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llvm-mirror/lib/MCA/Context.cpp
Andrea Di Biagio 13160fb6a6 [MCA][LSUnit] Track loads and stores until retirement.
Before this patch, loads and stores were only tracked by their corresponding
queues in the LSUnit from dispatch until execute stage. In practice we should be
more conservative and assume that memory opcodes leave their queues at
retirement stage.

Basically, loads should leave the load queue only when they have completed and
delivered their data. We conservatively assume that a load is completed when it
is retired. Stores should be tracked by the store queue from dispatch until
retirement. In practice, stores can only leave the store queue if their data can
be written to the data cache.

This is mostly a mechanical change. With this patch, the retire stage notifies
the LSUnit when a memory instruction is retired. That would triggers the release
of LDQ/STQ entries.  The only visible change is in memory tests for the bdver2
model. That is because bdver2 is the only model that defines the load/store
queue size.

This patch partially addresses PR39830.

Differential Revision: https://reviews.llvm.org/D68266

llvm-svn: 374034
2019-10-08 10:46:01 +00:00

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2.7 KiB
C++

//===---------------------------- Context.cpp -------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file defines a class for holding ownership of various simulated
/// hardware units. A Context also provides a utility routine for constructing
/// a default out-of-order pipeline with fetch, dispatch, execute, and retire
/// stages.
///
//===----------------------------------------------------------------------===//
#include "llvm/MCA/Context.h"
#include "llvm/MCA/HardwareUnits/RegisterFile.h"
#include "llvm/MCA/HardwareUnits/RetireControlUnit.h"
#include "llvm/MCA/HardwareUnits/Scheduler.h"
#include "llvm/MCA/Stages/DispatchStage.h"
#include "llvm/MCA/Stages/EntryStage.h"
#include "llvm/MCA/Stages/ExecuteStage.h"
#include "llvm/MCA/Stages/MicroOpQueueStage.h"
#include "llvm/MCA/Stages/RetireStage.h"
namespace llvm {
namespace mca {
std::unique_ptr<Pipeline>
Context::createDefaultPipeline(const PipelineOptions &Opts, SourceMgr &SrcMgr) {
const MCSchedModel &SM = STI.getSchedModel();
// Create the hardware units defining the backend.
auto RCU = std::make_unique<RetireControlUnit>(SM);
auto PRF = std::make_unique<RegisterFile>(SM, MRI, Opts.RegisterFileSize);
auto LSU = std::make_unique<LSUnit>(SM, Opts.LoadQueueSize,
Opts.StoreQueueSize, Opts.AssumeNoAlias);
auto HWS = std::make_unique<Scheduler>(SM, *LSU);
// Create the pipeline stages.
auto Fetch = std::make_unique<EntryStage>(SrcMgr);
auto Dispatch = std::make_unique<DispatchStage>(STI, MRI, Opts.DispatchWidth,
*RCU, *PRF);
auto Execute =
std::make_unique<ExecuteStage>(*HWS, Opts.EnableBottleneckAnalysis);
auto Retire = std::make_unique<RetireStage>(*RCU, *PRF, *LSU);
// Pass the ownership of all the hardware units to this Context.
addHardwareUnit(std::move(RCU));
addHardwareUnit(std::move(PRF));
addHardwareUnit(std::move(LSU));
addHardwareUnit(std::move(HWS));
// Build the pipeline.
auto StagePipeline = std::make_unique<Pipeline>();
StagePipeline->appendStage(std::move(Fetch));
if (Opts.MicroOpQueueSize)
StagePipeline->appendStage(std::make_unique<MicroOpQueueStage>(
Opts.MicroOpQueueSize, Opts.DecodersThroughput));
StagePipeline->appendStage(std::move(Dispatch));
StagePipeline->appendStage(std::move(Execute));
StagePipeline->appendStage(std::move(Retire));
return StagePipeline;
}
} // namespace mca
} // namespace llvm