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llvm-mirror/lib/CodeGen/ScheduleDAGInstrs.cpp
Hal Finkel 9be4aefa57 AA metadata refactoring (introduce AAMDNodes) 
In order to enable the preservation of noalias function parameter information
after inlining, and the representation of block-level __restrict__ pointer
information (etc.), additional kinds of aliasing metadata will be introduced.
This metadata needs to be carried around in AliasAnalysis::Location objects
(and MMOs at the SDAG level), and so we need to generalize the current scheme
(which is hard-coded to just one TBAA MDNode*).

This commit introduces only the necessary refactoring to allow for the
introduction of other aliasing metadata types, but does not actually introduce
any (that will come in a follow-up commit). What it does introduce is a new
AAMDNodes structure to hold all of the aliasing metadata nodes associated with
a particular memory-accessing instruction, and uses that structure instead of
the raw MDNode* in AliasAnalysis::Location, etc.

No functionality change intended.

llvm-svn: 213859
2014-07-24 12:16:19 +00:00

1534 lines
57 KiB
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//===---- ScheduleDAGInstrs.cpp - MachineInstr Rescheduling ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the ScheduleDAGInstrs class, which implements re-scheduling
// of MachineInstrs.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/CodeGen/RegisterPressure.h"
#include "llvm/CodeGen/ScheduleDFS.h"
#include "llvm/IR/Operator.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include <queue>
using namespace llvm;
#define DEBUG_TYPE "misched"
static cl::opt<bool> EnableAASchedMI("enable-aa-sched-mi", cl::Hidden,
cl::ZeroOrMore, cl::init(false),
cl::desc("Enable use of AA during MI GAD construction"));
static cl::opt<bool> UseTBAA("use-tbaa-in-sched-mi", cl::Hidden,
cl::init(true), cl::desc("Enable use of TBAA during MI GAD construction"));
ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
const MachineLoopInfo &mli,
const MachineDominatorTree &mdt,
bool IsPostRAFlag,
bool RemoveKillFlags,
LiveIntervals *lis)
: ScheduleDAG(mf), MLI(mli), MDT(mdt), MFI(mf.getFrameInfo()), LIS(lis),
IsPostRA(IsPostRAFlag), RemoveKillFlags(RemoveKillFlags),
CanHandleTerminators(false), FirstDbgValue(nullptr) {
assert((IsPostRA || LIS) && "PreRA scheduling requires LiveIntervals");
DbgValues.clear();
assert(!(IsPostRA && MRI.getNumVirtRegs()) &&
"Virtual registers must be removed prior to PostRA scheduling");
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
SchedModel.init(*ST.getSchedModel(), &ST, TII);
}
/// getUnderlyingObjectFromInt - This is the function that does the work of
/// looking through basic ptrtoint+arithmetic+inttoptr sequences.
static const Value *getUnderlyingObjectFromInt(const Value *V) {
do {
if (const Operator *U = dyn_cast<Operator>(V)) {
// If we find a ptrtoint, we can transfer control back to the
// regular getUnderlyingObjectFromInt.
if (U->getOpcode() == Instruction::PtrToInt)
return U->getOperand(0);
// If we find an add of a constant, a multiplied value, or a phi, it's
// likely that the other operand will lead us to the base
// object. We don't have to worry about the case where the
// object address is somehow being computed by the multiply,
// because our callers only care when the result is an
// identifiable object.
if (U->getOpcode() != Instruction::Add ||
(!isa<ConstantInt>(U->getOperand(1)) &&
Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
!isa<PHINode>(U->getOperand(1))))
return V;
V = U->getOperand(0);
} else {
return V;
}
assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
} while (1);
}
/// getUnderlyingObjects - This is a wrapper around GetUnderlyingObjects
/// and adds support for basic ptrtoint+arithmetic+inttoptr sequences.
static void getUnderlyingObjects(const Value *V,
SmallVectorImpl<Value *> &Objects) {
SmallPtrSet<const Value *, 16> Visited;
SmallVector<const Value *, 4> Working(1, V);
do {
V = Working.pop_back_val();
SmallVector<Value *, 4> Objs;
GetUnderlyingObjects(const_cast<Value *>(V), Objs);
for (SmallVectorImpl<Value *>::iterator I = Objs.begin(), IE = Objs.end();
I != IE; ++I) {
V = *I;
if (!Visited.insert(V))
continue;
if (Operator::getOpcode(V) == Instruction::IntToPtr) {
const Value *O =
getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
if (O->getType()->isPointerTy()) {
Working.push_back(O);
continue;
}
}
Objects.push_back(const_cast<Value *>(V));
}
} while (!Working.empty());
}
typedef PointerUnion<const Value *, const PseudoSourceValue *> ValueType;
typedef SmallVector<PointerIntPair<ValueType, 1, bool>, 4>
UnderlyingObjectsVector;
/// getUnderlyingObjectsForInstr - If this machine instr has memory reference
/// information and it can be tracked to a normal reference to a known
/// object, return the Value for that object.
static void getUnderlyingObjectsForInstr(const MachineInstr *MI,
const MachineFrameInfo *MFI,
UnderlyingObjectsVector &Objects) {
if (!MI->hasOneMemOperand() ||
(!(*MI->memoperands_begin())->getValue() &&
!(*MI->memoperands_begin())->getPseudoValue()) ||
(*MI->memoperands_begin())->isVolatile())
return;
if (const PseudoSourceValue *PSV =
(*MI->memoperands_begin())->getPseudoValue()) {
// For now, ignore PseudoSourceValues which may alias LLVM IR values
// because the code that uses this function has no way to cope with
// such aliases.
if (!PSV->isAliased(MFI)) {
bool MayAlias = PSV->mayAlias(MFI);
Objects.push_back(UnderlyingObjectsVector::value_type(PSV, MayAlias));
}
return;
}
const Value *V = (*MI->memoperands_begin())->getValue();
if (!V)
return;
SmallVector<Value *, 4> Objs;
getUnderlyingObjects(V, Objs);
for (SmallVectorImpl<Value *>::iterator I = Objs.begin(), IE = Objs.end();
I != IE; ++I) {
V = *I;
if (!isIdentifiedObject(V)) {
Objects.clear();
return;
}
Objects.push_back(UnderlyingObjectsVector::value_type(V, true));
}
}
void ScheduleDAGInstrs::startBlock(MachineBasicBlock *bb) {
BB = bb;
}
void ScheduleDAGInstrs::finishBlock() {
// Subclasses should no longer refer to the old block.
BB = nullptr;
}
/// Initialize the DAG and common scheduler state for the current scheduling
/// region. This does not actually create the DAG, only clears it. The
/// scheduling driver may call BuildSchedGraph multiple times per scheduling
/// region.
void ScheduleDAGInstrs::enterRegion(MachineBasicBlock *bb,
MachineBasicBlock::iterator begin,
MachineBasicBlock::iterator end,
unsigned regioninstrs) {
assert(bb == BB && "startBlock should set BB");
RegionBegin = begin;
RegionEnd = end;
NumRegionInstrs = regioninstrs;
}
/// Close the current scheduling region. Don't clear any state in case the
/// driver wants to refer to the previous scheduling region.
void ScheduleDAGInstrs::exitRegion() {
// Nothing to do.
