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llvm-project/llvm/lib/CodeGen/SplitKit.cpp

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//===- SplitKit.cpp - Toolkit for splitting live ranges -------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the SplitAnalysis class as well as mutator functions for
// live range splitting.
//
//===----------------------------------------------------------------------===//
#include "SplitKit.h"
#include "LiveRangeCalc.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/CodeGen/LiveRangeEdit.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SlotIndexes.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/CodeGen/VirtRegMap.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/LaneBitmask.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/BlockFrequency.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <iterator>
#include <limits>
#include <tuple>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "regalloc"
STATISTIC(NumFinished, "Number of splits finished");
STATISTIC(NumSimple, "Number of splits that were simple");
STATISTIC(NumCopies, "Number of copies inserted for splitting");
STATISTIC(NumRemats, "Number of rematerialized defs for splitting");
STATISTIC(NumRepairs, "Number of invalid live ranges repaired");
//===----------------------------------------------------------------------===//
// Last Insert Point Analysis
//===----------------------------------------------------------------------===//
InsertPointAnalysis::InsertPointAnalysis(const LiveIntervals &lis,
unsigned BBNum)
: LIS(lis), LastInsertPoint(BBNum) {}
SlotIndex
InsertPointAnalysis::computeLastInsertPoint(const LiveInterval &CurLI,
const MachineBasicBlock &MBB) {
unsigned Num = MBB.getNumber();
std::pair<SlotIndex, SlotIndex> &LIP = LastInsertPoint[Num];
SlotIndex MBBEnd = LIS.getMBBEndIdx(&MBB);
SmallVector<const MachineBasicBlock *, 1> EHPadSuccessors;
for (const MachineBasicBlock *SMBB : MBB.successors())
if (SMBB->isEHPad())
EHPadSuccessors.push_back(SMBB);
// Compute insert points on the first call. The pair is independent of the
// current live interval.
if (!LIP.first.isValid()) {
MachineBasicBlock::const_iterator FirstTerm = MBB.getFirstTerminator();
if (FirstTerm == MBB.end())
LIP.first = MBBEnd;
else
LIP.first = LIS.getInstructionIndex(*FirstTerm);
// If there is a landing pad successor, also find the call instruction.
if (EHPadSuccessors.empty())
return LIP.first;
// There may not be a call instruction (?) in which case we ignore LPad.
LIP.second = LIP.first;
for (MachineBasicBlock::const_iterator I = MBB.end(), E = MBB.begin();
I != E;) {
--I;
if (I->isCall()) {
LIP.second = LIS.getInstructionIndex(*I);
break;
}
}
}
// If CurLI is live into a landing pad successor, move the last insert point
// back to the call that may throw.
if (!LIP.second)
return LIP.first;
if (none_of(EHPadSuccessors, [&](const MachineBasicBlock *EHPad) {
return LIS.isLiveInToMBB(CurLI, EHPad);
}))
return LIP.first;
// Find the value leaving MBB.
const VNInfo *VNI = CurLI.getVNInfoBefore(MBBEnd);
if (!VNI)
return LIP.first;
// If the value leaving MBB was defined after the call in MBB, it can't
// really be live-in to the landing pad. This can happen if the landing pad
// has a PHI, and this register is undef on the exceptional edge.
// <rdar://problem/10664933>
if (!SlotIndex::isEarlierInstr(VNI->def, LIP.second) && VNI->def < MBBEnd)
return LIP.first;
// Value is properly live-in to the landing pad.
// Only allow inserts before the call.
return LIP.second;
}
MachineBasicBlock::iterator
InsertPointAnalysis::getLastInsertPointIter(const LiveInterval &CurLI,
MachineBasicBlock &MBB) {
SlotIndex LIP = getLastInsertPoint(CurLI, MBB);
if (LIP == LIS.getMBBEndIdx(&MBB))
return MBB.end();
return LIS.getInstructionFromIndex(LIP);
}
//===----------------------------------------------------------------------===//
// Split Analysis
//===----------------------------------------------------------------------===//
SplitAnalysis::SplitAnalysis(const VirtRegMap &vrm, const LiveIntervals &lis,
const MachineLoopInfo &mli)
: MF(vrm.getMachineFunction()), VRM(vrm), LIS(lis), Loops(mli),
TII(*MF.getSubtarget().getInstrInfo()), IPA(lis, MF.getNumBlockIDs()) {}
void SplitAnalysis::clear() {
UseSlots.clear();
UseBlocks.clear();
ThroughBlocks.clear();
CurLI = nullptr;
DidRepairRange = false;
}
/// analyzeUses - Count instructions, basic blocks, and loops using CurLI.
void SplitAnalysis::analyzeUses() {
assert(UseSlots.empty() && "Call clear first");
// First get all the defs from the interval values. This provides the correct
// slots for early clobbers.
for (const VNInfo *VNI : CurLI->valnos)
if (!VNI->isPHIDef() && !VNI->isUnused())
UseSlots.push_back(VNI->def);
// Get use slots form the use-def chain.
const MachineRegisterInfo &MRI = MF.getRegInfo();
for (MachineOperand &MO : MRI.use_nodbg_operands(CurLI->reg))
if (!MO.isUndef())
UseSlots.push_back(LIS.getInstructionIndex(*MO.getParent()).getRegSlot());
array_pod_sort(UseSlots.begin(), UseSlots.end());
// Remove duplicates, keeping the smaller slot for each instruction.
// That is what we want for early clobbers.
UseSlots.erase(std::unique(UseSlots.begin(), UseSlots.end(),
SlotIndex::isSameInstr),
UseSlots.end());
// Compute per-live block info.
if (!calcLiveBlockInfo()) {
// FIXME: calcLiveBlockInfo found inconsistencies in the live range.
// I am looking at you, RegisterCoalescer!
DidRepairRange = true;
++NumRepairs;
LLVM_DEBUG(dbgs() << "*** Fixing inconsistent live interval! ***\n");
const_cast<LiveIntervals&>(LIS)
.shrinkToUses(const_cast<LiveInterval*>(CurLI));
UseBlocks.clear();
ThroughBlocks.clear();
bool fixed = calcLiveBlockInfo();
(void)fixed;
assert(fixed && "Couldn't fix broken live interval");
}
LLVM_DEBUG(dbgs() << "Analyze counted " << UseSlots.size() << " instrs in "
<< UseBlocks.size() << " blocks, through "
<< NumThroughBlocks << " blocks.\n");
}
/// calcLiveBlockInfo - Fill the LiveBlocks array with information about blocks
/// where CurLI is live.
bool SplitAnalysis::calcLiveBlockInfo() {
ThroughBlocks.resize(MF.getNumBlockIDs());
NumThroughBlocks = NumGapBlocks = 0;
if (CurLI->empty())
return true;
LiveInterval::const_iterator LVI = CurLI->begin();
LiveInterval::const_iterator LVE = CurLI->end();
SmallVectorImpl<SlotIndex>::const_iterator UseI, UseE;
UseI = UseSlots.begin();
UseE = UseSlots.end();
// Loop over basic blocks where CurLI is live.
MachineFunction::iterator MFI =
LIS.getMBBFromIndex(LVI->start)->getIterator();
while (true) {
BlockInfo BI;
BI.MBB = &*MFI;
SlotIndex Start, Stop;
std::tie(Start, Stop) = LIS.getSlotIndexes()->getMBBRange(BI.MBB);
// If the block contains no uses, the range must be live through. At one
// point, RegisterCoalescer could create dangling ranges that ended
// mid-block.
if (UseI == UseE || *UseI >= Stop) {
++NumThroughBlocks;
ThroughBlocks.set(BI.MBB->getNumber());
// The range shouldn't end mid-block if there are no uses. This shouldn't
// happen.
if (LVI->end < Stop)
return false;
} else {
// This block has uses. Find the first and last uses in the block.
BI.FirstInstr = *UseI;
assert(BI.FirstInstr >= Start);
do ++UseI;
while (UseI != UseE && *UseI < Stop);
BI.LastInstr = UseI[-1];
assert(BI.LastInstr < Stop);
// LVI is the first live segment overlapping MBB.
BI.LiveIn = LVI->start <= Start;
// When not live in, the first use should be a def.
if (!BI.LiveIn) {
assert(LVI->start == LVI->valno->def && "Dangling Segment start");
assert(LVI->start == BI.FirstInstr && "First instr should be a def");
BI.FirstDef = BI.FirstInstr;
}
// Look for gaps in the live range.
BI.LiveOut = true;
while (LVI->end < Stop) {
SlotIndex LastStop = LVI->end;
if (++LVI == LVE || LVI->start >= Stop) {
BI.LiveOut = false;
BI.LastInstr = LastStop;
break;
}
if (LastStop < LVI->start) {
// There is a gap in the live range. Create duplicate entries for the
// live-in snippet and the live-out snippet.
