void EX_stage()
{
if((EX_latch->op_valid) || (!ID_latch->op_valid))
{
/* Either MEM has not completed its work ==> pipeline stall
Or ID has not yet given any new op ==> No work to do */
return;
}
Op *op = ID_latch->op;
EX_cycles_completed++;
if((op->opcode > 0) && (op->opcode < NUM_OP_TYPE))
{
// This is a valid opcode
int oplatency = get_op_latency(op);
if(EX_cycles_completed != oplatency)
{
// Operation not completed. Still more work to do.
return;
}
}
EX_latch->op = op;
EX_latch->op_valid = true;
ID_latch->op_valid = false;
EX_cycles_completed = 0;
return;
}
void EX_stage()
{
/* you must complete the function */
static int ex_latency = 0;
if(ID_latch->op_valid==true)
{
if(EX_latch->stage_stall==false)
{
if(ex_latency==0)
ex_latency=get_op_latency(ID_latch->op); //check execution latency of op
ex_latency--;
if(ex_latency==0)
{
ID_latch->op_valid=false; //set op as invalid for previous stage since op is already transferred
ID_latch->stage_stall=false; //if stage stalled remove stall
EX_latch->op=ID_latch->op; //transfer pointer to next stage
EX_latch->op_valid=true; // set op as valid for the stage
}
else
ID_latch->stage_stall=true;
}
else
ID_latch->stage_stall=true;
}
}
void EX_stage()
{
/* The very first execution(for any instrn) in EX_stage would always match the 2nd condition.
If latency>1 for an instrn, then 1st condition is matched in subsequent cycles in EX stage(so decrement latency)
Instrn moves to EX latch when latency becomes 0 */
// If any memory stage stall=TRUE, make sure EX_latch valid bit is TRUE so that MEM_stage executes in next cycle.
if(ex_stall==TRUE)
{
Op *ex_op=ID_latch->op; // read from ID_latch
latency--;
if(latency==0)
{
ex_stall=FALSE;
EX_latch->op=ex_op;
EX_latch->op_valid=TRUE;
ID_latch->op_valid=FALSE;
}
return;
}
if(mem_latency_stall==FALSE && mshr_stall==FALSE && ex_stall==FALSE)
{
if(ID_latch->op_valid==TRUE)
{
Op *ex_op=ID_latch->op; // read from ID_latch
latency=get_op_latency(ex_op);
if(latency>1)
{
ex_stall=TRUE;
latency--;
return;
}
else // single cycle instruction, so pass it to EX latch
{
EX_latch->op=ex_op;
EX_latch->op_valid=TRUE;
ID_latch->op_valid=FALSE;
return;
}
}
}
}