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

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//===-- PreAllocSplitting.cpp - Pre-allocation Interval Spltting Pass. ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the machine instruction level pre-register allocation
// live interval splitting pass. It finds live interval barriers, i.e.
// instructions which will kill all physical registers in certain register
// classes, and split all live intervals which cross the barrier.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "pre-alloc-split"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
static cl::opt<int> PreSplitLimit("pre-split-limit", cl::init(-1), cl::Hidden);
STATISTIC(NumSplits, "Number of intervals split");
namespace {
class VISIBILITY_HIDDEN PreAllocSplitting : public MachineFunctionPass {
MachineFunction *CurrMF;
const TargetMachine *TM;
const TargetInstrInfo *TII;
MachineFrameInfo *MFI;
MachineRegisterInfo *MRI;
LiveIntervals *LIs;
LiveStacks *LSs;
// Barrier - Current barrier being processed.
MachineInstr *Barrier;
// BarrierMBB - Basic block where the barrier resides in.
MachineBasicBlock *BarrierMBB;
// Barrier - Current barrier index.
unsigned BarrierIdx;
// CurrLI - Current live interval being split.
LiveInterval *CurrLI;
// CurrSLI - Current stack slot live interval.
LiveInterval *CurrSLI;
// CurrSValNo - Current val# for the stack slot live interval.
VNInfo *CurrSValNo;
// IntervalSSMap - A map from live interval to spill slots.
DenseMap<unsigned, int> IntervalSSMap;
// Def2SpillMap - A map from a def instruction index to spill index.
DenseMap<unsigned, unsigned> Def2SpillMap;
public:
static char ID;
PreAllocSplitting() : MachineFunctionPass(&ID) {}
virtual bool runOnMachineFunction(MachineFunction &MF);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveIntervals>();
AU.addPreserved<LiveIntervals>();
AU.addRequired<LiveStacks>();
AU.addPreserved<LiveStacks>();
AU.addPreserved<RegisterCoalescer>();
if (StrongPHIElim)
AU.addPreservedID(StrongPHIEliminationID);
else
AU.addPreservedID(PHIEliminationID);
MachineFunctionPass::getAnalysisUsage(AU);
}
virtual void releaseMemory() {
IntervalSSMap.clear();
Def2SpillMap.clear();
}
virtual const char *getPassName() const {
return "Pre-Register Allocaton Live Interval Splitting";
}
/// print - Implement the dump method.
virtual void print(std::ostream &O, const Module* M = 0) const {
LIs->print(O, M);
}
void print(std::ostream *O, const Module* M = 0) const {
if (O) print(*O, M);
}
private:
MachineBasicBlock::iterator
findNextEmptySlot(MachineBasicBlock*, MachineInstr*,
unsigned&);
MachineBasicBlock::iterator
findSpillPoint(MachineBasicBlock*, MachineInstr*, MachineInstr*,
SmallPtrSet<MachineInstr*, 4>&, unsigned&);
MachineBasicBlock::iterator
findRestorePoint(MachineBasicBlock*, MachineInstr*, unsigned,
SmallPtrSet<MachineInstr*, 4>&, unsigned&);
int CreateSpillStackSlot(unsigned, const TargetRegisterClass *);
bool IsAvailableInStack(MachineBasicBlock*, unsigned, unsigned, unsigned,
unsigned&, int&) const;
void UpdateSpillSlotInterval(VNInfo*, unsigned, unsigned);
void UpdateRegisterInterval(VNInfo*, unsigned, unsigned);
bool ShrinkWrapToLastUse(MachineBasicBlock*, VNInfo*,
SmallVector<MachineOperand*, 4>&,
SmallPtrSet<MachineInstr*, 4>&);
void ShrinkWrapLiveInterval(VNInfo*, MachineBasicBlock*, MachineBasicBlock*,
MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*, 8>&,
DenseMap<MachineBasicBlock*, SmallVector<MachineOperand*, 4> >&,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 4> >&,
SmallVector<MachineBasicBlock*, 4>&);
bool SplitRegLiveInterval(LiveInterval*);
bool SplitRegLiveIntervals(const TargetRegisterClass **);
};
} // end anonymous namespace
char PreAllocSplitting::ID = 0;
static RegisterPass<PreAllocSplitting>
X("pre-alloc-splitting", "Pre-Register Allocation Live Interval Splitting");
const PassInfo *const llvm::PreAllocSplittingID = &X;
/// findNextEmptySlot - Find a gap after the given machine instruction in the
/// instruction index map. If there isn't one, return end().
