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llvm / llvm / fbcef4fae71e52778d4e81c09ecd9572af8bae48 / . / lib / Target / X86 / MCTargetDesc / X86MCCodeEmitter.cpp
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//===-- X86MCCodeEmitter.cpp - Convert X86 code to machine code -----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the X86MCCodeEmitter class.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/X86BaseInfo.h"
#include "MCTargetDesc/X86FixupKinds.h"
#include "MCTargetDesc/X86MCTargetDesc.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <cstdlib>
using namespace llvm;
#define DEBUG_TYPE "mccodeemitter"
namespace {
class X86MCCodeEmitter : public MCCodeEmitter {
const MCInstrInfo &MCII;
MCContext &Ctx;
public:
X86MCCodeEmitter(const MCInstrInfo &mcii, MCContext &ctx)
: MCII(mcii), Ctx(ctx) {
}
X86MCCodeEmitter(const X86MCCodeEmitter &) = delete;
X86MCCodeEmitter &operator=(const X86MCCodeEmitter &) = delete;
~X86MCCodeEmitter() override = default;
bool is64BitMode(const MCSubtargetInfo &STI) const {
return STI.getFeatureBits()[X86::Mode64Bit];
}
bool is32BitMode(const MCSubtargetInfo &STI) const {
return STI.getFeatureBits()[X86::Mode32Bit];
}
bool is16BitMode(const MCSubtargetInfo &STI) const {
return STI.getFeatureBits()[X86::Mode16Bit];
}
/// Is16BitMemOperand - Return true if the specified instruction has
/// a 16-bit memory operand. Op specifies the operand # of the memoperand.
bool Is16BitMemOperand(const MCInst &MI, unsigned Op,
const MCSubtargetInfo &STI) const {
const MCOperand &BaseReg = MI.getOperand(Op+X86::AddrBaseReg);
const MCOperand &IndexReg = MI.getOperand(Op+X86::AddrIndexReg);
const MCOperand &Disp = MI.getOperand(Op+X86::AddrDisp);
if (is16BitMode(STI) && BaseReg.getReg() == 0 &&
Disp.isImm() && Disp.getImm() < 0x10000)
return true;
if ((BaseReg.getReg() != 0 &&
X86MCRegisterClasses[X86::GR16RegClassID].contains(BaseReg.getReg())) ||
(IndexReg.getReg() != 0 &&
X86MCRegisterClasses[X86::GR16RegClassID].contains(IndexReg.getReg())))
return true;
return false;
}
unsigned GetX86RegNum(const MCOperand &MO) const {
return Ctx.getRegisterInfo()->getEncodingValue(MO.getReg()) & 0x7;
}
unsigned getX86RegEncoding(const MCInst &MI, unsigned OpNum) const {
return Ctx.getRegisterInfo()->getEncodingValue(
MI.getOperand(OpNum).getReg());
}
// Does this register require a bit to be set in REX prefix.
bool isREXExtendedReg(const MCInst &MI, unsigned OpNum) const {
return (getX86RegEncoding(MI, OpNum) >> 3) & 1;
}
void EmitByte(uint8_t C, unsigned &CurByte, raw_ostream &OS) const {
OS << (char)C;
++CurByte;
}
void EmitConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
raw_ostream &OS) const {
// Output the constant in little endian byte order.
for (unsigned i = 0; i != Size; ++i) {
EmitByte(Val & 255, CurByte, OS);
Val >>= 8;
}
}
void EmitImmediate(const MCOperand &Disp, SMLoc Loc,
unsigned ImmSize, MCFixupKind FixupKind,
unsigned &CurByte, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
int ImmOffset = 0) const;
static uint8_t ModRMByte(unsigned Mod, unsigned RegOpcode, unsigned RM) {
assert(Mod < 4 && RegOpcode < 8 && RM < 8 && "ModRM Fields out of range!");
return RM | (RegOpcode << 3) | (Mod << 6);
}
void EmitRegModRMByte(const MCOperand &ModRMReg, unsigned RegOpcodeFld,
unsigned &CurByte, raw_ostream &OS) const {
EmitByte(ModRMByte(3, RegOpcodeFld, GetX86RegNum(ModRMReg)), CurByte, OS);
}
void EmitSIBByte(unsigned SS, unsigned Index, unsigned Base,
unsigned &CurByte, raw_ostream &OS) const {
// SIB byte is in the same format as the ModRMByte.
EmitByte(ModRMByte(SS, Index, Base), CurByte, OS);
}
void emitMemModRMByte(const MCInst &MI, unsigned Op, unsigned RegOpcodeField,
uint64_t TSFlags, bool Rex, unsigned &CurByte,
raw_ostream &OS, SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const;
void encodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const override;
void EmitVEXOpcodePrefix(uint64_t TSFlags, unsigned &CurByte, int MemOperand,
const MCInst &MI, const MCInstrDesc &Desc,
raw_ostream &OS) const;
void EmitSegmentOverridePrefix(unsigned &CurByte, unsigned SegOperand,
const MCInst &MI, raw_ostream &OS) const;
bool emitOpcodePrefix(uint64_t TSFlags, unsigned &CurByte, int MemOperand,
const MCInst &MI, const MCInstrDesc &Desc,
const MCSubtargetInfo &STI, raw_ostream &OS) const;
uint8_t DetermineREXPrefix(const MCInst &MI, uint64_t TSFlags,
int MemOperand, const MCInstrDesc &Desc) const;
bool isPCRel32Branch(const MCInst &MI) const;
};
} // end anonymous namespace
/// isDisp8 - Return true if this signed displacement fits in a 8-bit
/// sign-extended field.
static bool isDisp8(int Value) {
return Value == (int8_t)Value;
}
/// isCDisp8 - Return true if this signed displacement fits in a 8-bit
/// compressed dispacement field.
static bool isCDisp8(uint64_t TSFlags, int Value, int& CValue) {
assert(((TSFlags & X86II::EncodingMask) == X86II::EVEX) &&
"Compressed 8-bit displacement is only valid for EVEX inst.");
unsigned CD8_Scale =
(TSFlags & X86II::CD8_Scale_Mask) >> X86II::CD8_Scale_Shift;
if (CD8_Scale == 0) {
CValue = Value;
return isDisp8(Value);
}
unsigned Mask = CD8_Scale - 1;
assert((CD8_Scale & Mask) == 0 && "Invalid memory object size.");
if (Value & Mask) // Unaligned offset
return false;
Value /= (int)CD8_Scale;
bool Ret = (Value == (int8_t)Value);
if (Ret)
CValue = Value;
return Ret;
}
/// getImmFixupKind - Return the appropriate fixup kind to use for an immediate
/// in an instruction with the specified TSFlags.
static MCFixupKind getImmFixupKind(uint64_t TSFlags) {
unsigned Size = X86II::getSizeOfImm(TSFlags);
bool isPCRel = X86II::isImmPCRel(TSFlags);
if (X86II::isImmSigned(TSFlags)) {
switch (Size) {
default: llvm_unreachable("Unsupported signed fixup size!");
case 4: return MCFixupKind(X86::reloc_signed_4byte);
}
}
return MCFixup::getKindForSize(Size, isPCRel);
}
/// Is32BitMemOperand - Return true if the specified instruction has
/// a 32-bit memory operand. Op specifies the operand # of the memoperand.
static bool Is32BitMemOperand(const MCInst &MI, unsigned Op) {
const MCOperand &BaseReg = MI.getOperand(Op+X86::AddrBaseReg);
const MCOperand &IndexReg = MI.getOperand(Op+X86::AddrIndexReg);
if ((BaseReg.getReg() != 0 &&
X86MCRegisterClasses[X86::GR32RegClassID].contains(BaseReg.getReg())) ||
(IndexReg.getReg() != 0 &&
X86MCRegisterClasses[X86::GR32RegClassID].contains(IndexReg.getReg())))
return true;
if (BaseReg.getReg() == X86::EIP) {
assert(IndexReg.getReg() == 0 && "Invalid eip-based address.");
return true;
}
if (IndexReg.getReg() == X86::EIZ)
return true;
return false;
}
/// Is64BitMemOperand - Return true if the specified instruction has
/// a 64-bit memory operand. Op specifies the operand # of the memoperand.
