1 //===-- X86/X86MCCodeEmitter.cpp - Convert X86 code to machine code -------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the X86MCCodeEmitter class.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "x86-emitter"
16 #include "X86InstrInfo.h"
17 #include "llvm/MC/MCCodeEmitter.h"
18 #include "llvm/MC/MCInst.h"
19 #include "llvm/Support/raw_ostream.h"
23 class X86MCCodeEmitter : public MCCodeEmitter {
24 X86MCCodeEmitter(const X86MCCodeEmitter &); // DO NOT IMPLEMENT
25 void operator=(const X86MCCodeEmitter &); // DO NOT IMPLEMENT
26 const TargetMachine &TM;
27 const TargetInstrInfo &TII;
30 X86MCCodeEmitter(TargetMachine &tm)
31 : TM(tm), TII(*TM.getInstrInfo()) {
32 // FIXME: Get this from the right place.
36 ~X86MCCodeEmitter() {}
38 static unsigned GetX86RegNum(const MCOperand &MO) {
39 return X86RegisterInfo::getX86RegNum(MO.getReg());
42 void EmitByte(unsigned char C, raw_ostream &OS) const {
46 void EmitConstant(uint64_t Val, unsigned Size, raw_ostream &OS) const {
47 // Output the constant in little endian byte order.
48 for (unsigned i = 0; i != Size; ++i) {
49 EmitByte(Val & 255, OS);
54 inline static unsigned char ModRMByte(unsigned Mod, unsigned RegOpcode,
56 assert(Mod < 4 && RegOpcode < 8 && RM < 8 && "ModRM Fields out of range!");
57 return RM | (RegOpcode << 3) | (Mod << 6);
60 void EmitRegModRMByte(const MCOperand &ModRMReg, unsigned RegOpcodeFld,
61 raw_ostream &OS) const {
62 EmitByte(ModRMByte(3, RegOpcodeFld, GetX86RegNum(ModRMReg)), OS);
65 void EmitMemModRMByte(const MCInst &MI, unsigned Op,
66 unsigned RegOpcodeField, intptr_t PCAdj,
67 raw_ostream &OS) const;
69 void EncodeInstruction(const MCInst &MI, raw_ostream &OS) const;
73 } // end anonymous namespace
76 MCCodeEmitter *llvm::createX86MCCodeEmitter(const Target &,
78 return new X86MCCodeEmitter(TM);
82 /// isDisp8 - Return true if this signed displacement fits in a 8-bit
83 /// sign-extended field.
84 static bool isDisp8(int Value) {
85 return Value == (signed char)Value;
88 void X86MCCodeEmitter::EmitMemModRMByte(const MCInst &MI, unsigned Op,
89 unsigned RegOpcodeField,
91 raw_ostream &OS) const {
92 const MCOperand &Op3 = MI.getOperand(Op+3);
94 const MCOperand *DispForReloc = 0;
96 // Figure out what sort of displacement we have to handle here.
98 DispVal = Op3.getImm();
101 if (Op3.isGlobal()) {
103 } else if (Op3.isSymbol()) {
105 } else if (Op3.isCPI()) {
106 if (!MCE.earlyResolveAddresses() || Is64BitMode || IsPIC) {
109 DispVal += MCE.getConstantPoolEntryAddress(Op3.getIndex());
110 DispVal += Op3.getOffset();
114 if (!MCE.earlyResolveAddresses() || Is64BitMode || IsPIC) {
117 DispVal += MCE.getJumpTableEntryAddress(Op3.getIndex());
122 const MCOperand &Base = MI.getOperand(Op);
123 //const MCOperand &Scale = MI.getOperand(Op+1);
124 const MCOperand &IndexReg = MI.getOperand(Op+2);
125 unsigned BaseReg = Base.getReg();
127 // Is a SIB byte needed?
128 // If no BaseReg, issue a RIP relative instruction only if the MCE can
129 // resolve addresses on-the-fly, otherwise use SIB (Intel Manual 2A, table
130 // 2-7) and absolute references.
131 if ((!Is64BitMode || DispForReloc || BaseReg != 0) &&
132 IndexReg.getReg() == 0 &&
133 (BaseReg == X86::RIP || (BaseReg != 0 && BaseReg != X86::ESP))) {
134 if (BaseReg == 0 || BaseReg == X86::RIP) { // Just a displacement?