}
/// addSchedBarrierDeps - Add dependencies from instructions in the current
/// list of instructions being scheduled to scheduling barrier by adding
/// the exit SU to the register defs and use list. This is because we want to
/// make sure instructions which define registers that are either used by
/// the terminator or are live-out are properly scheduled. This is
/// especially important when the definition latency of the return value(s)
/// are too high to be hidden by the branch or when the liveout registers
/// used by instructions in the fallthrough block.
void ScheduleDAGInstrs::addSchedBarrierDeps() {
MachineInstr *ExitMI = RegionEnd != BB->end() ? &*RegionEnd : nullptr;
ExitSU.setInstr(ExitMI);
bool AllDepKnown = ExitMI &&
(ExitMI->isCall() || ExitMI->isBarrier());
if (ExitMI && AllDepKnown) {
// If it's a call or a barrier, add dependencies on the defs and uses of
// instruction.
for (unsigned i = 0, e = ExitMI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = ExitMI->getOperand(i);
if (!MO.isReg() || MO.isDef()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (TRI->isPhysicalRegister(Reg))
Uses.insert(PhysRegSUOper(&ExitSU, -1, Reg));
else {
assert(!IsPostRA && "Virtual register encountered after regalloc.");
if (MO.readsReg()) // ignore undef operands
addVRegUseDeps(&ExitSU, i);
}
}
} else {
// For others, e.g. fallthrough, conditional branch, assume the exit
// uses all the registers that are livein to the successor blocks.
assert(Uses.empty() && "Uses in set before adding deps?");
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI)
for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
E = (*SI)->livein_end(); I != E; ++I) {
unsigned Reg = *I;
if (!Uses.contains(Reg))
Uses.insert(PhysRegSUOper(&ExitSU, -1, Reg));
}
}
}
/// MO is an operand of SU's instruction that defines a physical register. Add
/// data dependencies from SU to any uses of the physical register.
void ScheduleDAGInstrs::addPhysRegDataDeps(SUnit *SU, unsigned OperIdx) {
const MachineOperand &MO = SU->getInstr()->getOperand(OperIdx);
assert(MO.isDef() && "expect physreg def");
// Ask the target if address-backscheduling is desirable, and if so how much.
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
Alias.isValid(); ++Alias) {
if (!Uses.contains(*Alias))
continue;
for (Reg2SUnitsMap::iterator I = Uses.find(*Alias); I != Uses.end(); ++I) {
SUnit *UseSU = I->SU;
if (UseSU == SU)
continue;
// Adjust the dependence latency using operand def/use information,
// then allow the target to perform its own adjustments.
int UseOp = I->OpIdx;
MachineInstr *RegUse = nullptr;
SDep Dep;
if (UseOp < 0)
Dep = SDep(SU, SDep::Artificial);
else {
// Set the hasPhysRegDefs only for physreg defs that have a use within
// the scheduling region.
SU->hasPhysRegDefs = true;
Dep = SDep(SU, SDep::Data, *Alias);
RegUse = UseSU->getInstr();
}
Dep.setLatency(
SchedModel.computeOperandLatency(SU->getInstr(), OperIdx, RegUse,
UseOp));
ST.adjustSchedDependency(SU, UseSU, Dep);
UseSU->addPred(Dep);
}
}
}
/// addPhysRegDeps - Add register dependencies (data, anti, and output) from
/// this SUnit to following instructions in the same scheduling region that
/// depend the physical register referenced at OperIdx.
void ScheduleDAGInstrs::addPhysRegDeps(SUnit *SU, unsigned OperIdx) {
MachineInstr *MI = SU->getInstr();
MachineOperand &MO = MI->getOperand(OperIdx);
// Optionally add output and anti dependencies. For anti
// dependencies we use a latency of 0 because for a multi-issue
// target we want to allow the defining instruction to issue
// in the same cycle as the using instruction.
// TODO: Using a latency of 1 here for output dependencies assumes
// there's no cost for reusing registers.
SDep::Kind Kind = MO.isUse() ? SDep::Anti : SDep::Output;
for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
Alias.isValid(); ++Alias) {
if (!Defs.contains(*Alias))
continue;
for (Reg2SUnitsMap::iterator I = Defs.find(*Alias); I != Defs.end(); ++I) {
SUnit *DefSU = I->SU;
if (DefSU == &ExitSU)
continue;
if (DefSU != SU &&
(Kind != SDep::Output || !MO.isDead() ||
!DefSU->getInstr()->registerDefIsDead(*Alias))) {
if (Kind == SDep::Anti)
DefSU->addPred(SDep(SU, Kind, /*Reg=*/*Alias));
else {
SDep Dep(SU, Kind, /*Reg=*/*Alias);
Dep.setLatency(
SchedModel.computeOutputLatency(MI, OperIdx, DefSU->getInstr()));
DefSU->addPred(Dep);
}
}
}
}
if (!MO.isDef()) {
SU->hasPhysRegUses = true;
// Either insert a new Reg2SUnits entry with an empty SUnits list, or
// retrieve the existing SUnits list for this register's uses.
// Push this SUnit on the use list.
Uses.insert(PhysRegSUOper(SU, OperIdx, MO.getReg()));
if (RemoveKillFlags)
MO.setIsKill(false);
}
else {
addPhysRegDataDeps(SU, OperIdx);
unsigned Reg = MO.getReg();
// clear this register's use list
if (Uses.contains(Reg))
Uses.eraseAll(Reg);
if (!MO.isDead()) {
Defs.eraseAll(Reg);
} else if (SU->isCall) {
// Calls will not be reordered because of chain dependencies (see
// below). Since call operands are dead, calls may continue to be added
// to the DefList making dependence checking quadratic in the size of
// the block. Instead, we leave only one call at the back of the
// DefList.
Reg2SUnitsMap::RangePair P = Defs.equal_range(Reg);
Reg2SUnitsMap::iterator B = P.first;
Reg2SUnitsMap::iterator I = P.second;
for (bool isBegin = I == B; !isBegin; /* empty */) {
isBegin = (--I) == B;
if (!I->SU->isCall)
break;
I = Defs.erase(I);
}
}
// Defs are pushed in the order they are visited and never reordered.
Defs.insert(PhysRegSUOper(SU, OperIdx, Reg));
}
}
/// addVRegDefDeps - Add register output and data dependencies from this SUnit
/// to instructions that occur later in the same scheduling region if they read
/// from or write to the virtual register defined at OperIdx.
///
/// TODO: Hoist loop induction variable increments. This has to be
/// reevaluated. Generally, IV scheduling should be done before coalescing.
void ScheduleDAGInstrs::addVRegDefDeps(SUnit *SU, unsigned OperIdx) {
const MachineInstr *MI = SU->getInstr();
unsigned Reg = MI->getOperand(OperIdx).getReg();
// Singly defined vregs do not have output/anti dependencies.
// The current operand is a def, so we have at least one.