#ifndef NDEBUG
static bool Is64BitMemOperand(const MCInst &MI, unsigned Op) {
const MCOperand &BaseReg = MI.getOperand(Op+X86::AddrBaseReg);
const MCOperand &IndexReg = MI.getOperand(Op+X86::AddrIndexReg);
if ((BaseReg.getReg() != 0 &&
X86MCRegisterClasses[X86::GR64RegClassID].contains(BaseReg.getReg())) ||
(IndexReg.getReg() != 0 &&
X86MCRegisterClasses[X86::GR64RegClassID].contains(IndexReg.getReg())))
return true;
return false;
}
#endif
/// StartsWithGlobalOffsetTable - Check if this expression starts with
/// _GLOBAL_OFFSET_TABLE_ and if it is of the form
/// _GLOBAL_OFFSET_TABLE_-symbol. This is needed to support PIC on ELF
/// i386 as _GLOBAL_OFFSET_TABLE_ is magical. We check only simple case that
/// are know to be used: _GLOBAL_OFFSET_TABLE_ by itself or at the start
/// of a binary expression.
enum GlobalOffsetTableExprKind {
GOT_None,
GOT_Normal,
GOT_SymDiff
};
static GlobalOffsetTableExprKind
StartsWithGlobalOffsetTable(const MCExpr *Expr) {
const MCExpr *RHS = nullptr;
if (Expr->getKind() == MCExpr::Binary) {
const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(Expr);
Expr = BE->getLHS();
RHS = BE->getRHS();
}
if (Expr->getKind() != MCExpr::SymbolRef)
return GOT_None;
const MCSymbolRefExpr *Ref = static_cast<const MCSymbolRefExpr*>(Expr);
const MCSymbol &S = Ref->getSymbol();
if (S.getName() != "_GLOBAL_OFFSET_TABLE_")
return GOT_None;
if (RHS && RHS->getKind() == MCExpr::SymbolRef)
return GOT_SymDiff;
return GOT_Normal;
}
static bool HasSecRelSymbolRef(const MCExpr *Expr) {
if (Expr->getKind() == MCExpr::SymbolRef) {
const MCSymbolRefExpr *Ref = static_cast<const MCSymbolRefExpr*>(Expr);
return Ref->getKind() == MCSymbolRefExpr::VK_SECREL;
}
return false;
}
bool X86MCCodeEmitter::isPCRel32Branch(const MCInst &MI) const {
unsigned Opcode = MI.getOpcode();
const MCInstrDesc &Desc = MCII.get(Opcode);
if ((Opcode != X86::CALL64pcrel32 && Opcode != X86::JMP_4) ||
getImmFixupKind(Desc.TSFlags) != FK_PCRel_4)
return false;
unsigned CurOp = X86II::getOperandBias(Desc);
const MCOperand &Op = MI.getOperand(CurOp);
if (!Op.isExpr())
return false;
const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Op.getExpr());
return Ref && Ref->getKind() == MCSymbolRefExpr::VK_None;
}
void X86MCCodeEmitter::
EmitImmediate(const MCOperand &DispOp, SMLoc Loc, unsigned Size,
MCFixupKind FixupKind, unsigned &CurByte, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups, int ImmOffset) const {
const MCExpr *Expr = nullptr;
if (DispOp.isImm()) {
// If this is a simple integer displacement that doesn't require a
// relocation, emit it now.
if (FixupKind != FK_PCRel_1 &&
FixupKind != FK_PCRel_2 &&
FixupKind != FK_PCRel_4) {
EmitConstant(DispOp.getImm()+ImmOffset, Size, CurByte, OS);
return;
}
Expr = MCConstantExpr::create(DispOp.getImm(), Ctx);
} else {
Expr = DispOp.getExpr();
}
// If we have an immoffset, add it to the expression.
if ((FixupKind == FK_Data_4 ||
FixupKind == FK_Data_8 ||
FixupKind == MCFixupKind(X86::reloc_signed_4byte))) {
GlobalOffsetTableExprKind Kind = StartsWithGlobalOffsetTable(Expr);
if (Kind != GOT_None) {
assert(ImmOffset == 0);
if (Size == 8) {
FixupKind = MCFixupKind(X86::reloc_global_offset_table8);
} else {
assert(Size == 4);
FixupKind = MCFixupKind(X86::reloc_global_offset_table);
}
if (Kind == GOT_Normal)
ImmOffset = CurByte;
} else if (Expr->getKind() == MCExpr::SymbolRef) {
if (HasSecRelSymbolRef(Expr)) {
FixupKind = MCFixupKind(FK_SecRel_4);
}
} else if (Expr->getKind() == MCExpr::Binary) {
const MCBinaryExpr *Bin = static_cast<const MCBinaryExpr*>(Expr);
if (HasSecRelSymbolRef(Bin->getLHS())
|| HasSecRelSymbolRef(Bin->getRHS())) {
FixupKind = MCFixupKind(FK_SecRel_4);
}
}
}
// If the fixup is pc-relative, we need to bias the value to be relative to
// the start of the field, not the end of the field.
if (FixupKind == FK_PCRel_4 ||
FixupKind == MCFixupKind(X86::reloc_riprel_4byte) ||
FixupKind == MCFixupKind(X86::reloc_riprel_4byte_movq_load) ||
FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax) ||
FixupKind == MCFixupKind(X86::reloc_riprel_4byte_relax_rex) ||
FixupKind == MCFixupKind(X86::reloc_branch_4byte_pcrel)) {
ImmOffset -= 4;
// If this is a pc-relative load off _GLOBAL_OFFSET_TABLE_:
// leaq _GLOBAL_OFFSET_TABLE_(%rip), %r15
// this needs to be a GOTPC32 relocation.
if (StartsWithGlobalOffsetTable(Expr) != GOT_None)
FixupKind = MCFixupKind(X86::reloc_global_offset_table);
}
if (FixupKind == FK_PCRel_2)
ImmOffset -= 2;
if (FixupKind == FK_PCRel_1)
ImmOffset -= 1;
if (ImmOffset)
Expr = MCBinaryExpr::createAdd(Expr, MCConstantExpr::create(ImmOffset, Ctx),
Ctx);
// Emit a symbolic constant as a fixup and 4 zeros.
Fixups.push_back(MCFixup::create(CurByte, Expr, FixupKind, Loc));
EmitConstant(0, Size, CurByte, OS);
}
void X86MCCodeEmitter::emitMemModRMByte(const MCInst &MI, unsigned Op,
unsigned RegOpcodeField,
uint64_t TSFlags, bool Rex,
unsigned &CurByte, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
const MCOperand &Disp = MI.getOperand(Op+X86::AddrDisp);
const MCOperand &Base = MI.getOperand(Op+X86::AddrBaseReg);
const MCOperand &Scale = MI.getOperand(Op+X86::AddrScaleAmt);
const MCOperand &IndexReg = MI.getOperand(Op+X86::AddrIndexReg);
unsigned BaseReg = Base.getReg();
bool HasEVEX = (TSFlags & X86II::EncodingMask) == X86II::EVEX;
// Handle %rip relative addressing.
if (BaseReg == X86::RIP ||
BaseReg == X86::EIP) { // [disp32+rIP] in X86-64 mode
assert(is64BitMode(STI) && "Rip-relative addressing requires 64-bit mode");
assert(IndexReg.getReg() == 0 && "Invalid rip-relative address");
EmitByte(ModRMByte(0, RegOpcodeField, 5), CurByte, OS);
unsigned Opcode = MI.getOpcode();
// movq loads are handled with a special relocation form which allows the
// linker to eliminate some loads for GOT references which end up in the
// same linkage unit.
unsigned FixupKind = [=]() {
switch (Opcode) {
default:
return X86::reloc_riprel_4byte;
case X86::MOV64rm:
assert(Rex);
return X86::reloc_riprel_4byte_movq_load;
case X86::CALL64m:
case X86::JMP64m:
case X86::TAILJMPm64:
case X86::TEST64mr:
case X86::ADC64rm:
case X86::ADD64rm:
case X86::AND64rm:
case X86::CMP64rm:
case X86::OR64rm:
case X86::SBB64rm:
case X86::SUB64rm:
case X86::XOR64rm:
return Rex ? X86::reloc_riprel_4byte_relax_rex
: X86::reloc_riprel_4byte_relax;
}
}();
// rip-relative addressing is actually relative to the *next* instruction.
// Since an immediate can follow the mod/rm byte for an instruction, this
// means that we need to bias the displacement field of the instruction with
// the size of the immediate field. If we have this case, add it into the
// expression to emit.