135 // Emit special case [disp32] encoding
136 EmitByte(ModRMByte(0, RegOpcodeField, 5), OS);
138 emitDisplacementField(DispForReloc, DispVal, PCAdj, true);
141 unsigned BaseRegNo = GetX86RegNum(Base);
142 if (!DispForReloc && DispVal == 0 && BaseRegNo != N86::EBP) {
143 // Emit simple indirect register encoding... [EAX] f.e.
144 EmitByte(ModRMByte(0, RegOpcodeField, BaseRegNo), OS);
145 } else if (!DispForReloc && isDisp8(DispVal)) {
146 // Emit the disp8 encoding... [REG+disp8]
147 EmitByte(ModRMByte(1, RegOpcodeField, BaseRegNo), OS);
148 EmitConstant(DispVal, 1, OS);
150 // Emit the most general non-SIB encoding: [REG+disp32]
151 EmitByte(ModRMByte(2, RegOpcodeField, BaseRegNo), OS);
153 emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
158 } else { // We need a SIB byte, so start by outputting the ModR/M byte first
159 assert(IndexReg.getReg() != X86::ESP &&
160 IndexReg.getReg() != X86::RSP && "Cannot use ESP as index reg!");
162 bool ForceDisp32 = false;
163 bool ForceDisp8 = false;
165 // If there is no base register, we emit the special case SIB byte with
166 // MOD=0, BASE=5, to JUST get the index, scale, and displacement.
167 EmitByte(ModRMByte(0, RegOpcodeField, 4), OS);
169 } else if (DispForReloc) {
170 // Emit the normal disp32 encoding.
171 EmitByte(ModRMByte(2, RegOpcodeField, 4), OS);
173 } else if (DispVal == 0 && BaseReg != X86::EBP) {
174 // Emit no displacement ModR/M byte
175 EmitByte(ModRMByte(0, RegOpcodeField, 4), OS);
176 } else if (isDisp8(DispVal)) {
177 // Emit the disp8 encoding.
178 EmitByte(ModRMByte(1, RegOpcodeField, 4), OS);
179 ForceDisp8 = true; // Make sure to force 8 bit disp if Base=EBP
181 // Emit the normal disp32 encoding.
182 EmitByte(ModRMByte(2, RegOpcodeField, 4), OS);
186 // Calculate what the SS field value should be...
187 static const unsigned SSTable[] = { ~0, 0, 1, ~0, 2, ~0, ~0, ~0, 3 };
188 unsigned SS = SSTable[Scale.getImm()];
191 // Handle the SIB byte for the case where there is no base, see Intel
192 // Manual 2A, table 2-7. The displacement has already been output.
194 if (IndexReg.getReg())
195 IndexRegNo = getX86RegNum(IndexReg.getReg());
196 else // Examples: [ESP+1*<noreg>+4] or [scaled idx]+disp32 (MOD=0,BASE=5)
198 emitSIBByte(SS, IndexRegNo, 5);
200 unsigned BaseRegNo = getX86RegNum(BaseReg);
202 if (IndexReg.getReg())
203 IndexRegNo = getX86RegNum(IndexReg.getReg());
205 IndexRegNo = 4; // For example [ESP+1*<noreg>+4]
206 emitSIBByte(SS, IndexRegNo, BaseRegNo);
209 // Do we need to output a displacement?
211 emitConstant(DispVal, 1);
212 } else if (DispVal != 0 || ForceDisp32) {
213 emitDisplacementField(DispForReloc, DispVal, PCAdj, IsPCRel);
220 void X86MCCodeEmitter::
221 EncodeInstruction(const MCInst &MI, raw_ostream &OS) const {
222 unsigned Opcode = MI.getOpcode();
223 const TargetInstrDesc &Desc = TII.get(Opcode);
224 unsigned TSFlags = Desc.TSFlags;
226 // FIXME: We should emit the prefixes in exactly the same order as GAS does,
227 // in order to provide diffability.
229 // Emit the lock opcode prefix as needed.
230 if (TSFlags & X86II::LOCK)
233 // Emit segment override opcode prefix as needed.
234 switch (TSFlags & X86II::SegOvrMask) {
235 default: assert(0 && "Invalid segment!");
236 case 0: break; // No segment override!