// Check here if there are any others...
if (MRI.hasOneDef(Reg))
return;
// Add output dependence to the next nearest def of this vreg.
//
// Unless this definition is dead, the output dependence should be
// transitively redundant with antidependencies from this definition's
// uses. We're conservative for now until we have a way to guarantee the uses
// are not eliminated sometime during scheduling. The output dependence edge
// is also useful if output latency exceeds def-use latency.
VReg2SUnitMap::iterator DefI = VRegDefs.find(Reg);
if (DefI == VRegDefs.end())
VRegDefs.insert(VReg2SUnit(Reg, SU));
else {
SUnit *DefSU = DefI->SU;
if (DefSU != SU && DefSU != &ExitSU) {
SDep Dep(SU, SDep::Output, Reg);
Dep.setLatency(
SchedModel.computeOutputLatency(MI, OperIdx, DefSU->getInstr()));
DefSU->addPred(Dep);
}
DefI->SU = SU;
}
}
/// addVRegUseDeps - Add a register data dependency if the instruction that
/// defines the virtual register used at OperIdx is mapped to an SUnit. Add a
/// register antidependency from this SUnit to instructions that occur later in
/// the same scheduling region if they write the virtual register.
///
/// TODO: Handle ExitSU "uses" properly.
void ScheduleDAGInstrs::addVRegUseDeps(SUnit *SU, unsigned OperIdx) {
MachineInstr *MI = SU->getInstr();
unsigned Reg = MI->getOperand(OperIdx).getReg();
// Record this local VReg use.
VReg2UseMap::iterator UI = VRegUses.find(Reg);
for (; UI != VRegUses.end(); ++UI) {
if (UI->SU == SU)
break;
}
if (UI == VRegUses.end())
VRegUses.insert(VReg2SUnit(Reg, SU));
// Lookup this operand's reaching definition.
assert(LIS && "vreg dependencies requires LiveIntervals");
LiveQueryResult LRQ
= LIS->getInterval(Reg).Query(LIS->getInstructionIndex(MI));
VNInfo *VNI = LRQ.valueIn();
// VNI will be valid because MachineOperand::readsReg() is checked by caller.
assert(VNI && "No value to read by operand");
MachineInstr *Def = LIS->getInstructionFromIndex(VNI->def);
// Phis and other noninstructions (after coalescing) have a NULL Def.
if (Def) {
SUnit *DefSU = getSUnit(Def);
if (DefSU) {
// The reaching Def lives within this scheduling region.
// Create a data dependence.
SDep dep(DefSU, SDep::Data, Reg);
// Adjust the dependence latency using operand def/use information, then
// allow the target to perform its own adjustments.
int DefOp = Def->findRegisterDefOperandIdx(Reg);
dep.setLatency(SchedModel.computeOperandLatency(Def, DefOp, MI, OperIdx));
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
ST.adjustSchedDependency(DefSU, SU, const_cast<SDep &>(dep));
SU->addPred(dep);
}
}
// Add antidependence to the following def of the vreg it uses.
VReg2SUnitMap::iterator DefI = VRegDefs.find(Reg);
if (DefI != VRegDefs.end() && DefI->SU != SU)
DefI->SU->addPred(SDep(SU, SDep::Anti, Reg));
}
/// Return true if MI is an instruction we are unable to reason about
/// (like a call or something with unmodeled side effects).
static inline bool isGlobalMemoryObject(AliasAnalysis *AA, MachineInstr *MI) {
if (MI->isCall() || MI->hasUnmodeledSideEffects() ||
(MI->hasOrderedMemoryRef() &&
(!MI->mayLoad() || !MI->isInvariantLoad(AA))))
return true;
return false;
}
// This MI might have either incomplete info, or known to be unsafe
// to deal with (i.e. volatile object).
static inline bool isUnsafeMemoryObject(MachineInstr *MI,
const MachineFrameInfo *MFI) {
if (!MI || MI->memoperands_empty())
return true;
// We purposefully do no check for hasOneMemOperand() here
// in hope to trigger an assert downstream in order to
// finish implementation.
if ((*MI->memoperands_begin())->isVolatile() ||
MI->hasUnmodeledSideEffects())
return true;
if ((*MI->memoperands_begin())->getPseudoValue()) {
// Similarly to getUnderlyingObjectForInstr:
// For now, ignore PseudoSourceValues which may alias LLVM IR values
// because the code that uses this function has no way to cope with
// such aliases.
return true;
}
const Value *V = (*MI->memoperands_begin())->getValue();
if (!V)
return true;
SmallVector<Value *, 4> Objs;
getUnderlyingObjects(V, Objs);
for (SmallVectorImpl<Value *>::iterator I = Objs.begin(),
IE = Objs.end(); I != IE; ++I) {
// Does this pointer refer to a distinct and identifiable object?
if (!isIdentifiedObject(*I))
return true;
}
return false;
}
/// This returns true if the two MIs need a chain edge betwee them.
/// If these are not even memory operations, we still may need
/// chain deps between them. The question really is - could
/// these two MIs be reordered during scheduling from memory dependency
/// point of view.
static bool MIsNeedChainEdge(AliasAnalysis *AA, const MachineFrameInfo *MFI,
MachineInstr *MIa,
MachineInstr *MIb) {
// Cover a trivial case - no edge is need to itself.
if (MIa == MIb)
return false;
// FIXME: Need to handle multiple memory operands to support all targets.
if (!MIa->hasOneMemOperand() || !MIb->hasOneMemOperand())
return true;
if (isUnsafeMemoryObject(MIa, MFI) || isUnsafeMemoryObject(MIb, MFI))
return true;
// If we are dealing with two "normal" loads, we do not need an edge
// between them - they could be reordered.
if (!MIa->mayStore() && !MIb->mayStore())
return false;
// To this point analysis is generic. From here on we do need AA.
if (!AA)
return true;
MachineMemOperand *MMOa = *MIa->memoperands_begin();
MachineMemOperand *MMOb = *MIb->memoperands_begin();
if (!MMOa->getValue() || !MMOb->getValue())
return true;
// The following interface to AA is fashioned after DAGCombiner::isAlias
// and operates with MachineMemOperand offset with some important
// assumptions:
// - LLVM fundamentally assumes flat address spaces.
// - MachineOperand offset can *only* result from legalization and
// cannot affect queries other than the trivial case of overlap
// checking.
// - These offsets never wrap and never step outside
// of allocated objects.
// - There should never be any negative offsets here.