++NumGapBlocks;
// Push the Live-in part.
BI.LiveOut = false;
UseBlocks.push_back(BI);
UseBlocks.back().LastInstr = LastStop;
// Set up BI for the live-out part.
BI.LiveIn = false;
BI.LiveOut = true;
BI.FirstInstr = BI.FirstDef = LVI->start;
}
// A Segment that starts in the middle of the block must be a def.
assert(LVI->start == LVI->valno->def && "Dangling Segment start");
if (!BI.FirstDef)
BI.FirstDef = LVI->start;
}
UseBlocks.push_back(BI);
// LVI is now at LVE or LVI->end >= Stop.
if (LVI == LVE)
break;
}
// Live segment ends exactly at Stop. Move to the next segment.
if (LVI->end == Stop && ++LVI == LVE)
break;
// Pick the next basic block.
if (LVI->start < Stop)
++MFI;
else
MFI = LIS.getMBBFromIndex(LVI->start)->getIterator();
}
assert(getNumLiveBlocks() == countLiveBlocks(CurLI) && "Bad block count");
return true;
}
unsigned SplitAnalysis::countLiveBlocks(const LiveInterval *cli) const {
if (cli->empty())
return 0;
LiveInterval *li = const_cast<LiveInterval*>(cli);
LiveInterval::iterator LVI = li->begin();
LiveInterval::iterator LVE = li->end();
unsigned Count = 0;
// Loop over basic blocks where li is live.
MachineFunction::const_iterator MFI =
LIS.getMBBFromIndex(LVI->start)->getIterator();
SlotIndex Stop = LIS.getMBBEndIdx(&*MFI);
while (true) {
++Count;
LVI = li->advanceTo(LVI, Stop);
if (LVI == LVE)
return Count;
do {
++MFI;
Stop = LIS.getMBBEndIdx(&*MFI);
} while (Stop <= LVI->start);
}
}
bool SplitAnalysis::isOriginalEndpoint(SlotIndex Idx) const {
unsigned OrigReg = VRM.getOriginal(CurLI->reg);
const LiveInterval &Orig = LIS.getInterval(OrigReg);
assert(!Orig.empty() && "Splitting empty interval?");
LiveInterval::const_iterator I = Orig.find(Idx);
// Range containing Idx should begin at Idx.
if (I != Orig.end() && I->start <= Idx)
return I->start == Idx;
// Range does not contain Idx, previous must end at Idx.
return I != Orig.begin() && (--I)->end == Idx;
}
void SplitAnalysis::analyze(const LiveInterval *li) {
clear();
CurLI = li;
analyzeUses();
}
//===----------------------------------------------------------------------===//
// Split Editor
//===----------------------------------------------------------------------===//
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
SplitEditor::SplitEditor(SplitAnalysis &sa, AliasAnalysis &aa,
LiveIntervals &lis, VirtRegMap &vrm,
MachineDominatorTree &mdt,
MachineBlockFrequencyInfo &mbfi)
: SA(sa), AA(aa), LIS(lis), VRM(vrm),
MRI(vrm.getMachineFunction().getRegInfo()), MDT(mdt),
TII(*vrm.getMachineFunction().getSubtarget().getInstrInfo()),
TRI(*vrm.getMachineFunction().getSubtarget().getRegisterInfo()),
MBFI(mbfi), RegAssign(Allocator) {}
void SplitEditor::reset(LiveRangeEdit &LRE, ComplementSpillMode SM) {
Edit = &LRE;
SpillMode = SM;
OpenIdx = 0;
RegAssign.clear();
Values.clear();
// Reset the LiveRangeCalc instances needed for this spill mode.
LRCalc[0].reset(&VRM.getMachineFunction(), LIS.getSlotIndexes(), &MDT,
&LIS.getVNInfoAllocator());
if (SpillMode)
LRCalc[1].reset(&VRM.getMachineFunction(), LIS.getSlotIndexes(), &MDT,
&LIS.getVNInfoAllocator());
// We don't need an AliasAnalysis since we will only be performing
// cheap-as-a-copy remats anyway.
Edit->anyRematerializable(nullptr);
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void SplitEditor::dump() const {
if (RegAssign.empty()) {
dbgs() << " empty\n";
return;
}
for (RegAssignMap::const_iterator I = RegAssign.begin(); I.valid(); ++I)
dbgs() << " [" << I.start() << ';' << I.stop() << "):" << I.value();
dbgs() << '\n';
}
#endif
LiveInterval::SubRange &SplitEditor::getSubRangeForMask(LaneBitmask LM,
LiveInterval &LI) {
for (LiveInterval::SubRange &S : LI.subranges())
if (S.LaneMask == LM)
return S;
llvm_unreachable("SubRange for this mask not found");
}
void SplitEditor::addDeadDef(LiveInterval &LI, VNInfo *VNI, bool Original) {
if (!LI.hasSubRanges()) {
LI.createDeadDef(VNI);
return;
}
SlotIndex Def = VNI->def;
if (Original) {
// If we are transferring a def from the original interval, make sure
// to only update the subranges for which the original subranges had
// a def at this location.
for (LiveInterval::SubRange &S : LI.subranges()) {
auto &PS = getSubRangeForMask(S.LaneMask, Edit->getParent());
VNInfo *PV = PS.getVNInfoAt(Def);
if (PV != nullptr && PV->def == Def)
S.createDeadDef(Def, LIS.getVNInfoAllocator());
}
} else {
// This is a new def: either from rematerialization, or from an inserted
// copy. Since rematerialization can regenerate a definition of a sub-
// register, we need to check which subranges need to be updated.
const MachineInstr *DefMI = LIS.getInstructionFromIndex(Def);
assert(DefMI != nullptr);
LaneBitmask LM;
for (const MachineOperand &DefOp : DefMI->defs()) {
unsigned R = DefOp.getReg();
if (R != LI.reg)
continue;
if (unsigned SR = DefOp.getSubReg())
LM |= TRI.getSubRegIndexLaneMask(SR);
else {
LM = MRI.getMaxLaneMaskForVReg(R);
break;
}
}
for (LiveInterval::SubRange &S : LI.subranges())
if ((S.LaneMask & LM).any())
S.createDeadDef(Def, LIS.getVNInfoAllocator());
}
}
VNInfo *SplitEditor::defValue(unsigned RegIdx,
const VNInfo *ParentVNI,
SlotIndex Idx,
bool Original) {
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(Edit->getParent().getVNInfoAt(Idx) == ParentVNI && "Bad Parent VNI");
LiveInterval *LI = &LIS.getInterval(Edit->get(RegIdx));
// Create a new value.
VNInfo *VNI = LI->getNextValue(Idx, LIS.getVNInfoAllocator());
bool Force = LI->hasSubRanges();
ValueForcePair FP(Force ? nullptr : VNI, Force);
// Use insert for lookup, so we can add missing values with a second lookup.
std::pair<ValueMap::iterator, bool> InsP =
Values.insert(std::make_pair(std::make_pair(RegIdx, ParentVNI->id), FP));
// This was the first time (RegIdx, ParentVNI) was mapped, and it is not
// forced. Keep it as a simple def without any liveness.
if (!Force && InsP.second)
return VNI;
// If the previous value was a simple mapping, add liveness for it now.
if (VNInfo *OldVNI = InsP.first->second.getPointer()) {
addDeadDef(*LI, OldVNI, Original);
// No longer a simple mapping. Switch to a complex mapping. If the
// interval has subranges, make it a forced mapping.
InsP.first->second = ValueForcePair(nullptr, Force);
}
// This is a complex mapping, add liveness for VNI
addDeadDef(*LI, VNI, Original);
return VNI;
}
void SplitEditor::forceRecompute(unsigned RegIdx, const VNInfo &ParentVNI) {
ValueForcePair &VFP = Values[std::make_pair(RegIdx, ParentVNI.id)];
VNInfo *VNI = VFP.getPointer();
// ParentVNI was either unmapped or already complex mapped. Either way, just
// set the force bit.
if (!VNI) {
VFP.setInt(true);
return;
}
// This was previously a single mapping. Make sure the old def is represented
// by a trivial live range.
addDeadDef(LIS.getInterval(Edit->get(RegIdx)), VNI, false);
// Mark as complex mapped, forced.