245 // Emit the repeat opcode prefix as needed.
246 if ((TSFlags & X86II::Op0Mask) == X86II::REP)
249 // Emit the operand size opcode prefix as needed.
250 if (TSFlags & X86II::OpSize)
253 // Emit the address size opcode prefix as needed.
254 if (TSFlags & X86II::AdSize)
257 bool Need0FPrefix = false;
258 switch (TSFlags & X86II::Op0Mask) {
259 default: assert(0 && "Invalid prefix!");
260 case 0: break; // No prefix!
261 case X86II::REP: break; // already handled.
262 case X86II::TB: // Two-byte opcode prefix
263 case X86II::T8: // 0F 38
264 case X86II::TA: // 0F 3A
267 case X86II::TF: // F2 0F 38
271 case X86II::XS: // F3 0F
275 case X86II::XD: // F2 0F
279 case X86II::D8: EmitByte(0xD8, OS); break;
280 case X86II::D9: EmitByte(0xD9, OS); break;
281 case X86II::DA: EmitByte(0xDA, OS); break;
282 case X86II::DB: EmitByte(0xDB, OS); break;
283 case X86II::DC: EmitByte(0xDC, OS); break;
284 case X86II::DD: EmitByte(0xDD, OS); break;
285 case X86II::DE: EmitByte(0xDE, OS); break;
286 case X86II::DF: EmitByte(0xDF, OS); break;
289 // Handle REX prefix.
290 #if 0 // FIXME: Add in, also, can this come before F2 etc to simplify emission?
292 if (unsigned REX = X86InstrInfo::determineREX(MI))
293 EmitByte(0x40 | REX, OS);
297 // 0x0F escape code must be emitted just before the opcode.
301 // FIXME: Pull this up into previous switch if REX can be moved earlier.
302 switch (TSFlags & X86II::Op0Mask) {
303 case X86II::TF: // F2 0F 38
304 case X86II::T8: // 0F 38
307 case X86II::TA: // 0F 3A
312 // If this is a two-address instruction, skip one of the register operands.
313 unsigned NumOps = Desc.getNumOperands();
315 if (NumOps > 1 && Desc.getOperandConstraint(1, TOI::TIED_TO) != -1)
317 else if (NumOps > 2 && Desc.getOperandConstraint(NumOps-1, TOI::TIED_TO)== 0)
318 // Skip the last source operand that is tied_to the dest reg. e.g. LXADD32
321 // FIXME: Can we kill off MRMInitReg??
323 unsigned char BaseOpcode = X86InstrInfo::getBaseOpcodeFor(Desc);
324 switch (TSFlags & X86II::FormMask) {
325 default: errs() << "FORM: " << (TSFlags & X86II::FormMask) << "\n";
326 assert(0 && "Unknown FormMask value in X86MCCodeEmitter!");
327 case X86II::RawFrm: {
328 EmitByte(BaseOpcode, OS);
333 assert(0 && "Unimpl RawFrm expr");
337 case X86II::AddRegFrm: {
338 EmitByte(BaseOpcode + GetX86RegNum(MI.getOperand(CurOp++)),OS);
342 const MCOperand &MO1 = MI.getOperand(CurOp++);
344 unsigned Size = X86InstrInfo::sizeOfImm(&Desc);
345 EmitConstant(MO1.getImm(), Size, OS);
349 assert(0 && "Unimpl AddRegFrm expr");
353 case X86II::MRMDestReg:
354 EmitByte(BaseOpcode, OS);
355 EmitRegModRMByte(MI.getOperand(CurOp),
356 GetX86RegNum(MI.getOperand(CurOp+1)), OS);
359 EmitConstant(MI.getOperand(CurOp++).getImm(),
360 X86InstrInfo::sizeOfImm(&Desc), OS);
363 case X86II::MRMDestMem:
364 EmitByte(BaseOpcode, OS);
365 EmitMemModRMByte(MI, CurOp,
366 GetX86RegNum(MI.getOperand(CurOp + X86AddrNumOperands)),
368 CurOp += X86AddrNumOperands + 1;
370 EmitConstant(MI.getOperand(CurOp++).getImm(),
371 X86InstrInfo::sizeOfImm(&Desc), OS);
376 if (!Desc.isVariadic() && CurOp != NumOps) {
377 errs() << "Cannot encode all operands of: ";