1 //===-- AVRMCCodeEmitter.cpp - Convert AVR Code to Machine Code -----------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file implements the AVRMCCodeEmitter class.
11 //===----------------------------------------------------------------------===//
13 #include "AVRMCCodeEmitter.h"
15 #include "MCTargetDesc/AVRMCExpr.h"
16 #include "MCTargetDesc/AVRMCTargetDesc.h"
18 #include "llvm/ADT/APFloat.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCExpr.h"
22 #include "llvm/MC/MCFixup.h"
23 #include "llvm/MC/MCInst.h"
24 #include "llvm/MC/MCInstrInfo.h"
25 #include "llvm/MC/MCRegisterInfo.h"
26 #include "llvm/MC/MCSubtargetInfo.h"
27 #include "llvm/Support/Casting.h"
28 #include "llvm/Support/EndianStream.h"
29 #include "llvm/Support/raw_ostream.h"
31 #define DEBUG_TYPE "mccodeemitter"
33 #define GET_INSTRMAP_INFO
34 #include "AVRGenInstrInfo.inc"
35 #undef GET_INSTRMAP_INFO
39 /// Performs a post-encoding step on a `LD` or `ST` instruction.
41 /// The encoding of the LD/ST family of instructions is inconsistent w.r.t
42 /// the pointer register and the addressing mode.
44 /// The permutations of the format are as followed:
45 /// ld Rd, X `1001 000d dddd 1100`
46 /// ld Rd, X+ `1001 000d dddd 1101`
47 /// ld Rd, -X `1001 000d dddd 1110`
49 /// ld Rd, Y `1000 000d dddd 1000`
50 /// ld Rd, Y+ `1001 000d dddd 1001`
51 /// ld Rd, -Y `1001 000d dddd 1010`
53 /// ld Rd, Z `1000 000d dddd 0000`
54 /// ld Rd, Z+ `1001 000d dddd 0001`
55 /// ld Rd, -Z `1001 000d dddd 0010`
58 /// Note this one inconsistent bit - it is 1 sometimes and 0 at other times.
59 /// There is no logical pattern. Looking at a truth table, the following
60 /// formula can be derived to fit the pattern:
63 /// inconsistent_bit = is_predec OR is_postinc OR is_reg_x
66 /// We manually set this bit in this post encoder method.
68 AVRMCCodeEmitter::loadStorePostEncoder(const MCInst &MI, unsigned EncodedValue,
69 const MCSubtargetInfo &STI) const {
71 assert(MI.getOperand(0).isReg() && MI.getOperand(1).isReg() &&
72 "the load/store operands must be registers");
74 unsigned Opcode = MI.getOpcode();
76 // check whether either of the registers are the X pointer register.
77 bool IsRegX = MI.getOperand(0).getReg() == AVR::R27R26 ||
78 MI.getOperand(1).getReg() == AVR::R27R26;
80 bool IsPredec = Opcode == AVR::LDRdPtrPd || Opcode == AVR::STPtrPdRr;
81 bool IsPostinc = Opcode == AVR::LDRdPtrPi || Opcode == AVR::STPtrPiRr;
83 // Check if we need to set the inconsistent bit
84 if (IsRegX || IsPredec || IsPostinc) {
85 EncodedValue |= (1 << 12);
91 template <AVR::Fixups Fixup>
93 AVRMCCodeEmitter::encodeRelCondBrTarget(const MCInst &MI, unsigned OpNo,
94 SmallVectorImpl<MCFixup> &Fixups,
95 const MCSubtargetInfo &STI) const {
96 const MCOperand &MO = MI.getOperand(OpNo);
99 Fixups.push_back(MCFixup::create(0, MO.getExpr(),
100 MCFixupKind(Fixup), MI.getLoc()));
106 // Take the size of the current instruction away.
107 // With labels, this is implicitly done.
108 auto target = MO.getImm();
109 AVR::fixups::adjustBranchTarget(target);
113 unsigned AVRMCCodeEmitter::encodeLDSTPtrReg(const MCInst &MI, unsigned OpNo,
114 SmallVectorImpl<MCFixup> &Fixups,
115 const MCSubtargetInfo &STI) const {
116 auto MO = MI.getOperand(OpNo);
118 // The operand should be a pointer register.
121 switch (MO.getReg()) {
122 case AVR::R27R26: return 0x03; // X: 0b11
123 case AVR::R29R28: return 0x02; // Y: 0b10
124 case AVR::R31R30: return 0x00; // Z: 0b00
126 llvm_unreachable("invalid pointer register");
130 /// Encodes a `memri` operand.
131 /// The operand is 7-bits.
