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llvm-project/llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp

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//===----- HexagonPacketizer.cpp - vliw packetizer ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements a simple VLIW packetizer using DFA. The packetizer works on
// machine basic blocks. For each instruction I in BB, the packetizer consults
// the DFA to see if machine resources are available to execute I. If so, the
// packetizer checks if I depends on any instruction J in the current packet.
// If no dependency is found, I is added to current packet and machine resource
// is marked as taken. If any dependency is found, a target API call is made to
// prune the dependence.
//
//===----------------------------------------------------------------------===//
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "HexagonTargetMachine.h"
#include "HexagonVLIWPacketizer.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
using namespace llvm;
#define DEBUG_TYPE "packets"
static cl::opt<bool> DisablePacketizer("disable-packetizer", cl::Hidden,
cl::ZeroOrMore, cl::init(false),
cl::desc("Disable Hexagon packetizer pass"));
static cl::opt<bool> PacketizeVolatiles("hexagon-packetize-volatiles",
cl::ZeroOrMore, cl::Hidden, cl::init(true),
cl::desc("Allow non-solo packetization of volatile memory references"));
static cl::opt<bool> EnableGenAllInsnClass("enable-gen-insn", cl::init(false),
cl::Hidden, cl::ZeroOrMore, cl::desc("Generate all instruction with TC"));
static cl::opt<bool> DisableVecDblNVStores("disable-vecdbl-nv-stores",
cl::init(false), cl::Hidden, cl::ZeroOrMore,
cl::desc("Disable vector double new-value-stores"));
extern cl::opt<bool> ScheduleInlineAsm;
namespace llvm {
FunctionPass *createHexagonPacketizer();
void initializeHexagonPacketizerPass(PassRegistry&);
}
namespace {
class HexagonPacketizer : public MachineFunctionPass {
public:
static char ID;
HexagonPacketizer() : MachineFunctionPass(ID) {
initializeHexagonPacketizerPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<AAResultsWrapperPass>();
AU.addRequired<MachineBranchProbabilityInfo>();
AU.addRequired<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
MachineFunctionPass::getAnalysisUsage(AU);
}
const char *getPassName() const override {
return "Hexagon Packetizer";
}
bool runOnMachineFunction(MachineFunction &Fn) override;
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().set(
MachineFunctionProperties::Property::AllVRegsAllocated);
}
private:
const HexagonInstrInfo *HII;
const HexagonRegisterInfo *HRI;
};
char HexagonPacketizer::ID = 0;
}
INITIALIZE_PASS_BEGIN(HexagonPacketizer, "packets", "Hexagon Packetizer",
false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_END(HexagonPacketizer, "packets", "Hexagon Packetizer",
false, false)
HexagonPacketizerList::HexagonPacketizerList(MachineFunction &MF,
MachineLoopInfo &MLI, AliasAnalysis *AA,
const MachineBranchProbabilityInfo *MBPI)
: VLIWPacketizerList(MF, MLI, AA), MBPI(MBPI), MLI(&MLI) {
HII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
HRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
addMutation(make_unique<HexagonSubtarget::HexagonDAGMutation>());
}
// Check if FirstI modifies a register that SecondI reads.
static bool hasWriteToReadDep(const MachineInstr &FirstI,
const MachineInstr &SecondI,
const TargetRegisterInfo *TRI) {
for (auto &MO : FirstI.operands()) {
if (!MO.isReg() || !MO.isDef())
continue;
unsigned R = MO.getReg();
if (SecondI.readsRegister(R, TRI))
return true;
}
return false;
}
static MachineBasicBlock::iterator moveInstrOut(MachineInstr &MI,
MachineBasicBlock::iterator BundleIt, bool Before) {
MachineBasicBlock::instr_iterator InsertPt;
if (Before)
InsertPt = BundleIt.getInstrIterator();
else
InsertPt = std::next(BundleIt).getInstrIterator();
MachineBasicBlock &B = *MI.getParent();
// The instruction should at least be bundled with the preceding instruction
// (there will always be one, i.e. BUNDLE, if nothing else).
assert(MI.isBundledWithPred());
if (MI.isBundledWithSucc()) {
MI.clearFlag(MachineInstr::BundledSucc);
MI.clearFlag(MachineInstr::BundledPred);
} else {
// If it's not bundled with the successor (i.e. it is the last one
// in the bundle), then we can simply unbundle it from the predecessor,
// which will take care of updating the predecessor's flag.
MI.unbundleFromPred();
}
B.splice(InsertPt, &B, MI.getIterator());
// Get the size of the bundle without asserting.
MachineBasicBlock::const_instr_iterator I = BundleIt.getInstrIterator();
MachineBasicBlock::const_instr_iterator E = B.instr_end();
unsigned Size = 0;
for (++I; I != E && I->isBundledWithPred(); ++I)
++Size;
// If there are still two or more instructions, then there is nothing
// else to be done.
if (Size > 1)
return BundleIt;
// Otherwise, extract the single instruction out and delete the bundle.
MachineBasicBlock::iterator NextIt = std::next(BundleIt);
MachineInstr &SingleI = *BundleIt->getNextNode();
SingleI.unbundleFromPred();
assert(!SingleI.isBundledWithSucc());
BundleIt->eraseFromParent();
return NextIt;
}
bool HexagonPacketizer::runOnMachineFunction(MachineFunction &MF) {
if (DisablePacketizer || skipFunction(*MF.getFunction()))
return false;
HII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
HRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
auto &MLI = getAnalysis<MachineLoopInfo>();
auto *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
auto *MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
if (EnableGenAllInsnClass)
HII->genAllInsnTimingClasses(MF);
// Instantiate the packetizer.
HexagonPacketizerList Packetizer(MF, MLI, AA, MBPI);
// DFA state table should not be empty.
assert(Packetizer.getResourceTracker() && "Empty DFA table!");
//
// Loop over all basic blocks and remove KILL pseudo-instructions
// These instructions confuse the dependence analysis. Consider:
// D0 = ... (Insn 0)
// R0 = KILL R0, D0 (Insn 1)
// R0 = ... (Insn 2)
// Here, Insn 1 will result in the dependence graph not emitting an output
// dependence between Insn 0 and Insn 2. This can lead to incorrect
// packetization
//
for (auto &MB : MF) {
auto End = MB.end();
auto MI = MB.begin();
while (MI != End) {
auto NextI = std::next(MI);
if (MI->isKill()) {
MB.erase(MI);
End = MB.end();
}
MI = NextI;
}
}
// Loop over all of the basic blocks.
for (auto &MB : MF) {
auto Begin = MB.begin(), End = MB.end();
while (Begin != End) {
// First the first non-boundary starting from the end of the last
// scheduling region.
MachineBasicBlock::iterator RB = Begin;
while (RB != End && HII->isSchedulingBoundary(*RB, &MB, MF))
++RB;
// First the first boundary starting from the beginning of the new
// region.