//
// FIXME: Modify API to hide this math from "user"
// FIXME: Even before we go to AA we can reason locally about some
// memory objects. It can save compile time, and possibly catch some
// corner cases not currently covered.
assert ((MMOa->getOffset() >= 0) && "Negative MachineMemOperand offset");
assert ((MMOb->getOffset() >= 0) && "Negative MachineMemOperand offset");
int64_t MinOffset = std::min(MMOa->getOffset(), MMOb->getOffset());
int64_t Overlapa = MMOa->getSize() + MMOa->getOffset() - MinOffset;
int64_t Overlapb = MMOb->getSize() + MMOb->getOffset() - MinOffset;
AliasAnalysis::AliasResult AAResult = AA->alias(
AliasAnalysis::Location(MMOa->getValue(), Overlapa,
UseTBAA ? MMOa->getAAInfo() : AAMDNodes()),
AliasAnalysis::Location(MMOb->getValue(), Overlapb,
UseTBAA ? MMOb->getAAInfo() : AAMDNodes()));
return (AAResult != AliasAnalysis::NoAlias);
}
/// This recursive function iterates over chain deps of SUb looking for
/// "latest" node that needs a chain edge to SUa.
static unsigned
iterateChainSucc(AliasAnalysis *AA, const MachineFrameInfo *MFI,
SUnit *SUa, SUnit *SUb, SUnit *ExitSU, unsigned *Depth,
SmallPtrSet<const SUnit*, 16> &Visited) {
if (!SUa || !SUb || SUb == ExitSU)
return *Depth;
// Remember visited nodes.
if (!Visited.insert(SUb))
return *Depth;
// If there is _some_ dependency already in place, do not
// descend any further.
// TODO: Need to make sure that if that dependency got eliminated or ignored
// for any reason in the future, we would not violate DAG topology.
// Currently it does not happen, but makes an implicit assumption about
// future implementation.
//
// Independently, if we encounter node that is some sort of global
// object (like a call) we already have full set of dependencies to it
// and we can stop descending.
if (SUa->isSucc(SUb) ||
isGlobalMemoryObject(AA, SUb->getInstr()))
return *Depth;
// If we do need an edge, or we have exceeded depth budget,
// add that edge to the predecessors chain of SUb,
// and stop descending.
if (*Depth > 200 ||
MIsNeedChainEdge(AA, MFI, SUa->getInstr(), SUb->getInstr())) {
SUb->addPred(SDep(SUa, SDep::MayAliasMem));
return *Depth;
}
// Track current depth.
(*Depth)++;
// Iterate over chain dependencies only.
for (SUnit::const_succ_iterator I = SUb->Succs.begin(), E = SUb->Succs.end();
I != E; ++I)
if (I->isCtrl())
iterateChainSucc (AA, MFI, SUa, I->getSUnit(), ExitSU, Depth, Visited);
return *Depth;
}
/// This function assumes that "downward" from SU there exist
/// tail/leaf of already constructed DAG. It iterates downward and
/// checks whether SU can be aliasing any node dominated
/// by it.
static void adjustChainDeps(AliasAnalysis *AA, const MachineFrameInfo *MFI,
SUnit *SU, SUnit *ExitSU, std::set<SUnit *> &CheckList,
unsigned LatencyToLoad) {
if (!SU)
return;
SmallPtrSet<const SUnit*, 16> Visited;
unsigned Depth = 0;
for (std::set<SUnit *>::iterator I = CheckList.begin(), IE = CheckList.end();
I != IE; ++I) {
if (SU == *I)
continue;
if (MIsNeedChainEdge(AA, MFI, SU->getInstr(), (*I)->getInstr())) {
SDep Dep(SU, SDep::MayAliasMem);
Dep.setLatency(((*I)->getInstr()->mayLoad()) ? LatencyToLoad : 0);
(*I)->addPred(Dep);
}
// Now go through all the chain successors and iterate from them.
// Keep track of visited nodes.
for (SUnit::const_succ_iterator J = (*I)->Succs.begin(),
JE = (*I)->Succs.end(); J != JE; ++J)
if (J->isCtrl())
iterateChainSucc (AA, MFI, SU, J->getSUnit(),
ExitSU, &Depth, Visited);
}
}
/// Check whether two objects need a chain edge, if so, add it
/// otherwise remember the rejected SU.
static inline
void addChainDependency (AliasAnalysis *AA, const MachineFrameInfo *MFI,
SUnit *SUa, SUnit *SUb,
std::set<SUnit *> &RejectList,
unsigned TrueMemOrderLatency = 0,
bool isNormalMemory = false) {
// If this is a false dependency,
// do not add the edge, but rememeber the rejected node.
if (!AA || MIsNeedChainEdge(AA, MFI, SUa->getInstr(), SUb->getInstr())) {
SDep Dep(SUa, isNormalMemory ? SDep::MayAliasMem : SDep::Barrier);
Dep.setLatency(TrueMemOrderLatency);
SUb->addPred(Dep);
}
else {
// Duplicate entries should be ignored.
RejectList.insert(SUb);
DEBUG(dbgs() << "\tReject chain dep between SU("
<< SUa->NodeNum << ") and SU("
<< SUb->NodeNum << ")\n");
}
}
/// Create an SUnit for each real instruction, numbered in top-down toplological
/// order. The instruction order A < B, implies that no edge exists from B to A.
///
/// Map each real instruction to its SUnit.
///
/// After initSUnits, the SUnits vector cannot be resized and the scheduler may
/// hang onto SUnit pointers. We may relax this in the future by using SUnit IDs
/// instead of pointers.
///
/// MachineScheduler relies on initSUnits numbering the nodes by their order in
/// the original instruction list.
void ScheduleDAGInstrs::initSUnits() {
// We'll be allocating one SUnit for each real instruction in the region,
// which is contained within a basic block.
SUnits.reserve(NumRegionInstrs);
for (MachineBasicBlock::iterator I = RegionBegin; I != RegionEnd; ++I) {
MachineInstr *MI = I;
if (MI->isDebugValue())
continue;
SUnit *SU = newSUnit(MI);
MISUnitMap[MI] = SU;
SU->isCall = MI->isCall();
SU->isCommutable = MI->isCommutable();
// Assign the Latency field of SU using target-provided information.
SU->Latency = SchedModel.computeInstrLatency(SU->getInstr());
// If this SUnit uses a reserved or unbuffered resource, mark it as such.
//
// Reserved resources block an instruction from issuing and stall the
// entire pipeline. These are identified by BufferSize=0.
//
// Unbuffered resources prevent execution of subsequent instructions that
// require the same resources. This is used for in-order execution pipelines
// within an out-of-order core. These are identified by BufferSize=1.
if (SchedModel.hasInstrSchedModel()) {
const MCSchedClassDesc *SC = getSchedClass(SU);
for (TargetSchedModel::ProcResIter
PI = SchedModel.getWriteProcResBegin(SC),
PE = SchedModel.getWriteProcResEnd(SC); PI != PE; ++PI) {
switch (SchedModel.getProcResource(PI->ProcResourceIdx)->BufferSize) {
case 0:
SU->hasReservedResource = true;
break;
case 1:
SU->isUnbuffered = true;
break;
default:
break;
}
}
}
}
}
/// If RegPressure is non-null, compute register pressure as a side effect. The
/// DAG builder is an efficient place to do it because it already visits
/// operands.
void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
RegPressureTracker *RPTracker,
PressureDiffs *PDiffs) {
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
bool UseAA = EnableAASchedMI.getNumOccurrences() > 0 ? EnableAASchedMI
: ST.useAA();
AliasAnalysis *AAForDep = UseAA ? AA : nullptr;
MISUnitMap.clear();
ScheduleDAG::clearDAG();
// Create an SUnit for each real instruction.
initSUnits();
if (PDiffs)
PDiffs->init(SUnits.size());
// We build scheduling units by walking a block's instruction list from bottom
// to top.