MachineBasicBlock::iterator
PreAllocSplitting::findNextEmptySlot(MachineBasicBlock *MBB, MachineInstr *MI,
unsigned &SpotIndex) {
MachineBasicBlock::iterator MII = MI;
if (++MII != MBB->end()) {
unsigned Index = LIs->findGapBeforeInstr(LIs->getInstructionIndex(MII));
if (Index) {
SpotIndex = Index;
return MII;
}
}
return MBB->end();
}
/// findSpillPoint - Find a gap as far away from the given MI that's suitable
/// for spilling the current live interval. The index must be before any
/// defs and uses of the live interval register in the mbb. Return begin() if
/// none is found.
MachineBasicBlock::iterator
PreAllocSplitting::findSpillPoint(MachineBasicBlock *MBB, MachineInstr *MI,
MachineInstr *DefMI,
SmallPtrSet<MachineInstr*, 4> &RefsInMBB,
unsigned &SpillIndex) {
MachineBasicBlock::iterator Pt = MBB->begin();
// Go top down if RefsInMBB is empty.
if (RefsInMBB.empty() && !DefMI) {
MachineBasicBlock::iterator MII = MBB->begin();
MachineBasicBlock::iterator EndPt = MI;
do {
++MII;
unsigned Index = LIs->getInstructionIndex(MII);
unsigned Gap = LIs->findGapBeforeInstr(Index);
if (Gap) {
Pt = MII;
SpillIndex = Gap;
break;
}
} while (MII != EndPt);
} else {
MachineBasicBlock::iterator MII = MI;
MachineBasicBlock::iterator EndPt = DefMI
? MachineBasicBlock::iterator(DefMI) : MBB->begin();
while (MII != EndPt && !RefsInMBB.count(MII)) {
unsigned Index = LIs->getInstructionIndex(MII);
if (LIs->hasGapBeforeInstr(Index)) {
Pt = MII;
SpillIndex = LIs->findGapBeforeInstr(Index, true);
}
--MII;
}
}
return Pt;
}
/// findRestorePoint - Find a gap in the instruction index map that's suitable
/// for restoring the current live interval value. The index must be before any
/// uses of the live interval register in the mbb. Return end() if none is
/// found.
MachineBasicBlock::iterator
PreAllocSplitting::findRestorePoint(MachineBasicBlock *MBB, MachineInstr *MI,
unsigned LastIdx,
SmallPtrSet<MachineInstr*, 4> &RefsInMBB,
unsigned &RestoreIndex) {
// FIXME: Allow spill to be inserted to the beginning of the mbb. Update mbb
// begin index accordingly.
MachineBasicBlock::iterator Pt = MBB->end();
unsigned EndIdx = LIs->getMBBEndIdx(MBB);
// Go bottom up if RefsInMBB is empty and the end of the mbb isn't beyond
// the last index in the live range.
if (RefsInMBB.empty() && LastIdx >= EndIdx) {
MachineBasicBlock::iterator MII = MBB->end();
MachineBasicBlock::iterator EndPt = MI;
--MII;
do {
unsigned Index = LIs->getInstructionIndex(MII);
unsigned Gap = LIs->findGapBeforeInstr(Index);
if (Gap) {
Pt = MII;
RestoreIndex = Gap;
break;
}
--MII;
} while (MII != EndPt);
} else {
MachineBasicBlock::iterator MII = MI;
MII = ++MII;
// FIXME: Limit the number of instructions to examine to reduce
// compile time?