MachineBasicBlock::iterator RE = RB;
while (RE != End && !HII->isSchedulingBoundary(*RE, &MB, MF))
++RE;
// Add the scheduling boundary if it's not block end.
if (RE != End)
++RE;
// If RB == End, then RE == End.
if (RB != End)
Packetizer.PacketizeMIs(&MB, RB, RE);
Begin = RE;
}
}
Packetizer.unpacketizeSoloInstrs(MF);
return true;
}
// Reserve resources for a constant extender. Trigger an assertion if the
// reservation fails.
void HexagonPacketizerList::reserveResourcesForConstExt() {
if (!tryAllocateResourcesForConstExt(true))
llvm_unreachable("Resources not available");
}
bool HexagonPacketizerList::canReserveResourcesForConstExt() {
return tryAllocateResourcesForConstExt(false);
}
// Allocate resources (i.e. 4 bytes) for constant extender. If succeeded,
// return true, otherwise, return false.
bool HexagonPacketizerList::tryAllocateResourcesForConstExt(bool Reserve) {
auto *ExtMI = MF.CreateMachineInstr(HII->get(Hexagon::A4_ext), DebugLoc());
bool Avail = ResourceTracker->canReserveResources(*ExtMI);
if (Reserve && Avail)
ResourceTracker->reserveResources(*ExtMI);
MF.DeleteMachineInstr(ExtMI);
return Avail;
}
bool HexagonPacketizerList::isCallDependent(const MachineInstr &MI,
SDep::Kind DepType, unsigned DepReg) {
// Check for LR dependence.
if (DepReg == HRI->getRARegister())
return true;
if (HII->isDeallocRet(MI))
if (DepReg == HRI->getFrameRegister() || DepReg == HRI->getStackRegister())
return true;
// Check if this is a predicate dependence.
const TargetRegisterClass* RC = HRI->getMinimalPhysRegClass(DepReg);
if (RC == &Hexagon::PredRegsRegClass)
return true;
// Assumes that the first operand of the CALLr is the function address.
if (HII->isIndirectCall(MI) && (DepType == SDep::Data)) {
MachineOperand MO = MI.getOperand(0);
if (MO.isReg() && MO.isUse() && (MO.getReg() == DepReg))
return true;
}
return false;
}
static bool isRegDependence(const SDep::Kind DepType) {
return DepType == SDep::Data || DepType == SDep::Anti ||
DepType == SDep::Output;
}
static bool isDirectJump(const MachineInstr &MI) {
return MI.getOpcode() == Hexagon::J2_jump;
}
static bool isSchedBarrier(const MachineInstr &MI) {
switch (MI.getOpcode()) {
case Hexagon::Y2_barrier:
return true;
}
return false;
}
static bool isControlFlow(const MachineInstr &MI) {
return MI.getDesc().isTerminator() || MI.getDesc().isCall();
}
/// Returns true if the instruction modifies a callee-saved register.
static bool doesModifyCalleeSavedReg(const MachineInstr &MI,
const TargetRegisterInfo *TRI) {
const MachineFunction &MF = *MI.getParent()->getParent();
for (auto *CSR = TRI->getCalleeSavedRegs(&MF); CSR && *CSR; ++CSR)
if (MI.modifiesRegister(*CSR, TRI))
return true;
return false;
}
// Returns true if an instruction can be promoted to .new predicate or
// new-value store.
bool HexagonPacketizerList::isNewifiable(const MachineInstr &MI,
const TargetRegisterClass *NewRC) {
// Vector stores can be predicated, and can be new-value stores, but
// they cannot be predicated on a .new predicate value.
if (NewRC == &Hexagon::PredRegsRegClass)
if (HII->isV60VectorInstruction(MI) && MI.mayStore())
return false;
return HII->isCondInst(MI) || HII->isJumpR(MI) || HII->mayBeNewStore(MI);
}
// Promote an instructiont to its .cur form.
// At this time, we have already made a call to canPromoteToDotCur and made
// sure that it can *indeed* be promoted.
bool HexagonPacketizerList::promoteToDotCur(MachineInstr &MI,
SDep::Kind DepType, MachineBasicBlock::iterator &MII,
const TargetRegisterClass* RC) {
assert(DepType == SDep::Data);
int CurOpcode = HII->getDotCurOp(MI);
MI.setDesc(HII->get(CurOpcode));
return true;
}
void HexagonPacketizerList::cleanUpDotCur() {
MachineInstr *MI = nullptr;
for (auto BI : CurrentPacketMIs) {
DEBUG(dbgs() << "Cleanup packet has "; BI->dump(););
if (BI->getOpcode() == Hexagon::V6_vL32b_cur_ai) {
MI = BI;
continue;
}
if (MI) {
for (auto &MO : BI->operands())
if (MO.isReg() && MO.getReg() == MI->getOperand(0).getReg())
return;
}
}
if (!MI)
return;
// We did not find a use of the CUR, so de-cur it.
MI->setDesc(HII->get(Hexagon::V6_vL32b_ai));
DEBUG(dbgs() << "Demoted CUR "; MI->dump(););
}
// Check to see if an instruction can be dot cur.
bool HexagonPacketizerList::canPromoteToDotCur(const MachineInstr &MI,
const SUnit *PacketSU, unsigned DepReg, MachineBasicBlock::iterator &MII,
const TargetRegisterClass *RC) {
if (!HII->isV60VectorInstruction(MI))
return false;
if (!HII->isV60VectorInstruction(*MII))
return false;
// Already a dot new instruction.
if (HII->isDotCurInst(MI) && !HII->mayBeCurLoad(MI))
return false;
if (!HII->mayBeCurLoad(MI))
return false;
// The "cur value" cannot come from inline asm.
if (PacketSU->getInstr()->isInlineAsm())
return false;
// Make sure candidate instruction uses cur.
DEBUG(dbgs() << "Can we DOT Cur Vector MI\n";
MI.dump();
dbgs() << "in packet\n";);
MachineInstr &MJ = *MII;
DEBUG({
dbgs() << "Checking CUR against ";
MJ.dump();
});
unsigned DestReg = MI.getOperand(0).getReg();
bool FoundMatch = false;
for (auto &MO : MJ.operands())
if (MO.isReg() && MO.getReg() == DestReg)
FoundMatch = true;
if (!FoundMatch)
return false;
// Check for existing uses of a vector register within the packet which
// would be affected by converting a vector load into .cur formt.
for (auto BI : CurrentPacketMIs) {
DEBUG(dbgs() << "packet has "; BI->dump(););
if (BI->readsRegister(DepReg, MF.getSubtarget().getRegisterInfo()))
return false;
}
DEBUG(dbgs() << "Can Dot CUR MI\n"; MI.dump(););
// We can convert the opcode into a .cur.
return true;
}
// Promote an instruction to its .new form. At this time, we have already
// made a call to canPromoteToDotNew and made sure that it can *indeed* be
// promoted.
