0e20666db3
This is likely to be a regressigion introduced by my last refactoring of the LSUnit (commit 5578ec32f9c4f). Before this patch, the "CurrentStoreBarrierGroupID" index was not correctly reset on store barrier executions. This was leading to unexpected crashes like the one reported as PR48024.
253 lines
8.9 KiB
C++
253 lines
8.9 KiB
C++
//===----------------------- LSUnit.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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/// A Load-Store Unit for the llvm-mca tool.
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///
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//===----------------------------------------------------------------------===//
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#include "llvm/MCA/HardwareUnits/LSUnit.h"
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#include "llvm/MCA/Instruction.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#define DEBUG_TYPE "llvm-mca"
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namespace llvm {
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namespace mca {
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LSUnitBase::LSUnitBase(const MCSchedModel &SM, unsigned LQ, unsigned SQ,
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bool AssumeNoAlias)
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: LQSize(LQ), SQSize(SQ), UsedLQEntries(0), UsedSQEntries(0),
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NoAlias(AssumeNoAlias), NextGroupID(1) {
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if (SM.hasExtraProcessorInfo()) {
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const MCExtraProcessorInfo &EPI = SM.getExtraProcessorInfo();
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if (!LQSize && EPI.LoadQueueID) {
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const MCProcResourceDesc &LdQDesc = *SM.getProcResource(EPI.LoadQueueID);
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LQSize = std::max(0, LdQDesc.BufferSize);
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}
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if (!SQSize && EPI.StoreQueueID) {
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const MCProcResourceDesc &StQDesc = *SM.getProcResource(EPI.StoreQueueID);
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SQSize = std::max(0, StQDesc.BufferSize);
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}
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}
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}
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LSUnitBase::~LSUnitBase() {}
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void LSUnitBase::cycleEvent() {
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for (const std::pair<unsigned, std::unique_ptr<MemoryGroup>> &G : Groups)
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G.second->cycleEvent();
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}
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#ifndef NDEBUG
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void LSUnitBase::dump() const {
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dbgs() << "[LSUnit] LQ_Size = " << getLoadQueueSize() << '\n';
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dbgs() << "[LSUnit] SQ_Size = " << getStoreQueueSize() << '\n';
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dbgs() << "[LSUnit] NextLQSlotIdx = " << getUsedLQEntries() << '\n';
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dbgs() << "[LSUnit] NextSQSlotIdx = " << getUsedSQEntries() << '\n';
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dbgs() << "\n";
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for (const auto &GroupIt : Groups) {
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const MemoryGroup &Group = *GroupIt.second;
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dbgs() << "[LSUnit] Group (" << GroupIt.first << "): "
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<< "[ #Preds = " << Group.getNumPredecessors()
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<< ", #GIssued = " << Group.getNumExecutingPredecessors()
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<< ", #GExecuted = " << Group.getNumExecutedPredecessors()
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<< ", #Inst = " << Group.getNumInstructions()
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<< ", #IIssued = " << Group.getNumExecuting()
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<< ", #IExecuted = " << Group.getNumExecuted() << '\n';
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}
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}
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#endif
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unsigned LSUnit::dispatch(const InstRef &IR) {
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const InstrDesc &Desc = IR.getInstruction()->getDesc();
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unsigned IsMemBarrier = Desc.HasSideEffects;
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assert((Desc.MayLoad || Desc.MayStore) && "Not a memory operation!");
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if (Desc.MayLoad)
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acquireLQSlot();
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if (Desc.MayStore)
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acquireSQSlot();
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if (Desc.MayStore) {
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unsigned NewGID = createMemoryGroup();
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MemoryGroup &NewGroup = getGroup(NewGID);
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NewGroup.addInstruction();
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// A store may not pass a previous load or load barrier.
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unsigned ImmediateLoadDominator =
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std::max(CurrentLoadGroupID, CurrentLoadBarrierGroupID);
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if (ImmediateLoadDominator) {
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MemoryGroup &IDom = getGroup(ImmediateLoadDominator);
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LLVM_DEBUG(dbgs() << "[LSUnit]: GROUP DEP: (" << ImmediateLoadDominator
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<< ") --> (" << NewGID << ")\n");
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IDom.addSuccessor(&NewGroup, !assumeNoAlias());
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}
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// A store may not pass a previous store barrier.
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if (CurrentStoreBarrierGroupID) {
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MemoryGroup &StoreGroup = getGroup(CurrentStoreBarrierGroupID);
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LLVM_DEBUG(dbgs() << "[LSUnit]: GROUP DEP: ("
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<< CurrentStoreBarrierGroupID
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<< ") --> (" << NewGID << ")\n");
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StoreGroup.addSuccessor(&NewGroup, true);
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}
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// A store may not pass a previous store.
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if (CurrentStoreGroupID &&
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(CurrentStoreGroupID != CurrentStoreBarrierGroupID)) {
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MemoryGroup &StoreGroup = getGroup(CurrentStoreGroupID);
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LLVM_DEBUG(dbgs() << "[LSUnit]: GROUP DEP: (" << CurrentStoreGroupID
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<< ") --> (" << NewGID << ")\n");
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StoreGroup.addSuccessor(&NewGroup, !assumeNoAlias());
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}
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CurrentStoreGroupID = NewGID;
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if (IsMemBarrier)
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CurrentStoreBarrierGroupID = NewGID;
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if (Desc.MayLoad) {
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CurrentLoadGroupID = NewGID;
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if (IsMemBarrier)
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CurrentLoadBarrierGroupID = NewGID;
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}
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return NewGID;
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}
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assert(Desc.MayLoad && "Expected a load!");
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unsigned ImmediateLoadDominator =
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std::max(CurrentLoadGroupID, CurrentLoadBarrierGroupID);
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// A new load group is created if we are in one of the following situations:
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// 1) This is a load barrier (by construction, a load barrier is always
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// assigned to a different memory group).