// Remember where a generic side-effecting instruction is as we procede.
SUnit *BarrierChain = nullptr, *AliasChain = nullptr;
// Memory references to specific known memory locations are tracked
// so that they can be given more precise dependencies. We track
// separately the known memory locations that may alias and those
// that are known not to alias
MapVector<ValueType, std::vector<SUnit *> > AliasMemDefs, NonAliasMemDefs;
MapVector<ValueType, std::vector<SUnit *> > AliasMemUses, NonAliasMemUses;
std::set<SUnit*> RejectMemNodes;
// Remove any stale debug info; sometimes BuildSchedGraph is called again
// without emitting the info from the previous call.
DbgValues.clear();
FirstDbgValue = nullptr;
assert(Defs.empty() && Uses.empty() &&
"Only BuildGraph should update Defs/Uses");
Defs.setUniverse(TRI->getNumRegs());
Uses.setUniverse(TRI->getNumRegs());
assert(VRegDefs.empty() && "Only BuildSchedGraph may access VRegDefs");
VRegUses.clear();
VRegDefs.setUniverse(MRI.getNumVirtRegs());
VRegUses.setUniverse(MRI.getNumVirtRegs());
// Model data dependencies between instructions being scheduled and the
// ExitSU.
addSchedBarrierDeps();
// Walk the list of instructions, from bottom moving up.
MachineInstr *DbgMI = nullptr;
for (MachineBasicBlock::iterator MII = RegionEnd, MIE = RegionBegin;
MII != MIE; --MII) {
MachineInstr *MI = std::prev(MII);
if (MI && DbgMI) {
DbgValues.push_back(std::make_pair(DbgMI, MI));
DbgMI = nullptr;
}
if (MI->isDebugValue()) {
DbgMI = MI;
continue;
}
SUnit *SU = MISUnitMap[MI];
assert(SU && "No SUnit mapped to this MI");
if (RPTracker) {
PressureDiff *PDiff = PDiffs ? &(*PDiffs)[SU->NodeNum] : nullptr;
RPTracker->recede(/*LiveUses=*/nullptr, PDiff);
assert(RPTracker->getPos() == std::prev(MII) &&
"RPTracker can't find MI");
}
assert(
(CanHandleTerminators || (!MI->isTerminator() && !MI->isPosition())) &&
"Cannot schedule terminators or labels!");
// Add register-based dependencies (data, anti, and output).
bool HasVRegDef = false;
for (unsigned j = 0, n = MI->getNumOperands(); j != n; ++j) {
const MachineOperand &MO = MI->getOperand(j);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (TRI->isPhysicalRegister(Reg))
addPhysRegDeps(SU, j);
else {
assert(!IsPostRA && "Virtual register encountered!");
if (MO.isDef()) {
HasVRegDef = true;
addVRegDefDeps(SU, j);
}
else if (MO.readsReg()) // ignore undef operands
addVRegUseDeps(SU, j);
}
}
// If we haven't seen any uses in this scheduling region, create a
// dependence edge to ExitSU to model the live-out latency. This is required
// for vreg defs with no in-region use, and prefetches with no vreg def.
//
// FIXME: NumDataSuccs would be more precise than NumSuccs here. This
// check currently relies on being called before adding chain deps.
if (SU->NumSuccs == 0 && SU->Latency > 1
&& (HasVRegDef || MI->mayLoad())) {
SDep Dep(SU, SDep::Artificial);
Dep.setLatency(SU->Latency - 1);
ExitSU.addPred(Dep);
}
// Add chain dependencies.
// Chain dependencies used to enforce memory order should have
// latency of 0 (except for true dependency of Store followed by
// aliased Load... we estimate that with a single cycle of latency
// assuming the hardware will bypass)
// Note that isStoreToStackSlot and isLoadFromStackSLot are not usable
// after stack slots are lowered to actual addresses.
// TODO: Use an AliasAnalysis and do real alias-analysis queries, and
// produce more precise dependence information.
unsigned TrueMemOrderLatency = MI->mayStore() ? 1 : 0;
if (isGlobalMemoryObject(AA, MI)) {
// Be conservative with these and add dependencies on all memory
// references, even those that are known to not alias.
for (MapVector<ValueType, std::vector<SUnit *> >::iterator I =
NonAliasMemDefs.begin(), E = NonAliasMemDefs.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i) {
I->second[i]->addPred(SDep(SU, SDep::Barrier));
}
}
for (MapVector<ValueType, std::vector<SUnit *> >::iterator I =
NonAliasMemUses.begin(), E = NonAliasMemUses.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i) {
SDep Dep(SU, SDep::Barrier);
Dep.setLatency(TrueMemOrderLatency);
I->second[i]->addPred(Dep);
}
}
// Add SU to the barrier chain.
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Barrier));
BarrierChain = SU;
// This is a barrier event that acts as a pivotal node in the DAG,
// so it is safe to clear list of exposed nodes.
adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes,
TrueMemOrderLatency);
RejectMemNodes.clear();
NonAliasMemDefs.clear();
NonAliasMemUses.clear();
// fall-through
new_alias_chain:
// Chain all possibly aliasing memory references though SU.
if (AliasChain) {
unsigned ChainLatency = 0;
if (AliasChain->getInstr()->mayLoad())
ChainLatency = TrueMemOrderLatency;
addChainDependency(AAForDep, MFI, SU, AliasChain, RejectMemNodes,
ChainLatency);
}
AliasChain = SU;
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
addChainDependency(AAForDep, MFI, SU, PendingLoads[k], RejectMemNodes,
TrueMemOrderLatency);
for (MapVector<ValueType, std::vector<SUnit *> >::iterator I =
AliasMemDefs.begin(), E = AliasMemDefs.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
addChainDependency(AAForDep, MFI, SU, I->second[i], RejectMemNodes);
}
for (MapVector<ValueType, std::vector<SUnit *> >::iterator I =
AliasMemUses.begin(), E = AliasMemUses.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
addChainDependency(AAForDep, MFI, SU, I->second[i], RejectMemNodes,
TrueMemOrderLatency);
}
adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes,
TrueMemOrderLatency);
PendingLoads.clear();
AliasMemDefs.clear();
AliasMemUses.clear();
} else if (MI->mayStore()) {
UnderlyingObjectsVector Objs;
getUnderlyingObjectsForInstr(MI, MFI, Objs);
if (Objs.empty()) {
// Treat all other stores conservatively.
goto new_alias_chain;
}
bool MayAlias = false;
for (UnderlyingObjectsVector::iterator K = Objs.begin(), KE = Objs.end();
K != KE; ++K) {
ValueType V = K->getPointer();
bool ThisMayAlias = K->getInt();
if (ThisMayAlias)
MayAlias = true;
// A store to a specific PseudoSourceValue. Add precise dependencies.
// Record the def in MemDefs, first adding a dep if there is
// an existing def.