// Note: rip-relative addressing using immediate displacement values should
// not be adjusted, assuming it was the user's intent.
int ImmSize = !Disp.isImm() && X86II::hasImm(TSFlags)
? X86II::getSizeOfImm(TSFlags)
: 0;
EmitImmediate(Disp, MI.getLoc(), 4, MCFixupKind(FixupKind),
CurByte, OS, Fixups, -ImmSize);
return;
}
unsigned BaseRegNo = BaseReg ? GetX86RegNum(Base) : -1U;
// 16-bit addressing forms of the ModR/M byte have a different encoding for
// the R/M field and are far more limited in which registers can be used.
if (Is16BitMemOperand(MI, Op, STI)) {
if (BaseReg) {
// For 32-bit addressing, the row and column values in Table 2-2 are
// basically the same. It's AX/CX/DX/BX/SP/BP/SI/DI in that order, with
// some special cases. And GetX86RegNum reflects that numbering.
// For 16-bit addressing it's more fun, as shown in the SDM Vol 2A,
// Table 2-1 "16-Bit Addressing Forms with the ModR/M byte". We can only
// use SI/DI/BP/BX, which have "row" values 4-7 in no particular order,
// while values 0-3 indicate the allowed combinations (base+index) of
// those: 0 for BX+SI, 1 for BX+DI, 2 for BP+SI, 3 for BP+DI.
//
// R16Table[] is a lookup from the normal RegNo, to the row values from
// Table 2-1 for 16-bit addressing modes. Where zero means disallowed.
static const unsigned R16Table[] = { 0, 0, 0, 7, 0, 6, 4, 5 };
unsigned RMfield = R16Table[BaseRegNo];
assert(RMfield && "invalid 16-bit base register");
if (IndexReg.getReg()) {
unsigned IndexReg16 = R16Table[GetX86RegNum(IndexReg)];
assert(IndexReg16 && "invalid 16-bit index register");
// We must have one of SI/DI (4,5), and one of BP/BX (6,7).
assert(((IndexReg16 ^ RMfield) & 2) &&
"invalid 16-bit base/index register combination");
assert(Scale.getImm() == 1 &&
"invalid scale for 16-bit memory reference");
// Allow base/index to appear in either order (although GAS doesn't).
if (IndexReg16 & 2)
RMfield = (RMfield & 1) | ((7 - IndexReg16) << 1);
else
RMfield = (IndexReg16 & 1) | ((7 - RMfield) << 1);
}
if (Disp.isImm() && isDisp8(Disp.getImm())) {
if (Disp.getImm() == 0 && RMfield != 6) {
// There is no displacement; just the register.
EmitByte(ModRMByte(0, RegOpcodeField, RMfield), CurByte, OS);
return;
}
// Use the [REG]+disp8 form, including for [BP] which cannot be encoded.
EmitByte(ModRMByte(1, RegOpcodeField, RMfield), CurByte, OS);
EmitImmediate(Disp, MI.getLoc(), 1, FK_Data_1, CurByte, OS, Fixups);
return;
}
// This is the [REG]+disp16 case.
EmitByte(ModRMByte(2, RegOpcodeField, RMfield), CurByte, OS);
} else {
// There is no BaseReg; this is the plain [disp16] case.
EmitByte(ModRMByte(0, RegOpcodeField, 6), CurByte, OS);
}
// Emit 16-bit displacement for plain disp16 or [REG]+disp16 cases.
EmitImmediate(Disp, MI.getLoc(), 2, FK_Data_2, CurByte, OS, Fixups);
return;
}
// Determine whether a SIB byte is needed.
// If no BaseReg, issue a RIP relative instruction only if the MCE can
// resolve addresses on-the-fly, otherwise use SIB (Intel Manual 2A, table
// 2-7) and absolute references.
if (// The SIB byte must be used if there is an index register.
IndexReg.getReg() == 0 &&
// The SIB byte must be used if the base is ESP/RSP/R12, all of which
// encode to an R/M value of 4, which indicates that a SIB byte is
// present.
BaseRegNo != N86::ESP &&
// If there is no base register and we're in 64-bit mode, we need a SIB
// byte to emit an addr that is just 'disp32' (the non-RIP relative form).
(!is64BitMode(STI) || BaseReg != 0)) {
if (BaseReg == 0) { // [disp32] in X86-32 mode
EmitByte(ModRMByte(0, RegOpcodeField, 5), CurByte, OS);
EmitImmediate(Disp, MI.getLoc(), 4, FK_Data_4, CurByte, OS, Fixups);
return;
}
// If the base is not EBP/ESP and there is no displacement, use simple
// indirect register encoding, this handles addresses like [EAX]. The
// encoding for [EBP] with no displacement means [disp32] so we handle it
// by emitting a displacement of 0 below.
if (Disp.isImm() && Disp.getImm() == 0 && BaseRegNo != N86::EBP) {
EmitByte(ModRMByte(0, RegOpcodeField, BaseRegNo), CurByte, OS);
return;
}
// Otherwise, if the displacement fits in a byte, encode as [REG+disp8].
if (Disp.isImm()) {
if (!HasEVEX && isDisp8(Disp.getImm())) {
EmitByte(ModRMByte(1, RegOpcodeField, BaseRegNo), CurByte, OS);
EmitImmediate(Disp, MI.getLoc(), 1, FK_Data_1, CurByte, OS, Fixups);
return;
}
// Try EVEX compressed 8-bit displacement first; if failed, fall back to
// 32-bit displacement.
int CDisp8 = 0;
if (HasEVEX && isCDisp8(TSFlags, Disp.getImm(), CDisp8)) {
EmitByte(ModRMByte(1, RegOpcodeField, BaseRegNo), CurByte, OS);
EmitImmediate(Disp, MI.getLoc(), 1, FK_Data_1, CurByte, OS, Fixups,
CDisp8 - Disp.getImm());
return;
}
}
// Otherwise, emit the most general non-SIB encoding: [REG+disp32]
EmitByte(ModRMByte(2, RegOpcodeField, BaseRegNo), CurByte, OS);
unsigned Opcode = MI.getOpcode();
unsigned FixupKind = Opcode == X86::MOV32rm ? X86::reloc_signed_4byte_relax
: X86::reloc_signed_4byte;
EmitImmediate(Disp, MI.getLoc(), 4, MCFixupKind(FixupKind), CurByte, OS,
Fixups);
return;
}
// We need a SIB byte, so start by outputting the ModR/M byte first
assert(IndexReg.getReg() != X86::ESP &&
IndexReg.getReg() != X86::RSP && "Cannot use ESP as index reg!");
bool ForceDisp32 = false;
bool ForceDisp8 = false;
int CDisp8 = 0;
int ImmOffset = 0;
if (BaseReg == 0) {
// If there is no base register, we emit the special case SIB byte with
// MOD=0, BASE=5, to JUST get the index, scale, and displacement.
EmitByte(ModRMByte(0, RegOpcodeField, 4), CurByte, OS);
ForceDisp32 = true;
} else if (!Disp.isImm()) {
// Emit the normal disp32 encoding.
EmitByte(ModRMByte(2, RegOpcodeField, 4), CurByte, OS);
ForceDisp32 = true;
} else if (Disp.getImm() == 0 &&
// Base reg can't be anything that ends up with '5' as the base
// reg, it is the magic [*] nomenclature that indicates no base.
BaseRegNo != N86::EBP) {
// Emit no displacement ModR/M byte
EmitByte(ModRMByte(0, RegOpcodeField, 4), CurByte, OS);
} else if (!HasEVEX && isDisp8(Disp.getImm())) {
// Emit the disp8 encoding.
EmitByte(ModRMByte(1, RegOpcodeField, 4), CurByte, OS);
ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
} else if (HasEVEX && isCDisp8(TSFlags, Disp.getImm(), CDisp8)) {
// Emit the disp8 encoding.
EmitByte(ModRMByte(1, RegOpcodeField, 4), CurByte, OS);
ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
ImmOffset = CDisp8 - Disp.getImm();
} else {
// Emit the normal disp32 encoding.
