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//===-- BPFMCCodeEmitter.cpp - Convert BPF 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 BPFMCCodeEmitter class.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/BPFMCTargetDesc.h"
#include "llvm/MC/MCCodeEmitter.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/MC/MCSymbol.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "mccodeemitter"
namespace {
class BPFMCCodeEmitter : public MCCodeEmitter {
BPFMCCodeEmitter(const BPFMCCodeEmitter &) = delete;
void operator=(const BPFMCCodeEmitter &) = delete;
const MCRegisterInfo &MRI;
public:
BPFMCCodeEmitter(const MCRegisterInfo &mri) : MRI(mri) {}
~BPFMCCodeEmitter() {}
// getBinaryCodeForInstr - TableGen'erated function for getting the
// binary encoding for an instruction.
uint64_t getBinaryCodeForInstr(const MCInst &MI,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const;
// getMachineOpValue - Return binary encoding of operand. If the machin
// operand requires relocation, record the relocation and return zero.
unsigned getMachineOpValue(const MCInst &MI, const MCOperand &MO,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const;
uint64_t getMemoryOpValue(const MCInst &MI, unsigned Op,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const;
void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const override;
};
}
MCCodeEmitter *llvm::createBPFMCCodeEmitter(const MCInstrInfo &MCII,
const MCRegisterInfo &MRI,
MCContext &Ctx) {
return new BPFMCCodeEmitter(MRI);
}
unsigned BPFMCCodeEmitter::getMachineOpValue(const MCInst &MI,
const MCOperand &MO,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
if (MO.isReg())
return MRI.getEncodingValue(MO.getReg());
if (MO.isImm())
return static_cast<unsigned>(MO.getImm());
assert(MO.isExpr());
const MCExpr *Expr = MO.getExpr();
assert(Expr->getKind() == MCExpr::SymbolRef);
if (MI.getOpcode() == BPF::JAL)
// func call name
Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_4));
else if (MI.getOpcode() == BPF::LD_imm64)
Fixups.push_back(MCFixup::Create(0, Expr, FK_SecRel_8));
else
// bb label
Fixups.push_back(MCFixup::Create(0, Expr, FK_PCRel_2));
return 0;
}
// Emit one byte through output stream
void EmitByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) {
OS << (char)C;
++CurByte;
}
// Emit a series of bytes (little endian)
void EmitLEConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
raw_ostream &OS) {
assert(Size <= 8 && "size too big in emit constant");
for (unsigned i = 0; i != Size; ++i) {
EmitByte(Val & 255, CurByte, OS);
Val >>= 8;
}
}
// Emit a series of bytes (big endian)
void EmitBEConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
raw_ostream &OS) {
assert(Size <= 8 && "size too big in emit constant");
for (int i = (Size - 1) * 8; i >= 0; i -= 8)
EmitByte((Val >> i) & 255, CurByte, OS);
}
void BPFMCCodeEmitter::EncodeInstruction(const MCInst &MI, raw_ostream &OS,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
unsigned Opcode = MI.getOpcode();
// Keep track of the current byte being emitted
unsigned CurByte = 0;
if (Opcode == BPF::LD_imm64 || Opcode == BPF::LD_pseudo) {
uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
EmitByte(Value >> 56, CurByte, OS);
EmitByte(((Value >> 48) & 0xff), CurByte, OS);
EmitLEConstant(0, 2, CurByte, OS);
EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS);
const MCOperand &MO = MI.getOperand(1);
uint64_t Imm = MO.isImm() ? MO.getImm() : 0;
EmitByte(0, CurByte, OS);
EmitByte(0, CurByte, OS);
EmitLEConstant(0, 2, CurByte, OS);
EmitLEConstant(Imm >> 32, 4, CurByte, OS);
} else {
// Get instruction encoding and emit it
uint64_t Value = getBinaryCodeForInstr(MI, Fixups, STI);
EmitByte(Value >> 56, CurByte, OS);
EmitByte((Value >> 48) & 0xff, CurByte, OS);
EmitLEConstant((Value >> 32) & 0xffff, 2, CurByte, OS);
EmitLEConstant(Value & 0xffffFFFF, 4, CurByte, OS);
}
}
// Encode BPF Memory Operand
uint64_t BPFMCCodeEmitter::getMemoryOpValue(const MCInst &MI, unsigned Op,
SmallVectorImpl<MCFixup> &Fixups,
const MCSubtargetInfo &STI) const {
uint64_t Encoding;
const MCOperand Op1 = MI.getOperand(1);
assert(Op1.isReg() && "First operand is not register.");
Encoding = MRI.getEncodingValue(Op1.getReg());
Encoding <<= 16;
MCOperand Op2 = MI.getOperand(2);
assert(Op2.isImm() && "Second operand is not immediate.");
Encoding |= Op2.getImm() & 0xffff;
return Encoding;
}
#include "BPFGenMCCodeEmitter.inc"
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