while (MII != MBB->end()) {
unsigned Index = LIs->getInstructionIndex(MII);
if (Index > LastIdx)
break;
unsigned Gap = LIs->findGapBeforeInstr(Index);
if (Gap) {
Pt = MII;
RestoreIndex = Gap;
}
if (RefsInMBB.count(MII))
break;
++MII;
}
}
return Pt;
}
/// CreateSpillStackSlot - Create a stack slot for the live interval being
/// split. If the live interval was previously split, just reuse the same
/// slot.
int PreAllocSplitting::CreateSpillStackSlot(unsigned Reg,
const TargetRegisterClass *RC) {
int SS;
DenseMap<unsigned, int>::iterator I = IntervalSSMap.find(Reg);
if (I != IntervalSSMap.end()) {
SS = I->second;
} else {
SS = MFI->CreateStackObject(RC->getSize(), RC->getAlignment());
IntervalSSMap[Reg] = SS;
}
// Create live interval for stack slot.
CurrSLI = &LSs->getOrCreateInterval(SS);
if (CurrSLI->hasAtLeastOneValue())
CurrSValNo = CurrSLI->getValNumInfo(0);
else
CurrSValNo = CurrSLI->getNextValue(~0U, 0, LSs->getVNInfoAllocator());
return SS;
}
/// IsAvailableInStack - Return true if register is available in a split stack
/// slot at the specified index.
bool
PreAllocSplitting::IsAvailableInStack(MachineBasicBlock *DefMBB,
unsigned Reg, unsigned DefIndex,
unsigned RestoreIndex, unsigned &SpillIndex,
int& SS) const {
if (!DefMBB)
return false;
DenseMap<unsigned, int>::iterator I = IntervalSSMap.find(Reg);
if (I == IntervalSSMap.end())
return false;
DenseMap<unsigned, unsigned>::iterator II = Def2SpillMap.find(DefIndex);
if (II == Def2SpillMap.end())
return false;
// If last spill of def is in the same mbb as barrier mbb (where restore will
// be), make sure it's not below the intended restore index.
// FIXME: Undo the previous spill?
assert(LIs->getMBBFromIndex(II->second) == DefMBB);
if (DefMBB == BarrierMBB && II->second >= RestoreIndex)
return false;
SS = I->second;
SpillIndex = II->second;
return true;
}
/// UpdateSpillSlotInterval - Given the specified val# of the register live
/// interval being split, and the spill and restore indicies, update the live
/// interval of the spill stack slot.
void
PreAllocSplitting::UpdateSpillSlotInterval(VNInfo *ValNo, unsigned SpillIndex,
unsigned RestoreIndex) {
assert(LIs->getMBBFromIndex(RestoreIndex) == BarrierMBB &&
"Expect restore in the barrier mbb");
MachineBasicBlock *MBB = LIs->getMBBFromIndex(SpillIndex);
if (MBB == BarrierMBB) {
// Intra-block spill + restore. We are done.
LiveRange SLR(SpillIndex, RestoreIndex, CurrSValNo);
CurrSLI->addRange(SLR);
return;
}
SmallPtrSet<MachineBasicBlock*, 4> Processed;
unsigned EndIdx = LIs->getMBBEndIdx(MBB);
LiveRange SLR(SpillIndex, EndIdx+1, CurrSValNo);
CurrSLI->addRange(SLR);
Processed.insert(MBB);
// Start from the spill mbb, figure out the extend of the spill slot's
// live interval.
SmallVector<MachineBasicBlock*, 4> WorkList;
const LiveRange *LR = CurrLI->getLiveRangeContaining(SpillIndex);
if (LR->end > EndIdx)
// If live range extend beyond end of mbb, add successors to work list.
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
WorkList.push_back(*SI);
while (!WorkList.empty()) {
MachineBasicBlock *MBB = WorkList.back();
WorkList.pop_back();
if (Processed.count(MBB))
continue;
unsigned Idx = LIs->getMBBStartIdx(MBB);
LR = CurrLI->getLiveRangeContaining(Idx);
if (LR && LR->valno == ValNo) {
EndIdx = LIs->getMBBEndIdx(MBB);
if (Idx <= RestoreIndex && RestoreIndex < EndIdx) {
// Spill slot live interval stops at the restore.