VFP = ValueForcePair(nullptr, true);
}
SlotIndex SplitEditor::buildSingleSubRegCopy(unsigned FromReg, unsigned ToReg,
MachineBasicBlock &MBB, MachineBasicBlock::iterator InsertBefore,
unsigned SubIdx, LiveInterval &DestLI, bool Late, SlotIndex Def) {
const MCInstrDesc &Desc = TII.get(TargetOpcode::COPY);
bool FirstCopy = !Def.isValid();
MachineInstr *CopyMI = BuildMI(MBB, InsertBefore, DebugLoc(), Desc)
.addReg(ToReg, RegState::Define | getUndefRegState(FirstCopy)
| getInternalReadRegState(!FirstCopy), SubIdx)
.addReg(FromReg, 0, SubIdx);
BumpPtrAllocator &Allocator = LIS.getVNInfoAllocator();
if (FirstCopy) {
SlotIndexes &Indexes = *LIS.getSlotIndexes();
Def = Indexes.insertMachineInstrInMaps(*CopyMI, Late).getRegSlot();
} else {
CopyMI->bundleWithPred();
}
LaneBitmask LaneMask = TRI.getSubRegIndexLaneMask(SubIdx);
DestLI.refineSubRanges(Allocator, LaneMask,
[Def, &Allocator](LiveInterval::SubRange& SR) {
SR.createDeadDef(Def, Allocator);
});
return Def;
}
SlotIndex SplitEditor::buildCopy(unsigned FromReg, unsigned ToReg,
LaneBitmask LaneMask, MachineBasicBlock &MBB,
MachineBasicBlock::iterator InsertBefore, bool Late, unsigned RegIdx) {
const MCInstrDesc &Desc = TII.get(TargetOpcode::COPY);
if (LaneMask.all() || LaneMask == MRI.getMaxLaneMaskForVReg(FromReg)) {
// The full vreg is copied.
MachineInstr *CopyMI =
BuildMI(MBB, InsertBefore, DebugLoc(), Desc, ToReg).addReg(FromReg);
SlotIndexes &Indexes = *LIS.getSlotIndexes();
return Indexes.insertMachineInstrInMaps(*CopyMI, Late).getRegSlot();
}
// Only a subset of lanes needs to be copied. The following is a simple
// heuristic to construct a sequence of COPYs. We could add a target
// specific callback if this turns out to be suboptimal.
LiveInterval &DestLI = LIS.getInterval(Edit->get(RegIdx));
// First pass: Try to find a perfectly matching subregister index. If none
// exists find the one covering the most lanemask bits.
SmallVector<unsigned, 8> PossibleIndexes;
unsigned BestIdx = 0;
unsigned BestCover = 0;
const TargetRegisterClass *RC = MRI.getRegClass(FromReg);
assert(RC == MRI.getRegClass(ToReg) && "Should have same reg class");
for (unsigned Idx = 1, E = TRI.getNumSubRegIndices(); Idx < E; ++Idx) {
// Is this index even compatible with the given class?
if (TRI.getSubClassWithSubReg(RC, Idx) != RC)
continue;
LaneBitmask SubRegMask = TRI.getSubRegIndexLaneMask(Idx);
// Early exit if we found a perfect match.
if (SubRegMask == LaneMask) {
BestIdx = Idx;
break;
}
// The index must not cover any lanes outside \p LaneMask.
if ((SubRegMask & ~LaneMask).any())
continue;
unsigned PopCount = SubRegMask.getNumLanes();
PossibleIndexes.push_back(Idx);
if (PopCount > BestCover) {
BestCover = PopCount;
BestIdx = Idx;
}
}
// Abort if we cannot possibly implement the COPY with the given indexes.
if (BestIdx == 0)
report_fatal_error("Impossible to implement partial COPY");
SlotIndex Def = buildSingleSubRegCopy(FromReg, ToReg, MBB, InsertBefore,
BestIdx, DestLI, Late, SlotIndex());
// Greedy heuristic: Keep iterating keeping the best covering subreg index
// each time.
LaneBitmask LanesLeft = LaneMask & ~(TRI.getSubRegIndexLaneMask(BestIdx));
while (LanesLeft.any()) {
unsigned BestIdx = 0;
int BestCover = std::numeric_limits<int>::min();
for (unsigned Idx : PossibleIndexes) {
LaneBitmask SubRegMask = TRI.getSubRegIndexLaneMask(Idx);
// Early exit if we found a perfect match.
if (SubRegMask == LanesLeft) {
BestIdx = Idx;
break;
}
// Try to cover as much of the remaining lanes as possible but
// as few of the already covered lanes as possible.
int Cover = (SubRegMask & LanesLeft).getNumLanes()
- (SubRegMask & ~LanesLeft).getNumLanes();
if (Cover > BestCover) {
BestCover = Cover;
BestIdx = Idx;
}
}
if (BestIdx == 0)
report_fatal_error("Impossible to implement partial COPY");
buildSingleSubRegCopy(FromReg, ToReg, MBB, InsertBefore, BestIdx,
DestLI, Late, Def);
LanesLeft &= ~TRI.getSubRegIndexLaneMask(BestIdx);
}
return Def;
}
VNInfo *SplitEditor::defFromParent(unsigned RegIdx,
VNInfo *ParentVNI,
SlotIndex UseIdx,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
SlotIndex Def;
LiveInterval *LI = &LIS.getInterval(Edit->get(RegIdx));
// We may be trying to avoid interference that ends at a deleted instruction,
// so always begin RegIdx 0 early and all others late.
bool Late = RegIdx != 0;
// Attempt cheap-as-a-copy rematerialization.
unsigned Original = VRM.getOriginal(Edit->get(RegIdx));
LiveInterval &OrigLI = LIS.getInterval(Original);
VNInfo *OrigVNI = OrigLI.getVNInfoAt(UseIdx);
unsigned Reg = LI->reg;
bool DidRemat = false;
if (OrigVNI) {
LiveRangeEdit::Remat RM(ParentVNI);
RM.OrigMI = LIS.getInstructionFromIndex(OrigVNI->def);
if (Edit->canRematerializeAt(RM, OrigVNI, UseIdx, true)) {
Def = Edit->rematerializeAt(MBB, I, Reg, RM, TRI, Late);
++NumRemats;
DidRemat = true;
}
}
if (!DidRemat) {
LaneBitmask LaneMask;
if (LI->hasSubRanges()) {
LaneMask = LaneBitmask::getNone();
for (LiveInterval::SubRange &S : LI->subranges())
LaneMask |= S.LaneMask;
} else {
LaneMask = LaneBitmask::getAll();
}
++NumCopies;
Def = buildCopy(Edit->getReg(), Reg, LaneMask, MBB, I, Late, RegIdx);
}
// Define the value in Reg.
return defValue(RegIdx, ParentVNI, Def, false);
}
/// Create a new virtual register and live interval.
unsigned SplitEditor::openIntv() {
// Create the complement as index 0.
if (Edit->empty())
Edit->createEmptyInterval();
// Create the open interval.
OpenIdx = Edit->size();
Edit->createEmptyInterval();
return OpenIdx;
}
void SplitEditor::selectIntv(unsigned Idx) {
assert(Idx != 0 && "Cannot select the complement interval");
assert(Idx < Edit->size() && "Can only select previously opened interval");
LLVM_DEBUG(dbgs() << " selectIntv " << OpenIdx << " -> " << Idx << '\n');
OpenIdx = Idx;
}
SlotIndex SplitEditor::enterIntvBefore(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before enterIntvBefore");
LLVM_DEBUG(dbgs() << " enterIntvBefore " << Idx);
Idx = Idx.getBaseIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
LLVM_DEBUG(dbgs() << ": not live\n");
return Idx;
}
LLVM_DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Idx);
assert(MI && "enterIntvBefore called with invalid index");
VNInfo *VNI = defFromParent(OpenIdx, ParentVNI, Idx, *MI->getParent(), MI);
return VNI->def;
}
SlotIndex SplitEditor::enterIntvAfter(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before enterIntvAfter");
LLVM_DEBUG(dbgs() << " enterIntvAfter " << Idx);
Idx = Idx.getBoundaryIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
LLVM_DEBUG(dbgs() << ": not live\n");
return Idx;
}
LLVM_DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Idx);
assert(MI && "enterIntvAfter called with invalid index");
VNInfo *VNI = defFromParent(OpenIdx, ParentVNI, Idx, *MI->getParent(),
std::next(MachineBasicBlock::iterator(MI)));
return VNI->def;
}
SlotIndex SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) {
assert(OpenIdx && "openIntv not called before enterIntvAtEnd");
SlotIndex End = LIS.getMBBEndIdx(&MBB);
SlotIndex Last = End.getPrevSlot();
LLVM_DEBUG(dbgs() << " enterIntvAtEnd " << printMBBReference(MBB) << ", "
<< Last);
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Last);
if (!ParentVNI) {
LLVM_DEBUG(dbgs() << ": not live\n");
return End;
}
LLVM_DEBUG(dbgs() << ": valno " << ParentVNI->id);
VNInfo *VNI = defFromParent(OpenIdx, ParentVNI, Last, MBB,
SA.getLastSplitPointIter(&MBB));
RegAssign.insert(VNI->def, End, OpenIdx);
LLVM_DEBUG(dump());
return VNI->def;
}
/// useIntv - indicate that all instructions in MBB should use OpenLI.
void SplitEditor::useIntv(const MachineBasicBlock &MBB) {
useIntv(LIS.getMBBStartIdx(&MBB), LIS.getMBBEndIdx(&MBB));
}
void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
assert(OpenIdx && "openIntv not called before useIntv");
LLVM_DEBUG(dbgs() << " useIntv [" << Start << ';' << End << "):");
RegAssign.insert(Start, End, OpenIdx);
LLVM_DEBUG(dump());
}
SlotIndex SplitEditor::leaveIntvAfter(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before leaveIntvAfter");
LLVM_DEBUG(dbgs() << " leaveIntvAfter " << Idx);
// The interval must be live beyond the instruction at Idx.