132 /// * The lower 6 bits is the immediate
133 /// * The upper bit is the pointer register bit (Z=0,Y=1)
134 unsigned AVRMCCodeEmitter::encodeMemri(const MCInst &MI, unsigned OpNo,
135 SmallVectorImpl<MCFixup> &Fixups,
136 const MCSubtargetInfo &STI) const {
137 auto RegOp = MI.getOperand(OpNo);
138 auto OffsetOp = MI.getOperand(OpNo + 1);
140 assert(RegOp.isReg() && "Expected register operand");
144 switch (RegOp.getReg()) {
146 llvm_unreachable("Expected either Y or Z register");
157 if (OffsetOp.isImm()) {
158 OffsetBits = OffsetOp.getImm();
159 } else if (OffsetOp.isExpr()) {
161 Fixups.push_back(MCFixup::create(0, OffsetOp.getExpr(),
162 MCFixupKind(AVR::fixup_6), MI.getLoc()));
164 llvm_unreachable("invalid value for offset");
167 return (RegBit << 6) | OffsetBits;
170 unsigned AVRMCCodeEmitter::encodeComplement(const MCInst &MI, unsigned OpNo,
171 SmallVectorImpl<MCFixup> &Fixups,
172 const MCSubtargetInfo &STI) const {
173 // The operand should be an immediate.
174 assert(MI.getOperand(OpNo).isImm());
176 auto Imm = MI.getOperand(OpNo).getImm();
180 template <AVR::Fixups Fixup, unsigned Offset>
181 unsigned AVRMCCodeEmitter::encodeImm(const MCInst &MI, unsigned OpNo,
182 SmallVectorImpl<MCFixup> &Fixups,
183 const MCSubtargetInfo &STI) const {
184 auto MO = MI.getOperand(OpNo);
187 if (isa<AVRMCExpr>(MO.getExpr())) {
188 // If the expression is already an AVRMCExpr (i.e. a lo8(symbol),
189 // we shouldn't perform any more fixups. Without this check, we would
190 // instead create a fixup to the symbol named 'lo8(symbol)' which
192 return getExprOpValue(MO.getExpr(), Fixups, STI);
195 MCFixupKind FixupKind = static_cast<MCFixupKind>(Fixup);
196 Fixups.push_back(MCFixup::create(Offset, MO.getExpr(), FixupKind, MI.getLoc()));
205 unsigned AVRMCCodeEmitter::encodeCallTarget(const MCInst &MI, unsigned OpNo,
206 SmallVectorImpl<MCFixup> &Fixups,
207 const MCSubtargetInfo &STI) const {
208 auto MO = MI.getOperand(OpNo);
211 MCFixupKind FixupKind = static_cast<MCFixupKind>(AVR::fixup_call);
212 Fixups.push_back(MCFixup::create(0, MO.getExpr(), FixupKind, MI.getLoc()));
218 auto Target = MO.getImm();
219 AVR::fixups::adjustBranchTarget(Target);
223 unsigned AVRMCCodeEmitter::getExprOpValue(const MCExpr *Expr,
224 SmallVectorImpl<MCFixup> &Fixups,
225 const MCSubtargetInfo &STI) const {
227 MCExpr::ExprKind Kind = Expr->getKind();
229 if (Kind == MCExpr::Binary) {
230 Expr = static_cast<const MCBinaryExpr *>(Expr)->getLHS();
231 Kind = Expr->getKind();
234 if (Kind == MCExpr::Target) {
235 AVRMCExpr const *AVRExpr = cast<AVRMCExpr>(Expr);
237 if (AVRExpr->evaluateAsConstant(Result)) {
241 MCFixupKind FixupKind = static_cast<MCFixupKind>(AVRExpr->getFixupKind());
242 Fixups.push_back(MCFixup::create(0, AVRExpr, FixupKind));
246 assert(Kind == MCExpr::SymbolRef);
250 unsigned AVRMCCodeEmitter::getMachineOpValue(const MCInst &MI,
252 SmallVectorImpl<MCFixup> &Fixups,
253 const MCSubtargetInfo &STI) const {
254 if (MO.isReg()) return Ctx.getRegisterInfo()->getEncodingValue(MO.getReg());
255 if (MO.isImm()) return static_cast<unsigned>(MO.getImm());
258 return static_cast<unsigned>(APFloat(MO.getFPImm())
263 // MO must be an Expr.
266 return getExprOpValue(MO.getExpr(), Fixups, STI);
269 void AVRMCCodeEmitter::emitInstruction(uint64_t Val, unsigned Size,
270 const MCSubtargetInfo &STI,
271 raw_ostream &OS) const {
272 size_t WordCount = Size / 2;
274 for (int64_t i = WordCount - 1; i >= 0; --i) {
275 uint16_t Word = (Val >> (i * 16)) & 0xFFFF;
276 support::endian::write(OS, Word, support::endianness::little);
280 void AVRMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
281 SmallVectorImpl<MCFixup> &Fixups,
282 const MCSubtargetInfo &STI) const {
283 const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
285 // Get byte count of instruction
286 unsigned Size = Desc.getSize();
288 assert(Size > 0 && "Instruction size cannot be zero");
290 uint64_t BinaryOpCode = getBinaryCodeForInstr(MI, Fixups, STI);
291 emitInstruction(BinaryOpCode, Size, STI, OS);
294 MCCodeEmitter *createAVRMCCodeEmitter(const MCInstrInfo &MCII,
295 const MCRegisterInfo &MRI,
297 return new AVRMCCodeEmitter(MCII, Ctx);
300 #include "AVRGenMCCodeEmitter.inc"
302 } // end of namespace llvm