/** lc3_execute
*
* Execute the given instruction
*
* @param state LC3 simulator
* @param instruction Command to execute
*/
void lc3_execute(lc3machine* state, unsigned short instruction)
{
// create all the different variables that make up each command
unsigned char strCommand = (instruction & 0xF000) >> 12;
unsigned char DR = (instruction & 0x0E00) >> 9;
unsigned char SR1 = (instruction & 0x01C0) >> 6;
unsigned char SR2 = instruction & 0x0007;
char bit5 = (instruction & 0x20) >> 5;
char bit9 = (instruction & 0x0200) >> 9;
char bit10 = (instruction & 0x0400) >> 10;
char bit11 = (instruction & 0x0800) >> 11;
char imm5 = (instruction & 0x1F) | (instruction & 0x10 ? 0xF0 : 0);
char offset6 = (instruction & 0x3F) | (instruction & 0x20 ? 0xE0 : 0);
unsigned char offset8 = instruction & 0xFF;
short offset9 = (instruction & 0x01FF) | (instruction & 0x100 ? 0xFF00 : 0);
short offset11 = (instruction & 0x07FF) | (instruction & 0x400 ? 0xFC00 : 0);
// figure out which command it is
if (strCommand == 1) { // ADD
state->regs[DR] = state->regs[SR1] + (bit5 ? imm5 : state->regs[SR2]);
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 5) { // AND
state->regs[DR] = state->regs[SR1] & (bit5 ? imm5 : state->regs[SR2]);
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 0) { // BR
if ((bit11 && state->cc == 4) || (bit10 && state->cc == 2) || (bit9 && state->cc == 1))
state->pc += offset9;
}
else if (strCommand == 12) { // JMP
state->pc = state->regs[SR1];
}
else if (strCommand == 4) { // JSR
state->regs[7] = state->pc;
state->pc = bit11 ? (state->pc + offset11) : state->regs[SR1];
}
else if (strCommand == 2) { // LD
state->regs[DR] = state->mem[state->pc + offset9]; // take into account array starts at 1
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 10) { // LDI
state->regs[DR] = state->mem[state->mem[state->pc + offset9]];
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 6) { // LDR
state->regs[DR] = state->mem[state->regs[SR1] + offset6];
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 14) { // LEA
state->regs[DR] = state->pc + offset9;
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 9) { // NOT
state->regs[DR] = ~ state->regs[SR1];
state->cc = state->regs[DR] > 0 ? 1 : (state->regs[DR] < 0 ? 4 : 2);
}
else if (strCommand == 3) { // ST
state->mem[state->pc + offset9] = state->regs[DR];
}
else if (strCommand == 11) { // STI
state->mem[state->mem[state->pc + offset9]] = state->regs[DR];
}
else if (strCommand == 7) { // STR
state->mem[state->regs[SR1] + offset6] = state->regs[DR];
}
else if(strCommand == 15) { // TRAP
state->regs[7] = state->pc;
lc3_trap(state, offset8);
}
}
void lc3_execute(lc3machine* state, unsigned short instruction)
{
// Get the opcode and choose actions based on that.
u32 operation = GET_SUBWORD(instruction, 15, 12);
switch (operation) {
case (LC3_OP_ADD): {
if (GET_SUBWORD(instruction, 5, 5)) {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 sr1 = GET_SUBWORD(instruction, 8, 6);
u32 imm5 = GET_SUBWORD(instruction, 4, 0);
lc3_add_imm(state, dr, sr1, imm5);
} else {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 sr1 = GET_SUBWORD(instruction, 8, 6);
u32 sr2 = GET_SUBWORD(instruction, 2, 0);
lc3_add_reg(state, dr, sr1, sr2);
}
break;
} case (LC3_OP_AND): {
if (GET_SUBWORD(instruction, 5, 5)) {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 sr1 = GET_SUBWORD(instruction, 8, 6);
u32 imm5 = GET_SUBWORD(instruction, 4, 0);
lc3_and_imm(state, dr, sr1, imm5);
} else {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 sr1 = GET_SUBWORD(instruction, 8, 6);
u32 sr2 = GET_SUBWORD(instruction, 2, 0);
lc3_and_reg(state, dr, sr1, sr2);
}
break;
} case (LC3_OP_BR): {
u32 cc = GET_SUBWORD(instruction, 11, 9);
u32 offset = GET_SUBWORD(instruction, 8, 0);
lc3_br(state, cc, offset);
break;
} case (LC3_OP_JMP): {
u32 reg = GET_SUBWORD(instruction, 8, 6);
lc3_jmp(state, reg);
break;
} case (LC3_OP_JSR): {
if (GET_SUBWORD(instruction, 11, 11)) {
u32 offset = GET_SUBWORD(instruction, 10, 0);
lc3_jsr_offset(state, offset);
} else {
u32 baser = GET_SUBWORD(instruction, 8, 6);
lc3_jsr_reg(state, baser);
}
break;
} case (LC3_OP_LD): {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 offset = GET_SUBWORD(instruction, 8, 0);
lc3_ld(state, dr, offset);
break;
} case (LC3_OP_LDI): {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 offset = GET_SUBWORD(instruction, 8, 0);
lc3_ldi(state, dr, offset);
break;
} case (LC3_OP_LDR): {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 baser = GET_SUBWORD(instruction, 8, 6);
u32 offset = GET_SUBWORD(instruction, 5, 0);
lc3_ldr(state, dr, baser, offset);
break;
} case (LC3_OP_LEA): {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 offset = GET_SUBWORD(instruction, 8, 0);
lc3_lea(state, dr, offset);
break;
} case (LC3_OP_NOT): {
u32 dr = GET_SUBWORD(instruction, 11, 9);
u32 sr = GET_SUBWORD(instruction, 8, 6);
lc3_not(state, dr, sr);
break;
} case (LC3_OP_RTI): {
// Not using RTI
break;
} case (LC3_OP_ST): {
u32 sr = GET_SUBWORD(instruction, 11, 9);
u32 offset = GET_SUBWORD(instruction, 8, 0);
lc3_st(state, sr, offset);
break;
} case (LC3_OP_STI): {
u32 sr = GET_SUBWORD(instruction, 11, 9);
u32 offset = GET_SUBWORD(instruction, 8, 0);
lc3_sti(state, sr, offset);
break;
} case (LC3_OP_STR): {
u32 sr = GET_SUBWORD(instruction, 11, 9);
u32 baser = GET_SUBWORD(instruction, 8, 6);
u32 offset = GET_SUBWORD(instruction, 5, 0);
lc3_str(state, sr, baser, offset);
break;
} case (LC3_OP_TRAP): {
u32 trapvect = GET_SUBWORD(instruction, 7, 0);
lc3_trap(state, trapvect);
break;
}
}
}