EmitByte(ModRMByte(2, RegOpcodeField, 4), CurByte, OS);
}
// Calculate what the SS field value should be...
static const unsigned SSTable[] = { ~0U, 0, 1, ~0U, 2, ~0U, ~0U, ~0U, 3 };
unsigned SS = SSTable[Scale.getImm()];
if (BaseReg == 0) {
// Handle the SIB byte for the case where there is no base, see Intel
// Manual 2A, table 2-7. The displacement has already been output.
unsigned IndexRegNo;
if (IndexReg.getReg())
IndexRegNo = GetX86RegNum(IndexReg);
else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
IndexRegNo = 4;
EmitSIBByte(SS, IndexRegNo, 5, CurByte, OS);
} else {
unsigned IndexRegNo;
if (IndexReg.getReg())
IndexRegNo = GetX86RegNum(IndexReg);
else
IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
EmitSIBByte(SS, IndexRegNo, GetX86RegNum(Base), CurByte, OS);
}
// Do we need to output a displacement?
if (ForceDisp8)
EmitImmediate(Disp, MI.getLoc(), 1, FK_Data_1, CurByte, OS, Fixups, ImmOffset);
else if (ForceDisp32 || Disp.getImm() != 0)
EmitImmediate(Disp, MI.getLoc(), 4, MCFixupKind(X86::reloc_signed_4byte),
CurByte, OS, Fixups);
}
/// EmitVEXOpcodePrefix - AVX instructions are encoded using a opcode prefix
/// called VEX.
void X86MCCodeEmitter::EmitVEXOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
int MemOperand, const MCInst &MI,
const MCInstrDesc &Desc,
raw_ostream &OS) const {
assert(!(TSFlags & X86II::LOCK) && "Can't have LOCK VEX.");
uint64_t Encoding = TSFlags & X86II::EncodingMask;
bool HasEVEX_K = TSFlags & X86II::EVEX_K;
bool HasVEX_4V = TSFlags & X86II::VEX_4V;
bool HasEVEX_RC = TSFlags & X86II::EVEX_RC;
// VEX_R: opcode externsion equivalent to REX.R in
// 1's complement (inverted) form
//
// 1: Same as REX_R=0 (must be 1 in 32-bit mode)
// 0: Same as REX_R=1 (64 bit mode only)
//
uint8_t VEX_R = 0x1;
uint8_t EVEX_R2 = 0x1;
// VEX_X: equivalent to REX.X, only used when a
// register is used for index in SIB Byte.
//
// 1: Same as REX.X=0 (must be 1 in 32-bit mode)
// 0: Same as REX.X=1 (64-bit mode only)
uint8_t VEX_X = 0x1;
// VEX_B:
//
// 1: Same as REX_B=0 (ignored in 32-bit mode)
// 0: Same as REX_B=1 (64 bit mode only)
//
uint8_t VEX_B = 0x1;
// VEX_W: opcode specific (use like REX.W, or used for
// opcode extension, or ignored, depending on the opcode byte)
uint8_t VEX_W = (TSFlags & X86II::VEX_W) ? 1 : 0;
// VEX_5M (VEX m-mmmmm field):
//
// 0b00000: Reserved for future use
// 0b00001: implied 0F leading opcode
// 0b00010: implied 0F 38 leading opcode bytes
// 0b00011: implied 0F 3A leading opcode bytes
// 0b00100-0b11111: Reserved for future use
// 0b01000: XOP map select - 08h instructions with imm byte
// 0b01001: XOP map select - 09h instructions with no imm byte
// 0b01010: XOP map select - 0Ah instructions with imm dword
uint8_t VEX_5M;
switch (TSFlags & X86II::OpMapMask) {
default: llvm_unreachable("Invalid prefix!");
case X86II::TB: VEX_5M = 0x1; break; // 0F
case X86II::T8: VEX_5M = 0x2; break; // 0F 38
case X86II::TA: VEX_5M = 0x3; break; // 0F 3A
case X86II::XOP8: VEX_5M = 0x8; break;
case X86II::XOP9: VEX_5M = 0x9; break;
case X86II::XOPA: VEX_5M = 0xA; break;
}
// VEX_4V (VEX vvvv field): a register specifier
// (in 1's complement form) or 1111 if unused.
uint8_t VEX_4V = 0xf;
uint8_t EVEX_V2 = 0x1;
// EVEX_L2/VEX_L (Vector Length):
//
// L2 L
// 0 0: scalar or 128-bit vector
// 0 1: 256-bit vector
// 1 0: 512-bit vector
//
uint8_t VEX_L = (TSFlags & X86II::VEX_L) ? 1 : 0;
uint8_t EVEX_L2 = (TSFlags & X86II::EVEX_L2) ? 1 : 0;
// VEX_PP: opcode extension providing equivalent
// functionality of a SIMD prefix
//
// 0b00: None
// 0b01: 66
// 0b10: F3
// 0b11: F2
//
uint8_t VEX_PP = 0;
switch (TSFlags & X86II::OpPrefixMask) {
case X86II::PD: VEX_PP = 0x1; break; // 66
case X86II::XS: VEX_PP = 0x2; break; // F3
case X86II::XD: VEX_PP = 0x3; break; // F2
}
// EVEX_U
uint8_t EVEX_U = 1; // Always '1' so far
// EVEX_z
uint8_t EVEX_z = (HasEVEX_K && (TSFlags & X86II::EVEX_Z)) ? 1 : 0;
// EVEX_b
uint8_t EVEX_b = (TSFlags & X86II::EVEX_B) ? 1 : 0;
// EVEX_rc
uint8_t EVEX_rc = 0;
// EVEX_aaa
uint8_t EVEX_aaa = 0;
bool EncodeRC = false;
// Classify VEX_B, VEX_4V, VEX_R, VEX_X
unsigned NumOps = Desc.getNumOperands();
unsigned CurOp = X86II::getOperandBias(Desc);
switch (TSFlags & X86II::FormMask) {
default: llvm_unreachable("Unexpected form in EmitVEXOpcodePrefix!");
case X86II::RawFrm:
break;
case X86II::MRMDestMem: {
// MRMDestMem instructions forms:
// MemAddr, src1(ModR/M)
// MemAddr, src1(VEX_4V), src2(ModR/M)
// MemAddr, src1(ModR/M), imm8
//
unsigned BaseRegEnc = getX86RegEncoding(MI, MemOperand + X86::AddrBaseReg);
VEX_B = ~(BaseRegEnc >> 3) & 1;
unsigned IndexRegEnc = getX86RegEncoding(MI, MemOperand+X86::AddrIndexReg);
VEX_X = ~(IndexRegEnc >> 3) & 1;
if (!HasVEX_4V) // Only needed with VSIB which don't use VVVV.
EVEX_V2 = ~(IndexRegEnc >> 4) & 1;
CurOp += X86::AddrNumOperands;
if (HasEVEX_K)
EVEX_aaa = getX86RegEncoding(MI, CurOp++);
if (HasVEX_4V) {
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
EVEX_V2 = ~(VRegEnc >> 4) & 1;
}
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
EVEX_R2 = ~(RegEnc >> 4) & 1;
break;
}
case X86II::MRMSrcMem: {
// MRMSrcMem instructions forms:
// src1(ModR/M), MemAddr
// src1(ModR/M), src2(VEX_4V), MemAddr
// src1(ModR/M), MemAddr, imm8
// src1(ModR/M), MemAddr, src2(Imm[7:4])
//
// FMA4:
// dst(ModR/M.reg), src1(VEX_4V), src2(ModR/M), src3(Imm[7:4])
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
EVEX_R2 = ~(RegEnc >> 4) & 1;
if (HasEVEX_K)
EVEX_aaa = getX86RegEncoding(MI, CurOp++);
if (HasVEX_4V) {
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
EVEX_V2 = ~(VRegEnc >> 4) & 1;
}
unsigned BaseRegEnc = getX86RegEncoding(MI, MemOperand + X86::AddrBaseReg);
VEX_B = ~(BaseRegEnc >> 3) & 1;
unsigned IndexRegEnc = getX86RegEncoding(MI, MemOperand+X86::AddrIndexReg);
VEX_X = ~(IndexRegEnc >> 3) & 1;
if (!HasVEX_4V) // Only needed with VSIB which don't use VVVV.
