LLVM  12.0.0git
Pipeline.h
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1 //===--------------------- Pipeline.h ---------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 /// \file
9 ///
10 /// This file implements an ordered container of stages that simulate the
11 /// pipeline of a hardware backend.
12 ///
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_MCA_PIPELINE_H
16 #define LLVM_MCA_PIPELINE_H
17 
18 #include "llvm/MCA/Stages/Stage.h"
19 #include "llvm/Support/Error.h"
20 
21 namespace llvm {
22 namespace mca {
23 
24 class HWEventListener;
25 
26 /// A pipeline for a specific subtarget.
27 ///
28 /// It emulates an out-of-order execution of instructions. Instructions are
29 /// fetched from a MCInst sequence managed by an initial 'Fetch' stage.
30 /// Instructions are firstly fetched, then dispatched to the schedulers, and
31 /// then executed.
32 ///
33 /// This class tracks the lifetime of an instruction from the moment where
34 /// it gets dispatched to the schedulers, to the moment where it finishes
35 /// executing and register writes are architecturally committed.
36 /// In particular, it monitors changes in the state of every instruction
37 /// in flight.
38 ///
39 /// Instructions are executed in a loop of iterations. The number of iterations
40 /// is defined by the SourceMgr object, which is managed by the initial stage
41 /// of the instruction pipeline.
42 ///
43 /// The Pipeline entry point is method 'run()' which executes cycles in a loop
44 /// until there are new instructions to dispatch, and not every instruction
45 /// has been retired.
46 ///
47 /// Internally, the Pipeline collects statistical information in the form of
48 /// histograms. For example, it tracks how the dispatch group size changes
49 /// over time.
50 class Pipeline {
51  Pipeline(const Pipeline &P) = delete;
52  Pipeline &operator=(const Pipeline &P) = delete;
53 
54  /// An ordered list of stages that define this instruction pipeline.
56  std::set<HWEventListener *> Listeners;
57  unsigned Cycles;
58 
59  Error runCycle();
60  bool hasWorkToProcess();
61  void notifyCycleBegin();
62  void notifyCycleEnd();
63 
64 public:
65  Pipeline() : Cycles(0) {}
66  void appendStage(std::unique_ptr<Stage> S);
67 
68  /// Returns the total number of simulated cycles.
70 
71  void addEventListener(HWEventListener *Listener);
72 };
73 } // namespace mca
74 } // namespace llvm
75 
76 #endif // LLVM_MCA_PIPELINE_H
void addEventListener(HWEventListener *Listener)
Definition: Pipeline.cpp:24
A pipeline for a specific subtarget.
Definition: Pipeline.h:50
This class represents lattice values for constants.
Definition: AllocatorList.h:23
Tagged union holding either a T or a Error.
Definition: APFloat.h:42
#define P(N)
This file defines a stage.
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:883
Expected< unsigned > run()
Returns the total number of simulated cycles.
Definition: Pipeline.cpp:37
void appendStage(std::unique_ptr< Stage > S)
Definition: Pipeline.cpp:75
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157