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//===-- AVRMCCodeEmitter.cpp - Convert AVR Code to Machine Code -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the AVRMCCodeEmitter class.
//
//===----------------------------------------------------------------------===//
#include "AVRMCCodeEmitter.h"
#include "MCTargetDesc/AVRMCExpr.h"
#include "MCTargetDesc/AVRMCTargetDesc.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/raw_ostream.h"
#define DEBUG_TYPE "mccodeemitter"
#define GET_INSTRMAP_INFO
#include "AVRGenInstrInfo.inc"
#undef GET_INSTRMAP_INFO
namespace llvm {
/// Performs a post-encoding step on a `LD` or `ST` instruction.
///
/// The encoding of the LD/ST family of instructions is inconsistent w.r.t
/// the pointer register and the addressing mode.
///
/// The permutations of the format are as followed:
/// ld Rd, X `1001 000d dddd 1100`
/// ld Rd, X+ `1001 000d dddd 1101`
/// ld Rd, -X `1001 000d dddd 1110`
///
/// ld Rd, Y `1000 000d dddd 1000`
/// ld Rd, Y+ `1001 000d dddd 1001`
/// ld Rd, -Y `1001 000d dddd 1010`
///
/// ld Rd, Z `1000 000d dddd 0000`
/// ld Rd, Z+ `1001 000d dddd 0001`
/// ld Rd, -Z `1001 000d dddd 0010`
/// ^
/// |
/// Note this one inconsistent bit - it is 1 sometimes and 0 at other times.
/// There is no logical pattern. Looking at a truth table, the following
/// formula can be derived to fit the pattern:
//
/// ```
/// inconsistent_bit = is_predec OR is_postinc OR is_reg_x
/// ```
//
/// We manually set this bit in this post encoder method.
unsigned
AVRMCCodeEmitter::loadStorePostEncoder(const MCInst &MI, unsigned EncodedValue,
const MCSubtargetInfo &STI) const {
assert(MI.getOperand(0).isReg() && MI.getOperand(1).isReg() &&
"the load/store operands must be registers");
unsigned Opcode = MI.getOpcode();
// check whether either of the registers are the X pointer register.
bool IsRegX = MI.getOperand(0).getReg() == AVR::R27R26 ||
MI.getOperand(1).getReg() == AVR::R27R26;
bool IsPredec = Opcode == AVR::LDRdPtrPd || Opcode == AVR::STPtrPdRr;
bool IsPostinc = Opcode == AVR::LDRdPtrPi || Opcode == AVR::STPtrPiRr;
// Check if we need to set the inconsistent bit
if (IsRegX || IsPredec || IsPostinc) {
EncodedValue |= (1 << 12);
}
return EncodedValue;
}
template <AVR::Fixups Fixup>
unsigned
AVRMCCodeEmitter::encodeRelCondBrTarget(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
const MCOperand &MO = MI.getOperand(OpNo);
if (MO.isExpr()) {
Fixups.push_back(MCFixup::create(0, MO.getExpr(),
MCFixupKind(Fixup), MI.getLoc()));
return 0;
}
assert(MO.isImm());
// Take the size of the current instruction away.
// With labels, this is implicitly done.
auto target = MO.getImm();
AVR::fixups::adjustBranchTarget(target);
return target;
}
unsigned AVRMCCodeEmitter::encodeLDSTPtrReg(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
auto MO = MI.getOperand(OpNo);
// The operand should be a pointer register.
assert(MO.isReg());
switch (MO.getReg()) {
case AVR::R27R26: return 0x03; // X: 0b11
case AVR::R29R28: return 0x02; // Y: 0b10
case AVR::R31R30: return 0x00; // Z: 0b00
default:
llvm_unreachable("invalid pointer register");
}
}
/// Encodes a `memri` operand.
/// The operand is 7-bits.
/// * The lower 6 bits is the immediate
/// * The upper bit is the pointer register bit (Z=0,Y=1)
unsigned AVRMCCodeEmitter::encodeMemri(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
auto RegOp = MI.getOperand(OpNo);
auto OffsetOp = MI.getOperand(OpNo + 1);
assert(RegOp.isReg() && "Expected register operand");
uint8_t RegBit = 0;
switch (RegOp.getReg()) {
default:
llvm_unreachable("Expected either Y or Z register");
case AVR::R31R30:
RegBit = 0;
break; // Z register
case AVR::R29R28:
RegBit = 1;
break; // Y register
}
int8_t OffsetBits;
if (OffsetOp.isImm()) {
OffsetBits = OffsetOp.getImm();
} else if (OffsetOp.isExpr()) {
OffsetBits = 0;
Fixups.push_back(MCFixup::create(0, OffsetOp.getExpr(),
MCFixupKind(AVR::fixup_6), MI.getLoc()));
} else {
llvm_unreachable("invalid value for offset");
}
return (RegBit << 6) | OffsetBits;
}
unsigned AVRMCCodeEmitter::encodeComplement(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
// The operand should be an immediate.