EVEX_V2 = ~(IndexRegEnc >> 4) & 1;
break;
}
case X86II::MRMSrcMem4VOp3: {
// Instruction format for 4VOp3:
// src1(ModR/M), MemAddr, src3(VEX_4V)
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
unsigned BaseRegEnc = getX86RegEncoding(MI, MemOperand + X86::AddrBaseReg);
VEX_B = ~(BaseRegEnc >> 3) & 1;
unsigned IndexRegEnc = getX86RegEncoding(MI, MemOperand+X86::AddrIndexReg);
VEX_X = ~(IndexRegEnc >> 3) & 1;
VEX_4V = ~getX86RegEncoding(MI, CurOp + X86::AddrNumOperands) & 0xf;
break;
}
case X86II::MRMSrcMemOp4: {
// dst(ModR/M.reg), src1(VEX_4V), src2(Imm[7:4]), src3(ModR/M),
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
unsigned BaseRegEnc = getX86RegEncoding(MI, MemOperand + X86::AddrBaseReg);
VEX_B = ~(BaseRegEnc >> 3) & 1;
unsigned IndexRegEnc = getX86RegEncoding(MI, MemOperand+X86::AddrIndexReg);
VEX_X = ~(IndexRegEnc >> 3) & 1;
break;
}
case X86II::MRM0m: case X86II::MRM1m:
case X86II::MRM2m: case X86II::MRM3m:
case X86II::MRM4m: case X86II::MRM5m:
case X86II::MRM6m: case X86II::MRM7m: {
// MRM[0-9]m instructions forms:
// MemAddr
// src1(VEX_4V), MemAddr
if (HasVEX_4V) {
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
EVEX_V2 = ~(VRegEnc >> 4) & 1;
}
if (HasEVEX_K)
EVEX_aaa = getX86RegEncoding(MI, CurOp++);
unsigned BaseRegEnc = getX86RegEncoding(MI, MemOperand + X86::AddrBaseReg);
VEX_B = ~(BaseRegEnc >> 3) & 1;
unsigned IndexRegEnc = getX86RegEncoding(MI, MemOperand+X86::AddrIndexReg);
VEX_X = ~(IndexRegEnc >> 3) & 1;
break;
}
case X86II::MRMSrcReg: {
// MRMSrcReg instructions forms:
// dst(ModR/M), src1(VEX_4V), src2(ModR/M), src3(Imm[7:4])
// dst(ModR/M), src1(ModR/M)
// dst(ModR/M), src1(ModR/M), imm8
//
// FMA4:
// dst(ModR/M.reg), src1(VEX_4V), src2(Imm[7:4]), src3(ModR/M),
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
EVEX_R2 = ~(RegEnc >> 4) & 1;
if (HasEVEX_K)
EVEX_aaa = getX86RegEncoding(MI, CurOp++);
if (HasVEX_4V) {
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
EVEX_V2 = ~(VRegEnc >> 4) & 1;
}
RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_B = ~(RegEnc >> 3) & 1;
VEX_X = ~(RegEnc >> 4) & 1;
if (EVEX_b) {
if (HasEVEX_RC) {
unsigned RcOperand = NumOps-1;
assert(RcOperand >= CurOp);
EVEX_rc = MI.getOperand(RcOperand).getImm();
assert(EVEX_rc <= 3 && "Invalid rounding control!");
}
EncodeRC = true;
}
break;
}
case X86II::MRMSrcReg4VOp3: {
// Instruction format for 4VOp3:
// src1(ModR/M), src2(ModR/M), src3(VEX_4V)
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_B = ~(RegEnc >> 3) & 1;
VEX_4V = ~getX86RegEncoding(MI, CurOp++) & 0xf;
break;
}
case X86II::MRMSrcRegOp4: {
// dst(ModR/M.reg), src1(VEX_4V), src2(Imm[7:4]), src3(ModR/M),
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
// Skip second register source (encoded in Imm[7:4])
++CurOp;
RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_B = ~(RegEnc >> 3) & 1;
VEX_X = ~(RegEnc >> 4) & 1;
break;
}
case X86II::MRMDestReg: {
// MRMDestReg instructions forms:
// dst(ModR/M), src(ModR/M)
// dst(ModR/M), src(ModR/M), imm8
// dst(ModR/M), src1(VEX_4V), src2(ModR/M)
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_B = ~(RegEnc >> 3) & 1;
VEX_X = ~(RegEnc >> 4) & 1;
if (HasEVEX_K)
EVEX_aaa = getX86RegEncoding(MI, CurOp++);
if (HasVEX_4V) {
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
EVEX_V2 = ~(VRegEnc >> 4) & 1;
}
RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_R = ~(RegEnc >> 3) & 1;
EVEX_R2 = ~(RegEnc >> 4) & 1;
if (EVEX_b)
EncodeRC = true;
break;
}
case X86II::MRM0r: case X86II::MRM1r:
case X86II::MRM2r: case X86II::MRM3r:
case X86II::MRM4r: case X86II::MRM5r:
case X86II::MRM6r: case X86II::MRM7r: {
// MRM0r-MRM7r instructions forms:
// dst(VEX_4V), src(ModR/M), imm8
if (HasVEX_4V) {
unsigned VRegEnc = getX86RegEncoding(MI, CurOp++);
VEX_4V = ~VRegEnc & 0xf;
EVEX_V2 = ~(VRegEnc >> 4) & 1;
}
if (HasEVEX_K)
EVEX_aaa = getX86RegEncoding(MI, CurOp++);
unsigned RegEnc = getX86RegEncoding(MI, CurOp++);
VEX_B = ~(RegEnc >> 3) & 1;
VEX_X = ~(RegEnc >> 4) & 1;
break;
}
}
if (Encoding == X86II::VEX || Encoding == X86II::XOP) {
// VEX opcode prefix can have 2 or 3 bytes
//
// 3 bytes:
// +-----+ +--------------+ +-------------------+
// | C4h | | RXB | m-mmmm | | W | vvvv | L | pp |
// +-----+ +--------------+ +-------------------+
// 2 bytes:
// +-----+ +-------------------+
// | C5h | | R | vvvv | L | pp |
// +-----+ +-------------------+
//
// XOP uses a similar prefix:
// +-----+ +--------------+ +-------------------+
// | 8Fh | | RXB | m-mmmm | | W | vvvv | L | pp |
// +-----+ +--------------+ +-------------------+
uint8_t LastByte = VEX_PP | (VEX_L << 2) | (VEX_4V << 3);
// Can we use the 2 byte VEX prefix?
if (!(MI.getFlags() & X86::IP_USE_VEX3) &&
Encoding == X86II::VEX && VEX_B && VEX_X && !VEX_W && (VEX_5M == 1)) {
EmitByte(0xC5, CurByte, OS);
EmitByte(LastByte | (VEX_R << 7), CurByte, OS);
return;
}
// 3 byte VEX prefix
EmitByte(Encoding == X86II::XOP ? 0x8F : 0xC4, CurByte, OS);
EmitByte(VEX_R << 7 | VEX_X << 6 | VEX_B << 5 | VEX_5M, CurByte, OS);
EmitByte(LastByte | (VEX_W << 7), CurByte, OS);
} else {
assert(Encoding == X86II::EVEX && "unknown encoding!");
// EVEX opcode prefix can have 4 bytes
//
// +-----+ +--------------+ +-------------------+ +------------------------+
// | 62h | | RXBR' | 00mm | | W | vvvv | U | pp | | z | L'L | b | v' | aaa |
// +-----+ +--------------+ +-------------------+ +------------------------+
assert((VEX_5M & 0x3) == VEX_5M
&& "More than 2 significant bits in VEX.m-mmmm fields for EVEX!");
EmitByte(0x62, CurByte, OS);
EmitByte((VEX_R << 7) |
(VEX_X << 6) |
(VEX_B << 5) |
(EVEX_R2 << 4) |
VEX_5M, CurByte, OS);
EmitByte((VEX_W << 7) |
(VEX_4V << 3) |
(EVEX_U << 2) |
VEX_PP, CurByte, OS);
if (EncodeRC)
EmitByte((EVEX_z << 7) |
(EVEX_rc << 5) |
(EVEX_b << 4) |
(EVEX_V2 << 3) |
EVEX_aaa, CurByte, OS);
else
EmitByte((EVEX_z << 7) |
(EVEX_L2 << 6) |
(VEX_L << 5) |
(EVEX_b << 4) |
(EVEX_V2 << 3) |
EVEX_aaa, CurByte, OS);
}
}
/// DetermineREXPrefix - Determine if the MCInst has to be encoded with a X86-64
/// REX prefix which specifies 1) 64-bit instructions, 2) non-default operand
/// size, and 3) use of X86-64 extended registers.
uint8_t X86MCCodeEmitter::DetermineREXPrefix(const MCInst &MI, uint64_t TSFlags,
int MemOperand,
const MCInstrDesc &Desc) const {
uint8_t REX = 0;
bool UsesHighByteReg = false;
if (TSFlags & X86II::REX_W)
REX |= 1 << 3; // set REX.W
if (MI.getNumOperands() == 0) return REX;
unsigned NumOps = MI.getNumOperands();
unsigned CurOp = X86II::getOperandBias(Desc);
// If it accesses SPL, BPL, SIL, or DIL, then it requires a 0x40 REX prefix.
for (unsigned i = CurOp; i != NumOps; ++i) {
const MCOperand &MO = MI.getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == X86::AH || Reg == X86::BH || Reg == X86::CH || Reg == X86::DH)
UsesHighByteReg = true;
if (X86II::isX86_64NonExtLowByteReg(Reg))
// FIXME: The caller of DetermineREXPrefix slaps this prefix onto anything
// that returns non-zero.
