/*
* Description:
* Moves an instruction from the execution stage to common data bus (if possible)
* Inputs:
* current_cycle: the cycle we are at
* Returns:
* None
*/
void execute_To_CDB(int current_cycle) {
/* ECE552: YOUR CODE GOES HERE */
//First Check for completed store instructions that don't need access to CDB
//Check if CDB is free afterwards to look for oldest completed instruction
//Then check that the functional unit is allocated &&
//execute variable has been set &&
//current_cycle > tom_execute_cycle + LATENCY
// Get the oldest instruction that fits the criteria above and give it access to the CDB
/* ECE552 Assignment 3 - BEGIN CODE */
int i;
for(i = 0; i < FU_INT_SIZE; i++){
if(fuINT[i] &&
fuINT[i]->tom_execute_cycle != 0 &&
fuINT[i]->tom_cdb_cycle == 0){
if(current_cycle > (fuINT[i]->tom_execute_cycle + FU_INT_LATENCY)){
if(!WRITES_CDB(fuINT[i]->op)){
removeFromRS(fuINT[i]);
fuINT[i] = NULL;
}
}
}
}
if(!commonDataBus){ //YES CDB is free
instruction_t *oldest = NULL;
int i;
for(i = 0; i < FU_INT_SIZE; i++){
if(fuINT[i] &&
fuINT[i]->tom_execute_cycle != 0 &&
fuINT[i]->tom_cdb_cycle == 0){
if(current_cycle > (fuINT[i]->tom_execute_cycle + FU_INT_LATENCY)){
if(!oldest ||
fuINT[i]->index < oldest->index){
oldest = fuINT[i];
}
}
}
}
for(i = 0; i < FU_FP_SIZE; i++){
if(fuFP[i] &&
fuFP[i]->tom_execute_cycle != 0 &&
fuFP[i]->tom_cdb_cycle == 0 &&
current_cycle > (fuFP[i]->tom_execute_cycle + FU_FP_LATENCY)){
if(!oldest ||
fuFP[i]->index < oldest->index){
oldest = fuFP[i];
}
}
}
//We have a candidate for the CDB
//set the common data bus
//set it's FU to NULL
//set it's reservation station to NULL
if(oldest){
commonDataBus = oldest;
oldest->tom_cdb_cycle = current_cycle;
removeFromRS(oldest);
removeFromFU(oldest);
}
}
/* ECE552 Assignment 3 - END CODE */
}
/*
* Description:
* Moves an instruction from the execution stage to common data bus (if possible)
* Inputs:
* current_cycle: the cycle we are at
* Returns:
* None
*/
void execute_To_CDB(int current_cycle) {
/* ECE552 Assignment 4 - BEGIN CODE */
int i;
for (i = 0; i < FU_INT_SIZE; i++)
{
if (fuINT[i] != NULL && fuINT[i]->tom_execute_cycle + FU_INT_LATENCY <= current_cycle)
{
insn_struct* currentINT = reservINT;
insn_struct* prevINT = NULL;
while (currentINT != NULL)
{
if (fuINT[i] == currentINT->insn)
{
if (prevINT == NULL)
{
/* is the head of list */
if (WRITES_CDB(currentINT->insn->op))
{
commonDataBus = currentINT->insn;
commonDataBus->tom_cdb_cycle = current_cycle;
}
reservINT = currentINT->next;
currentINT->insn = NULL;
free(currentINT);
currentINT = NULL;
break;
}
else
{
if (WRITES_CDB(currentINT->insn->op))
{
commonDataBus = currentINT->insn;
commonDataBus->tom_cdb_cycle = current_cycle;
}
prevINT->next = currentINT->next;
currentINT->insn = NULL;
free(currentINT);
currentINT = NULL;
prevINT = NULL;
break;
}
}
}
}
}
for (i = 0; i < FU_FP_SIZE; i++)
{
if (fuFP[i] != NULL && fuFP[i]->tom_execute_cycle + FU_FP_LATENCY <= current_cycle)
{
insn_struct* currentFP = reservFP;
insn_struct* prevFP = NULL;
while (currentFP != NULL)
{
if (fuFP[i] == currentFP->insn)
{
if (prevFP == NULL)
{
/* is the head of list */
if (WRITES_CDB(currentFP->insn->op))
{
commonDataBus = currentFP->insn;
commonDataBus->tom_cdb_cycle = current_cycle;
}
reservFP = currentFP->next;
currentFP->insn = NULL;
free(currentFP);
currentFP = NULL;
break;
}
else
{
if (WRITES_CDB(currentFP->insn->op))
{
commonDataBus = currentFP->insn;
commonDataBus->tom_cdb_cycle = current_cycle;
}
prevFP->next = currentFP->next;
currentFP->insn = NULL;
free(currentFP);
currentFP = NULL;
prevFP = NULL;
break;
}
}
}
}
}
/* ECE552 Assignment 4 - END CODE */
}