SlotIndex Boundary = Idx.getBoundaryIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Boundary);
if (!ParentVNI) {
LLVM_DEBUG(dbgs() << ": not live\n");
return Boundary.getNextSlot();
}
LLVM_DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Boundary);
assert(MI && "No instruction at index");
// In spill mode, make live ranges as short as possible by inserting the copy
// before MI. This is only possible if that instruction doesn't redefine the
// value. The inserted COPY is not a kill, and we don't need to recompute
// the source live range. The spiller also won't try to hoist this copy.
if (SpillMode && !SlotIndex::isSameInstr(ParentVNI->def, Idx) &&
MI->readsVirtualRegister(Edit->getReg())) {
forceRecompute(0, *ParentVNI);
defFromParent(0, ParentVNI, Idx, *MI->getParent(), MI);
return Idx;
}
VNInfo *VNI = defFromParent(0, ParentVNI, Boundary, *MI->getParent(),
std::next(MachineBasicBlock::iterator(MI)));
return VNI->def;
}
SlotIndex SplitEditor::leaveIntvBefore(SlotIndex Idx) {
assert(OpenIdx && "openIntv not called before leaveIntvBefore");
LLVM_DEBUG(dbgs() << " leaveIntvBefore " << Idx);
// The interval must be live into the instruction at Idx.
Idx = Idx.getBaseIndex();
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
LLVM_DEBUG(dbgs() << ": not live\n");
return Idx.getNextSlot();
}
LLVM_DEBUG(dbgs() << ": valno " << ParentVNI->id << '\n');
MachineInstr *MI = LIS.getInstructionFromIndex(Idx);
assert(MI && "No instruction at index");
VNInfo *VNI = defFromParent(0, ParentVNI, Idx, *MI->getParent(), MI);
return VNI->def;
}
SlotIndex SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
assert(OpenIdx && "openIntv not called before leaveIntvAtTop");
SlotIndex Start = LIS.getMBBStartIdx(&MBB);
LLVM_DEBUG(dbgs() << " leaveIntvAtTop " << printMBBReference(MBB) << ", "
<< Start);
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Start);
if (!ParentVNI) {
LLVM_DEBUG(dbgs() << ": not live\n");
return Start;
}
VNInfo *VNI = defFromParent(0, ParentVNI, Start, MBB,
MBB.SkipPHIsLabelsAndDebug(MBB.begin()));
RegAssign.insert(Start, VNI->def, OpenIdx);
LLVM_DEBUG(dump());
return VNI->def;
}
void SplitEditor::overlapIntv(SlotIndex Start, SlotIndex End) {
assert(OpenIdx && "openIntv not called before overlapIntv");
const VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(Start);
assert(ParentVNI == Edit->getParent().getVNInfoBefore(End) &&
"Parent changes value in extended range");
assert(LIS.getMBBFromIndex(Start) == LIS.getMBBFromIndex(End) &&
"Range cannot span basic blocks");
// The complement interval will be extended as needed by LRCalc.extend().
if (ParentVNI)
forceRecompute(0, *ParentVNI);
LLVM_DEBUG(dbgs() << " overlapIntv [" << Start << ';' << End << "):");
RegAssign.insert(Start, End, OpenIdx);
LLVM_DEBUG(dump());
}
//===----------------------------------------------------------------------===//
// Spill modes
//===----------------------------------------------------------------------===//
void SplitEditor::removeBackCopies(SmallVectorImpl<VNInfo*> &Copies) {
LiveInterval *LI = &LIS.getInterval(Edit->get(0));
LLVM_DEBUG(dbgs() << "Removing " << Copies.size() << " back-copies.\n");
RegAssignMap::iterator AssignI;
AssignI.setMap(RegAssign);
for (unsigned i = 0, e = Copies.size(); i != e; ++i) {
SlotIndex Def = Copies[i]->def;
MachineInstr *MI = LIS.getInstructionFromIndex(Def);
assert(MI && "No instruction for back-copy");
MachineBasicBlock *MBB = MI->getParent();
MachineBasicBlock::iterator MBBI(MI);
bool AtBegin;
do AtBegin = MBBI == MBB->begin();
while (!AtBegin && (--MBBI)->isDebugInstr());
LLVM_DEBUG(dbgs() << "Removing " << Def << '\t' << *MI);
LIS.removeVRegDefAt(*LI, Def);
LIS.RemoveMachineInstrFromMaps(*MI);
MI->eraseFromParent();
// Adjust RegAssign if a register assignment is killed at Def. We want to
// avoid calculating the live range of the source register if possible.
AssignI.find(Def.getPrevSlot());
if (!AssignI.valid() || AssignI.start() >= Def)
continue;
// If MI doesn't kill the assigned register, just leave it.
if (AssignI.stop() != Def)
continue;
unsigned RegIdx = AssignI.value();
if (AtBegin || !MBBI->readsVirtualRegister(Edit->getReg())) {
LLVM_DEBUG(dbgs() << " cannot find simple kill of RegIdx " << RegIdx
<< '\n');
forceRecompute(RegIdx, *Edit->getParent().getVNInfoAt(Def));
} else {
SlotIndex Kill = LIS.getInstructionIndex(*MBBI).getRegSlot();
LLVM_DEBUG(dbgs() << " move kill to " << Kill << '\t' << *MBBI);
AssignI.setStop(Kill);
}
}
}
MachineBasicBlock*
SplitEditor::findShallowDominator(MachineBasicBlock *MBB,
MachineBasicBlock *DefMBB) {
if (MBB == DefMBB)
return MBB;
assert(MDT.dominates(DefMBB, MBB) && "MBB must be dominated by the def.");
const MachineLoopInfo &Loops = SA.Loops;
const MachineLoop *DefLoop = Loops.getLoopFor(DefMBB);
MachineDomTreeNode *DefDomNode = MDT[DefMBB];
// Best candidate so far.
MachineBasicBlock *BestMBB = MBB;
unsigned BestDepth = std::numeric_limits<unsigned>::max();
while (true) {
const MachineLoop *Loop = Loops.getLoopFor(MBB);
// MBB isn't in a loop, it doesn't get any better. All dominators have a
// higher frequency by definition.
if (!Loop) {
LLVM_DEBUG(dbgs() << "Def in " << printMBBReference(*DefMBB)
<< " dominates " << printMBBReference(*MBB)
<< " at depth 0\n");
return MBB;
}
// We'll never be able to exit the DefLoop.
if (Loop == DefLoop) {
LLVM_DEBUG(dbgs() << "Def in " << printMBBReference(*DefMBB)
<< " dominates " << printMBBReference(*MBB)
<< " in the same loop\n");
return MBB;
}
// Least busy dominator seen so far.
unsigned Depth = Loop->getLoopDepth();
if (Depth < BestDepth) {
BestMBB = MBB;
BestDepth = Depth;
LLVM_DEBUG(dbgs() << "Def in " << printMBBReference(*DefMBB)
<< " dominates " << printMBBReference(*MBB)
<< " at depth " << Depth << '\n');
}
// Leave loop by going to the immediate dominator of the loop header.
// This is a bigger stride than simply walking up the dominator tree.