bool HexagonPacketizerList::promoteToDotNew(MachineInstr &MI,
SDep::Kind DepType, MachineBasicBlock::iterator &MII,
const TargetRegisterClass* RC) {
assert (DepType == SDep::Data);
int NewOpcode;
if (RC == &Hexagon::PredRegsRegClass)
NewOpcode = HII->getDotNewPredOp(MI, MBPI);
else
NewOpcode = HII->getDotNewOp(MI);
MI.setDesc(HII->get(NewOpcode));
return true;
}
bool HexagonPacketizerList::demoteToDotOld(MachineInstr &MI) {
int NewOpcode = HII->getDotOldOp(MI.getOpcode());
MI.setDesc(HII->get(NewOpcode));
return true;
}
bool HexagonPacketizerList::useCallersSP(MachineInstr &MI) {
unsigned Opc = MI.getOpcode();
switch (Opc) {
case Hexagon::S2_storerd_io:
case Hexagon::S2_storeri_io:
case Hexagon::S2_storerh_io:
case Hexagon::S2_storerb_io:
break;
default:
llvm_unreachable("Unexpected instruction");
}
unsigned FrameSize = MF.getFrameInfo().getStackSize();
MachineOperand &Off = MI.getOperand(1);
int64_t NewOff = Off.getImm() - (FrameSize + HEXAGON_LRFP_SIZE);
if (HII->isValidOffset(Opc, NewOff)) {
Off.setImm(NewOff);
return true;
}
return false;
}
void HexagonPacketizerList::useCalleesSP(MachineInstr &MI) {
unsigned Opc = MI.getOpcode();
switch (Opc) {
case Hexagon::S2_storerd_io:
case Hexagon::S2_storeri_io:
case Hexagon::S2_storerh_io:
case Hexagon::S2_storerb_io:
break;
default:
llvm_unreachable("Unexpected instruction");
}
unsigned FrameSize = MF.getFrameInfo().getStackSize();
MachineOperand &Off = MI.getOperand(1);
Off.setImm(Off.getImm() + FrameSize + HEXAGON_LRFP_SIZE);
}
enum PredicateKind {
PK_False,
PK_True,
PK_Unknown
};
/// Returns true if an instruction is predicated on p0 and false if it's
/// predicated on !p0.
static PredicateKind getPredicateSense(const MachineInstr &MI,
const HexagonInstrInfo *HII) {
if (!HII->isPredicated(MI))
return PK_Unknown;
if (HII->isPredicatedTrue(MI))
return PK_True;
return PK_False;
}
static const MachineOperand &getPostIncrementOperand(const MachineInstr &MI,
const HexagonInstrInfo *HII) {
assert(HII->isPostIncrement(MI) && "Not a post increment operation.");
#ifndef NDEBUG
// Post Increment means duplicates. Use dense map to find duplicates in the
// list. Caution: Densemap initializes with the minimum of 64 buckets,
// whereas there are at most 5 operands in the post increment.
DenseSet<unsigned> DefRegsSet;
for (auto &MO : MI.operands())
if (MO.isReg() && MO.isDef())
DefRegsSet.insert(MO.getReg());
for (auto &MO : MI.operands())
if (MO.isReg() && MO.isUse() && DefRegsSet.count(MO.getReg()))
return MO;
#else
if (MI.mayLoad()) {
const MachineOperand &Op1 = MI.getOperand(1);
// The 2nd operand is always the post increment operand in load.
assert(Op1.isReg() && "Post increment operand has be to a register.");
return Op1;
}
if (MI.getDesc().mayStore()) {
const MachineOperand &Op0 = MI.getOperand(0);
// The 1st operand is always the post increment operand in store.
assert(Op0.isReg() && "Post increment operand has be to a register.");
return Op0;
}
#endif
// we should never come here.
llvm_unreachable("mayLoad or mayStore not set for Post Increment operation");
}
// Get the value being stored.
static const MachineOperand& getStoreValueOperand(const MachineInstr &MI) {
// value being stored is always the last operand.
return MI.getOperand(MI.getNumOperands()-1);
}
static bool isLoadAbsSet(const MachineInstr &MI) {
unsigned Opc = MI.getOpcode();
switch (Opc) {
case Hexagon::L4_loadrd_ap:
case Hexagon::L4_loadrb_ap:
case Hexagon::L4_loadrh_ap:
case Hexagon::L4_loadrub_ap:
case Hexagon::L4_loadruh_ap:
case Hexagon::L4_loadri_ap:
return true;
}
return false;
}
static const MachineOperand &getAbsSetOperand(const MachineInstr &MI) {
assert(isLoadAbsSet(MI));
return MI.getOperand(1);
}
// Can be new value store?
// Following restrictions are to be respected in convert a store into
// a new value store.
// 1. If an instruction uses auto-increment, its address register cannot
// be a new-value register. Arch Spec 5.4.2.1
// 2. If an instruction uses absolute-set addressing mode, its address
// register cannot be a new-value register. Arch Spec 5.4.2.1.
// 3. If an instruction produces a 64-bit result, its registers cannot be used
// as new-value registers. Arch Spec 5.4.2.2.
// 4. If the instruction that sets the new-value register is conditional, then
// the instruction that uses the new-value register must also be conditional,
// and both must always have their predicates evaluate identically.
// Arch Spec 5.4.2.3.
// 5. There is an implied restriction that a packet cannot have another store,
// if there is a new value store in the packet. Corollary: if there is
// already a store in a packet, there can not be a new value store.
// Arch Spec: 3.4.4.2
bool HexagonPacketizerList::canPromoteToNewValueStore(const MachineInstr &MI,
const MachineInstr &PacketMI, unsigned DepReg) {
// Make sure we are looking at the store, that can be promoted.
if (!HII->mayBeNewStore(MI))
return false;
// Make sure there is dependency and can be new value'd.
const MachineOperand &Val = getStoreValueOperand(MI);
if (Val.isReg() && Val.getReg() != DepReg)
return false;
const MCInstrDesc& MCID = PacketMI.getDesc();
// First operand is always the result.
const TargetRegisterClass *PacketRC = HII->getRegClass(MCID, 0, HRI, MF);
// Double regs can not feed into new value store: PRM section: 5.4.2.2.
if (PacketRC == &Hexagon::DoubleRegsRegClass)
return false;
// New-value stores are of class NV (slot 0), dual stores require class ST
// in slot 0 (PRM 5.5).
for (auto I : CurrentPacketMIs) {
SUnit *PacketSU = MIToSUnit.find(I)->second;
if (PacketSU->getInstr()->mayStore())
return false;
}
// Make sure it's NOT the post increment register that we are going to
// new value.
if (HII->isPostIncrement(MI) &&
getPostIncrementOperand(MI, HII).getReg() == DepReg) {
return false;
}
if (HII->isPostIncrement(PacketMI) && PacketMI.mayLoad() &&
getPostIncrementOperand(PacketMI, HII).getReg() == DepReg) {
// If source is post_inc, or absolute-set addressing, it can not feed
// into new value store
// r3 = memw(r2++#4)
// memw(r30 + #-1404) = r2.new -> can not be new value store
// arch spec section: 5.4.2.1.
return false;
}
if (isLoadAbsSet(PacketMI) && getAbsSetOperand(PacketMI).getReg() == DepReg)
return false;
// If the source that feeds the store is predicated, new value store must
// also be predicated.
if (HII->isPredicated(PacketMI)) {
if (!HII->isPredicated(MI))
return false;
// Check to make sure that they both will have their predicates
// evaluate identically.
unsigned predRegNumSrc = 0;
unsigned predRegNumDst = 0;
const TargetRegisterClass* predRegClass = nullptr;
// Get predicate register used in the source instruction.
for (auto &MO : PacketMI.operands()) {
if (!MO.isReg())
continue;
predRegNumSrc = MO.getReg();
predRegClass = HRI->getMinimalPhysRegClass(predRegNumSrc);
if (predRegClass == &Hexagon::PredRegsRegClass)
break;
}
assert((predRegClass == &Hexagon::PredRegsRegClass) &&
"predicate register not found in a predicated PacketMI instruction");
// Get predicate register used in new-value store instruction.
for (auto &MO : MI.operands()) {
if (!MO.isReg())
continue;
predRegNumDst = MO.getReg();
predRegClass = HRI->getMinimalPhysRegClass(predRegNumDst);
if (predRegClass == &Hexagon::PredRegsRegClass)
break;
}
assert((predRegClass == &Hexagon::PredRegsRegClass) &&
"predicate register not found in a predicated MI instruction");
// New-value register producer and user (store) need to satisfy these
// constraints:
// 1) Both instructions should be predicated on the same register.
