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// Todo:
// Add a couple of the branch fields to DynInst. Figure out where DynInst
// should try to compute the target of a PC-relative branch. Try to avoid
// having so many returns within the code.
// Fix up squashing too, as it's too
// dependent upon the iew stage continually telling it to squash.
#ifndef __CPU_BETA_CPU_SIMPLE_DECODE_HH__
#define __CPU_BETA_CPU_SIMPLE_DECODE_HH__
#include <queue>
#include "base/statistics.hh"
#include "base/timebuf.hh"
template<class Impl>
class SimpleDecode
{
private:
// Typedefs from the Impl.
typedef typename Impl::ISA ISA;
typedef typename Impl::FullCPU FullCPU;
typedef typename Impl::DynInstPtr DynInstPtr;
typedef typename Impl::Params Params;
typedef typename Impl::CPUPol CPUPol;
// Typedefs from the CPU policy.
typedef typename CPUPol::FetchStruct FetchStruct;
typedef typename CPUPol::DecodeStruct DecodeStruct;
typedef typename CPUPol::TimeStruct TimeStruct;
// Typedefs from the ISA.
typedef typename ISA::Addr Addr;
public:
// The only time decode will become blocked is if dispatch becomes
// blocked, which means IQ or ROB is probably full.
enum Status {
Running,
Idle,
Squashing,
Blocked,
Unblocking
};
private:
// May eventually need statuses on a per thread basis.
Status _status;
public:
SimpleDecode(Params ¶ms);
void regStats();
void setCPU(FullCPU *cpu_ptr);
void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr);
void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
void tick();
void decode();
private:
inline bool fetchInstsValid();
void block();
inline void unblock();
void squash(DynInstPtr &inst);
public:
// Might want to make squash a friend function.
void squash();
private:
// Interfaces to objects outside of decode.
/** CPU interface. */
FullCPU *cpu;
/** Time buffer interface. */
TimeBuffer<TimeStruct> *timeBuffer;
/** Wire to get rename's output from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromRename;
/** Wire to get iew's information from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromIEW;
/** Wire to get commit's information from backwards time buffer. */
typename TimeBuffer<TimeStruct>::wire fromCommit;
/** Wire to write information heading to previous stages. */
// Might not be the best name as not only fetch will read it.
typename TimeBuffer<TimeStruct>::wire toFetch;
/** Decode instruction queue. */
TimeBuffer<DecodeStruct> *decodeQueue;
/** Wire used to write any information heading to rename. */
typename TimeBuffer<DecodeStruct>::wire toRename;
/** Fetch instruction queue interface. */
TimeBuffer<FetchStruct> *fetchQueue;
/** Wire to get fetch's output from fetch queue. */
typename TimeBuffer<FetchStruct>::wire fromFetch;
/** Skid buffer between fetch and decode. */
std::queue<FetchStruct> skidBuffer;
//Consider making these unsigned to avoid any confusion.
/** Rename to decode delay, in ticks. */
unsigned renameToDecodeDelay;
/** IEW to decode delay, in ticks. */
unsigned iewToDecodeDelay;
/** Commit to decode delay, in ticks. */
unsigned commitToDecodeDelay;
/** Fetch to decode delay, in ticks. */
unsigned fetchToDecodeDelay;
/** The width of decode, in instructions. */
unsigned decodeWidth;
/** The instruction that decode is currently on. It needs to have
* persistent state so that when a stall occurs in the middle of a
* group of instructions, it can restart at the proper instruction.
*/
unsigned numInst;
Stats::Scalar<> decodeIdleCycles;
Stats::Scalar<> decodeBlockedCycles;
Stats::Scalar<> decodeUnblockCycles;
Stats::Scalar<> decodeSquashCycles;
Stats::Scalar<> decodeBranchMispred;
Stats::Scalar<> decodeControlMispred;
Stats::Scalar<> decodeDecodedInsts;
Stats::Scalar<> decodeSquashedInsts;
};
#endif // __CPU_BETA_CPU_SIMPLE_DECODE_HH__
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