MachineDomTreeNode *IDom = MDT[Loop->getHeader()]->getIDom();
// Too far up the dominator tree?
if (!IDom || !MDT.dominates(DefDomNode, IDom))
return BestMBB;
MBB = IDom->getBlock();
}
}
void SplitEditor::computeRedundantBackCopies(
DenseSet<unsigned> &NotToHoistSet, SmallVectorImpl<VNInfo *> &BackCopies) {
LiveInterval *LI = &LIS.getInterval(Edit->get(0));
LiveInterval *Parent = &Edit->getParent();
SmallVector<SmallPtrSet<VNInfo *, 8>, 8> EqualVNs(Parent->getNumValNums());
SmallPtrSet<VNInfo *, 8> DominatedVNIs;
// Aggregate VNIs having the same value as ParentVNI.
for (VNInfo *VNI : LI->valnos) {
if (VNI->isUnused())
continue;
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(VNI->def);
EqualVNs[ParentVNI->id].insert(VNI);
}
// For VNI aggregation of each ParentVNI, collect dominated, i.e.,
// redundant VNIs to BackCopies.
for (unsigned i = 0, e = Parent->getNumValNums(); i != e; ++i) {
VNInfo *ParentVNI = Parent->getValNumInfo(i);
if (!NotToHoistSet.count(ParentVNI->id))
continue;
SmallPtrSetIterator<VNInfo *> It1 = EqualVNs[ParentVNI->id].begin();
SmallPtrSetIterator<VNInfo *> It2 = It1;
for (; It1 != EqualVNs[ParentVNI->id].end(); ++It1) {
It2 = It1;
for (++It2; It2 != EqualVNs[ParentVNI->id].end(); ++It2) {
if (DominatedVNIs.count(*It1) || DominatedVNIs.count(*It2))
continue;
MachineBasicBlock *MBB1 = LIS.getMBBFromIndex((*It1)->def);
MachineBasicBlock *MBB2 = LIS.getMBBFromIndex((*It2)->def);
if (MBB1 == MBB2) {
DominatedVNIs.insert((*It1)->def < (*It2)->def ? (*It2) : (*It1));
} else if (MDT.dominates(MBB1, MBB2)) {
DominatedVNIs.insert(*It2);
} else if (MDT.dominates(MBB2, MBB1)) {
DominatedVNIs.insert(*It1);
}
}
}
if (!DominatedVNIs.empty()) {
forceRecompute(0, *ParentVNI);
for (auto VNI : DominatedVNIs) {
BackCopies.push_back(VNI);
}
DominatedVNIs.clear();
}
}
}
/// For SM_Size mode, find a common dominator for all the back-copies for
/// the same ParentVNI and hoist the backcopies to the dominator BB.
/// For SM_Speed mode, if the common dominator is hot and it is not beneficial
/// to do the hoisting, simply remove the dominated backcopies for the same
/// ParentVNI.
void SplitEditor::hoistCopies() {
// Get the complement interval, always RegIdx 0.
LiveInterval *LI = &LIS.getInterval(Edit->get(0));
LiveInterval *Parent = &Edit->getParent();
// Track the nearest common dominator for all back-copies for each ParentVNI,
// indexed by ParentVNI->id.
using DomPair = std::pair<MachineBasicBlock *, SlotIndex>;
SmallVector<DomPair, 8> NearestDom(Parent->getNumValNums());
// The total cost of all the back-copies for each ParentVNI.
SmallVector<BlockFrequency, 8> Costs(Parent->getNumValNums());
// The ParentVNI->id set for which hoisting back-copies are not beneficial
// for Speed.
DenseSet<unsigned> NotToHoistSet;
// Find the nearest common dominator for parent values with multiple
// back-copies. If a single back-copy dominates, put it in DomPair.second.
for (VNInfo *VNI : LI->valnos) {
if (VNI->isUnused())
continue;
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(VNI->def);
assert(ParentVNI && "Parent not live at complement def");
// Don't hoist remats. The complement is probably going to disappear
// completely anyway.
if (Edit->didRematerialize(ParentVNI))
continue;
MachineBasicBlock *ValMBB = LIS.getMBBFromIndex(VNI->def);
DomPair &Dom = NearestDom[ParentVNI->id];
// Keep directly defined parent values. This is either a PHI or an
// instruction in the complement range. All other copies of ParentVNI
// should be eliminated.
if (VNI->def == ParentVNI->def) {
LLVM_DEBUG(dbgs() << "Direct complement def at " << VNI->def << '\n');
Dom = DomPair(ValMBB, VNI->def);
continue;
}
// Skip the singly mapped values. There is nothing to gain from hoisting a
// single back-copy.
if (Values.lookup(std::make_pair(0, ParentVNI->id)).getPointer()) {
LLVM_DEBUG(dbgs() << "Single complement def at " << VNI->def << '\n');
continue;
}
if (!Dom.first) {
// First time we see ParentVNI. VNI dominates itself.
Dom = DomPair(ValMBB, VNI->def);
} else if (Dom.first == ValMBB) {
// Two defs in the same block. Pick the earlier def.
if (!Dom.second.isValid() || VNI->def < Dom.second)
Dom.second = VNI->def;
} else {
// Different basic blocks. Check if one dominates.
MachineBasicBlock *Near =
MDT.findNearestCommonDominator(Dom.first, ValMBB);
if (Near == ValMBB)
// Def ValMBB dominates.
Dom = DomPair(ValMBB, VNI->def);
else if (Near != Dom.first)
// None dominate. Hoist to common dominator, need new def.
Dom = DomPair(Near, SlotIndex());
Costs[ParentVNI->id] += MBFI.getBlockFreq(ValMBB);
}
LLVM_DEBUG(dbgs() << "Multi-mapped complement " << VNI->id << '@'
<< VNI->def << " for parent " << ParentVNI->id << '@'
<< ParentVNI->def << " hoist to "
<< printMBBReference(*Dom.first) << ' ' << Dom.second
<< '\n');
}
// Insert the hoisted copies.
for (unsigned i = 0, e = Parent->getNumValNums(); i != e; ++i) {
DomPair &Dom = NearestDom[i];
if (!Dom.first || Dom.second.isValid())
continue;
// This value needs a hoisted copy inserted at the end of Dom.first.
VNInfo *ParentVNI = Parent->getValNumInfo(i);
MachineBasicBlock *DefMBB = LIS.getMBBFromIndex(ParentVNI->def);
// Get a less loopy dominator than Dom.first.
Dom.first = findShallowDominator(Dom.first, DefMBB);
if (SpillMode == SM_Speed &&
MBFI.getBlockFreq(Dom.first) > Costs[ParentVNI->id]) {
NotToHoistSet.insert(ParentVNI->id);
continue;
}
SlotIndex Last = LIS.getMBBEndIdx(Dom.first).getPrevSlot();
Dom.second =
defFromParent(0, ParentVNI, Last, *Dom.first,
SA.getLastSplitPointIter(Dom.first))->def;
}
// Remove redundant back-copies that are now known to be dominated by another
// def with the same value.
SmallVector<VNInfo*, 8> BackCopies;
for (VNInfo *VNI : LI->valnos) {
if (VNI->isUnused())
continue;
VNInfo *ParentVNI = Edit->getParent().getVNInfoAt(VNI->def);
const DomPair &Dom = NearestDom[ParentVNI->id];
if (!Dom.first || Dom.second == VNI->def ||
NotToHoistSet.count(ParentVNI->id))
continue;
BackCopies.push_back(VNI);
forceRecompute(0, *ParentVNI);
}
// If it is not beneficial to hoist all the BackCopies, simply remove
// redundant BackCopies in speed mode.
if (SpillMode == SM_Speed && !NotToHoistSet.empty())
computeRedundantBackCopies(NotToHoistSet, BackCopies);
removeBackCopies(BackCopies);
}
/// transferValues - Transfer all possible values to the new live ranges.
/// Values that were rematerialized are left alone, they need LRCalc.extend().
bool SplitEditor::transferValues() {
bool Skipped = false;
RegAssignMap::const_iterator AssignI = RegAssign.begin();
for (const LiveRange::Segment &S : Edit->getParent()) {
LLVM_DEBUG(dbgs() << " blit " << S << ':');
VNInfo *ParentVNI = S.valno;
// RegAssign has holes where RegIdx 0 should be used.
SlotIndex Start = S.start;
AssignI.advanceTo(Start);
do {
unsigned RegIdx;
SlotIndex End = S.end;
if (!AssignI.valid()) {
RegIdx = 0;
} else if (AssignI.start() <= Start) {
RegIdx = AssignI.value();
if (AssignI.stop() < End) {
End = AssignI.stop();
++AssignI;
}
} else {
RegIdx = 0;
End = std::min(End, AssignI.start());
}
// The interval [Start;End) is continuously mapped to RegIdx, ParentVNI.
LLVM_DEBUG(dbgs() << " [" << Start << ';' << End << ")=" << RegIdx << '('
<< printReg(Edit->get(RegIdx)) << ')');
LiveInterval &LI = LIS.getInterval(Edit->get(RegIdx));
// Check for a simply defined value that can be blitted directly.
ValueForcePair VFP = Values.lookup(std::make_pair(RegIdx, ParentVNI->id));
if (VNInfo *VNI = VFP.getPointer()) {
LLVM_DEBUG(dbgs() << ':' << VNI->id);
LI.addSegment(LiveInterval::Segment(Start, End, VNI));
Start = End;
continue;
}
// Skip values with forced recomputation.
if (VFP.getInt()) {
LLVM_DEBUG(dbgs() << "(recalc)");
Skipped = true;
Start = End;
continue;
}
LiveRangeCalc &LRC = getLRCalc(RegIdx);
// This value has multiple defs in RegIdx, but it wasn't rematerialized,
// so the live range is accurate. Add live-in blocks in [Start;End) to the
// LiveInBlocks.
MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start)->getIterator();
SlotIndex BlockStart, BlockEnd;
std::tie(BlockStart, BlockEnd) = LIS.getSlotIndexes()->getMBBRange(&*MBB);
// The first block may be live-in, or it may have its own def.
if (Start != BlockStart) {
VNInfo *VNI = LI.extendInBlock(BlockStart, std::min(BlockEnd, End));
assert(VNI && "Missing def for complex mapped value");
LLVM_DEBUG(dbgs() << ':' << VNI->id << "*" << printMBBReference(*MBB));
// MBB has its own def. Is it also live-out?
if (BlockEnd <= End)
LRC.setLiveOutValue(&*MBB, VNI);
// Skip to the next block for live-in.
++MBB;
BlockStart = BlockEnd;
}
// Handle the live-in blocks covered by [Start;End).
assert(Start <= BlockStart && "Expected live-in block");
while (BlockStart < End) {
LLVM_DEBUG(dbgs() << ">" << printMBBReference(*MBB));
BlockEnd = LIS.getMBBEndIdx(&*MBB);
if (BlockStart == ParentVNI->def) {
// This block has the def of a parent PHI, so it isn't live-in.
assert(ParentVNI->isPHIDef() && "Non-phi defined at block start?");
VNInfo *VNI = LI.extendInBlock(BlockStart, std::min(BlockEnd, End));
assert(VNI && "Missing def for complex mapped parent PHI");
if (End >= BlockEnd)
LRC.setLiveOutValue(&*MBB, VNI); // Live-out as well.
} else {
// This block needs a live-in value. The last block covered may not
// be live-out.
if (End < BlockEnd)
LRC.addLiveInBlock(LI, MDT[&*MBB], End);
else {
// Live-through, and we don't know the value.
LRC.addLiveInBlock(LI, MDT[&*MBB]);
LRC.setLiveOutValue(&*MBB, nullptr);
}
}
BlockStart = BlockEnd;
++MBB;
}
Start = End;
} while (Start != S.end);
LLVM_DEBUG(dbgs() << '\n');
}
LRCalc[0].calculateValues();
if (SpillMode)
LRCalc[1].calculateValues();
return Skipped;
}
static bool removeDeadSegment(SlotIndex Def, LiveRange &LR) {
const LiveRange::Segment *Seg = LR.getSegmentContaining(Def);
if (Seg == nullptr)
return true;
if (Seg->end != Def.getDeadSlot())
return false;
// This is a dead PHI. Remove it.
LR.removeSegment(*Seg, true);
return true;
}
void SplitEditor::extendPHIRange(MachineBasicBlock &B, LiveRangeCalc &LRC,
LiveRange &LR, LaneBitmask LM,
ArrayRef<SlotIndex> Undefs) {
for (MachineBasicBlock *P : B.predecessors()) {
SlotIndex End = LIS.getMBBEndIdx(P);
SlotIndex LastUse = End.getPrevSlot();
// The predecessor may not have a live-out value. That is OK, like an
// undef PHI operand.
LiveInterval &PLI = Edit->getParent();
// Need the cast because the inputs to ?: would otherwise be deemed
// "incompatible": SubRange vs LiveInterval.
LiveRange &PSR = !LM.all() ? getSubRangeForMask(LM, PLI)
: static_cast<LiveRange&>(PLI);
if (PSR.liveAt(LastUse))
LRC.extend(LR, End, /*PhysReg=*/0, Undefs);
}
}
void SplitEditor::extendPHIKillRanges() {
// Extend live ranges to be live-out for successor PHI values.
// Visit each PHI def slot in the parent live interval. If the def is dead,
// remove it. Otherwise, extend the live interval to reach the end indexes
// of all predecessor blocks.
LiveInterval &ParentLI = Edit->getParent();
for (const VNInfo *V : ParentLI.valnos) {
if (V->isUnused() || !V->isPHIDef())
continue;
unsigned RegIdx = RegAssign.lookup(V->def);
LiveInterval &LI = LIS.getInterval(Edit->get(RegIdx));
LiveRangeCalc &LRC = getLRCalc(RegIdx);
MachineBasicBlock &B = *LIS.getMBBFromIndex(V->def);
if (!removeDeadSegment(V->def, LI))
extendPHIRange(B, LRC, LI, LaneBitmask::getAll(), /*Undefs=*/{});
}
SmallVector<SlotIndex, 4> Undefs;
LiveRangeCalc SubLRC;
for (LiveInterval::SubRange &PS : ParentLI.subranges()) {
for (const VNInfo *V : PS.valnos) {
if (V->isUnused() || !V->isPHIDef())
continue;
unsigned RegIdx = RegAssign.lookup(V->def);
LiveInterval &LI = LIS.getInterval(Edit->get(RegIdx));
LiveInterval::SubRange &S = getSubRangeForMask(PS.LaneMask, LI);
if (removeDeadSegment(V->def, S))
continue;
MachineBasicBlock &B = *LIS.getMBBFromIndex(V->def);
SubLRC.reset(&VRM.getMachineFunction(), LIS.getSlotIndexes(), &MDT,
&LIS.getVNInfoAllocator());
Undefs.clear();
LI.computeSubRangeUndefs(Undefs, PS.LaneMask, MRI, *LIS.getSlotIndexes());
extendPHIRange(B, SubLRC, S, PS.LaneMask, Undefs);
}
}
}
/// rewriteAssigned - Rewrite all uses of Edit->getReg().
void SplitEditor::rewriteAssigned(bool ExtendRanges) {
struct ExtPoint {
ExtPoint(const MachineOperand &O, unsigned R, SlotIndex N)
: MO(O), RegIdx(R), Next(N) {}
MachineOperand MO;
unsigned RegIdx;
SlotIndex Next;
};
SmallVector<ExtPoint,4> ExtPoints;
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(Edit->getReg()),
RE = MRI.reg_end(); RI != RE;) {
MachineOperand &MO = *RI;
MachineInstr *MI = MO.getParent();
++RI;
// LiveDebugVariables should have handled all DBG_VALUE instructions.
if (MI->isDebugValue()) {
LLVM_DEBUG(dbgs() << "Zapping " << *MI);
MO.setReg(0);
continue;
}
// <undef> operands don't really read the register, so it doesn't matter
// which register we choose. When the use operand is tied to a def, we must
// use the same register as the def, so just do that always.
SlotIndex Idx = LIS.getInstructionIndex(*MI);
if (MO.isDef() || MO.isUndef())
Idx = Idx.getRegSlot(MO.isEarlyClobber());
// Rewrite to the mapped register at Idx.
unsigned RegIdx = RegAssign.lookup(Idx);
LiveInterval &LI = LIS.getInterval(Edit->get(RegIdx));
MO.setReg(LI.reg);
LLVM_DEBUG(dbgs() << " rewr " << printMBBReference(*MI->getParent())
<< '\t' << Idx << ':' << RegIdx << '\t' << *MI);
// Extend liveness to Idx if the instruction reads reg.
if (!ExtendRanges || MO.isUndef())
continue;
// Skip instructions that don't read Reg.
if (MO.isDef()) {
if (!MO.getSubReg() && !MO.isEarlyClobber())
continue;
// We may want to extend a live range for a partial redef, or for a use
// tied to an early clobber.
Idx = Idx.getPrevSlot();
if (!Edit->getParent().liveAt(Idx))
continue;
} else
Idx = Idx.getRegSlot(true);
SlotIndex Next = Idx.getNextSlot();
if (LI.hasSubRanges()) {
// We have to delay extending subranges until we have seen all operands
// defining the register. This is because a <def,read-undef> operand
// will create an "undef" point, and we cannot extend any subranges
// until all of them have been accounted for.
if (MO.isUse())
ExtPoints.push_back(ExtPoint(MO, RegIdx, Next));
} else {
LiveRangeCalc &LRC = getLRCalc(RegIdx);
LRC.extend(LI, Next, 0, ArrayRef<SlotIndex>());
}
}
for (ExtPoint &EP : ExtPoints) {
LiveInterval &LI = LIS.getInterval(Edit->get(EP.RegIdx));
assert(LI.hasSubRanges());
LiveRangeCalc SubLRC;
unsigned Reg = EP.MO.getReg(), Sub = EP.MO.getSubReg();
LaneBitmask LM = Sub != 0 ? TRI.getSubRegIndexLaneMask(Sub)
: MRI.getMaxLaneMaskForVReg(Reg);
for (LiveInterval::SubRange &S : LI.subranges()) {
if ((S.LaneMask & LM).none())
continue;
// The problem here can be that the new register may have been created
// for a partially defined original register. For example:
// %0:subreg_hireg<def,read-undef> = ...
// ...