REX |= 0x40; // REX fixed encoding prefix
}
switch (TSFlags & X86II::FormMask) {
case X86II::AddRegFrm:
REX |= isREXExtendedReg(MI, CurOp++) << 0; // REX.B
break;
case X86II::MRMSrcReg:
case X86II::MRMSrcRegCC:
REX |= isREXExtendedReg(MI, CurOp++) << 2; // REX.R
REX |= isREXExtendedReg(MI, CurOp++) << 0; // REX.B
break;
case X86II::MRMSrcMem:
case X86II::MRMSrcMemCC:
REX |= isREXExtendedReg(MI, CurOp++) << 2; // REX.R
REX |= isREXExtendedReg(MI, MemOperand+X86::AddrBaseReg) << 0; // REX.B
REX |= isREXExtendedReg(MI, MemOperand+X86::AddrIndexReg) << 1; // REX.X
CurOp += X86::AddrNumOperands;
break;
case X86II::MRMDestReg:
REX |= isREXExtendedReg(MI, CurOp++) << 0; // REX.B
REX |= isREXExtendedReg(MI, CurOp++) << 2; // REX.R
break;
case X86II::MRMDestMem:
REX |= isREXExtendedReg(MI, MemOperand+X86::AddrBaseReg) << 0; // REX.B
REX |= isREXExtendedReg(MI, MemOperand+X86::AddrIndexReg) << 1; // REX.X
CurOp += X86::AddrNumOperands;
REX |= isREXExtendedReg(MI, CurOp++) << 2; // REX.R
break;
case X86II::MRMXmCC: case X86II::MRMXm:
case X86II::MRM0m: case X86II::MRM1m:
case X86II::MRM2m: case X86II::MRM3m:
case X86II::MRM4m: case X86II::MRM5m:
case X86II::MRM6m: case X86II::MRM7m:
REX |= isREXExtendedReg(MI, MemOperand+X86::AddrBaseReg) << 0; // REX.B
REX |= isREXExtendedReg(MI, MemOperand+X86::AddrIndexReg) << 1; // REX.X
break;
case X86II::MRMXrCC: case X86II::MRMXr:
case X86II::MRM0r: case X86II::MRM1r:
case X86II::MRM2r: case X86II::MRM3r:
case X86II::MRM4r: case X86II::MRM5r:
case X86II::MRM6r: case X86II::MRM7r:
REX |= isREXExtendedReg(MI, CurOp++) << 0; // REX.B
break;
}
if (REX && UsesHighByteReg)
report_fatal_error("Cannot encode high byte register in REX-prefixed instruction");
return REX;
}
/// EmitSegmentOverridePrefix - Emit segment override opcode prefix as needed
void X86MCCodeEmitter::EmitSegmentOverridePrefix(unsigned &CurByte,
unsigned SegOperand,
const MCInst &MI,
raw_ostream &OS) const {
// Check for explicit segment override on memory operand.
switch (MI.getOperand(SegOperand).getReg()) {
default: llvm_unreachable("Unknown segment register!");
case 0: break;
case X86::CS: EmitByte(0x2E, CurByte, OS); break;
case X86::SS: EmitByte(0x36, CurByte, OS); break;
case X86::DS: EmitByte(0x3E, CurByte, OS); break;
case X86::ES: EmitByte(0x26, CurByte, OS); break;
case X86::FS: EmitByte(0x64, CurByte, OS); break;
case X86::GS: EmitByte(0x65, CurByte, OS); break;
}
}
/// Emit all instruction prefixes prior to the opcode.
///
/// MemOperand is the operand # of the start of a memory operand if present. If
/// Not present, it is -1.
///
/// Returns true if a REX prefix was used.
bool X86MCCodeEmitter::emitOpcodePrefix(uint64_t TSFlags, unsigned &CurByte,
int MemOperand, const MCInst &MI,
const MCInstrDesc &Desc,
const MCSubtargetInfo &STI,
raw_ostream &OS) const {
bool Ret = false;
// Emit the operand size opcode prefix as needed.
if ((TSFlags & X86II::OpSizeMask) == (is16BitMode(STI) ? X86II::OpSize32
: X86II::OpSize16))
EmitByte(0x66, CurByte, OS);
// Emit the LOCK opcode prefix.
if (TSFlags & X86II::LOCK || MI.getFlags() & X86::IP_HAS_LOCK)
EmitByte(0xF0, CurByte, OS);
// Emit the NOTRACK opcode prefix.
if (TSFlags & X86II::NOTRACK || MI.getFlags() & X86::IP_HAS_NOTRACK)
EmitByte(0x3E, CurByte, OS);
switch (TSFlags & X86II::OpPrefixMask) {
case X86II::PD: // 66
EmitByte(0x66, CurByte, OS);
break;
case X86II::XS: // F3
EmitByte(0xF3, CurByte, OS);
break;
case X86II::XD: // F2
EmitByte(0xF2, CurByte, OS);
break;
}
// Handle REX prefix.
// FIXME: Can this come before F2 etc to simplify emission?
if (is64BitMode(STI)) {
if (uint8_t REX = DetermineREXPrefix(MI, TSFlags, MemOperand, Desc)) {
EmitByte(0x40 | REX, CurByte, OS);
Ret = true;
}
} else {
assert(!(TSFlags & X86II::REX_W) && "REX.W requires 64bit mode.");
}
// 0x0F escape code must be emitted just before the opcode.
switch (TSFlags & X86II::OpMapMask) {
case X86II::TB: // Two-byte opcode map
case X86II::T8: // 0F 38
case X86II::TA: // 0F 3A
case X86II::ThreeDNow: // 0F 0F, second 0F emitted by caller.
EmitByte(0x0F, CurByte, OS);
break;
}
switch (TSFlags & X86II::OpMapMask) {
case X86II::T8: // 0F 38
EmitByte(0x38, CurByte, OS);
break;
case X86II::TA: // 0F 3A
EmitByte(0x3A, CurByte, OS);
break;
}
return Ret;
}
void X86MCCodeEmitter::
encodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
unsigned Opcode = MI.getOpcode();
const MCInstrDesc &Desc = MCII.get(Opcode);
uint64_t TSFlags = Desc.TSFlags;
unsigned Flags = MI.getFlags();
// Pseudo instructions don't get encoded.
if ((TSFlags & X86II::FormMask) == X86II::Pseudo)
return;
unsigned NumOps = Desc.getNumOperands();
unsigned CurOp = X86II::getOperandBias(Desc);
// Keep track of the current byte being emitted.
unsigned CurByte = 0;
// Encoding type for this instruction.
uint64_t Encoding = TSFlags & X86II::EncodingMask;
// It uses the VEX.VVVV field?
bool HasVEX_4V = TSFlags & X86II::VEX_4V;
bool HasVEX_I8Reg = (TSFlags & X86II::ImmMask) == X86II::Imm8Reg;
// It uses the EVEX.aaa field?
bool HasEVEX_K = TSFlags & X86II::EVEX_K;
bool HasEVEX_RC = TSFlags & X86II::EVEX_RC;
// Used if a register is encoded in 7:4 of immediate.
unsigned I8RegNum = 0;
// Determine where the memory operand starts, if present.
int MemoryOperand = X86II::getMemoryOperandNo(TSFlags);
if (MemoryOperand != -1) MemoryOperand += CurOp;
// Emit segment override opcode prefix as needed.
if (MemoryOperand >= 0)
EmitSegmentOverridePrefix(CurByte, MemoryOperand+X86::AddrSegmentReg,
MI, OS);
// Emit the repeat opcode prefix as needed.
if (TSFlags & X86II::REP || Flags & X86::IP_HAS_REPEAT)
EmitByte(0xF3, CurByte, OS);
if (Flags & X86::IP_HAS_REPEAT_NE)
EmitByte(0xF2, CurByte, OS);
// Emit the address size opcode prefix as needed.