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// 2) There is no load in flight (by construction we always keep loads and
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// stores into separate memory groups).
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// 3) There is a load barrier in flight. This load depends on it.
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// 4) There is an intervening store between the last load dispatched to the
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// LSU and this load. We always create a new group even if this load
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// does not alias the last dispatched store.
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// 5) There is no intervening store and there is an active load group.
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// However that group has already started execution, so we cannot add
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// this load to it.
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bool ShouldCreateANewGroup =
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IsMemBarrier || !ImmediateLoadDominator ||
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CurrentLoadBarrierGroupID == ImmediateLoadDominator ||
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ImmediateLoadDominator <= CurrentStoreGroupID ||
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getGroup(ImmediateLoadDominator).isExecuting();
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if (ShouldCreateANewGroup) {
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unsigned NewGID = createMemoryGroup();
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MemoryGroup &NewGroup = getGroup(NewGID);
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NewGroup.addInstruction();
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// A load may not pass a previous store or store barrier
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// unless flag 'NoAlias' is set.
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if (!assumeNoAlias() && CurrentStoreGroupID) {
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MemoryGroup &StoreGroup = getGroup(CurrentStoreGroupID);
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LLVM_DEBUG(dbgs() << "[LSUnit]: GROUP DEP: (" << CurrentStoreGroupID
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<< ") --> (" << NewGID << ")\n");
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StoreGroup.addSuccessor(&NewGroup, true);
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}
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// A load barrier may not pass a previous load or load barrier.
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if (IsMemBarrier) {
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if (ImmediateLoadDominator) {
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MemoryGroup &LoadGroup = getGroup(ImmediateLoadDominator);
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LLVM_DEBUG(dbgs() << "[LSUnit]: GROUP DEP: ("
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<< ImmediateLoadDominator
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<< ") --> (" << NewGID << ")\n");
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LoadGroup.addSuccessor(&NewGroup, true);
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}
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} else {
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// A younger load cannot pass a older load barrier.
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if (CurrentLoadBarrierGroupID) {
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MemoryGroup &LoadGroup = getGroup(CurrentLoadBarrierGroupID);
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LLVM_DEBUG(dbgs() << "[LSUnit]: GROUP DEP: ("
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<< CurrentLoadBarrierGroupID
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<< ") --> (" << NewGID << ")\n");
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LoadGroup.addSuccessor(&NewGroup, true);
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}
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}
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CurrentLoadGroupID = NewGID;
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if (IsMemBarrier)
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CurrentLoadBarrierGroupID = NewGID;
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return NewGID;
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}
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// A load may pass a previous load.
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MemoryGroup &Group = getGroup(CurrentLoadGroupID);
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Group.addInstruction();
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return CurrentLoadGroupID;
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}
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LSUnit::Status LSUnit::isAvailable(const InstRef &IR) const {
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const InstrDesc &Desc = IR.getInstruction()->getDesc();
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if (Desc.MayLoad && isLQFull())
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return LSUnit::LSU_LQUEUE_FULL;
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if (Desc.MayStore && isSQFull())
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return LSUnit::LSU_SQUEUE_FULL;
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return LSUnit::LSU_AVAILABLE;
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}
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void LSUnitBase::onInstructionExecuted(const InstRef &IR) {
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unsigned GroupID = IR.getInstruction()->getLSUTokenID();
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auto It = Groups.find(GroupID);
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assert(It != Groups.end() && "Instruction not dispatched to the LS unit");
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It->second->onInstructionExecuted();
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if (It->second->isExecuted())
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Groups.erase(It);
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}
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void LSUnitBase::onInstructionRetired(const InstRef &IR) {
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const InstrDesc &Desc = IR.getInstruction()->getDesc();
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bool IsALoad = Desc.MayLoad;
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bool IsAStore = Desc.MayStore;
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assert((IsALoad || IsAStore) && "Expected a memory operation!");
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if (IsALoad) {
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releaseLQSlot();
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LLVM_DEBUG(dbgs() << "[LSUnit]: Instruction idx=" << IR.getSourceIndex()
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<< " has been removed from the load queue.\n");
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}
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if (IsAStore) {
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releaseSQSlot();
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LLVM_DEBUG(dbgs() << "[LSUnit]: Instruction idx=" << IR.getSourceIndex()
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<< " has been removed from the store queue.\n");
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}
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}
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void LSUnit::onInstructionExecuted(const InstRef &IR) {
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const Instruction &IS = *IR.getInstruction();
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if (!IS.isMemOp())
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return;
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LSUnitBase::onInstructionExecuted(IR);
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unsigned GroupID = IS.getLSUTokenID();
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if (!isValidGroupID(GroupID)) {
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if (GroupID == CurrentLoadGroupID)
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CurrentLoadGroupID = 0;
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if (GroupID == CurrentStoreGroupID)
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CurrentStoreGroupID = 0;
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if (GroupID == CurrentLoadBarrierGroupID)
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CurrentLoadBarrierGroupID = 0;
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if (GroupID == CurrentStoreBarrierGroupID)
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CurrentStoreBarrierGroupID = 0;
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}
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}
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} // namespace mca
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} // namespace llvm
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