MapVector<ValueType, std::vector<SUnit *> >::iterator I =
((ThisMayAlias) ? AliasMemDefs.find(V) : NonAliasMemDefs.find(V));
MapVector<ValueType, std::vector<SUnit *> >::iterator IE =
((ThisMayAlias) ? AliasMemDefs.end() : NonAliasMemDefs.end());
if (I != IE) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
addChainDependency(AAForDep, MFI, SU, I->second[i], RejectMemNodes,
0, true);
// If we're not using AA, then we only need one store per object.
if (!AAForDep)
I->second.clear();
I->second.push_back(SU);
} else {
if (ThisMayAlias) {
if (!AAForDep)
AliasMemDefs[V].clear();
AliasMemDefs[V].push_back(SU);
} else {
if (!AAForDep)
NonAliasMemDefs[V].clear();
NonAliasMemDefs[V].push_back(SU);
}
}
// Handle the uses in MemUses, if there are any.
MapVector<ValueType, std::vector<SUnit *> >::iterator J =
((ThisMayAlias) ? AliasMemUses.find(V) : NonAliasMemUses.find(V));
MapVector<ValueType, std::vector<SUnit *> >::iterator JE =
((ThisMayAlias) ? AliasMemUses.end() : NonAliasMemUses.end());
if (J != JE) {
for (unsigned i = 0, e = J->second.size(); i != e; ++i)
addChainDependency(AAForDep, MFI, SU, J->second[i], RejectMemNodes,
TrueMemOrderLatency, true);
J->second.clear();
}
}
if (MayAlias) {
// Add dependencies from all the PendingLoads, i.e. loads
// with no underlying object.
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
addChainDependency(AAForDep, MFI, SU, PendingLoads[k], RejectMemNodes,
TrueMemOrderLatency);
// Add dependence on alias chain, if needed.
if (AliasChain)
addChainDependency(AAForDep, MFI, SU, AliasChain, RejectMemNodes);
// But we also should check dependent instructions for the
// SU in question.
adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes,
TrueMemOrderLatency);
}
// Add dependence on barrier chain, if needed.
// There is no point to check aliasing on barrier event. Even if
// SU and barrier _could_ be reordered, they should not. In addition,
// we have lost all RejectMemNodes below barrier.
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Barrier));
} else if (MI->mayLoad()) {
bool MayAlias = true;
if (MI->isInvariantLoad(AA)) {
// Invariant load, no chain dependencies needed!
} else {
UnderlyingObjectsVector Objs;
getUnderlyingObjectsForInstr(MI, MFI, Objs);
if (Objs.empty()) {
// A load with no underlying object. Depend on all
// potentially aliasing stores.
for (MapVector<ValueType, std::vector<SUnit *> >::iterator I =
AliasMemDefs.begin(), E = AliasMemDefs.end(); I != E; ++I)
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
addChainDependency(AAForDep, MFI, SU, I->second[i],
RejectMemNodes);
PendingLoads.push_back(SU);
MayAlias = true;
} else {
MayAlias = false;
}
for (UnderlyingObjectsVector::iterator
J = Objs.begin(), JE = Objs.end(); J != JE; ++J) {
ValueType V = J->getPointer();
bool ThisMayAlias = J->getInt();
if (ThisMayAlias)
MayAlias = true;
// A load from a specific PseudoSourceValue. Add precise dependencies.
MapVector<ValueType, std::vector<SUnit *> >::iterator I =
((ThisMayAlias) ? AliasMemDefs.find(V) : NonAliasMemDefs.find(V));
MapVector<ValueType, std::vector<SUnit *> >::iterator IE =
((ThisMayAlias) ? AliasMemDefs.end() : NonAliasMemDefs.end());
if (I != IE)
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
addChainDependency(AAForDep, MFI, SU, I->second[i],
RejectMemNodes, 0, true);
if (ThisMayAlias)
AliasMemUses[V].push_back(SU);
else
NonAliasMemUses[V].push_back(SU);
}
if (MayAlias)
adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes, /*Latency=*/0);
// Add dependencies on alias and barrier chains, if needed.
if (MayAlias && AliasChain)
addChainDependency(AAForDep, MFI, SU, AliasChain, RejectMemNodes);
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Barrier));
}
}
}
if (DbgMI)
FirstDbgValue = DbgMI;
Defs.clear();
Uses.clear();
VRegDefs.clear();
PendingLoads.clear();
}
/// \brief Initialize register live-range state for updating kills.
void ScheduleDAGInstrs::startBlockForKills(MachineBasicBlock *BB) {
// Start with no live registers.
LiveRegs.reset();
// Examine the live-in regs of all successors.
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI) {
for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
E = (*SI)->livein_end(); I != E; ++I) {
unsigned Reg = *I;
// Repeat, for reg and all subregs.
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
}
bool ScheduleDAGInstrs::toggleKillFlag(MachineInstr *MI, MachineOperand &MO) {
// Setting kill flag...
if (!MO.isKill()) {
MO.setIsKill(true);
return false;
}
// If MO itself is live, clear the kill flag...
if (LiveRegs.test(MO.getReg())) {
MO.setIsKill(false);
return false;
}
// If any subreg of MO is live, then create an imp-def for that
// subreg and keep MO marked as killed.
MO.setIsKill(false);
bool AllDead = true;
const unsigned SuperReg = MO.getReg();
MachineInstrBuilder MIB(MF, MI);
for (MCSubRegIterator SubRegs(SuperReg, TRI); SubRegs.isValid(); ++SubRegs) {
if (LiveRegs.test(*SubRegs)) {
MIB.addReg(*SubRegs, RegState::ImplicitDefine);
AllDead = false;
}
}
if(AllDead)
MO.setIsKill(true);
return false;
}
// FIXME: Reuse the LivePhysRegs utility for this.
void ScheduleDAGInstrs::fixupKills(MachineBasicBlock *MBB) {
DEBUG(dbgs() << "Fixup kills for BB#" << MBB->getNumber() << '\n');
LiveRegs.resize(TRI->getNumRegs());
BitVector killedRegs(TRI->getNumRegs());
startBlockForKills(MBB);
// Examine block from end to start...
unsigned Count = MBB->size();
for (MachineBasicBlock::iterator I = MBB->end(), E = MBB->begin();
I != E; --Count) {
MachineInstr *MI = --I;
if (MI->isDebugValue())
continue;
// Update liveness. Registers that are defed but not used in this
// instruction are now dead. Mark register and all subregs as they
// are completely defined.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegMask())
LiveRegs.clearBitsNotInMask(MO.getRegMask());
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (!MO.isDef()) continue;
// Ignore two-addr defs.
if (MI->isRegTiedToUseOperand(i)) continue;
// Repeat for reg and all subregs.
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.reset(*SubRegs);
}
// Examine all used registers and set/clear kill flag. When a
// register is used multiple times we only set the kill flag on
// the first use. Don't set kill flags on undef operands.
killedRegs.reset();
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
unsigned Reg = MO.getReg();
if ((Reg == 0) || MRI.isReserved(Reg)) continue;
bool kill = false;
if (!killedRegs.test(Reg)) {
kill = true;
// A register is not killed if any subregs are live...
