void do_if_stage()
{
exc_t nstatus = EXC_NONE;
word_t fetchpc = gen_f_pc();
word_t valp = fetchpc;
bool_t fetch_ok;
byte_t instr;
byte_t regids = HPACK(REG_NONE, REG_NONE);
word_t valc = 0;
/* JB */
if (gen_F_bubble()) {
memcpy (if_id_next, &bubble_if_id, if_id_state->count);
// fprintf (stderr, "%s\n", format_if_id(if_id_next));
return;
}
f_pc = fetchpc;
if (fetchpc == 0) {
sim_log("Fetch: Fetch pc = 0, nominal pc = 0x%x\n",
pc_curr->pc);
}
/* Ready to fetch instruction. Speculatively fetch register byte
and immediate word
*/
fetch_ok = get_byte_val(mem, valp, &instr);
if(gen_instr_next_ifun() != -1)
if_id_next->ifun = gen_instr_next_ifun();
else{
if (fetch_ok) {
if_id_next->icode = GET_ICODE(instr);
if_id_next->ifun = GET_FUN(instr);
} else {
if_id_next->icode = I_NOP;
if_id_next->ifun = 0;
nstatus = EXC_ADDR;
}
}
fetch_ok = TRUE;
valp++;
if (fetch_ok && gen_need_regids()) {
fetch_ok = get_byte_val(mem, valp, ®ids);
valp ++;
}
if_id_next->ra = HI4(regids);
if_id_next->rb = LO4(regids);
if (fetch_ok && gen_need_valC()) {
fetch_ok = get_word_val(mem, valp, &valc);
valp+= 4;
}
if_id_next->valp = valp;
if_id_next->valc = valc;
if (gen_instr_next_ifun() == -1)
pc_next->pc = gen_new_F_predPC();
if (!gen_instr_valid())
{
byte_t instr = HPACK(if_id_next->icode, if_id_next->ifun);
sim_log("Fetch: Instruction code %s (0x%x) invalid\n",
iname(instr), instr);
nstatus = EXC_INSTR;
}
pc_next->exception = (nstatus == EXC_NONE) ? EXC_NONE : EXC_BUBBLE;
if_id_next->stage_pc = fetchpc;
if_id_next->exception = nstatus;
/* Recompute icode for one-write implementation of popl */
if_id_next->icode = gen_new_D_icode();
sim_log("Fetch: Fetched %s at 0x%x, ra = %s, rb = %s, valp = 0x%x, status = %s\n",
iname(HPACK(if_id_next->icode, if_id_next->ifun)),
if_id_next->stage_pc,
reg_name(if_id_next->ra), reg_name(if_id_next->rb),
if_id_next->valp,
exc_name(nstatus));
}
/* Return resulting exception status */
static exc_t sim_step()
{
word_t aluA;
word_t aluB;
word_t alufun;
exc_t status = update_state(); /* Update state from last cycle */
if (plusmode) {
pc = gen_pc();
}
valp = pc;
if(gen_instr_next_ifun () !=-1)
ifun = gen_instr_next_ifun();
else if (get_byte_val(mem, valp, &instr)) {
icode = HI4(instr);
ifun = LO4(instr);
} else {
instr = HPACK(I_NOP,0);
icode = I_NOP;
ifun = 0;
status = EXC_ADDR;
sim_log("Couldn't fetch at address 0x%x\n", valp);
}
valp++;
if (gen_need_regids()) {
byte_t regids;
if (get_byte_val(mem, valp, ®ids)) {
ra = GET_RA(regids);
rb = GET_RB(regids);
} else {
ra = REG_NONE;
rb = REG_NONE;
status = EXC_ADDR;
sim_log("Couldn't fetch at address 0x%x\n", valp);
}
valp++;
} else {
ra = REG_NONE;
rb = REG_NONE;
}
if (gen_need_valC()) {
if (get_word_val(mem, valp, &valc)) {
} else {
valc = 0;
status = EXC_ADDR;
sim_log("Couldn't fetch at address 0x%x\n", valp);
}
valp+=4;
} else {
valc = 0;
}
if (status == EXC_NONE && !gen_instr_valid()) {
status = EXC_INSTR;
}
sim_log("IF: Fetched %s at 0x%x. ra=%s, rb=%s, valC = 0x%x\n",
iname(HPACK(icode,ifun)), pc, reg_name(ra), reg_name(rb), valc);
if (status == EXC_NONE && icode == I_HALT) {
status = EXC_HALT;
}
srcA = gen_srcA();
if (srcA != REG_NONE) {
vala = get_reg_val(reg, srcA);
} else {
vala = 0;
}
srcB = gen_srcB();
if (srcB != REG_NONE) {
valb = get_reg_val(reg, srcB);
} else {
valb = 0;
}
destE = gen_dstE();
destM = gen_dstM();
aluA = gen_aluA();
aluB = gen_aluB();
alufun = gen_alufun();
vale = compute_alu(alufun, aluA, aluB);
cc_in = cc;
if (gen_set_cc())
cc_in = compute_cc(alufun, aluA, aluB);
bcond = (icode == I_JXX) && take_branch(cc, ifun);
mem_addr = gen_mem_addr();
mem_data = gen_mem_data();
if (status == EXC_NONE && gen_mem_read()) {
if (!get_word_val(mem, mem_addr, &valm)) {
sim_log("Couldn't read at address 0x%x\n", mem_addr);
return EXC_ADDR;
}
} else
valm = 0;
mem_write = status == EXC_NONE && gen_mem_write();
if (plusmode) {
prev_icode_in = icode;
prev_ifun_in = ifun;
prev_valc_in = valc;
prev_valm_in = valm;
prev_valp_in = valp;
prev_bcond_in = bcond;
} else {
/* Update PC */
if(gen_instr_next_ifun() == -1)
pc_in = gen_new_pc();
}
sim_report();
return status;
}