// 2) If producer of the new-value register is .new predicated then store
// should also be .new predicated and if producer is not .new predicated
// then store should not be .new predicated.
// 3) Both new-value register producer and user should have same predicate
// sense, i.e, either both should be negated or both should be non-negated.
if (predRegNumDst != predRegNumSrc ||
HII->isDotNewInst(PacketMI) != HII->isDotNewInst(MI) ||
getPredicateSense(MI, HII) != getPredicateSense(PacketMI, HII))
return false;
}
// Make sure that other than the new-value register no other store instruction
// register has been modified in the same packet. Predicate registers can be
// modified by they should not be modified between the producer and the store
// instruction as it will make them both conditional on different values.
// We already know this to be true for all the instructions before and
// including PacketMI. Howerver, we need to perform the check for the
// remaining instructions in the packet.
unsigned StartCheck = 0;
for (auto I : CurrentPacketMIs) {
SUnit *TempSU = MIToSUnit.find(I)->second;
MachineInstr &TempMI = *TempSU->getInstr();
// Following condition is true for all the instructions until PacketMI is
// reached (StartCheck is set to 0 before the for loop).
// StartCheck flag is 1 for all the instructions after PacketMI.
if (&TempMI != &PacketMI && !StartCheck) // Start processing only after
continue; // encountering PacketMI.
StartCheck = 1;
if (&TempMI == &PacketMI) // We don't want to check PacketMI for dependence.
continue;
for (auto &MO : MI.operands())
if (MO.isReg() && TempSU->getInstr()->modifiesRegister(MO.getReg(), HRI))
return false;
}
// Make sure that for non-POST_INC stores:
// 1. The only use of reg is DepReg and no other registers.
// This handles V4 base+index registers.
// The following store can not be dot new.
// Eg. r0 = add(r0, #3)
// memw(r1+r0<<#2) = r0
if (!HII->isPostIncrement(MI)) {
for (unsigned opNum = 0; opNum < MI.getNumOperands()-1; opNum++) {
const MachineOperand &MO = MI.getOperand(opNum);
if (MO.isReg() && MO.getReg() == DepReg)
return false;
}
}
// If data definition is because of implicit definition of the register,
// do not newify the store. Eg.
// %R9<def> = ZXTH %R12, %D6<imp-use>, %R12<imp-def>
// S2_storerh_io %R8, 2, %R12<kill>; mem:ST2[%scevgep343]
for (auto &MO : PacketMI.operands()) {
if (!MO.isReg() || !MO.isDef() || !MO.isImplicit())
continue;
unsigned R = MO.getReg();
if (R == DepReg || HRI->isSuperRegister(DepReg, R))
return false;
}
// Handle imp-use of super reg case. There is a target independent side
// change that should prevent this situation but I am handling it for
// just-in-case. For example, we cannot newify R2 in the following case:
// %R3<def> = A2_tfrsi 0;
// S2_storeri_io %R0<kill>, 0, %R2<kill>, %D1<imp-use,kill>;
for (auto &MO : MI.operands()) {
if (MO.isReg() && MO.isUse() && MO.isImplicit() && MO.getReg() == DepReg)
return false;
}
// Can be dot new store.
return true;
}
// Can this MI to promoted to either new value store or new value jump.
bool HexagonPacketizerList::canPromoteToNewValue(const MachineInstr &MI,
const SUnit *PacketSU, unsigned DepReg,
MachineBasicBlock::iterator &MII) {
if (!HII->mayBeNewStore(MI))
return false;
// Check to see the store can be new value'ed.
MachineInstr &PacketMI = *PacketSU->getInstr();
if (canPromoteToNewValueStore(MI, PacketMI, DepReg))
return true;
// Check to see the compare/jump can be new value'ed.
// This is done as a pass on its own. Don't need to check it here.
return false;
}
static bool isImplicitDependency(const MachineInstr &I, unsigned DepReg) {
for (auto &MO : I.operands())
if (MO.isReg() && MO.isDef() && (MO.getReg() == DepReg) && MO.isImplicit())
return true;
return false;
}
// Check to see if an instruction can be dot new
// There are three kinds.
// 1. dot new on predicate - V2/V3/V4
// 2. dot new on stores NV/ST - V4
// 3. dot new on jump NV/J - V4 -- This is generated in a pass.
bool HexagonPacketizerList::canPromoteToDotNew(const MachineInstr &MI,
const SUnit *PacketSU, unsigned DepReg, MachineBasicBlock::iterator &MII,
const TargetRegisterClass* RC) {
// Already a dot new instruction.
if (HII->isDotNewInst(MI) && !HII->mayBeNewStore(MI))
return false;
if (!isNewifiable(MI, RC))
return false;
const MachineInstr &PI = *PacketSU->getInstr();
// The "new value" cannot come from inline asm.
if (PI.isInlineAsm())
return false;
// IMPLICIT_DEFs won't materialize as real instructions, so .new makes no
// sense.
if (PI.isImplicitDef())
return false;
// If dependency is trough an implicitly defined register, we should not
// newify the use.
if (isImplicitDependency(PI, DepReg))
return false;
const MCInstrDesc& MCID = PI.getDesc();
const TargetRegisterClass *VecRC = HII->getRegClass(MCID, 0, HRI, MF);
if (DisableVecDblNVStores && VecRC == &Hexagon::VecDblRegsRegClass)
return false;
// predicate .new
if (RC == &Hexagon::PredRegsRegClass)
if (HII->isCondInst(MI) || HII->isJumpR(MI))
return HII->predCanBeUsedAsDotNew(PI, DepReg);
if (RC != &Hexagon::PredRegsRegClass && !HII->mayBeNewStore(MI))
return false;
// Create a dot new machine instruction to see if resources can be
// allocated. If not, bail out now.
int NewOpcode = HII->getDotNewOp(MI);
const MCInstrDesc &D = HII->get(NewOpcode);
MachineInstr *NewMI = MF.CreateMachineInstr(D, DebugLoc());
bool ResourcesAvailable = ResourceTracker->canReserveResources(*NewMI);
MF.DeleteMachineInstr(NewMI);
if (!ResourcesAvailable)
return false;
// New Value Store only. New Value Jump generated as a separate pass.
if (!canPromoteToNewValue(MI, PacketSU, DepReg, MII))
return false;
return true;
}
// Go through the packet instructions and search for an anti dependency between
// them and DepReg from MI. Consider this case:
// Trying to add
// a) %R1<def> = TFRI_cdNotPt %P3, 2
// to this packet:
// {
// b) %P0<def> = C2_or %P3<kill>, %P0<kill>
// c) %P3<def> = C2_tfrrp %R23
// d) %R1<def> = C2_cmovenewit %P3, 4
// }
// The P3 from a) and d) will be complements after
// a)'s P3 is converted to .new form
// Anti-dep between c) and b) is irrelevant for this case
bool HexagonPacketizerList::restrictingDepExistInPacket(MachineInstr &MI,
unsigned DepReg) {
SUnit *PacketSUDep = MIToSUnit.find(&MI)->second;
for (auto I : CurrentPacketMIs) {
// We only care for dependencies to predicated instructions
if (!HII->isPredicated(*I))
continue;
// Scheduling Unit for current insn in the packet
SUnit *PacketSU = MIToSUnit.find(I)->second;
// Look at dependencies between current members of the packet and
// predicate defining instruction MI. Make sure that dependency is
// on the exact register we care about.