LiveRange SLR(Idx, RestoreIndex, CurrSValNo);
CurrSLI->addRange(SLR);
} else if (LR->end > EndIdx) {
// Live range extends beyond end of mbb, process successors.
LiveRange SLR(Idx, EndIdx+1, CurrSValNo);
CurrSLI->addRange(SLR);
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
WorkList.push_back(*SI);
} else {
LiveRange SLR(Idx, LR->end, CurrSValNo);
CurrSLI->addRange(SLR);
}
Processed.insert(MBB);
}
}
}
/// UpdateRegisterInterval - Given the specified val# of the current live
/// interval is being split, and the spill and restore indices, update the live
/// interval accordingly.
void
PreAllocSplitting::UpdateRegisterInterval(VNInfo *ValNo, unsigned SpillIndex,
unsigned RestoreIndex) {
assert(LIs->getMBBFromIndex(RestoreIndex) == BarrierMBB &&
"Expect restore in the barrier mbb");
SmallVector<std::pair<unsigned,unsigned>, 4> Before;
SmallVector<std::pair<unsigned,unsigned>, 4> After;
SmallVector<unsigned, 4> BeforeKills;
SmallVector<unsigned, 4> AfterKills;
SmallPtrSet<const LiveRange*, 4> Processed;
// First, let's figure out which parts of the live interval is now defined
// by the restore, which are defined by the original definition.
const LiveRange *LR = CurrLI->getLiveRangeContaining(RestoreIndex);
After.push_back(std::make_pair(RestoreIndex, LR->end));
if (CurrLI->isKill(ValNo, LR->end))
AfterKills.push_back(LR->end);
assert(LR->contains(SpillIndex));
if (SpillIndex > LR->start) {
Before.push_back(std::make_pair(LR->start, SpillIndex));
BeforeKills.push_back(SpillIndex);
}
Processed.insert(LR);
// Start from the restore mbb, figure out what part of the live interval
// are defined by the restore.
SmallVector<MachineBasicBlock*, 4> WorkList;
MachineBasicBlock *MBB = BarrierMBB;
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
WorkList.push_back(*SI);
while (!WorkList.empty()) {
MBB = WorkList.back();
WorkList.pop_back();
unsigned Idx = LIs->getMBBStartIdx(MBB);
LR = CurrLI->getLiveRangeContaining(Idx);
if (LR && LR->valno == ValNo && !Processed.count(LR)) {
After.push_back(std::make_pair(LR->start, LR->end));
if (CurrLI->isKill(ValNo, LR->end))
AfterKills.push_back(LR->end);
Idx = LIs->getMBBEndIdx(MBB);
if (LR->end > Idx) {
// Live range extend beyond at least one mbb. Let's see what other
// mbbs it reaches.
LIs->findReachableMBBs(LR->start, LR->end, WorkList);
}
Processed.insert(LR);
}
}
for (LiveInterval::iterator I = CurrLI->begin(), E = CurrLI->end();
I != E; ++I) {
LiveRange *LR = I;
if (LR->valno == ValNo && !Processed.count(LR)) {
Before.push_back(std::make_pair(LR->start, LR->end));
if (CurrLI->isKill(ValNo, LR->end))
BeforeKills.push_back(LR->end);
}
}
// Now create new val#s to represent the live ranges defined by the old def
// those defined by the restore.