bool need_address_override;
uint64_t AdSize = TSFlags & X86II::AdSizeMask;
if ((is16BitMode(STI) && AdSize == X86II::AdSize32) ||
(is32BitMode(STI) && AdSize == X86II::AdSize16) ||
(is64BitMode(STI) && AdSize == X86II::AdSize32)) {
need_address_override = true;
} else if (MemoryOperand < 0) {
need_address_override = false;
} else if (is64BitMode(STI)) {
assert(!Is16BitMemOperand(MI, MemoryOperand, STI));
need_address_override = Is32BitMemOperand(MI, MemoryOperand);
} else if (is32BitMode(STI)) {
assert(!Is64BitMemOperand(MI, MemoryOperand));
need_address_override = Is16BitMemOperand(MI, MemoryOperand, STI);
} else {
assert(is16BitMode(STI));
assert(!Is64BitMemOperand(MI, MemoryOperand));
need_address_override = !Is16BitMemOperand(MI, MemoryOperand, STI);
}
if (need_address_override)
EmitByte(0x67, CurByte, OS);
bool Rex = false;
if (Encoding == 0)
Rex = emitOpcodePrefix(TSFlags, CurByte, MemoryOperand, MI, Desc, STI, OS);
else
EmitVEXOpcodePrefix(TSFlags, CurByte, MemoryOperand, MI, Desc, OS);
uint8_t BaseOpcode = X86II::getBaseOpcodeFor(TSFlags);
if ((TSFlags & X86II::OpMapMask) == X86II::ThreeDNow)
BaseOpcode = 0x0F; // Weird 3DNow! encoding.
unsigned OpcodeOffset = 0;
uint64_t Form = TSFlags & X86II::FormMask;
switch (Form) {
default: errs() << "FORM: " << Form << "\n";
llvm_unreachable("Unknown FormMask value in X86MCCodeEmitter!");
case X86II::Pseudo:
llvm_unreachable("Pseudo instruction shouldn't be emitted");
case X86II::RawFrmDstSrc: {
unsigned siReg = MI.getOperand(1).getReg();
assert(((siReg == X86::SI && MI.getOperand(0).getReg() == X86::DI) ||
(siReg == X86::ESI && MI.getOperand(0).getReg() == X86::EDI) ||
(siReg == X86::RSI && MI.getOperand(0).getReg() == X86::RDI)) &&
"SI and DI register sizes do not match");
// Emit segment override opcode prefix as needed (not for %ds).
if (MI.getOperand(2).getReg() != X86::DS)
EmitSegmentOverridePrefix(CurByte, 2, MI, OS);
// Emit AdSize prefix as needed.
if ((!is32BitMode(STI) && siReg == X86::ESI) ||
(is32BitMode(STI) && siReg == X86::SI))
EmitByte(0x67, CurByte, OS);
CurOp += 3; // Consume operands.
EmitByte(BaseOpcode, CurByte, OS);
break;
}
case X86II::RawFrmSrc: {
unsigned siReg = MI.getOperand(0).getReg();
// Emit segment override opcode prefix as needed (not for %ds).
if (MI.getOperand(1).getReg() != X86::DS)
EmitSegmentOverridePrefix(CurByte, 1, MI, OS);
// Emit AdSize prefix as needed.
if ((!is32BitMode(STI) && siReg == X86::ESI) ||
(is32BitMode(STI) && siReg == X86::SI))
EmitByte(0x67, CurByte, OS);
CurOp += 2; // Consume operands.
EmitByte(BaseOpcode, CurByte, OS);
break;
}
case X86II::RawFrmDst: {
unsigned siReg = MI.getOperand(0).getReg();
// Emit AdSize prefix as needed.
if ((!is32BitMode(STI) && siReg == X86::EDI) ||
(is32BitMode(STI) && siReg == X86::DI))
EmitByte(0x67, CurByte, OS);
++CurOp; // Consume operand.
EmitByte(BaseOpcode, CurByte, OS);
break;
}
case X86II::AddCCFrm: {
// This will be added to the opcode in the fallthrough.
OpcodeOffset = MI.getOperand(NumOps - 1).getImm();
assert(OpcodeOffset < 16 && "Unexpected opcode offset!");
--NumOps; // Drop the operand from the end.
LLVM_FALLTHROUGH;
case X86II::RawFrm:
EmitByte(BaseOpcode + OpcodeOffset, CurByte, OS);
if (!is64BitMode(STI) || !isPCRel32Branch(MI))
break;
const MCOperand &Op = MI.getOperand(CurOp++);
EmitImmediate(Op, MI.getLoc(), X86II::getSizeOfImm(TSFlags),
MCFixupKind(X86::reloc_branch_4byte_pcrel), CurByte, OS,
Fixups);
break;
}
case X86II::RawFrmMemOffs:
// Emit segment override opcode prefix as needed.
EmitSegmentOverridePrefix(CurByte, 1, MI, OS);
EmitByte(BaseOpcode, CurByte, OS);
EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(),
X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
CurByte, OS, Fixups);
++CurOp; // skip segment operand
break;
case X86II::RawFrmImm8:
EmitByte(BaseOpcode, CurByte, OS);
EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(),
X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
CurByte, OS, Fixups);
EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(), 1, FK_Data_1, CurByte,
OS, Fixups);
break;
case X86II::RawFrmImm16:
EmitByte(BaseOpcode, CurByte, OS);
EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(),
X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
CurByte, OS, Fixups);
EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(), 2, FK_Data_2, CurByte,
OS, Fixups);
break;
case X86II::AddRegFrm:
EmitByte(BaseOpcode + GetX86RegNum(MI.getOperand(CurOp++)), CurByte, OS);
break;
case X86II::MRMDestReg: {
EmitByte(BaseOpcode, CurByte, OS);
unsigned SrcRegNum = CurOp + 1;
if (HasEVEX_K) // Skip writemask
++SrcRegNum;
if (HasVEX_4V) // Skip 1st src (which is encoded in VEX_VVVV)
++SrcRegNum;
EmitRegModRMByte(MI.getOperand(CurOp),
GetX86RegNum(MI.getOperand(SrcRegNum)), CurByte, OS);
CurOp = SrcRegNum + 1;
break;
}
case X86II::MRMDestMem: {
EmitByte(BaseOpcode, CurByte, OS);
unsigned SrcRegNum = CurOp + X86::AddrNumOperands;
if (HasEVEX_K) // Skip writemask
++SrcRegNum;
if (HasVEX_4V) // Skip 1st src (which is encoded in VEX_VVVV)
++SrcRegNum;
emitMemModRMByte(MI, CurOp, GetX86RegNum(MI.getOperand(SrcRegNum)), TSFlags,
Rex, CurByte, OS, Fixups, STI);
CurOp = SrcRegNum + 1;
break;
}
case X86II::MRMSrcReg: {
EmitByte(BaseOpcode, CurByte, OS);
unsigned SrcRegNum = CurOp + 1;
if (HasEVEX_K) // Skip writemask
++SrcRegNum;
if (HasVEX_4V) // Skip 1st src (which is encoded in VEX_VVVV)
++SrcRegNum;
EmitRegModRMByte(MI.getOperand(SrcRegNum),
GetX86RegNum(MI.getOperand(CurOp)), CurByte, OS);
CurOp = SrcRegNum + 1;
if (HasVEX_I8Reg)
I8RegNum = getX86RegEncoding(MI, CurOp++);
// do not count the rounding control operand
if (HasEVEX_RC)
--NumOps;
break;
}
case X86II::MRMSrcReg4VOp3: {
EmitByte(BaseOpcode, CurByte, OS);
unsigned SrcRegNum = CurOp + 1;
EmitRegModRMByte(MI.getOperand(SrcRegNum),
GetX86RegNum(MI.getOperand(CurOp)), CurByte, OS);
CurOp = SrcRegNum + 1;
++CurOp; // Encoded in VEX.VVVV
break;
}
case X86II::MRMSrcRegOp4: {
EmitByte(BaseOpcode, CurByte, OS);
unsigned SrcRegNum = CurOp + 1;
// Skip 1st src (which is encoded in VEX_VVVV)
++SrcRegNum;
// Capture 2nd src (which is encoded in Imm[7:4])
assert(HasVEX_I8Reg && "MRMSrcRegOp4 should imply VEX_I8Reg");
I8RegNum = getX86RegEncoding(MI, SrcRegNum++);
EmitRegModRMByte(MI.getOperand(SrcRegNum),
GetX86RegNum(MI.getOperand(CurOp)), CurByte, OS);
CurOp = SrcRegNum + 1;
break;
}
case X86II::MRMSrcRegCC: {
unsigned FirstOp = CurOp++;
unsigned SecondOp = CurOp++;
unsigned CC = MI.getOperand(CurOp++).getImm();
EmitByte(BaseOpcode + CC, CurByte, OS);
EmitRegModRMByte(MI.getOperand(SecondOp),
GetX86RegNum(MI.getOperand(FirstOp)), CurByte, OS);
break;
}
case X86II::MRMSrcMem: {
unsigned FirstMemOp = CurOp+1;
if (HasEVEX_K) // Skip writemask
++FirstMemOp;
if (HasVEX_4V)
++FirstMemOp; // Skip the register source (which is encoded in VEX_VVVV).
