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// Todo: Probably add in support for scheduling events (more than one as
// well) on the case of the ROB being empty or full. Considering tracking
// free entries instead of insts in ROB. Differentiate between squashing
// all instructions after the instruction, and all instructions after *and*
// including that instruction.
#ifndef __CPU_BETA_CPU_ROB_HH__
#define __CPU_BETA_CPU_ROB_HH__
#include <utility>
#include <vector>
/**
* ROB class. Uses the instruction list that exists within the CPU to
* represent the ROB. This class doesn't contain that list, but instead
* a pointer to the CPU to get access to the list. The ROB, in this first
* implementation, is largely what drives squashing.
*/
template <class Impl>
class ROB
{
public:
//Typedefs from the Impl.
typedef typename Impl::FullCPU FullCPU;
typedef typename Impl::DynInstPtr DynInstPtr;
typedef std::pair<RegIndex, PhysRegIndex> UnmapInfo_t;
typedef typename list<DynInstPtr>::iterator InstIt_t;
public:
/** ROB constructor.
* @params _numEntries Number of entries in ROB.
* @params _squashWidth Number of instructions that can be squashed in a
* single cycle.
*/
ROB(unsigned _numEntries, unsigned _squashWidth);
/** Function to set the CPU pointer, necessary due to which object the ROB
* is created within.
* @params cpu_ptr Pointer to the implementation specific full CPU object.
*/
void setCPU(FullCPU *cpu_ptr);
/** Function to insert an instruction into the ROB. The parameter inst is
* not truly required, but is useful for checking correctness. Note
* that whatever calls this function must ensure that there is enough
* space within the ROB for the new instruction.
* @params inst The instruction being inserted into the ROB.
* @todo Remove the parameter once correctness is ensured.
*/
void insertInst(DynInstPtr &inst);
/** Returns pointer to the head instruction within the ROB. There is
* no guarantee as to the return value if the ROB is empty.
* @retval Pointer to the DynInst that is at the head of the ROB.
*/
DynInstPtr readHeadInst() { return cpu->instList.front(); }
DynInstPtr readTailInst() { return (*tail); }
void retireHead();
bool isHeadReady();
unsigned numFreeEntries();
bool isFull()
{ return numInstsInROB == numEntries; }
bool isEmpty()
{ return numInstsInROB == 0; }
void doSquash();
void squash(InstSeqNum squash_num);
uint64_t readHeadPC();
uint64_t readHeadNextPC();
InstSeqNum readHeadSeqNum();
uint64_t readTailPC();
InstSeqNum readTailSeqNum();
/** Checks if the ROB is still in the process of squashing instructions.
* @retval Whether or not the ROB is done squashing.
*/
bool isDoneSquashing() const { return doneSquashing; }
/** This is more of a debugging function than anything. Use
* numInstsInROB to get the instructions in the ROB unless you are
* double checking that variable.
*/
int countInsts();
private:
/** Pointer to the CPU. */
FullCPU *cpu;
/** Number of instructions in the ROB. */
unsigned numEntries;
/** Number of instructions that can be squashed in a single cycle. */
unsigned squashWidth;
/** Iterator pointing to the instruction which is the last instruction
* in the ROB. This may at times be invalid (ie when the ROB is empty),
* however it should never be incorrect.
*/
InstIt_t tail;
/** Iterator used for walking through the list of instructions when
* squashing. Used so that there is persistent state between cycles;
* when squashing, the instructions are marked as squashed but not
* immediately removed, meaning the tail iterator remains the same before
* and after a squash.
* This will always be set to cpu->instList.end() if it is invalid.
*/
InstIt_t squashIt;
/** Number of instructions in the ROB. */
int numInstsInROB;
/** The sequence number of the squashed instruction. */
InstSeqNum squashedSeqNum;
/** Is the ROB done squashing. */
bool doneSquashing;
};
#endif //__CPU_BETA_CPU_ROB_HH__
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