if (PacketSU->isSucc(PacketSUDep)) {
for (unsigned i = 0; i < PacketSU->Succs.size(); ++i) {
auto &Dep = PacketSU->Succs[i];
if (Dep.getSUnit() == PacketSUDep && Dep.getKind() == SDep::Anti &&
Dep.getReg() == DepReg)
return true;
}
}
}
return false;
}
/// Gets the predicate register of a predicated instruction.
static unsigned getPredicatedRegister(MachineInstr &MI,
const HexagonInstrInfo *QII) {
/// We use the following rule: The first predicate register that is a use is
/// the predicate register of a predicated instruction.
assert(QII->isPredicated(MI) && "Must be predicated instruction");
for (auto &Op : MI.operands()) {
if (Op.isReg() && Op.getReg() && Op.isUse() &&
Hexagon::PredRegsRegClass.contains(Op.getReg()))
return Op.getReg();
}
llvm_unreachable("Unknown instruction operand layout");
return 0;
}
// Given two predicated instructions, this function detects whether
// the predicates are complements.
bool HexagonPacketizerList::arePredicatesComplements(MachineInstr &MI1,
MachineInstr &MI2) {
// If we don't know the predicate sense of the instructions bail out early, we
// need it later.
if (getPredicateSense(MI1, HII) == PK_Unknown ||
getPredicateSense(MI2, HII) == PK_Unknown)
return false;
// Scheduling unit for candidate.
SUnit *SU = MIToSUnit[&MI1];
// One corner case deals with the following scenario:
// Trying to add
// a) %R24<def> = A2_tfrt %P0, %R25
// to this packet:
// {
// b) %R25<def> = A2_tfrf %P0, %R24
// c) %P0<def> = C2_cmpeqi %R26, 1
// }
//
// On general check a) and b) are complements, but presence of c) will
// convert a) to .new form, and then it is not a complement.
// We attempt to detect it by analyzing existing dependencies in the packet.
// Analyze relationships between all existing members of the packet.
// Look for Anti dependecy on the same predicate reg as used in the
// candidate.
for (auto I : CurrentPacketMIs) {
// Scheduling Unit for current insn in the packet.
SUnit *PacketSU = MIToSUnit.find(I)->second;
// If this instruction in the packet is succeeded by the candidate...
if (PacketSU->isSucc(SU)) {
for (unsigned i = 0; i < PacketSU->Succs.size(); ++i) {
auto Dep = PacketSU->Succs[i];
// The corner case exist when there is true data dependency between
// candidate and one of current packet members, this dep is on
// predicate reg, and there already exist anti dep on the same pred in
// the packet.
if (Dep.getSUnit() == SU && Dep.getKind() == SDep::Data &&
Hexagon::PredRegsRegClass.contains(Dep.getReg())) {
// Here I know that I is predicate setting instruction with true
// data dep to candidate on the register we care about - c) in the
// above example. Now I need to see if there is an anti dependency
// from c) to any other instruction in the same packet on the pred
// reg of interest.
if (restrictingDepExistInPacket(*I, Dep.getReg()))
return false;
}
}
}
}
// If the above case does not apply, check regular complement condition.
// Check that the predicate register is the same and that the predicate
// sense is different We also need to differentiate .old vs. .new: !p0
// is not complementary to p0.new.
unsigned PReg1 = getPredicatedRegister(MI1, HII);
unsigned PReg2 = getPredicatedRegister(MI2, HII);
return PReg1 == PReg2 &&
Hexagon::PredRegsRegClass.contains(PReg1) &&
Hexagon::PredRegsRegClass.contains(PReg2) &&
getPredicateSense(MI1, HII) != getPredicateSense(MI2, HII) &&
HII->isDotNewInst(MI1) == HII->isDotNewInst(MI2);
}
// Initialize packetizer flags.
void HexagonPacketizerList::initPacketizerState() {
Dependence = false;
PromotedToDotNew = false;
GlueToNewValueJump = false;
GlueAllocframeStore = false;
FoundSequentialDependence = false;
}
// Ignore bundling of pseudo instructions.
bool HexagonPacketizerList::ignorePseudoInstruction(const MachineInstr &MI,
const MachineBasicBlock *) {
if (MI.isDebugValue())
return true;
if (MI.isCFIInstruction())
return false;
// We must print out inline assembly.
if (MI.isInlineAsm())
return false;
if (MI.isImplicitDef())
return false;
// We check if MI has any functional units mapped to it. If it doesn't,
// we ignore the instruction.
const MCInstrDesc& TID = MI.getDesc();
auto *IS = ResourceTracker->getInstrItins()->beginStage(TID.getSchedClass());
unsigned FuncUnits = IS->getUnits();
return !FuncUnits;
}
bool HexagonPacketizerList::isSoloInstruction(const MachineInstr &MI) {
if (MI.isEHLabel() || MI.isCFIInstruction())
return true;
// Consider inline asm to not be a solo instruction by default.
// Inline asm will be put in a packet temporarily, but then it will be
// removed, and placed outside of the packet (before or after, depending
// on dependencies). This is to reduce the impact of inline asm as a
// "packet splitting" instruction.
if (MI.isInlineAsm() && !ScheduleInlineAsm)
return true;
// From Hexagon V4 Programmer's Reference Manual 3.4.4 Grouping constraints:
// trap, pause, barrier, icinva, isync, and syncht are solo instructions.
// They must not be grouped with other instructions in a packet.
if (isSchedBarrier(MI))
return true;
if (HII->isSolo(MI))
return true;
if (MI.getOpcode() == Hexagon::A2_nop)
return true;
return false;
}
// Quick check if instructions MI and MJ cannot coexist in the same packet.
// Limit the tests to be "one-way", e.g. "if MI->isBranch and MJ->isInlineAsm",
// but not the symmetric case: "if MJ->isBranch and MI->isInlineAsm".
