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-rw-r--r--cpu/o3/fetch.hh236
1 files changed, 203 insertions, 33 deletions
diff --git a/cpu/o3/fetch.hh b/cpu/o3/fetch.hh
index cc64800d9..f0f3f2745 100644
--- a/cpu/o3/fetch.hh
+++ b/cpu/o3/fetch.hh
@@ -26,11 +26,8 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
-// Todo: SMT fetch,
-// Add a way to get a stage's current status.
-
-#ifndef __CPU_O3_CPU_SIMPLE_FETCH_HH__
-#define __CPU_O3_CPU_SIMPLE_FETCH_HH__
+#ifndef __CPU_O3_FETCH_HH__
+#define __CPU_O3_FETCH_HH__
#include "base/statistics.hh"
#include "base/timebuf.hh"
@@ -39,13 +36,15 @@
#include "sim/eventq.hh"
/**
- * SimpleFetch class to fetch a single instruction each cycle. SimpleFetch
- * will stall if there's an Icache miss, but otherwise assumes a one cycle
- * Icache hit.
+ * DefaultFetch class handles both single threaded and SMT fetch. Its width is
+ * specified by the parameters; each cycle it tries to fetch that many
+ * instructions. It supports using a branch predictor to predict direction and
+ * targets.
+ * It supports the idling functionalitiy of the CPU by indicating to the CPU
+ * when it is active and inactive.
*/
-
template <class Impl>
-class SimpleFetch
+class DefaultFetch
{
public:
/** Typedefs from Impl. */
@@ -55,56 +54,125 @@ class SimpleFetch
typedef typename Impl::FullCPU FullCPU;
typedef typename Impl::Params Params;
+ /** Typedefs from the CPU policy. */
typedef typename CPUPol::BPredUnit BPredUnit;
typedef typename CPUPol::FetchStruct FetchStruct;
typedef typename CPUPol::TimeStruct TimeStruct;
/** Typedefs from ISA. */
typedef TheISA::MachInst MachInst;
+ typedef TheISA::ExtMachInst ExtMachInst;
public:
- enum Status {
+ /** Overall fetch status. Used to determine if the CPU can deschedule itsef
+ * due to a lack of activity.
+ */
+ enum FetchStatus {
+ Active,
+ Inactive
+ };
+
+ /** Individual thread status. */
+ enum ThreadStatus {
Running,
Idle,
Squashing,
Blocked,
+ Fetching,
+ TrapPending,
+ QuiescePending,
IcacheMissStall,
IcacheMissComplete
};
- // May eventually need statuses on a per thread basis.
- Status _status;
+ /** Fetching Policy, Add new policies here.*/
+ enum FetchPriority {
+ SingleThread,
+ RoundRobin,
+ Branch,
+ IQ,
+ LSQ
+ };
- bool stalled;
+ private:
+ /** Fetch status. */
+ FetchStatus _status;
+
+ /** Per-thread status. */
+ ThreadStatus fetchStatus[Impl::MaxThreads];
+
+ /** Fetch policy. */
+ FetchPriority fetchPolicy;
+
+ /** List that has the threads organized by priority. */
+ std::list<unsigned> priorityList;
public:
class CacheCompletionEvent : public Event
{
private:
- SimpleFetch *fetch;
+ MemReqPtr req;
+ /** Pointer to fetch. */
+ DefaultFetch *fetch;
+ /** Thread id. */
+// unsigned threadId;
public:
- CacheCompletionEvent(SimpleFetch *_fetch);
+ /** Constructs a cache completion event, which tells fetch when the
+ * cache miss is complete.
