RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-24 03:33:20 +01:00
Code Issues Projects Releases Wiki Activity
ceb5b7477b
llvm-mirror/lib/CodeGen/PreAllocSplitting.cpp
Owen Anderson 3ef1e1ff3f Don't walk into predecessors in which the vreg is not live when doing shrinkwrapping. 
This lets several failing tests get farther along, but doesn't completely fix any of them.

llvm-svn: 59086
2008-11-11 22:11:27 +00:00

952 lines
33 KiB
C++
Raw Blame History

//===-- 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/MachineDominators.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);
AU.addRequired<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
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 **);
bool createsNewJoin(LiveRange* LR, MachineBasicBlock* DefMBB,
MachineBasicBlock* BarrierMBB);
};
} // 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;
if (!CurrLI->liveAt(LIs->getMBBEndIdx(Pred)-1))
return;
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;
// If this would create a new join point, do not split.
if (DefMI && createsNewJoin(LR, DefMI->getParent(), Barrier->getParent()))
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::createsNewJoin(LiveRange* LR,
MachineBasicBlock* DefMBB,
MachineBasicBlock* BarrierMBB) {
if (DefMBB == BarrierMBB)
return false;
if (LR->valno->hasPHIKill)
return false;
unsigned MBBEnd = LIs->getMBBEndIdx(BarrierMBB);
if (LR->end < MBBEnd)
return false;
MachineLoopInfo& MLI = getAnalysis<MachineLoopInfo>();
if (MLI.getLoopFor(DefMBB) != MLI.getLoopFor(BarrierMBB))
return true;
MachineDominatorTree& MDT = getAnalysis<MachineDominatorTree>();
SmallPtrSet<MachineBasicBlock*, 4> Visited;
typedef std::pair<MachineBasicBlock*,
MachineBasicBlock::succ_iterator> ItPair;
SmallVector<ItPair, 4> Stack;
Stack.push_back(std::make_pair(BarrierMBB, BarrierMBB->succ_begin()));
while (!Stack.empty()) {
ItPair P = Stack.back();
Stack.pop_back();
MachineBasicBlock* PredMBB = P.first;
MachineBasicBlock::succ_iterator S = P.second;
if (S == PredMBB->succ_end())
continue;
else if (Visited.count(*S)) {
Stack.push_back(std::make_pair(PredMBB, ++S));
continue;
} else
Stack.push_back(std::make_pair(PredMBB, S+1));
MachineBasicBlock* MBB = *S;
Visited.insert(MBB);
if (MBB == BarrierMBB)
return true;
MachineDomTreeNode* DefMDTN = MDT.getNode(DefMBB);
MachineDomTreeNode* BarrierMDTN = MDT.getNode(BarrierMBB);
MachineDomTreeNode* MDTN = MDT.getNode(MBB)->getIDom();
while (MDTN) {
if (MDTN == DefMDTN)
return true;
else if (MDTN == BarrierMDTN)
break;
MDTN = MDTN->getIDom();
}
MBBEnd = LIs->getMBBEndIdx(MBB);
if (LR->end > MBBEnd)
Stack.push_back(std::make_pair(MBB, MBB->succ_begin()));
}
return false;
}
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;
}
Reference in New Issue View Git Blame Copy Permalink