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
if (LiveRegs.test(*SubRegs)) {
kill = false;
break;
}
}
// If subreg is not live, then register is killed if it became
// live in this instruction
if (kill)
kill = !LiveRegs.test(Reg);
}
if (MO.isKill() != kill) {
DEBUG(dbgs() << "Fixing " << MO << " in ");
// Warning: toggleKillFlag may invalidate MO.
toggleKillFlag(MI, MO);
DEBUG(MI->dump());
}
killedRegs.set(Reg);
}
// Mark any used register (that is not using undef) and subregs as
// now live...
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
unsigned Reg = MO.getReg();
if ((Reg == 0) || MRI.isReserved(Reg)) continue;
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
}
void ScheduleDAGInstrs::dumpNode(const SUnit *SU) const {
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
SU->getInstr()->dump();
#endif
}
std::string ScheduleDAGInstrs::getGraphNodeLabel(const SUnit *SU) const {
std::string s;
raw_string_ostream oss(s);
if (SU == &EntrySU)
oss << "<entry>";
else if (SU == &ExitSU)
oss << "<exit>";
else
SU->getInstr()->print(oss, &TM, /*SkipOpers=*/true);
return oss.str();
}
/// Return the basic block label. It is not necessarilly unique because a block
/// contains multiple scheduling regions. But it is fine for visualization.
std::string ScheduleDAGInstrs::getDAGName() const {
return "dag." + BB->getFullName();
}
//===----------------------------------------------------------------------===//
// SchedDFSResult Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// \brief Internal state used to compute SchedDFSResult.
class SchedDFSImpl {
SchedDFSResult &R;
/// Join DAG nodes into equivalence classes by their subtree.
IntEqClasses SubtreeClasses;
/// List PredSU, SuccSU pairs that represent data edges between subtrees.
std::vector<std::pair<const SUnit*, const SUnit*> > ConnectionPairs;
struct RootData {
unsigned NodeID;
unsigned ParentNodeID; // Parent node (member of the parent subtree).
unsigned SubInstrCount; // Instr count in this tree only, not children.
RootData(unsigned id): NodeID(id),
ParentNodeID(SchedDFSResult::InvalidSubtreeID),
SubInstrCount(0) {}
unsigned getSparseSetIndex() const { return NodeID; }
};
SparseSet<RootData> RootSet;
public:
SchedDFSImpl(SchedDFSResult &r): R(r), SubtreeClasses(R.DFSNodeData.size()) {
RootSet.setUniverse(R.DFSNodeData.size());
}
/// Return true if this node been visited by the DFS traversal.
///
/// During visitPostorderNode the Node's SubtreeID is assigned to the Node
/// ID. Later, SubtreeID is updated but remains valid.
bool isVisited(const SUnit *SU) const {
return R.DFSNodeData[SU->NodeNum].SubtreeID
!= SchedDFSResult::InvalidSubtreeID;
}
/// Initialize this node's instruction count. We don't need to flag the node
/// visited until visitPostorder because the DAG cannot have cycles.
void visitPreorder(const SUnit *SU) {
R.DFSNodeData[SU->NodeNum].InstrCount =
SU->getInstr()->isTransient() ? 0 : 1;
}
/// Called once for each node after all predecessors are visited. Revisit this
/// node's predecessors and potentially join them now that we know the ILP of
/// the other predecessors.
void visitPostorderNode(const SUnit *SU) {
// Mark this node as the root of a subtree. It may be joined with its
// successors later.
R.DFSNodeData[SU->NodeNum].SubtreeID = SU->NodeNum;
RootData RData(SU->NodeNum);
RData.SubInstrCount = SU->getInstr()->isTransient() ? 0 : 1;
// If any predecessors are still in their own subtree, they either cannot be
// joined or are large enough to remain separate. If this parent node's
// total instruction count is not greater than a child subtree by at least
// the subtree limit, then try to join it now since splitting subtrees is
// only useful if multiple high-pressure paths are possible.
unsigned InstrCount = R.DFSNodeData[SU->NodeNum].InstrCount;
for (SUnit::const_pred_iterator
PI = SU->Preds.begin(), PE = SU->Preds.end(); PI != PE; ++PI) {
if (PI->getKind() != SDep::Data)
continue;
unsigned PredNum = PI->getSUnit()->NodeNum;
if ((InstrCount - R.DFSNodeData[PredNum].InstrCount) < R.SubtreeLimit)
joinPredSubtree(*PI, SU, /*CheckLimit=*/false);
// Either link or merge the TreeData entry from the child to the parent.
if (R.DFSNodeData[PredNum].SubtreeID == PredNum) {
// If the predecessor's parent is invalid, this is a tree edge and the
// current node is the parent.
if (RootSet[PredNum].ParentNodeID == SchedDFSResult::InvalidSubtreeID)
RootSet[PredNum].ParentNodeID = SU->NodeNum;
}
else if (RootSet.count(PredNum)) {
// The predecessor is not a root, but is still in the root set. This
// must be the new parent that it was just joined to. Note that
// RootSet[PredNum].ParentNodeID may either be invalid or may still be
// set to the original parent.
RData.SubInstrCount += RootSet[PredNum].SubInstrCount;
RootSet.erase(PredNum);
}
}
RootSet[SU->NodeNum] = RData;
}
/// Called once for each tree edge after calling visitPostOrderNode on the
/// predecessor. Increment the parent node's instruction count and
/// preemptively join this subtree to its parent's if it is small enough.
void visitPostorderEdge(const SDep &PredDep, const SUnit *Succ) {
R.DFSNodeData[Succ->NodeNum].InstrCount
+= R.DFSNodeData[PredDep.getSUnit()->NodeNum].InstrCount;
joinPredSubtree(PredDep, Succ);
}
/// Add a connection for cross edges.
void visitCrossEdge(const SDep &PredDep, const SUnit *Succ) {
ConnectionPairs.push_back(std::make_pair(PredDep.getSUnit(), Succ));
}
/// Set each node's subtree ID to the representative ID and record connections
/// between trees.
void finalize() {
SubtreeClasses.compress();
R.DFSTreeData.resize(SubtreeClasses.getNumClasses());
assert(SubtreeClasses.getNumClasses() == RootSet.size()
&& "number of roots should match trees");
for (SparseSet<RootData>::const_iterator
RI = RootSet.begin(), RE = RootSet.end(); RI != RE; ++RI) {
unsigned TreeID = SubtreeClasses[RI->NodeID];
if (RI->ParentNodeID != SchedDFSResult::InvalidSubtreeID)
R.DFSTreeData[TreeID].ParentTreeID = SubtreeClasses[RI->ParentNodeID];
R.DFSTreeData[TreeID].SubInstrCount = RI->SubInstrCount;
// Note that SubInstrCount may be greater than InstrCount if we joined
// subtrees across a cross edge. InstrCount will be attributed to the
// original parent, while SubInstrCount will be attributed to the joined
// parent.