// For full test call this function twice:
// cannotCoexistAsymm(MI, MJ) || cannotCoexistAsymm(MJ, MI)
// Doing the test only one way saves the amount of code in this function,
// since every test would need to be repeated with the MI and MJ reversed.
static bool cannotCoexistAsymm(const MachineInstr &MI, const MachineInstr &MJ,
const HexagonInstrInfo &HII) {
const MachineFunction *MF = MI.getParent()->getParent();
if (MF->getSubtarget<HexagonSubtarget>().hasV60TOpsOnly() &&
HII.isHVXMemWithAIndirect(MI, MJ))
return true;
// An inline asm cannot be together with a branch, because we may not be
// able to remove the asm out after packetizing (i.e. if the asm must be
// moved past the bundle). Similarly, two asms cannot be together to avoid
// complications when determining their relative order outside of a bundle.
if (MI.isInlineAsm())
return MJ.isInlineAsm() || MJ.isBranch() || MJ.isBarrier() ||
MJ.isCall() || MJ.isTerminator();
switch (MI.getOpcode()) {
case (Hexagon::S2_storew_locked):
case (Hexagon::S4_stored_locked):
case (Hexagon::L2_loadw_locked):
case (Hexagon::L4_loadd_locked):
case (Hexagon::Y4_l2fetch): {
// These instructions can only be grouped with ALU32 or non-floating-point
// XTYPE instructions. Since there is no convenient way of identifying fp
// XTYPE instructions, only allow grouping with ALU32 for now.
unsigned TJ = HII.getType(MJ);
if (TJ != HexagonII::TypeALU32)
return true;
break;
}
default:
break;
}
// "False" really means that the quick check failed to determine if
// I and J cannot coexist.
return false;
}
// Full, symmetric check.
bool HexagonPacketizerList::cannotCoexist(const MachineInstr &MI,
const MachineInstr &MJ) {
return cannotCoexistAsymm(MI, MJ, *HII) || cannotCoexistAsymm(MJ, MI, *HII);
}
void HexagonPacketizerList::unpacketizeSoloInstrs(MachineFunction &MF) {
for (auto &B : MF) {
MachineBasicBlock::iterator BundleIt;
MachineBasicBlock::instr_iterator NextI;
for (auto I = B.instr_begin(), E = B.instr_end(); I != E; I = NextI) {
NextI = std::next(I);
MachineInstr &MI = *I;
if (MI.isBundle())
BundleIt = I;
if (!MI.isInsideBundle())
continue;
// Decide on where to insert the instruction that we are pulling out.
// Debug instructions always go before the bundle, but the placement of
// INLINE_ASM depends on potential dependencies. By default, try to
// put it before the bundle, but if the asm writes to a register that
// other instructions in the bundle read, then we need to place it
// after the bundle (to preserve the bundle semantics).
bool InsertBeforeBundle;
if (MI.isInlineAsm())
InsertBeforeBundle = !hasWriteToReadDep(MI, *BundleIt, HRI);
else if (MI.isDebugValue())
InsertBeforeBundle = true;
else
continue;
BundleIt = moveInstrOut(MI, BundleIt, InsertBeforeBundle);
}
}
}
// Check if a given instruction is of class "system".
static bool isSystemInstr(const MachineInstr &MI) {
unsigned Opc = MI.getOpcode();
switch (Opc) {
case Hexagon::Y2_barrier:
case Hexagon::Y2_dcfetchbo:
return true;
}
return false;
}
bool HexagonPacketizerList::hasDeadDependence(const MachineInstr &I,
const MachineInstr &J) {
// The dependence graph may not include edges between dead definitions,
// so without extra checks, we could end up packetizing two instruction
// defining the same (dead) register.
if (I.isCall() || J.isCall())
return false;
if (HII->isPredicated(I) || HII->isPredicated(J))
return false;
BitVector DeadDefs(Hexagon::NUM_TARGET_REGS);
for (auto &MO : I.operands()) {
if (!MO.isReg() || !MO.isDef() || !MO.isDead())
continue;
DeadDefs[MO.getReg()] = true;
}
for (auto &MO : J.operands()) {
if (!MO.isReg() || !MO.isDef() || !MO.isDead())
continue;
unsigned R = MO.getReg();
if (R != Hexagon::USR_OVF && DeadDefs[R])
return true;
}
return false;
}
bool HexagonPacketizerList::hasControlDependence(const MachineInstr &I,
const MachineInstr &J) {
// A save callee-save register function call can only be in a packet
// with instructions that don't write to the callee-save registers.
if ((HII->isSaveCalleeSavedRegsCall(I) &&
doesModifyCalleeSavedReg(J, HRI)) ||
(HII->isSaveCalleeSavedRegsCall(J) &&
doesModifyCalleeSavedReg(I, HRI)))
return true;
// Two control flow instructions cannot go in the same packet.
if (isControlFlow(I) && isControlFlow(J))
return true;
// \ref-manual (7.3.4) A loop setup packet in loopN or spNloop0 cannot
// contain a speculative indirect jump,
// a new-value compare jump or a dealloc_return.
auto isBadForLoopN = [this] (const MachineInstr &MI) -> bool {
if (MI.isCall() || HII->isDeallocRet(MI) || HII->isNewValueJump(MI))
return true;
if (HII->isPredicated(MI) && HII->isPredicatedNew(MI) && HII->isJumpR(MI))
return true;
return false;
};
if (HII->isLoopN(I) && isBadForLoopN(J))
return true;
if (HII->isLoopN(J) && isBadForLoopN(I))
return true;
// dealloc_return cannot appear in the same packet as a conditional or
// unconditional jump.
return HII->isDeallocRet(I) &&
(J.isBranch() || J.isCall() || J.isBarrier());
}
bool HexagonPacketizerList::hasV4SpecificDependence(const MachineInstr &I,
const MachineInstr &J) {
bool SysI = isSystemInstr(I), SysJ = isSystemInstr(J);
bool StoreI = I.mayStore(), StoreJ = J.mayStore();
if ((SysI && StoreJ) || (SysJ && StoreI))
return true;
if (StoreI && StoreJ) {
if (HII->isNewValueInst(J) || HII->isMemOp(J) || HII->isMemOp(I))
return true;
} else {
// A memop cannot be in the same packet with another memop or a store.
// Two stores can be together, but here I and J cannot both be stores.
bool MopStI = HII->isMemOp(I) || StoreI;
bool MopStJ = HII->isMemOp(J) || StoreJ;
if (MopStI && MopStJ)
return true;
}
return (StoreJ && HII->isDeallocRet(I)) || (StoreI && HII->isDeallocRet(J));
}
// SUI is the current instruction that is out side of the current packet.
// SUJ is the current instruction inside the current packet against which that
// SUI will be packetized.
bool HexagonPacketizerList::isLegalToPacketizeTogether(SUnit *SUI, SUnit *SUJ) {
assert(SUI->getInstr() && SUJ->getInstr());
MachineInstr &I = *SUI->getInstr();
MachineInstr &J = *SUJ->getInstr();
// Clear IgnoreDepMIs when Packet starts.
if (CurrentPacketMIs.size() == 1)
IgnoreDepMIs.clear();
MachineBasicBlock::iterator II = I.getIterator();
// Solo instructions cannot go in the packet.
assert(!isSoloInstruction(I) && "Unexpected solo instr!");
if (cannotCoexist(I, J))
return false;
Dependence = hasDeadDependence(I, J) || hasControlDependence(I, J);
if (Dependence)
return false;
// V4 allows dual stores. It does not allow second store, if the first
// store is not in SLOT0. New value store, new value jump, dealloc_return
// and memop always take SLOT0. Arch spec 3.4.4.2.
Dependence = hasV4SpecificDependence(I, J);
if (Dependence)
return false;
// If an instruction feeds new value jump, glue it.
MachineBasicBlock::iterator NextMII = I.getIterator();
++NextMII;
if (NextMII != I.getParent()->end() && HII->isNewValueJump(*NextMII)) {
MachineInstr &NextMI = *NextMII;
bool secondRegMatch = false;
const MachineOperand &NOp0 = NextMI.getOperand(0);
const MachineOperand &NOp1 = NextMI.getOperand(1);
if (NOp1.isReg() && I.getOperand(0).getReg() == NOp1.getReg())
secondRegMatch = true;
for (auto T : CurrentPacketMIs) {
SUnit *PacketSU = MIToSUnit.find(T)->second;
MachineInstr &PI = *PacketSU->getInstr();
// NVJ can not be part of the dual jump - Arch Spec: section 7.8.
if (PI.isCall()) {
Dependence = true;
break;
}
// Validate:
// 1. Packet does not have a store in it.