assert(MI.getOperand(OpNo).isImm());
auto Imm = MI.getOperand(OpNo).getImm();
return (~0) - Imm;
}
template <AVR::Fixups Fixup, unsigned Offset>
unsigned AVRMCCodeEmitter::encodeImm(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
auto MO = MI.getOperand(OpNo);
if (MO.isExpr()) {
if (isa<AVRMCExpr>(MO.getExpr())) {
// If the expression is already an AVRMCExpr (i.e. a lo8(symbol),
// we shouldn't perform any more fixups. Without this check, we would
// instead create a fixup to the symbol named 'lo8(symbol)' which
// is not correct.
return getExprOpValue(MO.getExpr(), Fixups, STI);
}
MCFixupKind FixupKind = static_cast<MCFixupKind>(Fixup);
Fixups.push_back(MCFixup::create(Offset, MO.getExpr(), FixupKind, MI.getLoc()));
return 0;
}
assert(MO.isImm());
return MO.getImm();
}
unsigned AVRMCCodeEmitter::encodeCallTarget(const MCInst &MI, unsigned OpNo,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
auto MO = MI.getOperand(OpNo);
if (MO.isExpr()) {
MCFixupKind FixupKind = static_cast<MCFixupKind>(AVR::fixup_call);
Fixups.push_back(MCFixup::create(0, MO.getExpr(), FixupKind, MI.getLoc()));
return 0;
}
assert(MO.isImm());
auto Target = MO.getImm();
AVR::fixups::adjustBranchTarget(Target);
return Target;
}
unsigned AVRMCCodeEmitter::getExprOpValue(const MCExpr *Expr,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
MCExpr::ExprKind Kind = Expr->getKind();
if (Kind == MCExpr::Binary) {
Expr = static_cast<const MCBinaryExpr *>(Expr)->getLHS();
Kind = Expr->getKind();
}
if (Kind == MCExpr::Target) {
AVRMCExpr const *AVRExpr = cast<AVRMCExpr>(Expr);
int64_t Result;
if (AVRExpr->evaluateAsConstant(Result)) {
return Result;
}
MCFixupKind FixupKind = static_cast<MCFixupKind>(AVRExpr->getFixupKind());
Fixups.push_back(MCFixup::create(0, AVRExpr, FixupKind));
return 0;
}
assert(Kind == MCExpr::SymbolRef);
return 0;
}
unsigned AVRMCCodeEmitter::getMachineOpValue(const MCInst &MI,
const MCOperand &MO,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
if (MO.isReg()) return Ctx.getRegisterInfo()->getEncodingValue(MO.getReg());
if (MO.isImm()) return static_cast<unsigned>(MO.getImm());
if (MO.isFPImm())
return static_cast<unsigned>(APFloat(MO.getFPImm())
.bitcastToAPInt()
.getHiBits(32)
.getLimitedValue());
// MO must be an Expr.
assert(MO.isExpr());
return getExprOpValue(MO.getExpr(), Fixups, STI);
}
void AVRMCCodeEmitter::emitInstruction(uint64_t Val, unsigned Size,
const MCSubtargetInfo &STI,
raw_ostream &OS) const {
const uint16_t *Words = reinterpret_cast<uint16_t const *>(&Val);
size_t WordCount = Size / 2;
for (int64_t i = WordCount - 1; i >= 0; --i) {
uint16_t Word = Words[i];
OS << (uint8_t) ((Word & 0x00ff) >> 0);
OS << (uint8_t) ((Word & 0xff00) >> 8);
}
}
void AVRMCCodeEmitter::encodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
const MCInstrDesc &Desc = MCII.get(MI.getOpcode());
// Get byte count of instruction
unsigned Size = Desc.getSize();
assert(Size > 0 && "Instruction size cannot be zero");
uint64_t BinaryOpCode = getBinaryCodeForInstr(MI, Fixups, STI);
emitInstruction(BinaryOpCode, Size, STI, OS);
}
MCCodeEmitter *createAVRMCCodeEmitter(const MCInstrInfo &MCII,
const MCRegisterInfo &MRI,
MCContext &Ctx) {
return new AVRMCCodeEmitter(MCII, Ctx);
}
#include "AVRGenMCCodeEmitter.inc"
} // end of namespace llvm