+ */
+ CacheCompletionEvent(MemReqPtr &_req, DefaultFetch *_fetch);
+ /** Processes cache completion event. */
virtual void process();
+ /** Returns the description of the cache completion event. */
virtual const char *description();
};
public:
- /** SimpleFetch constructor. */
- SimpleFetch(Params &params);
+ /** DefaultFetch constructor. */
+ DefaultFetch(Params *params);
+ /** Returns the name of fetch. */
+ std::string name() const;
+
+ /** Registers statistics. */
void regStats();
+ /** Sets CPU pointer. */
void setCPU(FullCPU *cpu_ptr);
+ /** Sets the main backwards communication time buffer pointer. */
void setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer);
+ /** Sets pointer to list of active threads. */
+ void setActiveThreads(std::list<unsigned> *at_ptr);
+
+ /** Sets pointer to time buffer used to communicate to the next stage. */
void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
- void processCacheCompletion();
+ /** Sets pointer to page table. */
+// void setPageTable(PageTable *pt_ptr);
+
+ /** Initialize stage. */
+ void initStage();
+
+ /** Processes cache completion event. */
+ void processCacheCompletion(MemReqPtr &req);
+
+ void wakeFromQuiesce();
private:
+ /** Changes the status of this stage to active, and indicates this to the
+ * CPU.
+ */
+ inline void switchToActive();
+
+ /** Changes the status of this stage to inactive, and indicates this to the
+ * CPU.
+ */
+ inline void switchToInactive();
+
/**
* Looks up in the branch predictor to see if the next PC should be
* either next PC+=MachInst or a branch target.
@@ -120,24 +188,54 @@ class SimpleFetch
* fault that happened. Puts the data into the class variable
* cacheData.
* @param fetch_PC The PC address that is being fetched from.
+ * @param ret_fault The fault reference that will be set to the result of
+ * the icache access.
+ * @param tid Thread id.
* @return Any fault that occured.
*/
- Fault fetchCacheLine(Addr fetch_PC);
+ bool fetchCacheLine(Addr fetch_PC, Fault &ret_fault, unsigned tid);
- inline void doSquash(const Addr &new_PC);
+ /** Squashes a specific thread and resets the PC. */
+ inline void doSquash(const Addr &new_PC, unsigned tid);
- void squashFromDecode(const Addr &new_PC, const InstSeqNum &seq_num);
+ /** Squashes a specific thread and resets the PC. Also tells the CPU to
+ * remove any instructions between fetch and decode that should be sqaushed.
+ */
+ void squashFromDecode(const Addr &new_PC, const InstSeqNum &seq_num,
+ unsigned tid);
+
+ /** Checks if a thread is stalled. */
+ bool checkStall(unsigned tid) const;
+
+ /** Updates overall fetch stage status; to be called at the end of each
+ * cycle. */
+ FetchStatus updateFetchStatus();
public:
- // Figure out PC vs next PC and how it should be updated
- void squash(const Addr &new_PC);
+ /** Squashes a specific thread and resets the PC. Also tells the CPU to
+ * remove any instructions that are not in the ROB. The source of this
+ * squash should be the commit stage.
+ */
+ void squash(const Addr &new_PC, unsigned tid);
+ /** Ticks the fetch stage, processing all inputs signals and fetching
+ * as many instructions as possible.
+ */
void tick();
- void fetch();
+ /** Checks all input signals and updates the status as necessary.
+ * @return: Returns if the status has changed due to input signals.
+ */
+ bool checkSignalsAndUpdate(unsigned tid);
- // Align an address (typically a PC) to the start of an I-cache block.
- // We fold in the PISA 64- to 32-bit conversion here as well.
+ /** Does the actual fetching of instructions and passing them on to the
+ * next stage.
+ * @param status_change fetch() sets this variable if there was a status
+ * change (ie switching to IcacheMissStall).
