRegs[0], &SavedRegs[SavedRegIdx]);
CompactUnwindEncoding |= (SavedRegIdx & 0x7) << 10;
// Get the encoding of the saved registers when we don't have a frame
// pointer.
uint32_t RegEnc = encodeCompactUnwindRegistersWithoutFrame(SavedRegIdx);
if (RegEnc == ~0U) return CU::UNWIND_MODE_DWARF;
// Encode the register encoding.
CompactUnwindEncoding |=
RegEnc & CU::UNWIND_FRAMELESS_STACK_REG_PERMUTATION;
}
return CompactUnwindEncoding;
}
private:
/// Get the compact unwind number for a given register. The number
/// corresponds to the enum lists in compact_unwind_encoding.h.
int getCompactUnwindRegNum(unsigned Reg) const {
static const MCPhysReg CU32BitRegs[7] = {
X86::EBX, X86::ECX, X86::EDX, X86::EDI, X86::ESI, X86::EBP, 0
};
static const MCPhysReg CU64BitRegs[] = {
X86::RBX, X86::R12, X86::R13, X86::R14, X86::R15, X86::RBP, 0
};
const MCPhysReg *CURegs = Is64Bit ? CU64BitRegs : CU32BitRegs;
for (int Idx = 1; *CURegs; ++CURegs, ++Idx)
if (*CURegs == Reg)
return Idx;
return -1;
}
/// Return the registers encoded for a compact encoding with a frame
/// pointer.
uint32_t encodeCompactUnwindRegistersWithFrame() const {
// Encode the registers in the order they were saved --- 3-bits per
// register. The list of saved registers is assumed to be in reverse
// order. The registers are numbered from 1 to CU_NUM_SAVED_REGS.
uint32_t RegEnc = 0;
for (int i = 0, Idx = 0; i != CU_NUM_SAVED_REGS; ++i) {
unsigned Reg = SavedRegs[i];
if (Reg == 0) break;
int CURegNum = getCompactUnwindRegNum(Reg);
if (CURegNum == -1) return ~0U;
// Encode the 3-bit register number in order, skipping over 3-bits for
// each register.
RegEnc |= (CURegNum & 0x7) << (Idx++ * 3);
}
assert((RegEnc & 0x3FFFF) == RegEnc &&
"Invalid compact register encoding!");
return RegEnc;
}
/// Create the permutation encoding used with frameless stacks. It is
/// passed the number of registers to be saved and an array of the registers
/// saved.
uint32_t encodeCompactUnwindRegistersWithoutFrame(unsigned RegCount) const {
// The saved registers are numbered from 1 to 6. In order to encode the
// order in which they were saved, we re-number them according to their
// place in the register order. The re-numbering is relative to the last
// re-numbered register. E.g., if we have registers {6, 2, 4, 5} saved in
// that order:
//
// Orig Re-Num
// ---- ------
// 6 6
// 2 2
// 4 3
// 5 3
//
for (unsigned i = 0; i < RegCount; ++i) {
int CUReg = getCompactUnwindRegNum(SavedRegs[i]);
if (CUReg == -1) return ~0U;
SavedRegs[i] = CUReg;
}
// Reverse the list.
std::reverse(&SavedRegs[0], &SavedRegs[CU_NUM_SAVED_REGS]);
uint32_t RenumRegs[CU_NUM_SAVED_REGS];
for (unsigned i = CU_NUM_SAVED_REGS - RegCount; i < CU_NUM_SAVED_REGS; ++i){
unsigned Countless = 0;
for (unsigned j = CU_NUM_SAVED_REGS - RegCount; j < i; ++j)
if (SavedRegs[j] < SavedRegs[i])
++Countless;
RenumRegs[i] = SavedRegs[i] - Countless - 1;
}
// Take the renumbered values and encode them into a 10-bit number.