// 2. If the first operand of the nvj is newified, and the second
// operand is also a reg, it (second reg) is not defined in
// the same packet.
// 3. If the second operand of the nvj is newified, (which means
// first operand is also a reg), first reg is not defined in
// the same packet.
if (PI.getOpcode() == Hexagon::S2_allocframe || PI.mayStore() ||
HII->isLoopN(PI)) {
Dependence = true;
break;
}
// Check #2/#3.
const MachineOperand &OpR = secondRegMatch ? NOp0 : NOp1;
if (OpR.isReg() && PI.modifiesRegister(OpR.getReg(), HRI)) {
Dependence = true;
break;
}
}
if (Dependence)
return false;
GlueToNewValueJump = true;
}
// There no dependency between a prolog instruction and its successor.
if (!SUJ->isSucc(SUI))
return true;
for (unsigned i = 0; i < SUJ->Succs.size(); ++i) {
if (FoundSequentialDependence)
break;
if (SUJ->Succs[i].getSUnit() != SUI)
continue;
SDep::Kind DepType = SUJ->Succs[i].getKind();
// For direct calls:
// Ignore register dependences for call instructions for packetization
// purposes except for those due to r31 and predicate registers.
//
// For indirect calls:
// Same as direct calls + check for true dependences to the register
// used in the indirect call.
//
// We completely ignore Order dependences for call instructions.
//
// For returns:
// Ignore register dependences for return instructions like jumpr,
// dealloc return unless we have dependencies on the explicit uses
// of the registers used by jumpr (like r31) or dealloc return
// (like r29 or r30).
//
// TODO: Currently, jumpr is handling only return of r31. So, the
// following logic (specificaly isCallDependent) is working fine.
// We need to enable jumpr for register other than r31 and then,
// we need to rework the last part, where it handles indirect call
// of that (isCallDependent) function. Bug 6216 is opened for this.
unsigned DepReg = 0;
const TargetRegisterClass *RC = nullptr;
if (DepType == SDep::Data) {
DepReg = SUJ->Succs[i].getReg();
RC = HRI->getMinimalPhysRegClass(DepReg);
}
if (I.isCall() || HII->isJumpR(I) || HII->isTailCall(I)) {
if (!isRegDependence(DepType))
continue;
if (!isCallDependent(I, DepType, SUJ->Succs[i].getReg()))
continue;
}
if (DepType == SDep::Data) {
if (canPromoteToDotCur(J, SUJ, DepReg, II, RC))
if (promoteToDotCur(J, DepType, II, RC))
continue;
}
// Data dpendence ok if we have load.cur.
if (DepType == SDep::Data && HII->isDotCurInst(J)) {
if (HII->isV60VectorInstruction(I))
continue;
}
// For instructions that can be promoted to dot-new, try to promote.
if (DepType == SDep::Data) {
if (canPromoteToDotNew(I, SUJ, DepReg, II, RC)) {
if (promoteToDotNew(I, DepType, II, RC)) {
PromotedToDotNew = true;
continue;
}
}
if (HII->isNewValueJump(I))
continue;
}
// For predicated instructions, if the predicates are complements then
// there can be no dependence.
if (HII->isPredicated(I) && HII->isPredicated(J) &&
arePredicatesComplements(I, J)) {
// Not always safe to do this translation.
// DAG Builder attempts to reduce dependence edges using transitive
// nature of dependencies. Here is an example:
//
// r0 = tfr_pt ... (1)
// r0 = tfr_pf ... (2)
// r0 = tfr_pt ... (3)
//
// There will be an output dependence between (1)->(2) and (2)->(3).
// However, there is no dependence edge between (1)->(3). This results
// in all 3 instructions going in the same packet. We ignore dependce
// only once to avoid this situation.
auto Itr = find(IgnoreDepMIs, &J);
if (Itr != IgnoreDepMIs.end()) {
Dependence = true;
return false;
}
IgnoreDepMIs.push_back(&I);
continue;
}
// Ignore Order dependences between unconditional direct branches
// and non-control-flow instructions.
if (isDirectJump(I) && !J.isBranch() && !J.isCall() &&
DepType == SDep::Order)
continue;
// Ignore all dependences for jumps except for true and output
// dependences.
if (I.isConditionalBranch() && DepType != SDep::Data &&
DepType != SDep::Output)
continue;
// Ignore output dependences due to superregs. We can write to two
// different subregisters of R1:0 for instance in the same cycle.
// If neither I nor J defines DepReg, then this is a superfluous output
// dependence. The dependence must be of the form:
// R0 = ...
// R1 = ...
// and there is an output dependence between the two instructions with
// DepReg = D0.
// We want to ignore these dependences. Ideally, the dependence
// constructor should annotate such dependences. We can then avoid this
// relatively expensive check.
//
if (DepType == SDep::Output) {
// DepReg is the register that's responsible for the dependence.
unsigned DepReg = SUJ->Succs[i].getReg();
// Check if I and J really defines DepReg.
if (!I.definesRegister(DepReg) && !J.definesRegister(DepReg))
continue;
FoundSequentialDependence = true;
break;
}
// For Order dependences:
// 1. On V4 or later, volatile loads/stores can be packetized together,
// unless other rules prevent is.
// 2. Store followed by a load is not allowed.
// 3. Store followed by a store is only valid on V4 or later.
// 4. Load followed by any memory operation is allowed.
if (DepType == SDep::Order) {
if (!PacketizeVolatiles) {
bool OrdRefs = I.hasOrderedMemoryRef() || J.hasOrderedMemoryRef();
if (OrdRefs) {
FoundSequentialDependence = true;
break;
}
}
// J is first, I is second.
bool LoadJ = J.mayLoad(), StoreJ = J.mayStore();
bool LoadI = I.mayLoad(), StoreI = I.mayStore();
if (StoreJ) {
// Two stores are only allowed on V4+. Load following store is never
// allowed.
if (LoadI) {
FoundSequentialDependence = true;
break;
}
} else if (!LoadJ || (!LoadI && !StoreI)) {
// If J is neither load nor store, assume a dependency.
// If J is a load, but I is neither, also assume a dependency.
FoundSequentialDependence = true;
break;
}
// Store followed by store: not OK on V2.
// Store followed by load: not OK on all.
// Load followed by store: OK on all.
// Load followed by load: OK on all.
continue;
}
// For V4, special case ALLOCFRAME. Even though there is dependency
// between ALLOCFRAME and subsequent store, allow it to be packetized
// in a same packet. This implies that the store is using the caller's
// SP. Hence, offset needs to be updated accordingly.
if (DepType == SDep::Data && J.getOpcode() == Hexagon::S2_allocframe) {
unsigned Opc = I.getOpcode();
switch (Opc) {
case Hexagon::S2_storerd_io:
case Hexagon::S2_storeri_io:
case Hexagon::S2_storerh_io:
case Hexagon::S2_storerb_io:
if (I.getOperand(0).getReg() == HRI->getStackRegister()) {
// Since this store is to be glued with allocframe in the same
// packet, it will use SP of the previous stack frame, i.e.
