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//===--------------------- Backend.h ----------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file implements an OoO backend for the llvm-mca tool.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_TOOLS_LLVM_MCA_BACKEND_H
#define LLVM_TOOLS_LLVM_MCA_BACKEND_H
#include "Scheduler.h"
#include "Stage.h"
#include "llvm/ADT/SmallVector.h"
namespace mca {
class HWEventListener;
class HWInstructionEvent;
class HWStallEvent;
/// An out of order backend for a specific subtarget.
///
/// It emulates an out-of-order execution of instructions. Instructions are
/// fetched from a MCInst sequence managed by an initial 'Fetch' stage.
/// Instructions are firstly fetched, then dispatched to the schedulers, and
/// then executed.
///
/// This class tracks the lifetime of an instruction from the moment where
/// it gets dispatched to the schedulers, to the moment where it finishes
/// executing and register writes are architecturally committed.
/// In particular, it monitors changes in the state of every instruction
/// in flight.
///
/// Instructions are executed in a loop of iterations. The number of iterations
/// is defined by the SourceMgr object, which is managed by the initial stage
/// of the instruction pipeline.
///
/// The Backend entry point is method 'run()' which executes cycles in a loop
/// until there are new instructions to dispatch, and not every instruction
/// has been retired.
///
/// Internally, the Backend collects statistical information in the form of
/// histograms. For example, it tracks how the dispatch group size changes
/// over time.
class Backend {
/// An ordered list of stages that define this backend's instruction pipeline.
llvm::SmallVector<std::unique_ptr<Stage>, 8> Stages;
std::set<HWEventListener *> Listeners;
unsigned Cycles;
bool executeStages(InstRef &IR);
void postExecuteStages(const InstRef &IR);
bool hasWorkToProcess();
void runCycle(unsigned Cycle);
public:
Backend(unsigned DispatchWidth = 0, unsigned RegisterFileSize = 0,
unsigned LoadQueueSize = 0, unsigned StoreQueueSize = 0,
bool AssumeNoAlias = false)
: Cycles(0) {}
void appendStage(std::unique_ptr<Stage> S) { Stages.push_back(std::move(S)); }
void run();
void addEventListener(HWEventListener *Listener);
void notifyCycleBegin(unsigned Cycle);
void notifyInstructionEvent(const HWInstructionEvent &Event);
void notifyStallEvent(const HWStallEvent &Event);
void notifyResourceAvailable(const ResourceRef &RR);
void notifyReservedBuffers(llvm::ArrayRef<unsigned> Buffers);
void notifyReleasedBuffers(llvm::ArrayRef<unsigned> Buffers);
void notifyCycleEnd(unsigned Cycle);
};
} // namespace mca
#endif
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