EmitByte(BaseOpcode, CurByte, OS);
emitMemModRMByte(MI, FirstMemOp, GetX86RegNum(MI.getOperand(CurOp)),
TSFlags, Rex, CurByte, OS, Fixups, STI);
CurOp = FirstMemOp + X86::AddrNumOperands;
if (HasVEX_I8Reg)
I8RegNum = getX86RegEncoding(MI, CurOp++);
break;
}
case X86II::MRMSrcMem4VOp3: {
unsigned FirstMemOp = CurOp+1;
EmitByte(BaseOpcode, CurByte, OS);
emitMemModRMByte(MI, FirstMemOp, GetX86RegNum(MI.getOperand(CurOp)),
TSFlags, Rex, CurByte, OS, Fixups, STI);
CurOp = FirstMemOp + X86::AddrNumOperands;
++CurOp; // Encoded in VEX.VVVV.
break;
}
case X86II::MRMSrcMemOp4: {
unsigned FirstMemOp = CurOp+1;
++FirstMemOp; // Skip the register source (which is encoded in VEX_VVVV).
// Capture second register source (encoded in Imm[7:4])
assert(HasVEX_I8Reg && "MRMSrcRegOp4 should imply VEX_I8Reg");
I8RegNum = getX86RegEncoding(MI, FirstMemOp++);
EmitByte(BaseOpcode, CurByte, OS);
emitMemModRMByte(MI, FirstMemOp, GetX86RegNum(MI.getOperand(CurOp)),
TSFlags, Rex, CurByte, OS, Fixups, STI);
CurOp = FirstMemOp + X86::AddrNumOperands;
break;
}
case X86II::MRMSrcMemCC: {
unsigned RegOp = CurOp++;
unsigned FirstMemOp = CurOp;
CurOp = FirstMemOp + X86::AddrNumOperands;
unsigned CC = MI.getOperand(CurOp++).getImm();
EmitByte(BaseOpcode + CC, CurByte, OS);
emitMemModRMByte(MI, FirstMemOp, GetX86RegNum(MI.getOperand(RegOp)),
TSFlags, Rex, CurByte, OS, Fixups, STI);
break;
}
case X86II::MRMXrCC: {
unsigned RegOp = CurOp++;
unsigned CC = MI.getOperand(CurOp++).getImm();
EmitByte(BaseOpcode + CC, CurByte, OS);
EmitRegModRMByte(MI.getOperand(RegOp), 0, CurByte, OS);
break;
}
case X86II::MRMXr:
case X86II::MRM0r: case X86II::MRM1r:
case X86II::MRM2r: case X86II::MRM3r:
case X86II::MRM4r: case X86II::MRM5r:
case X86II::MRM6r: case X86II::MRM7r:
if (HasVEX_4V) // Skip the register dst (which is encoded in VEX_VVVV).
++CurOp;
if (HasEVEX_K) // Skip writemask
++CurOp;
EmitByte(BaseOpcode, CurByte, OS);
EmitRegModRMByte(MI.getOperand(CurOp++),
(Form == X86II::MRMXr) ? 0 : Form-X86II::MRM0r,
CurByte, OS);
break;
case X86II::MRMXmCC: {
unsigned FirstMemOp = CurOp;
CurOp = FirstMemOp + X86::AddrNumOperands;
unsigned CC = MI.getOperand(CurOp++).getImm();
EmitByte(BaseOpcode + CC, CurByte, OS);
emitMemModRMByte(MI, FirstMemOp, 0, TSFlags, Rex, CurByte, OS, Fixups, STI);
break;
}
case X86II::MRMXm:
case X86II::MRM0m: case X86II::MRM1m:
case X86II::MRM2m: case X86II::MRM3m:
case X86II::MRM4m: case X86II::MRM5m:
case X86II::MRM6m: case X86II::MRM7m:
if (HasVEX_4V) // Skip the register dst (which is encoded in VEX_VVVV).
++CurOp;
if (HasEVEX_K) // Skip writemask
++CurOp;
EmitByte(BaseOpcode, CurByte, OS);
emitMemModRMByte(MI, CurOp,
(Form == X86II::MRMXm) ? 0 : Form - X86II::MRM0m, TSFlags,
Rex, CurByte, OS, Fixups, STI);
CurOp += X86::AddrNumOperands;
break;
case X86II::MRM_C0: case X86II::MRM_C1: case X86II::MRM_C2:
case X86II::MRM_C3: case X86II::MRM_C4: case X86II::MRM_C5:
case X86II::MRM_C6: case X86II::MRM_C7: case X86II::MRM_C8:
case X86II::MRM_C9: case X86II::MRM_CA: case X86II::MRM_CB:
case X86II::MRM_CC: case X86II::MRM_CD: case X86II::MRM_CE:
case X86II::MRM_CF: case X86II::MRM_D0: case X86II::MRM_D1:
case X86II::MRM_D2: case X86II::MRM_D3: case X86II::MRM_D4:
case X86II::MRM_D5: case X86II::MRM_D6: case X86II::MRM_D7:
case X86II::MRM_D8: case X86II::MRM_D9: case X86II::MRM_DA:
case X86II::MRM_DB: case X86II::MRM_DC: case X86II::MRM_DD:
case X86II::MRM_DE: case X86II::MRM_DF: case X86II::MRM_E0:
case X86II::MRM_E1: case X86II::MRM_E2: case X86II::MRM_E3:
case X86II::MRM_E4: case X86II::MRM_E5: case X86II::MRM_E6:
case X86II::MRM_E7: case X86II::MRM_E8: case X86II::MRM_E9:
case X86II::MRM_EA: case X86II::MRM_EB: case X86II::MRM_EC:
case X86II::MRM_ED: case X86II::MRM_EE: case X86II::MRM_EF:
case X86II::MRM_F0: case X86II::MRM_F1: case X86II::MRM_F2:
case X86II::MRM_F3: case X86II::MRM_F4: case X86II::MRM_F5:
case X86II::MRM_F6: case X86II::MRM_F7: case X86II::MRM_F8:
case X86II::MRM_F9: case X86II::MRM_FA: case X86II::MRM_FB:
case X86II::MRM_FC: case X86II::MRM_FD: case X86II::MRM_FE:
case X86II::MRM_FF:
EmitByte(BaseOpcode, CurByte, OS);
EmitByte(0xC0 + Form - X86II::MRM_C0, CurByte, OS);
break;
}
if (HasVEX_I8Reg) {
// The last source register of a 4 operand instruction in AVX is encoded
// in bits[7:4] of a immediate byte.
assert(I8RegNum < 16 && "Register encoding out of range");
I8RegNum <<= 4;
if (CurOp != NumOps) {
unsigned Val = MI.getOperand(CurOp++).getImm();
assert(Val < 16 && "Immediate operand value out of range");
I8RegNum |= Val;
}
EmitImmediate(MCOperand::createImm(I8RegNum), MI.getLoc(), 1, FK_Data_1,
CurByte, OS, Fixups);
} else {
// If there is a remaining operand, it must be a trailing immediate. Emit it
// according to the right size for the instruction. Some instructions
// (SSE4a extrq and insertq) have two trailing immediates.
while (CurOp != NumOps && NumOps - CurOp <= 2) {
EmitImmediate(MI.getOperand(CurOp++), MI.getLoc(),
X86II::getSizeOfImm(TSFlags), getImmFixupKind(TSFlags),
CurByte, OS, Fixups);
}
}
if ((TSFlags & X86II::OpMapMask) == X86II::ThreeDNow)
EmitByte(X86II::getBaseOpcodeFor(TSFlags), CurByte, OS);
#ifndef NDEBUG
// FIXME: Verify.
if (/*!Desc.isVariadic() &&*/ CurOp != NumOps) {
errs() << "Cannot encode all operands of: ";
MI.dump();
errs() << '\n';
abort();
}
#endif
}
MCCodeEmitter *llvm::createX86MCCodeEmitter(const MCInstrInfo &MCII,
const MCRegisterInfo &MRI,
MCContext &Ctx) {
return new X86MCCodeEmitter(MCII, Ctx);
}