unsigned AfterDef = ValNo->def;
MachineInstr *AfterCopy = ValNo->copy;
bool HasPHIKill = ValNo->hasPHIKill;
CurrLI->removeValNo(ValNo);
VNInfo *BValNo = (Before.empty())
? NULL
: CurrLI->getNextValue(AfterDef, AfterCopy, LIs->getVNInfoAllocator());
if (BValNo)
CurrLI->addKills(BValNo, BeforeKills);
VNInfo *AValNo = (After.empty())
? NULL
: CurrLI->getNextValue(RestoreIndex, 0, LIs->getVNInfoAllocator());
if (AValNo) {
AValNo->hasPHIKill = HasPHIKill;
CurrLI->addKills(AValNo, AfterKills);
}
for (unsigned i = 0, e = Before.size(); i != e; ++i) {
unsigned Start = Before[i].first;
unsigned End = Before[i].second;
CurrLI->addRange(LiveRange(Start, End, BValNo));
}
for (unsigned i = 0, e = After.size(); i != e; ++i) {
unsigned Start = After[i].first;
unsigned End = After[i].second;
CurrLI->addRange(LiveRange(Start, End, AValNo));
}
}
/// ShrinkWrapToLastUse - There are uses of the current live interval in the
/// given block, shrink wrap the live interval to the last use (i.e. remove
/// from last use to the end of the mbb). In case mbb is the where the barrier
/// is, remove from the last use to the barrier.
bool
PreAllocSplitting::ShrinkWrapToLastUse(MachineBasicBlock *MBB, VNInfo *ValNo,
SmallVector<MachineOperand*, 4> &Uses,
SmallPtrSet<MachineInstr*, 4> &UseMIs) {
MachineOperand *LastMO = 0;
MachineInstr *LastMI = 0;
if (MBB != BarrierMBB && Uses.size() == 1) {
// Single use, no need to traverse the block. We can't assume this for the
// barrier bb though since the use is probably below the barrier.
LastMO = Uses[0];
LastMI = LastMO->getParent();
} else {
MachineBasicBlock::iterator MEE = MBB->begin();
MachineBasicBlock::iterator MII;
if (MBB == BarrierMBB)
MII = Barrier;
else
MII = MBB->end();
while (MII != MEE) {
--MII;
MachineInstr *UseMI = &*MII;
if (!UseMIs.count(UseMI))
continue;
for (unsigned i = 0, e = UseMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = UseMI->getOperand(i);
if (MO.isReg() && MO.getReg() == CurrLI->reg) {
LastMO = &MO;
break;
}
}
LastMI = UseMI;
break;
}
}
// Cut off live range from last use (or beginning of the mbb if there
// are no uses in it) to the end of the mbb.
unsigned RangeStart, RangeEnd = LIs->getMBBEndIdx(MBB)+1;
if (LastMI) {
RangeStart = LIs->getUseIndex(LIs->getInstructionIndex(LastMI))+1;
assert(!LastMO->isKill() && "Last use already terminates the interval?");
LastMO->setIsKill();
} else {
assert(MBB == BarrierMBB);
RangeStart = LIs->getMBBStartIdx(MBB);
}
if (MBB == BarrierMBB)
RangeEnd = LIs->getUseIndex(BarrierIdx)+1;
CurrLI->removeRange(RangeStart, RangeEnd);
if (LastMI)
CurrLI->addKill(ValNo, RangeStart);
// Return true if the last use becomes a new kill.
return LastMI;
}
/// ShrinkWrapLiveInterval - Recursively traverse the predecessor
/// chain to find the new 'kills' and shrink wrap the live interval to the
/// new kill indices.
void
PreAllocSplitting::ShrinkWrapLiveInterval(VNInfo *ValNo, MachineBasicBlock *MBB,
MachineBasicBlock *SuccMBB, MachineBasicBlock *DefMBB,
SmallPtrSet<MachineBasicBlock*, 8> &Visited,
DenseMap<MachineBasicBlock*, SmallVector<MachineOperand*, 4> > &Uses,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 4> > &UseMIs,
SmallVector<MachineBasicBlock*, 4> &UseMBBs) {
if (Visited.count(MBB))
return;
// If live interval is live in another successor path, then we can't process
// this block. But we may able to do so after all the successors have been
// processed.
if (MBB != BarrierMBB) {
for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI) {
MachineBasicBlock *SMBB = *SI;
if (SMBB == SuccMBB)
continue;
if (CurrLI->liveAt(LIs->getMBBStartIdx(SMBB)))
return;
}
}
Visited.insert(MBB);
DenseMap<MachineBasicBlock*, SmallVector<MachineOperand*, 4> >::iterator
UMII = Uses.find(MBB);
if (UMII != Uses.end()) {
// At least one use in this mbb, lets look for the kill.
