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//===-- HexagonHazardRecognizer.cpp - Hexagon Post RA Hazard Recognizer ---===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file defines the hazard recognizer for scheduling on Hexagon.
// Use a DFA based hazard recognizer.
//
//===----------------------------------------------------------------------===//
#include "HexagonHazardRecognizer.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
using namespace llvm;
#define DEBUG_TYPE "post-RA-sched"
void HexagonHazardRecognizer::Reset() {
LLVM_DEBUG(dbgs() << "Reset hazard recognizer\n");
Resources->clearResources();
PacketNum = 0;
UsesDotCur = nullptr;
DotCurPNum = -1;
UsesLoad = false;
PrefVectorStoreNew = nullptr;
RegDefs.clear();
}
ScheduleHazardRecognizer::HazardType
HexagonHazardRecognizer::getHazardType(SUnit *SU, int stalls) {
MachineInstr *MI = SU->getInstr();
if (!MI || TII->isZeroCost(MI->getOpcode()))
return NoHazard;
if (!Resources->canReserveResources(*MI)) {
LLVM_DEBUG(dbgs() << "*** Hazard in cycle " << PacketNum << ", " << *MI);
HazardType RetVal = Hazard;
if (isNewStore(*MI)) {
// The .new store version uses different resources so check if it
// causes a hazard.
MachineFunction *MF = MI->getParent()->getParent();
MachineInstr *NewMI =
MF->CreateMachineInstr(TII->get(TII->getDotNewOp(*MI)),
MI->getDebugLoc());
if (Resources->canReserveResources(*NewMI))
RetVal = NoHazard;
LLVM_DEBUG(dbgs() << "*** Try .new version? " << (RetVal == NoHazard)
<< "\n");
MF->deleteMachineInstr(NewMI);
}
return RetVal;
}
if (SU == UsesDotCur && DotCurPNum != (int)PacketNum) {
LLVM_DEBUG(dbgs() << "*** .cur Hazard in cycle " << PacketNum << ", "
<< *MI);
return Hazard;
}
return NoHazard;
}
void HexagonHazardRecognizer::AdvanceCycle() {
LLVM_DEBUG(dbgs() << "Advance cycle, clear state\n");
Resources->clearResources();
if (DotCurPNum != -1 && DotCurPNum != (int)PacketNum) {
UsesDotCur = nullptr;
DotCurPNum = -1;
}
UsesLoad = false;
PrefVectorStoreNew = nullptr;
PacketNum++;
RegDefs.clear();
}
/// Handle the cases when we prefer one instruction over another. Case 1 - we
/// prefer not to generate multiple loads in the packet to avoid a potential
/// bank conflict. Case 2 - if a packet contains a dot cur instruction, then we
/// prefer the instruction that can use the dot cur result. However, if the use
/// is not scheduled in the same packet, then prefer other instructions in the
/// subsequent packet. Case 3 - we prefer a vector store that can be converted
/// to a .new store. The packetizer will not generate the .new store if the
/// store doesn't have resources to fit in the packet (but the .new store may
/// have resources). We attempt to schedule the store as soon as possible to
/// help packetize the two instructions together.
bool HexagonHazardRecognizer::ShouldPreferAnother(SUnit *SU) {
if (PrefVectorStoreNew != nullptr && PrefVectorStoreNew != SU)
return true;
if (UsesLoad && SU->isInstr() && SU->getInstr()->mayLoad())
return true;
return UsesDotCur && ((SU == UsesDotCur) ^ (DotCurPNum == (int)PacketNum));
}
/// Return true if the instruction would be converted to a new value store when
/// packetized.
bool HexagonHazardRecognizer::isNewStore(MachineInstr &MI) {
if (!TII->mayBeNewStore(MI))
return false;
MachineOperand &MO = MI.getOperand(MI.getNumOperands() - 1);
return MO.isReg() && RegDefs.contains(MO.getReg());
}
void HexagonHazardRecognizer::EmitInstruction(SUnit *SU) {
MachineInstr *MI = SU->getInstr();
if (!MI)
return;
// Keep the set of definitions for each packet, which is used to determine
// if a .new can be used.
for (const MachineOperand &MO : MI->operands())
if (MO.isReg() && MO.isDef() && !MO.isImplicit())
RegDefs.insert(MO.getReg());
if (TII->isZeroCost(MI->getOpcode()))
return;
if (!Resources->canReserveResources(*MI) || isNewStore(*MI)) {
// It must be a .new store since other instructions must be able to be
// reserved at this point.
assert(TII->mayBeNewStore(*MI) && "Expecting .new store");
MachineFunction *MF = MI->getParent()->getParent();
MachineInstr *NewMI =
MF->CreateMachineInstr(TII->get(TII->getDotNewOp(*MI)),
MI->getDebugLoc());
if (Resources->canReserveResources(*NewMI))
Resources->reserveResources(*NewMI);
else
Resources->reserveResources(*MI);
MF->deleteMachineInstr(NewMI);
} else
Resources->reserveResources(*MI);
LLVM_DEBUG(dbgs() << " Add instruction " << *MI);
// When scheduling a dot cur instruction, check if there is an instruction
// that can use the dot cur in the same packet. If so, we'll attempt to
// schedule it before other instructions. We only do this if the load has a
// single zero-latency use.
if (TII->mayBeCurLoad(*MI))
for (auto &S : SU->Succs)
if (S.isAssignedRegDep() && S.getLatency() == 0 &&
S.getSUnit()->NumPredsLeft == 1) {
UsesDotCur = S.getSUnit();
DotCurPNum = PacketNum;
break;
}
if (SU == UsesDotCur) {
UsesDotCur = nullptr;
DotCurPNum = -1;
}
UsesLoad = MI->mayLoad();
if (TII->isHVXVec(*MI) && !MI->mayLoad() && !MI->mayStore())
for (auto &S : SU->Succs)
if (S.isAssignedRegDep() && S.getLatency() == 0 &&
TII->mayBeNewStore(*S.getSUnit()->getInstr()) &&
Resources->canReserveResources(*S.getSUnit()->getInstr())) {
PrefVectorStoreNew = S.getSUnit();
break;
}
}
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