+ */
+ void fetch(bool &status_change);
+
+ /** Align a PC to the start of an I-cache block. */
Addr icacheBlockAlignPC(Addr addr)
{
addr = TheISA::realPCToFetchPC(addr);
@@ -145,6 +243,22 @@ class SimpleFetch
}
private:
+ /** Returns the appropriate thread to fetch, given the fetch policy. */
+ int getFetchingThread(FetchPriority &fetch_priority);
+
+ /** Returns the appropriate thread to fetch using a round robin policy. */
+ int roundRobin();
+
+ /** Returns the appropriate thread to fetch using the IQ count policy. */
+ int iqCount();
+
+ /** Returns the appropriate thread to fetch using the LSQ count policy. */
+ int lsqCount();
+
+ /** Returns the appropriate thread to fetch using the branch count policy. */
+ int branchCount();
+
+ private:
/** Pointer to the FullCPU. */
FullCPU *cpu;
@@ -176,8 +290,31 @@ class SimpleFetch
/** BPredUnit. */
BPredUnit branchPred;
+ Addr PC[Impl::MaxThreads];
+
+ Addr nextPC[Impl::MaxThreads];
+
/** Memory request used to access cache. */
- MemReqPtr memReq;
+ MemReqPtr memReq[Impl::MaxThreads];
+
+ /** Variable that tracks if fetch has written to the time buffer this
+ * cycle. Used to tell CPU if there is activity this cycle.
+ */
+ bool wroteToTimeBuffer;
+
+ /** Tracks how many instructions has been fetched this cycle. */
+ int numInst;
+
+ /** Source of possible stalls. */
+ struct Stalls {
+ bool decode;
+ bool rename;
+ bool iew;
+ bool commit;
+ };
+
+ /** Tracks which stages are telling fetch to stall. */
+ Stalls stalls[Impl::MaxThreads];
/** Decode to fetch delay, in ticks. */
unsigned decodeToFetchDelay;
@@ -201,23 +338,56 @@ class SimpleFetch
Addr cacheBlkMask;
/** The cache line being fetched. */
- uint8_t *cacheData;
+ uint8_t *cacheData[Impl::MaxThreads];
/** Size of instructions. */
int instSize;
/** Icache stall statistics. */
- Counter lastIcacheStall;
+ Counter lastIcacheStall[Impl::MaxThreads];
+
+ /** List of Active Threads */
+ std::list<unsigned> *activeThreads;
+
+ /** Number of threads. */
+ unsigned numThreads;
+ /** Number of threads that are actively fetching. */
+ unsigned numFetchingThreads;
+
+ /** Thread ID being fetched. */
+ int threadFetched;
+
+ bool interruptPending;
+
+#if !FULL_SYSTEM
+ /** Page table pointer. */
+// PageTable *pTable;
+#endif
+
+ // @todo: Consider making these vectors and tracking on a per thread basis.
+ /** Stat for total number of cycles stalled due to an icache miss. */
Stats::Scalar<> icacheStallCycles;
+ /** Stat for total number of fetched instructions. */
Stats::Scalar<> fetchedInsts;
+ /** Stat for total number of predicted branches. */
Stats::Scalar<> predictedBranches;
+ /** Stat for total number of cycles spent fetching. */
Stats::Scalar<> fetchCycles;
+ /** Stat for total number of cycles spent squashing. */
Stats::Scalar<> fetchSquashCycles;
+ /** Stat for total number of cycles spent blocked due to other stages in
+ * the pipeline.
+ */
+ Stats::Scalar<> fetchIdleCycles;
Stats::Scalar<> fetchBlockedCycles;
+ /** Stat for total number of fetched cache lines. */
Stats::Scalar<> fetchedCacheLines;
-
- Stats::Distribution<> fetch_nisn_dist;
+ /** Distribution of number of instructions fetched each cycle. */
+ Stats::Distribution<> fetchNisnDist;
+ Stats::Formula idleRate;
+ Stats::Formula branchRate;
+ Stats::Formula fetchRate;
};
-#endif //__CPU_O3_CPU_SIMPLE_FETCH_HH__
+#endif //__CPU_O3_FETCH_HH__
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-13 16:53:08 +0000