// caller's SP. Therefore, we need to recalculate offset
// according to this change.
GlueAllocframeStore = useCallersSP(I);
if (GlueAllocframeStore)
continue;
}
default:
break;
}
}
// There are certain anti-dependencies that cannot be ignored.
// Specifically:
// J2_call ... %R0<imp-def> ; SUJ
// R0 = ... ; SUI
// Those cannot be packetized together, since the call will observe
// the effect of the assignment to R0.
if (DepType == SDep::Anti && J.isCall()) {
// Check if I defines any volatile register. We should also check
// registers that the call may read, but these happen to be a
// subset of the volatile register set.
for (const MCPhysReg *P = J.getDesc().ImplicitDefs; P && *P; ++P) {
if (!I.modifiesRegister(*P, HRI))
continue;
FoundSequentialDependence = true;
break;
}
}
// Skip over remaining anti-dependences. Two instructions that are
// anti-dependent can share a packet, since in most such cases all
// operands are read before any modifications take place.
// The exceptions are branch and call instructions, since they are
// executed after all other instructions have completed (at least
// conceptually).
if (DepType != SDep::Anti) {
FoundSequentialDependence = true;
break;
}
}
if (FoundSequentialDependence) {
Dependence = true;
return false;
}
return true;
}
bool HexagonPacketizerList::isLegalToPruneDependencies(SUnit *SUI, SUnit *SUJ) {
assert(SUI->getInstr() && SUJ->getInstr());
MachineInstr &I = *SUI->getInstr();
MachineInstr &J = *SUJ->getInstr();
if (cannotCoexist(I, J))
return false;
if (!Dependence)
return true;
// Check if the instruction was promoted to a dot-new. If so, demote it
// back into a dot-old.
if (PromotedToDotNew)
demoteToDotOld(I);
cleanUpDotCur();
// Check if the instruction (must be a store) was glued with an allocframe
// instruction. If so, restore its offset to its original value, i.e. use
// current SP instead of caller's SP.
if (GlueAllocframeStore) {
useCalleesSP(I);
GlueAllocframeStore = false;
}
return false;
}
MachineBasicBlock::iterator
HexagonPacketizerList::addToPacket(MachineInstr &MI) {
MachineBasicBlock::iterator MII = MI.getIterator();
MachineBasicBlock *MBB = MI.getParent();
if (MI.isImplicitDef()) {
unsigned R = MI.getOperand(0).getReg();
if (Hexagon::IntRegsRegClass.contains(R)) {
MCSuperRegIterator S(R, HRI, false);
MI.addOperand(MachineOperand::CreateReg(*S, true, true));
}
return MII;
}
assert(ResourceTracker->canReserveResources(MI));
bool ExtMI = HII->isExtended(MI) || HII->isConstExtended(MI);
bool Good = true;
if (GlueToNewValueJump) {
MachineInstr &NvjMI = *++MII;
// We need to put both instructions in the same packet: MI and NvjMI.
// Either of them can require a constant extender. Try to add both to
// the current packet, and if that fails, end the packet and start a
// new one.
ResourceTracker->reserveResources(MI);
if (ExtMI)
Good = tryAllocateResourcesForConstExt(true);
bool ExtNvjMI = HII->isExtended(NvjMI) || HII->isConstExtended(NvjMI);
if (Good) {
if (ResourceTracker->canReserveResources(NvjMI))
ResourceTracker->reserveResources(NvjMI);
else
Good = false;
}
if (Good && ExtNvjMI)
Good = tryAllocateResourcesForConstExt(true);
if (!Good) {
endPacket(MBB, MI);
assert(ResourceTracker->canReserveResources(MI));
ResourceTracker->reserveResources(MI);
if (ExtMI) {
assert(canReserveResourcesForConstExt());
tryAllocateResourcesForConstExt(true);
}
assert(ResourceTracker->canReserveResources(NvjMI));
ResourceTracker->reserveResources(NvjMI);
if (ExtNvjMI) {
assert(canReserveResourcesForConstExt());
reserveResourcesForConstExt();
}
}
CurrentPacketMIs.push_back(&MI);
CurrentPacketMIs.push_back(&NvjMI);
return MII;
}
ResourceTracker->reserveResources(MI);
if (ExtMI && !tryAllocateResourcesForConstExt(true)) {
endPacket(MBB, MI);
if (PromotedToDotNew)
demoteToDotOld(MI);
if (GlueAllocframeStore) {
useCalleesSP(MI);
GlueAllocframeStore = false;
}
ResourceTracker->reserveResources(MI);
reserveResourcesForConstExt();
}
CurrentPacketMIs.push_back(&MI);
return MII;
}
void HexagonPacketizerList::endPacket(MachineBasicBlock *MBB,
MachineBasicBlock::iterator MI) {
OldPacketMIs = CurrentPacketMIs;
VLIWPacketizerList::endPacket(MBB, MI);
}
bool HexagonPacketizerList::shouldAddToPacket(const MachineInstr &MI) {
return !producesStall(MI);
}
// Return true when ConsMI uses a register defined by ProdMI.
static bool isDependent(const MachineInstr &ProdMI,
const MachineInstr &ConsMI) {
if (!ProdMI.getOperand(0).isReg())
return false;
unsigned DstReg = ProdMI.getOperand(0).getReg();
for (auto &Op : ConsMI.operands())
if (Op.isReg() && Op.isUse() && Op.getReg() == DstReg)
// The MIs depend on each other.
return true;
return false;
}
// V60 forward scheduling.
bool HexagonPacketizerList::producesStall(const MachineInstr &I) {
// Check whether the previous packet is in a different loop. If this is the
// case, there is little point in trying to avoid a stall because that would
// favor the rare case (loop entry) over the common case (loop iteration).
//
// TODO: We should really be able to check all the incoming edges if this is
// the first packet in a basic block, so we can avoid stalls from the loop
// backedge.
if (!OldPacketMIs.empty()) {
auto *OldBB = OldPacketMIs.front()->getParent();
auto *ThisBB = I.getParent();
if (MLI->getLoopFor(OldBB) != MLI->getLoopFor(ThisBB))
return false;
}
// Check for stall between two vector instructions.
if (HII->isV60VectorInstruction(I)) {
for (auto J : OldPacketMIs) {
if (!HII->isV60VectorInstruction(*J))
continue;
if (isDependent(*J, I) && !HII->isVecUsableNextPacket(*J, I))
return true;
}
return false;
}
// Check for stall between two scalar instructions. First, check that
// there is no definition of a use in the current packet, because it
// may be a candidate for .new.
for (auto J : CurrentPacketMIs)
if (!HII->isV60VectorInstruction(*J) && isDependent(*J, I))
return false;
// Check for stall between I and instructions in the previous packet.
if (MF.getSubtarget<HexagonSubtarget>().useBSBScheduling()) {
for (auto J : OldPacketMIs) {
if (HII->isV60VectorInstruction(*J))
continue;
if (!HII->isLateInstrFeedsEarlyInstr(*J, I))
continue;
if (isDependent(*J, I) && !HII->canExecuteInBundle(*J, I))
return true;
}
}
return false;
}
//===----------------------------------------------------------------------===//
// Public Constructor Functions
//===----------------------------------------------------------------------===//
FunctionPass *llvm::createHexagonPacketizer() {
return new HexagonPacketizer();
}
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