// %1 = COPY %0
if (S.empty())
continue;
SubLRC.reset(&VRM.getMachineFunction(), LIS.getSlotIndexes(), &MDT,
&LIS.getVNInfoAllocator());
SmallVector<SlotIndex, 4> Undefs;
LI.computeSubRangeUndefs(Undefs, S.LaneMask, MRI, *LIS.getSlotIndexes());
SubLRC.extend(S, EP.Next, 0, Undefs);
}
}
for (unsigned R : *Edit) {
LiveInterval &LI = LIS.getInterval(R);
if (!LI.hasSubRanges())
continue;
LI.clear();
LI.removeEmptySubRanges();
LIS.constructMainRangeFromSubranges(LI);
}
}
void SplitEditor::deleteRematVictims() {
SmallVector<MachineInstr*, 8> Dead;
for (LiveRangeEdit::iterator I = Edit->begin(), E = Edit->end(); I != E; ++I){
LiveInterval *LI = &LIS.getInterval(*I);
for (const LiveRange::Segment &S : LI->segments) {
// Dead defs end at the dead slot.
if (S.end != S.valno->def.getDeadSlot())
continue;
if (S.valno->isPHIDef())
continue;
MachineInstr *MI = LIS.getInstructionFromIndex(S.valno->def);
assert(MI && "Missing instruction for dead def");
MI->addRegisterDead(LI->reg, &TRI);
if (!MI->allDefsAreDead())
continue;
LLVM_DEBUG(dbgs() << "All defs dead: " << *MI);
Dead.push_back(MI);
}
}
if (Dead.empty())
return;
Edit->eliminateDeadDefs(Dead, None, &AA);
}
void SplitEditor::forceRecomputeVNI(const VNInfo &ParentVNI) {
// Fast-path for common case.
if (!ParentVNI.isPHIDef()) {
for (unsigned I = 0, E = Edit->size(); I != E; ++I)
forceRecompute(I, ParentVNI);
return;
}
// Trace value through phis.
SmallPtrSet<const VNInfo *, 8> Visited; ///< whether VNI was/is in worklist.
SmallVector<const VNInfo *, 4> WorkList;
Visited.insert(&ParentVNI);
WorkList.push_back(&ParentVNI);
const LiveInterval &ParentLI = Edit->getParent();
const SlotIndexes &Indexes = *LIS.getSlotIndexes();
do {
const VNInfo &VNI = *WorkList.back();
WorkList.pop_back();
for (unsigned I = 0, E = Edit->size(); I != E; ++I)
forceRecompute(I, VNI);
if (!VNI.isPHIDef())
continue;
MachineBasicBlock &MBB = *Indexes.getMBBFromIndex(VNI.def);
for (const MachineBasicBlock *Pred : MBB.predecessors()) {
SlotIndex PredEnd = Indexes.getMBBEndIdx(Pred);
VNInfo *PredVNI = ParentLI.getVNInfoBefore(PredEnd);
assert(PredVNI && "Value available in PhiVNI predecessor");
if (Visited.insert(PredVNI).second)
WorkList.push_back(PredVNI);
}
} while(!WorkList.empty());
}
void SplitEditor::finish(SmallVectorImpl<unsigned> *LRMap) {
++NumFinished;
// At this point, the live intervals in Edit contain VNInfos corresponding to
// the inserted copies.
// Add the original defs from the parent interval.
for (const VNInfo *ParentVNI : Edit->getParent().valnos) {
if (ParentVNI->isUnused())
continue;
unsigned RegIdx = RegAssign.lookup(ParentVNI->def);
defValue(RegIdx, ParentVNI, ParentVNI->def, true);
// Force rematted values to be recomputed everywhere.
// The new live ranges may be truncated.
if (Edit->didRematerialize(ParentVNI))
forceRecomputeVNI(*ParentVNI);
}
// Hoist back-copies to the complement interval when in spill mode.
switch (SpillMode) {
case SM_Partition:
// Leave all back-copies as is.
break;
case SM_Size:
case SM_Speed:
// hoistCopies will behave differently between size and speed.
hoistCopies();
}
// Transfer the simply mapped values, check if any are skipped.
bool Skipped = transferValues();
// Rewrite virtual registers, possibly extending ranges.
rewriteAssigned(Skipped);
if (Skipped)
extendPHIKillRanges();
else
++NumSimple;
// Delete defs that were rematted everywhere.
if (Skipped)
deleteRematVictims();
// Get rid of unused values and set phi-kill flags.
for (unsigned Reg : *Edit) {
LiveInterval &LI = LIS.getInterval(Reg);
LI.removeEmptySubRanges();
LI.RenumberValues();
}
// Provide a reverse mapping from original indices to Edit ranges.
if (LRMap) {
LRMap->clear();
for (unsigned i = 0, e = Edit->size(); i != e; ++i)
LRMap->push_back(i);
}
// Now check if any registers were separated into multiple components.
ConnectedVNInfoEqClasses ConEQ(LIS);
for (unsigned i = 0, e = Edit->size(); i != e; ++i) {
// Don't use iterators, they are invalidated by create() below.
unsigned VReg = Edit->get(i);
LiveInterval &LI = LIS.getInterval(VReg);
SmallVector<LiveInterval*, 8> SplitLIs;
LIS.splitSeparateComponents(LI, SplitLIs);
unsigned Original = VRM.getOriginal(VReg);
for (LiveInterval *SplitLI : SplitLIs)
VRM.setIsSplitFromReg(SplitLI->reg, Original);
// The new intervals all map back to i.
if (LRMap)
LRMap->resize(Edit->size(), i);
}
// Calculate spill weight and allocation hints for new intervals.
Edit->calculateRegClassAndHint(VRM.getMachineFunction(), SA.Loops, MBFI);
assert(!LRMap || LRMap->size() == Edit->size());
}
//===----------------------------------------------------------------------===//
// Single Block Splitting
//===----------------------------------------------------------------------===//
bool SplitAnalysis::shouldSplitSingleBlock(const BlockInfo &BI,
bool SingleInstrs) const {
// Always split for multiple instructions.
if (!BI.isOneInstr())
return true;
// Don't split for single instructions unless explicitly requested.
if (!SingleInstrs)
return false;
// Splitting a live-through range always makes progress.
if (BI.LiveIn && BI.LiveOut)
return true;
// No point in isolating a copy. It has no register class constraints.
if (LIS.getInstructionFromIndex(BI.FirstInstr)->isCopyLike())
return false;
// Finally, don't isolate an end point that was created by earlier splits.
return isOriginalEndpoint(BI.FirstInstr);
}
void SplitEditor::splitSingleBlock(const SplitAnalysis::BlockInfo &BI) {
openIntv();
SlotIndex LastSplitPoint = SA.getLastSplitPoint(BI.MBB->getNumber());
SlotIndex SegStart = enterIntvBefore(std::min(BI.FirstInstr,
LastSplitPoint));
if (!BI.LiveOut || BI.LastInstr < LastSplitPoint) {
useIntv(SegStart, leaveIntvAfter(BI.LastInstr));
} else {
// The last use is after the last valid split point.
SlotIndex SegStop = leaveIntvBefore(LastSplitPoint);
useIntv(SegStart, SegStop);
overlapIntv(SegStop, BI.LastInstr);
}
}
//===----------------------------------------------------------------------===//
// Global Live Range Splitting Support
//===----------------------------------------------------------------------===//
// These methods support a method of global live range splitting that uses a
// global algorithm to decide intervals for CFG edges. They will insert split
// points and color intervals in basic blocks while avoiding interference.
//
// Note that splitSingleBlock is also useful for blocks where both CFG edges
// are on the stack.
void SplitEditor::splitLiveThroughBlock(unsigned MBBNum,
unsigned IntvIn, SlotIndex LeaveBefore,
unsigned IntvOut, SlotIndex EnterAfter){
SlotIndex Start, Stop;
std::tie(Start, Stop) = LIS.getSlotIndexes()->getMBBRange(MBBNum);
LLVM_DEBUG(dbgs() << "%bb." << MBBNum << " [" << Start << ';' << Stop
<< ") intf " << LeaveBefore << '-' << EnterAfter
<< ", live-through " << IntvIn << " -> " << IntvOut);
assert((IntvIn || IntvOut) && "Use splitSingleBlock for isolated blocks");
assert((!LeaveBefore || LeaveBefore < Stop) && "Interference after block");
assert((!IntvIn || !LeaveBefore || LeaveBefore > Start) && "Impossible intf");
assert((!EnterAfter || EnterAfter >= Start) && "Interference before block");
MachineBasicBlock *MBB = VRM.getMachineFunction().getBlockNumbered(MBBNum);
if (!IntvOut) {
LLVM_DEBUG(dbgs() << ", spill on entry.\n");
//
// <<<<<<<<< Possible LeaveBefore interference.
// |-----------| Live through.
// -____________ Spill on entry.
//
selectIntv(IntvIn);
SlotIndex Idx = leaveIntvAtTop(*MBB);
assert((!LeaveBefore || Idx <= LeaveBefore) && "Interference");
(void)Idx;
return;
}
if (!IntvIn) {
LLVM_DEBUG(dbgs() << ", reload on exit.\n");
//
// >>>>>>> Possible EnterAfter interference.