uint32_t permutationEncoding = 0;
switch (RegCount) {
case 6:
permutationEncoding |= 120 * RenumRegs[0] + 24 * RenumRegs[1]
+ 6 * RenumRegs[2] + 2 * RenumRegs[3]
+ RenumRegs[4];
break;
case 5:
permutationEncoding |= 120 * RenumRegs[1] + 24 * RenumRegs[2]
+ 6 * RenumRegs[3] + 2 * RenumRegs[4]
+ RenumRegs[5];
break;
case 4:
permutationEncoding |= 60 * RenumRegs[2] + 12 * RenumRegs[3]
+ 3 * RenumRegs[4] + RenumRegs[5];
break;
case 3:
permutationEncoding |= 20 * RenumRegs[3] + 4 * RenumRegs[4]
+ RenumRegs[5];
break;
case 2:
permutationEncoding |= 5 * RenumRegs[4] + RenumRegs[5];
break;
case 1:
permutationEncoding |= RenumRegs[5];
break;
}
assert((permutationEncoding & 0x3FF) == permutationEncoding &&
"Invalid compact register encoding!");
return permutationEncoding;
}
public:
DarwinX86AsmBackend(const Target &T, const MCRegisterInfo &MRI,
const MCSubtargetInfo &STI, bool Is64Bit)
: X86AsmBackend(T, STI), MRI(MRI), Is64Bit(Is64Bit) {
memset(SavedRegs, 0, sizeof(SavedRegs));
OffsetSize = Is64Bit ? 8 : 4;
MoveInstrSize = Is64Bit ? 3 : 2;
StackDivide = Is64Bit ? 8 : 4;
}
};
class DarwinX86_32AsmBackend : public DarwinX86AsmBackend {
public:
DarwinX86_32AsmBackend(const Target &T, const MCRegisterInfo &MRI,
const MCSubtargetInfo &STI)
: DarwinX86AsmBackend(T, MRI, STI, false) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86MachObjectWriter(/*Is64Bit=*/false,
MachO::CPU_TYPE_I386,
MachO::CPU_SUBTYPE_I386_ALL);
}
/// Generate the compact unwind encoding for the CFI instructions.
uint32_t generateCompactUnwindEncoding(
ArrayRef<MCCFIInstruction> Instrs) const override {
return generateCompactUnwindEncodingImpl(Instrs);
}
};
class DarwinX86_64AsmBackend : public DarwinX86AsmBackend {
const MachO::CPUSubTypeX86 Subtype;
public:
DarwinX86_64AsmBackend(const Target &T, const MCRegisterInfo &MRI,
const MCSubtargetInfo &STI, MachO::CPUSubTypeX86 st)
: DarwinX86AsmBackend(T, MRI, STI, true), Subtype(st) {}
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createX86MachObjectWriter(/*Is64Bit=*/true, MachO::CPU_TYPE_X86_64,
Subtype);
}
/// Generate the compact unwind encoding for the CFI instructions.
uint32_t generateCompactUnwindEncoding(
ArrayRef<MCCFIInstruction> Instrs) const override {
return generateCompactUnwindEncodingImpl(Instrs);
}
};
} // end anonymous namespace
MCAsmBackend *llvm::createX86_32AsmBackend(const Target &T,
const MCSubtargetInfo &STI,
const MCRegisterInfo &MRI,
const MCTargetOptions &Options) {
const Triple &TheTriple = STI.getTargetTriple();
if (TheTriple.isOSBinFormatMachO())
return new DarwinX86_32AsmBackend(T, MRI, STI);
if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
return new WindowsX86AsmBackend(T, false, STI);
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
if (TheTriple.isOSIAMCU())
return new ELFX86_IAMCUAsmBackend(T, OSABI, STI);
return new ELFX86_32AsmBackend(T, OSABI, STI);
}
MCAsmBackend *llvm::createX86_64AsmBackend(const Target &T,
const MCSubtargetInfo &STI,
const MCRegisterInfo &MRI,
const MCTargetOptions &Options) {
const Triple &TheTriple = STI.getTargetTriple();
if (TheTriple.isOSBinFormatMachO()) {
MachO::CPUSubTypeX86 CS =
StringSwitch<MachO::CPUSubTypeX86>(TheTriple.getArchName())
.Case("x86_64h", MachO::CPU_SUBTYPE_X86_64_H)
.Default(MachO::CPU_SUBTYPE_X86_64_ALL);
return new DarwinX86_64AsmBackend(T, MRI, STI, CS);
}
if (TheTriple.isOSWindows() && TheTriple.isOSBinFormatCOFF())
return new WindowsX86AsmBackend(T, true, STI);
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TheTriple.getOS());
if (TheTriple.getEnvironment() == Triple::GNUX32)
return new ELFX86_X32AsmBackend(T, OSABI, STI);
return new ELFX86_64AsmBackend(T, OSABI, STI);
}
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