}
R.SubtreeConnections.resize(SubtreeClasses.getNumClasses());
R.SubtreeConnectLevels.resize(SubtreeClasses.getNumClasses());
DEBUG(dbgs() << R.getNumSubtrees() << " subtrees:\n");
for (unsigned Idx = 0, End = R.DFSNodeData.size(); Idx != End; ++Idx) {
R.DFSNodeData[Idx].SubtreeID = SubtreeClasses[Idx];
DEBUG(dbgs() << " SU(" << Idx << ") in tree "
<< R.DFSNodeData[Idx].SubtreeID << '\n');
}
for (std::vector<std::pair<const SUnit*, const SUnit*> >::const_iterator
I = ConnectionPairs.begin(), E = ConnectionPairs.end();
I != E; ++I) {
unsigned PredTree = SubtreeClasses[I->first->NodeNum];
unsigned SuccTree = SubtreeClasses[I->second->NodeNum];
if (PredTree == SuccTree)
continue;
unsigned Depth = I->first->getDepth();
addConnection(PredTree, SuccTree, Depth);
addConnection(SuccTree, PredTree, Depth);
}
}
protected:
/// Join the predecessor subtree with the successor that is its DFS
/// parent. Apply some heuristics before joining.
bool joinPredSubtree(const SDep &PredDep, const SUnit *Succ,
bool CheckLimit = true) {
assert(PredDep.getKind() == SDep::Data && "Subtrees are for data edges");
// Check if the predecessor is already joined.
const SUnit *PredSU = PredDep.getSUnit();
unsigned PredNum = PredSU->NodeNum;
if (R.DFSNodeData[PredNum].SubtreeID != PredNum)
return false;
// Four is the magic number of successors before a node is considered a
// pinch point.
unsigned NumDataSucs = 0;
for (SUnit::const_succ_iterator SI = PredSU->Succs.begin(),
SE = PredSU->Succs.end(); SI != SE; ++SI) {
if (SI->getKind() == SDep::Data) {
if (++NumDataSucs >= 4)
return false;
}
}
if (CheckLimit && R.DFSNodeData[PredNum].InstrCount > R.SubtreeLimit)
return false;
R.DFSNodeData[PredNum].SubtreeID = Succ->NodeNum;
SubtreeClasses.join(Succ->NodeNum, PredNum);
return true;
}
/// Called by finalize() to record a connection between trees.
void addConnection(unsigned FromTree, unsigned ToTree, unsigned Depth) {
if (!Depth)
return;
do {
SmallVectorImpl<SchedDFSResult::Connection> &Connections =
R.SubtreeConnections[FromTree];
for (SmallVectorImpl<SchedDFSResult::Connection>::iterator
I = Connections.begin(), E = Connections.end(); I != E; ++I) {
if (I->TreeID == ToTree) {
I->Level = std::max(I->Level, Depth);
return;
}
}
Connections.push_back(SchedDFSResult::Connection(ToTree, Depth));
FromTree = R.DFSTreeData[FromTree].ParentTreeID;
} while (FromTree != SchedDFSResult::InvalidSubtreeID);
}
};
} // namespace llvm
namespace {
/// \brief Manage the stack used by a reverse depth-first search over the DAG.
class SchedDAGReverseDFS {
std::vector<std::pair<const SUnit*, SUnit::const_pred_iterator> > DFSStack;
public:
bool isComplete() const { return DFSStack.empty(); }
void follow(const SUnit *SU) {
DFSStack.push_back(std::make_pair(SU, SU->Preds.begin()));
}
void advance() { ++DFSStack.back().second; }
const SDep *backtrack() {
DFSStack.pop_back();
return DFSStack.empty() ? nullptr : std::prev(DFSStack.back().second);
}
const SUnit *getCurr() const { return DFSStack.back().first; }
SUnit::const_pred_iterator getPred() const { return DFSStack.back().second; }
SUnit::const_pred_iterator getPredEnd() const {
return getCurr()->Preds.end();
}
};
} // anonymous
static bool hasDataSucc(const SUnit *SU) {
for (SUnit::const_succ_iterator
SI = SU->Succs.begin(), SE = SU->Succs.end(); SI != SE; ++SI) {
if (SI->getKind() == SDep::Data && !SI->getSUnit()->isBoundaryNode())
return true;
}
return false;
}
/// Compute an ILP metric for all nodes in the subDAG reachable via depth-first
/// search from this root.
void SchedDFSResult::compute(ArrayRef<SUnit> SUnits) {
if (!IsBottomUp)
llvm_unreachable("Top-down ILP metric is unimplemnted");
SchedDFSImpl Impl(*this);
for (ArrayRef<SUnit>::const_iterator
SI = SUnits.begin(), SE = SUnits.end(); SI != SE; ++SI) {
const SUnit *SU = &*SI;
if (Impl.isVisited(SU) || hasDataSucc(SU))
continue;
SchedDAGReverseDFS DFS;
Impl.visitPreorder(SU);
DFS.follow(SU);
for (;;) {
// Traverse the leftmost path as far as possible.
while (DFS.getPred() != DFS.getPredEnd()) {
const SDep &PredDep = *DFS.getPred();
DFS.advance();
// Ignore non-data edges.
if (PredDep.getKind() != SDep::Data
|| PredDep.getSUnit()->isBoundaryNode()) {
continue;
}
// An already visited edge is a cross edge, assuming an acyclic DAG.
if (Impl.isVisited(PredDep.getSUnit())) {
Impl.visitCrossEdge(PredDep, DFS.getCurr());
continue;
}
Impl.visitPreorder(PredDep.getSUnit());
DFS.follow(PredDep.getSUnit());
}
// Visit the top of the stack in postorder and backtrack.
const SUnit *Child = DFS.getCurr();
const SDep *PredDep = DFS.backtrack();
Impl.visitPostorderNode(Child);
if (PredDep)
Impl.visitPostorderEdge(*PredDep, DFS.getCurr());
if (DFS.isComplete())
break;
}
}
Impl.finalize();
}
/// The root of the given SubtreeID was just scheduled. For all subtrees
/// connected to this tree, record the depth of the connection so that the
/// nearest connected subtrees can be prioritized.
void SchedDFSResult::scheduleTree(unsigned SubtreeID) {
for (SmallVectorImpl<Connection>::const_iterator
I = SubtreeConnections[SubtreeID].begin(),
E = SubtreeConnections[SubtreeID].end(); I != E; ++I) {
SubtreeConnectLevels[I->TreeID] =
std::max(SubtreeConnectLevels[I->TreeID], I->Level);
DEBUG(dbgs() << " Tree: " << I->TreeID
<< " @" << SubtreeConnectLevels[I->TreeID] << '\n');
}
}
LLVM_DUMP_METHOD
void ILPValue::print(raw_ostream &OS) const {
OS << InstrCount << " / " << Length << " = ";
if (!Length)
OS << "BADILP";
else
OS << format("%g", ((double)InstrCount / Length));
}
LLVM_DUMP_METHOD
void ILPValue::dump() const {
dbgs() << *this << '\n';
}
namespace llvm {
LLVM_DUMP_METHOD
raw_ostream &operator<<(raw_ostream &OS, const ILPValue &Val) {
Val.print(OS);
return OS;
}
} // namespace llvm
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