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 4> >::iterator
UMII2 = UseMIs.find(MBB);
if (ShrinkWrapToLastUse(MBB, ValNo, UMII->second, UMII2->second))
// Found a kill, shrink wrapping of this path ends here.
return;
} else if (MBB == DefMBB) {
// There are no uses after the def.
MachineInstr *DefMI = LIs->getInstructionFromIndex(ValNo->def);
if (UseMBBs.empty()) {
// The only use must be below barrier in the barrier block. It's safe to
// remove the def.
LIs->RemoveMachineInstrFromMaps(DefMI);
DefMI->eraseFromParent();
CurrLI->removeRange(ValNo->def, LIs->getMBBEndIdx(MBB)+1);
}
} else if (MBB == BarrierMBB) {
// Remove entire live range from start of mbb to barrier.
CurrLI->removeRange(LIs->getMBBStartIdx(MBB),
LIs->getUseIndex(BarrierIdx)+1);
} else {
// Remove entire live range of the mbb out of the live interval.
CurrLI->removeRange(LIs->getMBBStartIdx(MBB), LIs->getMBBEndIdx(MBB)+1);
}
if (MBB == DefMBB)
// Reached the def mbb, stop traversing this path further.
return;
// Traverse the pathes up the predecessor chains further.
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock *Pred = *PI;
if (Pred == MBB)
continue;
if (Pred == DefMBB && ValNo->hasPHIKill)
// Pred is the def bb and the def reaches other val#s, we must
// allow the value to be live out of the bb.
continue;
ShrinkWrapLiveInterval(ValNo, Pred, MBB, DefMBB, Visited,
Uses, UseMIs, UseMBBs);
}
return;
}
/// SplitRegLiveInterval - Split (spill and restore) the given live interval
/// so it would not cross the barrier that's being processed. Shrink wrap
/// (minimize) the live interval to the last uses.
bool PreAllocSplitting::SplitRegLiveInterval(LiveInterval *LI) {
CurrLI = LI;
// Find live range where current interval cross the barrier.
LiveInterval::iterator LR =
CurrLI->FindLiveRangeContaining(LIs->getUseIndex(BarrierIdx));
VNInfo *ValNo = LR->valno;
if (ValNo->def == ~1U) {
// Defined by a dead def? How can this be?
assert(0 && "Val# is defined by a dead def?");
abort();
}
// FIXME: For now, if definition is rematerializable, do not split.
MachineInstr *DefMI = (ValNo->def != ~0U)
? LIs->getInstructionFromIndex(ValNo->def) : NULL;
if (DefMI && LIs->isReMaterializable(*LI, ValNo, DefMI))
return false;
// Find all references in the barrier mbb.
SmallPtrSet<MachineInstr*, 4> RefsInMBB;
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(CurrLI->reg),
E = MRI->reg_end(); I != E; ++I) {
MachineInstr *RefMI = &*I;
if (RefMI->getParent() == BarrierMBB)
RefsInMBB.insert(RefMI);
}
// Find a point to restore the value after the barrier.
unsigned RestoreIndex;
MachineBasicBlock::iterator RestorePt =
findRestorePoint(BarrierMBB, Barrier, LR->end, RefsInMBB, RestoreIndex);
if (RestorePt == BarrierMBB->end())
return false;
// Add a spill either before the barrier or after the definition.
MachineBasicBlock *DefMBB = DefMI ? DefMI->getParent() : NULL;
const TargetRegisterClass *RC = MRI->getRegClass(CurrLI->reg);
unsigned SpillIndex = 0;
MachineInstr *SpillMI = NULL;
int SS = -1;
if (ValNo->def == ~0U) {
// If it's defined by a phi, we must split just before the barrier.
MachineBasicBlock::iterator SpillPt =
findSpillPoint(BarrierMBB, Barrier, NULL, RefsInMBB, SpillIndex);
if (SpillPt == BarrierMBB->begin())
return false; // No gap to insert spill.
// Add spill.
