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      1 //===--------------------- Pipeline.h ---------------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 /// \file
     10 ///
     11 /// This file implements an ordered container of stages that simulate the
     12 /// pipeline of a hardware backend.
     13 ///
     14 //===----------------------------------------------------------------------===//
     15 
     16 #ifndef LLVM_TOOLS_LLVM_MCA_PIPELINE_H
     17 #define LLVM_TOOLS_LLVM_MCA_PIPELINE_H
     18 
     19 #include "Scheduler.h"
     20 #include "Stage.h"
     21 #include "llvm/ADT/SmallVector.h"
     22 
     23 namespace mca {
     24 
     25 class HWEventListener;
     26 class HWInstructionEvent;
     27 class HWStallEvent;
     28 
     29 /// A pipeline for a specific subtarget.
     30 ///
     31 /// It emulates an out-of-order execution of instructions. Instructions are
     32 /// fetched from a MCInst sequence managed by an initial 'Fetch' stage.
     33 /// Instructions are firstly fetched, then dispatched to the schedulers, and
     34 /// then executed.
     35 ///
     36 /// This class tracks the lifetime of an instruction from the moment where
     37 /// it gets dispatched to the schedulers, to the moment where it finishes
     38 /// executing and register writes are architecturally committed.
     39 /// In particular, it monitors changes in the state of every instruction
     40 /// in flight.
     41 ///
     42 /// Instructions are executed in a loop of iterations. The number of iterations
     43 /// is defined by the SourceMgr object, which is managed by the initial stage
     44 /// of the instruction pipeline.
     45 ///
     46 /// The Pipeline entry point is method 'run()' which executes cycles in a loop
     47 /// until there are new instructions to dispatch, and not every instruction
     48 /// has been retired.
     49 ///
     50 /// Internally, the Pipeline collects statistical information in the form of
     51 /// histograms. For example, it tracks how the dispatch group size changes
     52 /// over time.
     53 class Pipeline {
     54   Pipeline(const Pipeline &P) = delete;
     55   Pipeline &operator=(const Pipeline &P) = delete;
     56 
     57   /// An ordered list of stages that define this instruction pipeline.
     58   llvm::SmallVector<std::unique_ptr<Stage>, 8> Stages;
     59   std::set<HWEventListener *> Listeners;
     60   unsigned Cycles;
     61 
     62   void preExecuteStages();
     63   bool executeStages(InstRef &IR);
     64   void postExecuteStages();
     65   void runCycle();
     66 
     67   bool hasWorkToProcess();
     68   void notifyCycleBegin();
     69   void notifyCycleEnd();
     70 
     71 public:
     72   Pipeline() : Cycles(0) {}
     73   void appendStage(std::unique_ptr<Stage> S) { Stages.push_back(std::move(S)); }
     74   void run();
     75   void addEventListener(HWEventListener *Listener);
     76 };
     77 } // namespace mca
     78 
     79 #endif // LLVM_TOOLS_LLVM_MCA_PIPELINE_H
     80