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#include "programmemory.h"
#include <sstream>
#include "qtmipsexception.h"
#include "instructions/arithmetic.h"
#include "instructions/loadstore.h"
#include "instructions/nop.h"
#include "instructions/shift.h"
ProgramMemory::ProgramMemory(ProgramLoader *loader, MemoryAccess *memory) {
this->memory = memory;
// Load program to memory (just dump it byte by byte, decode is done on demand)
for (int i = 0; i < loader->get_nsec(); i++) {
std::uint32_t base_address = loader->get_address(i);
std::vector<std::uint8_t> data = loader->get_data(i);
for (auto it = data.begin(); it < data.end(); it++) {
memory->write_byte(base_address + i, *it);
}
}
}
#define MASKSUB(VAR, LEN, OFFSET) ((VAR & ~((1 << (LEN+OFFSET+1)) - 1)) >> OFFSET)
Instruction *ProgramMemory::at(std::uint32_t address) {
if (address % 4)
// TODO different exception (unaligned address)
throw std::exception();
// Read instruction from memory
std::uint32_t dt = this->memory->read_word(address);
// Decode instruction
Instruction *inst;
std::uint8_t opcode = dt >> 26; // upper 6 bits
if (opcode == 0) { // Arithmetic and shift instructions
return this->decode_r(dt);
} else if (opcode == 2 || opcode == 3) { // Jump instructions
return decode_j(dt);
} else {
return decode_i(dt);
}
}
// TODO implement
#define I_UNKNOWN(DATA) do { std::stringstream ss; ss << std::hex << DATA; throw QTMIPS_EXCEPTION(UnsupportedInstruction, "Unknown instruction, can't decode", ss.str()); } while(false);
#define I_UNSUPPORTED(INST) throw QTMIPS_EXCEPTION(UnsupportedInstruction, "Decoded unsupported unstruction", #INST)
Instruction *ProgramMemory::decode_r(std::uint32_t dt) {
std::uint8_t func = MASKSUB(dt, 6, 0);
if (!func)
return new InstructionNop();
std::uint8_t rs, rt, rd, sa;
rs = MASKSUB(dt, 5, 21);
rt = MASKSUB(dt, 5, 16);
rd = MASKSUB(dt, 5, 11);
sa = MASKSUB(dt, 5, 6);
if (func < 8) { // Shift instructions
bool variable = false;
enum InstructionShiftT t;
switch (func) {
case 0:
t = IST_LL;
break;
case 2:
t = IST_RL;
break;
case 3:
t = IST_RA;
break;
case 4:
t = IST_LL;
variable = true;
break;
case 6:
t = IST_RL;
variable = true;
break;
case 7:
t = IST_RA;
variable = true;
break;
default:
I_UNKNOWN(dt);
}
if (variable)
return new InstructionShiftVariable(t, rs, rt, rd);
else
return new InstructionShift(t, rt, rd, sa);
} else if (func < 10) { // Jump instructions
// TODO
I_UNKNOWN(dt);
} else { // TODO filter rest
I_UNKNOWN(dt);
}
}
Instruction *ProgramMemory::decode_j(std::uint32_t dt) {
std::uint32_t address = MASKSUB(dt, 26, 0);
// TODO
I_UNKNOWN(dt);
}
Instruction *ProgramMemory::decode_i(std::uint32_t dt) {
// InstructionI
std::uint8_t rs, rt;
rs = MASKSUB(dt, 5, 21);
rt = MASKSUB(dt, 5, 16);
std::uint16_t immediate = MASKSUB(dt, 16, 0);
// TODO
I_UNKNOWN(dt);
}
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