SS = CreateSpillStackSlot(CurrLI->reg, RC);
TII->storeRegToStackSlot(*BarrierMBB, SpillPt, CurrLI->reg, true, SS, RC);
SpillMI = prior(SpillPt);
LIs->InsertMachineInstrInMaps(SpillMI, SpillIndex);
} else if (!IsAvailableInStack(DefMBB, CurrLI->reg, ValNo->def,
RestoreIndex, SpillIndex, SS)) {
// If it's already split, just restore the value. There is no need to spill
// the def again.
if (!DefMI)
return false; // Def is dead. Do nothing.
// Check if it's possible to insert a spill after the def MI.
MachineBasicBlock::iterator SpillPt;
if (DefMBB == BarrierMBB) {
// Add spill after the def and the last use before the barrier.
SpillPt = findSpillPoint(BarrierMBB, Barrier, DefMI, RefsInMBB, SpillIndex);
if (SpillPt == DefMBB->begin())
return false; // No gap to insert spill.
} else {
SpillPt = findNextEmptySlot(DefMBB, DefMI, SpillIndex);
if (SpillPt == DefMBB->end())
return false; // No gap to insert spill.
}
// Add spill. The store instruction kills the register if def is before
// the barrier in the barrier block.
SS = CreateSpillStackSlot(CurrLI->reg, RC);
TII->storeRegToStackSlot(*DefMBB, SpillPt, CurrLI->reg,
DefMBB == BarrierMBB, SS, RC);
SpillMI = prior(SpillPt);
LIs->InsertMachineInstrInMaps(SpillMI, SpillIndex);
}
// Remember def instruction index to spill index mapping.
if (DefMI && SpillMI)
Def2SpillMap[ValNo->def] = SpillIndex;
// Add restore.
TII->loadRegFromStackSlot(*BarrierMBB, RestorePt, CurrLI->reg, SS, RC);
MachineInstr *LoadMI = prior(RestorePt);
LIs->InsertMachineInstrInMaps(LoadMI, RestoreIndex);
// If live interval is spilled in the same block as the barrier, just
// create a hole in the interval.
if (!DefMBB ||
(SpillMI && SpillMI->getParent() == BarrierMBB)) {
// Update spill stack slot live interval.
UpdateSpillSlotInterval(ValNo, LIs->getUseIndex(SpillIndex)+1,
LIs->getDefIndex(RestoreIndex));
UpdateRegisterInterval(ValNo, LIs->getUseIndex(SpillIndex)+1,
LIs->getDefIndex(RestoreIndex));
++NumSplits;
return true;
}
// Update spill stack slot live interval.
UpdateSpillSlotInterval(ValNo, LIs->getUseIndex(SpillIndex)+1,
LIs->getDefIndex(RestoreIndex));
// Shrink wrap the live interval by walking up the CFG and find the
// new kills.
// Now let's find all the uses of the val#.
DenseMap<MachineBasicBlock*, SmallVector<MachineOperand*, 4> > Uses;
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 4> > UseMIs;
SmallPtrSet<MachineBasicBlock*, 4> Seen;
SmallVector<MachineBasicBlock*, 4> UseMBBs;
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(CurrLI->reg),
UE = MRI->use_end(); UI != UE; ++UI) {
MachineOperand &UseMO = UI.getOperand();
MachineInstr *UseMI = UseMO.getParent();
unsigned UseIdx = LIs->getInstructionIndex(UseMI);
LiveInterval::iterator ULR = CurrLI->FindLiveRangeContaining(UseIdx);
if (ULR->valno != ValNo)
continue;
MachineBasicBlock *UseMBB = UseMI->getParent();
// Remember which other mbb's use this val#.
if (Seen.insert(UseMBB) && UseMBB != BarrierMBB)
UseMBBs.push_back(UseMBB);
DenseMap<MachineBasicBlock*, SmallVector<MachineOperand*, 4> >::iterator
UMII = Uses.find(UseMBB);
if (UMII != Uses.end()) {
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 4> >::iterator
UMII2 = UseMIs.find(UseMBB);
UMII->second.push_back(&UseMO);
UMII2->second.insert(UseMI);
} else {
SmallVector<MachineOperand*, 4> Ops;
Ops.push_back(&UseMO);
Uses.insert(std::make_pair(UseMBB, Ops));
SmallPtrSet<MachineInstr*, 4> MIs;
MIs.insert(UseMI);
UseMIs.insert(std::make_pair(UseMBB, MIs));
}
}
// Walk up the predecessor chains.