// |-----------| Live through.
// ___________-- Reload on exit.
//
selectIntv(IntvOut);
SlotIndex Idx = enterIntvAtEnd(*MBB);
assert((!EnterAfter || Idx >= EnterAfter) && "Interference");
(void)Idx;
return;
}
if (IntvIn == IntvOut && !LeaveBefore && !EnterAfter) {
LLVM_DEBUG(dbgs() << ", straight through.\n");
//
// |-----------| Live through.
// ------------- Straight through, same intv, no interference.
//
selectIntv(IntvOut);
useIntv(Start, Stop);
return;
}
// We cannot legally insert splits after LSP.
SlotIndex LSP = SA.getLastSplitPoint(MBBNum);
assert((!IntvOut || !EnterAfter || EnterAfter < LSP) && "Impossible intf");
if (IntvIn != IntvOut && (!LeaveBefore || !EnterAfter ||
LeaveBefore.getBaseIndex() > EnterAfter.getBoundaryIndex())) {
LLVM_DEBUG(dbgs() << ", switch avoiding interference.\n");
//
// >>>> <<<< Non-overlapping EnterAfter/LeaveBefore interference.
// |-----------| Live through.
// ------======= Switch intervals between interference.
//
selectIntv(IntvOut);
SlotIndex Idx;
if (LeaveBefore && LeaveBefore < LSP) {
Idx = enterIntvBefore(LeaveBefore);
useIntv(Idx, Stop);
} else {
Idx = enterIntvAtEnd(*MBB);
}
selectIntv(IntvIn);
useIntv(Start, Idx);
assert((!LeaveBefore || Idx <= LeaveBefore) && "Interference");
assert((!EnterAfter || Idx >= EnterAfter) && "Interference");
return;
}
LLVM_DEBUG(dbgs() << ", create local intv for interference.\n");
//
// >>><><><><<<< Overlapping EnterAfter/LeaveBefore interference.
// |-----------| Live through.
// ==---------== Switch intervals before/after interference.
//
assert(LeaveBefore <= EnterAfter && "Missed case");
selectIntv(IntvOut);
SlotIndex Idx = enterIntvAfter(EnterAfter);
useIntv(Idx, Stop);
assert((!EnterAfter || Idx >= EnterAfter) && "Interference");
selectIntv(IntvIn);
Idx = leaveIntvBefore(LeaveBefore);
useIntv(Start, Idx);
assert((!LeaveBefore || Idx <= LeaveBefore) && "Interference");
}
void SplitEditor::splitRegInBlock(const SplitAnalysis::BlockInfo &BI,
unsigned IntvIn, SlotIndex LeaveBefore) {
SlotIndex Start, Stop;
std::tie(Start, Stop) = LIS.getSlotIndexes()->getMBBRange(BI.MBB);
LLVM_DEBUG(dbgs() << printMBBReference(*BI.MBB) << " [" << Start << ';'
<< Stop << "), uses " << BI.FirstInstr << '-'
<< BI.LastInstr << ", reg-in " << IntvIn
<< ", leave before " << LeaveBefore
<< (BI.LiveOut ? ", stack-out" : ", killed in block"));
assert(IntvIn && "Must have register in");
assert(BI.LiveIn && "Must be live-in");
assert((!LeaveBefore || LeaveBefore > Start) && "Bad interference");
if (!BI.LiveOut && (!LeaveBefore || LeaveBefore >= BI.LastInstr)) {
LLVM_DEBUG(dbgs() << " before interference.\n");
//
// <<< Interference after kill.
// |---o---x | Killed in block.
// ========= Use IntvIn everywhere.
//
selectIntv(IntvIn);
useIntv(Start, BI.LastInstr);
return;
}
SlotIndex LSP = SA.getLastSplitPoint(BI.MBB->getNumber());
if (!LeaveBefore || LeaveBefore > BI.LastInstr.getBoundaryIndex()) {
//
// <<< Possible interference after last use.
// |---o---o---| Live-out on stack.
// =========____ Leave IntvIn after last use.
//
// < Interference after last use.
// |---o---o--o| Live-out on stack, late last use.
// ============ Copy to stack after LSP, overlap IntvIn.
// \_____ Stack interval is live-out.
//
if (BI.LastInstr < LSP) {
LLVM_DEBUG(dbgs() << ", spill after last use before interference.\n");
selectIntv(IntvIn);
SlotIndex Idx = leaveIntvAfter(BI.LastInstr);
useIntv(Start, Idx);
assert((!LeaveBefore || Idx <= LeaveBefore) && "Interference");
} else {
LLVM_DEBUG(dbgs() << ", spill before last split point.\n");
selectIntv(IntvIn);
SlotIndex Idx = leaveIntvBefore(LSP);
overlapIntv(Idx, BI.LastInstr);
useIntv(Start, Idx);
assert((!LeaveBefore || Idx <= LeaveBefore) && "Interference");
}
return;
}
// The interference is overlapping somewhere we wanted to use IntvIn. That
// means we need to create a local interval that can be allocated a
// different register.
unsigned LocalIntv = openIntv();
(void)LocalIntv;
LLVM_DEBUG(dbgs() << ", creating local interval " << LocalIntv << ".\n");
if (!BI.LiveOut || BI.LastInstr < LSP) {
//
// <<<<<<< Interference overlapping uses.
// |---o---o---| Live-out on stack.
// =====----____ Leave IntvIn before interference, then spill.
//
SlotIndex To = leaveIntvAfter(BI.LastInstr);
SlotIndex From = enterIntvBefore(LeaveBefore);
useIntv(From, To);
selectIntv(IntvIn);
useIntv(Start, From);
assert((!LeaveBefore || From <= LeaveBefore) && "Interference");
return;
}
// <<<<<<< Interference overlapping uses.
// |---o---o--o| Live-out on stack, late last use.
// =====------- Copy to stack before LSP, overlap LocalIntv.
// \_____ Stack interval is live-out.
//
SlotIndex To = leaveIntvBefore(LSP);
overlapIntv(To, BI.LastInstr);
SlotIndex From = enterIntvBefore(std::min(To, LeaveBefore));
useIntv(From, To);
selectIntv(IntvIn);
useIntv(Start, From);
assert((!LeaveBefore || From <= LeaveBefore) && "Interference");
}
void SplitEditor::splitRegOutBlock(const SplitAnalysis::BlockInfo &BI,
unsigned IntvOut, SlotIndex EnterAfter) {
SlotIndex Start, Stop;
std::tie(Start, Stop) = LIS.getSlotIndexes()->getMBBRange(BI.MBB);
LLVM_DEBUG(dbgs() << printMBBReference(*BI.MBB) << " [" << Start << ';'
<< Stop << "), uses " << BI.FirstInstr << '-'
<< BI.LastInstr << ", reg-out " << IntvOut
<< ", enter after " << EnterAfter
<< (BI.LiveIn ? ", stack-in" : ", defined in block"));
SlotIndex LSP = SA.getLastSplitPoint(BI.MBB->getNumber());
assert(IntvOut && "Must have register out");
assert(BI.LiveOut && "Must be live-out");
assert((!EnterAfter || EnterAfter < LSP) && "Bad interference");
if (!BI.LiveIn && (!EnterAfter || EnterAfter <= BI.FirstInstr)) {
LLVM_DEBUG(dbgs() << " after interference.\n");
//
// >>>> Interference before def.
// | o---o---| Defined in block.
// ========= Use IntvOut everywhere.
//
selectIntv(IntvOut);
useIntv(BI.FirstInstr, Stop);
return;
}
if (!EnterAfter || EnterAfter < BI.FirstInstr.getBaseIndex()) {
LLVM_DEBUG(dbgs() << ", reload after interference.\n");
//
// >>>> Interference before def.
// |---o---o---| Live-through, stack-in.
// ____========= Enter IntvOut before first use.
//
selectIntv(IntvOut);
SlotIndex Idx = enterIntvBefore(std::min(LSP, BI.FirstInstr));
useIntv(Idx, Stop);
assert((!EnterAfter || Idx >= EnterAfter) && "Interference");
return;
}
// The interference is overlapping somewhere we wanted to use IntvOut. That
// means we need to create a local interval that can be allocated a
// different register.
LLVM_DEBUG(dbgs() << ", interference overlaps uses.\n");
//
// >>>>>>> Interference overlapping uses.
// |---o---o---| Live-through, stack-in.
// ____---====== Create local interval for interference range.
//
selectIntv(IntvOut);
SlotIndex Idx = enterIntvAfter(EnterAfter);
useIntv(Idx, Stop);
assert((!EnterAfter || Idx >= EnterAfter) && "Interference");
openIntv();
SlotIndex From = enterIntvBefore(std::min(Idx, BI.FirstInstr));
useIntv(From, Idx);
}
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