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449e2cbd5e
The original change was pushed in main as commit f7a23ecece52. It was then reverted by commit a04f01bab2 because it caused linker failures on buildbots that don't build the AMDGPU target. -- Some instructions are not defined well enough within the target’s scheduling model for llvm-mca to be able to properly simulate its behaviour. The ideal solution to this situation is to modify the scheduling model, but that’s not always a viable strategy. Maybe other parts of the backend depend on that instruction being modelled the way that it is. Or maybe the instruction is quite complex and it’s difficult to fully capture its behaviour with tablegen. The CustomBehaviour class (which I will refer to as CB frequently) is designed to provide intuitive scaffolding for developers to implement the correct modelling for these instructions. More details are available in the original commit log message (f7a23ecece52). Differential Revision: https://reviews.llvm.org/D104149
94 lines
3.6 KiB
C++
94 lines
3.6 KiB
C++
//===---------------------------- Context.cpp -------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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/// \file
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///
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/// This file defines a class for holding ownership of various simulated
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/// hardware units. A Context also provides a utility routine for constructing
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/// a default out-of-order pipeline with fetch, dispatch, execute, and retire
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/// stages.
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/MCA/Context.h"
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#include "llvm/MCA/HardwareUnits/RegisterFile.h"
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#include "llvm/MCA/HardwareUnits/RetireControlUnit.h"
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#include "llvm/MCA/HardwareUnits/Scheduler.h"
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#include "llvm/MCA/Stages/DispatchStage.h"
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#include "llvm/MCA/Stages/EntryStage.h"
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#include "llvm/MCA/Stages/ExecuteStage.h"
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#include "llvm/MCA/Stages/InOrderIssueStage.h"
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#include "llvm/MCA/Stages/MicroOpQueueStage.h"
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#include "llvm/MCA/Stages/RetireStage.h"
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namespace llvm {
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namespace mca {
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std::unique_ptr<Pipeline>
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Context::createDefaultPipeline(const PipelineOptions &Opts, SourceMgr &SrcMgr,
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CustomBehaviour &CB) {
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const MCSchedModel &SM = STI.getSchedModel();
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if (!SM.isOutOfOrder())
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return createInOrderPipeline(Opts, SrcMgr, CB);
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// Create the hardware units defining the backend.
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auto RCU = std::make_unique<RetireControlUnit>(SM);
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auto PRF = std::make_unique<RegisterFile>(SM, MRI, Opts.RegisterFileSize);
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auto LSU = std::make_unique<LSUnit>(SM, Opts.LoadQueueSize,
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Opts.StoreQueueSize, Opts.AssumeNoAlias);
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auto HWS = std::make_unique<Scheduler>(SM, *LSU);
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// Create the pipeline stages.
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auto Fetch = std::make_unique<EntryStage>(SrcMgr);
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auto Dispatch =
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std::make_unique<DispatchStage>(STI, MRI, Opts.DispatchWidth, *RCU, *PRF);
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auto Execute =
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std::make_unique<ExecuteStage>(*HWS, Opts.EnableBottleneckAnalysis);
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auto Retire = std::make_unique<RetireStage>(*RCU, *PRF, *LSU);
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// Pass the ownership of all the hardware units to this Context.
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addHardwareUnit(std::move(RCU));
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addHardwareUnit(std::move(PRF));
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addHardwareUnit(std::move(LSU));
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addHardwareUnit(std::move(HWS));
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// Build the pipeline.
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auto StagePipeline = std::make_unique<Pipeline>();
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StagePipeline->appendStage(std::move(Fetch));
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if (Opts.MicroOpQueueSize)
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StagePipeline->appendStage(std::make_unique<MicroOpQueueStage>(
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Opts.MicroOpQueueSize, Opts.DecodersThroughput));
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StagePipeline->appendStage(std::move(Dispatch));
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StagePipeline->appendStage(std::move(Execute));
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StagePipeline->appendStage(std::move(Retire));
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return StagePipeline;
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}
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std::unique_ptr<Pipeline>
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Context::createInOrderPipeline(const PipelineOptions &Opts, SourceMgr &SrcMgr,
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CustomBehaviour &CB) {
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const MCSchedModel &SM = STI.getSchedModel();
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auto PRF = std::make_unique<RegisterFile>(SM, MRI, Opts.RegisterFileSize);
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// Create the pipeline stages.
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auto Entry = std::make_unique<EntryStage>(SrcMgr);
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auto InOrderIssue = std::make_unique<InOrderIssueStage>(STI, *PRF, CB);
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auto StagePipeline = std::make_unique<Pipeline>();
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// Pass the ownership of all the hardware units to this Context.
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addHardwareUnit(std::move(PRF));
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// Build the pipeline.
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StagePipeline->appendStage(std::move(Entry));
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StagePipeline->appendStage(std::move(InOrderIssue));
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return StagePipeline;
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}
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} // namespace mca
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} // namespace llvm
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