SmallPtrSet<MachineBasicBlock*, 8> Visited;
ShrinkWrapLiveInterval(ValNo, BarrierMBB, NULL, DefMBB, Visited,
Uses, UseMIs, UseMBBs);
// FIXME: If ValNo->hasPHIKill is false, then renumber the val# by
// the restore.
// Remove live range from barrier to the restore. FIXME: Find a better
// point to re-start the live interval.
UpdateRegisterInterval(ValNo, LIs->getUseIndex(BarrierIdx)+1,
LIs->getDefIndex(RestoreIndex));
++NumSplits;
return true;
}
/// SplitRegLiveIntervals - Split all register live intervals that cross the
/// barrier that's being processed.
bool
PreAllocSplitting::SplitRegLiveIntervals(const TargetRegisterClass **RCs) {
// First find all the virtual registers whose live intervals are intercepted
// by the current barrier.
SmallVector<LiveInterval*, 8> Intervals;
for (const TargetRegisterClass **RC = RCs; *RC; ++RC) {
if (TII->IgnoreRegisterClassBarriers(*RC))
continue;
std::vector<unsigned> &VRs = MRI->getRegClassVirtRegs(*RC);
for (unsigned i = 0, e = VRs.size(); i != e; ++i) {
unsigned Reg = VRs[i];
if (!LIs->hasInterval(Reg))
continue;
LiveInterval *LI = &LIs->getInterval(Reg);
if (LI->liveAt(BarrierIdx) && !Barrier->readsRegister(Reg))
// Virtual register live interval is intercepted by the barrier. We
// should split and shrink wrap its interval if possible.
Intervals.push_back(LI);
}
}
// Process the affected live intervals.
bool Change = false;
while (!Intervals.empty()) {
if (PreSplitLimit != -1 && (int)NumSplits == PreSplitLimit)
break;
LiveInterval *LI = Intervals.back();
Intervals.pop_back();
Change |= SplitRegLiveInterval(LI);
}
return Change;
}
bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
CurrMF = &MF;
TM = &MF.getTarget();
TII = TM->getInstrInfo();
MFI = MF.getFrameInfo();
MRI = &MF.getRegInfo();
LIs = &getAnalysis<LiveIntervals>();
LSs = &getAnalysis<LiveStacks>();
bool MadeChange = false;
// Make sure blocks are numbered in order.
MF.RenumberBlocks();
#if 0
// FIXME: Go top down.
MachineBasicBlock *Entry = MF.begin();
SmallPtrSet<MachineBasicBlock*,16> Visited;
for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
DFI != E; ++DFI) {
BarrierMBB = *DFI;
for (MachineBasicBlock::iterator I = BarrierMBB->begin(),
E = BarrierMBB->end(); I != E; ++I) {
Barrier = &*I;
const TargetRegisterClass **BarrierRCs =
Barrier->getDesc().getRegClassBarriers();
if (!BarrierRCs)
continue;
BarrierIdx = LIs->getInstructionIndex(Barrier);
MadeChange |= SplitRegLiveIntervals(BarrierRCs);
}
}
#else
for (MachineFunction::reverse_iterator I = MF.rbegin(), E = MF.rend();
I != E; ++I) {
BarrierMBB = &*I;
for (MachineBasicBlock::reverse_iterator II = BarrierMBB->rbegin(),
EE = BarrierMBB->rend(); II != EE; ++II) {
Barrier = &*II;
const TargetRegisterClass **BarrierRCs =
Barrier->getDesc().getRegClassBarriers();
if (!BarrierRCs)
continue;
BarrierIdx = LIs->getInstructionIndex(Barrier);
MadeChange |= SplitRegLiveIntervals(BarrierRCs);
}
}
#endif
return MadeChange;
}
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