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llvm/lib/CodeGen/PreAllocSplitting.cpp
Lang Hames ffd1326ff8 Improved tracking of value number kills. VN kills are now represented 
as an (index,bool) pair. The bool flag records whether the kill is a
PHI kill or not. This code will be used to enable splitting of live
intervals containing PHI-kills.

A slight change to live interval weights introduced an extra spill
into lsr-code-insertion (outside the critical sections). The test 
condition has been updated to reflect this.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75097 91177308-0d34-0410-b5e6-96231b3b80d8
2009-07-09 03:57:02 +00:00

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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 "VirtRegMap.h"
#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);
static cl::opt<int> DeadSplitLimit("dead-split-limit", cl::init(-1), cl::Hidden);
static cl::opt<int> RestoreFoldLimit("restore-fold-limit", cl::init(-1), cl::Hidden);
STATISTIC(NumSplits, "Number of intervals split");
STATISTIC(NumRemats, "Number of intervals split by rematerialization");
STATISTIC(NumFolds, "Number of intervals split with spill folding");
STATISTIC(NumRestoreFolds, "Number of intervals split with restore folding");
STATISTIC(NumRenumbers, "Number of intervals renumbered into new registers");
STATISTIC(NumDeadSpills, "Number of dead spills removed");
namespace {
class VISIBILITY_HIDDEN PreAllocSplitting : public MachineFunctionPass {
MachineFunction *CurrMF;
const TargetMachine *TM;
const TargetInstrInfo *TII;
const TargetRegisterInfo* TRI;
MachineFrameInfo *MFI;
MachineRegisterInfo *MRI;
LiveIntervals *LIs;
LiveStacks *LSs;
VirtRegMap *VRM;
// 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.addRequired<VirtRegMap>();
AU.addPreserved<MachineDominatorTree>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreserved<VirtRegMap>();
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);
bool SplitRegLiveInterval(LiveInterval*);
bool SplitRegLiveIntervals(const TargetRegisterClass **,
SmallPtrSet<LiveInterval*, 8>&);
bool createsNewJoin(LiveRange* LR, MachineBasicBlock* DefMBB,
MachineBasicBlock* BarrierMBB);
bool Rematerialize(unsigned vreg, VNInfo* ValNo,
MachineInstr* DefMI,
MachineBasicBlock::iterator RestorePt,
unsigned RestoreIdx,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB);
MachineInstr* FoldSpill(unsigned vreg, const TargetRegisterClass* RC,
MachineInstr* DefMI,
MachineInstr* Barrier,
MachineBasicBlock* MBB,
int& SS,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB);
MachineInstr* FoldRestore(unsigned vreg,
const TargetRegisterClass* RC,
MachineInstr* Barrier,
MachineBasicBlock* MBB,
int SS,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB);
void RenumberValno(VNInfo* VN);
void ReconstructLiveInterval(LiveInterval* LI);
bool removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split);
unsigned getNumberOfNonSpills(SmallPtrSet<MachineInstr*, 4>& MIs,
unsigned Reg, int FrameIndex, bool& TwoAddr);
VNInfo* PerformPHIConstruction(MachineBasicBlock::iterator Use,
MachineBasicBlock* MBB, LiveInterval* LI,
SmallPtrSet<MachineInstr*, 4>& Visited,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
DenseMap<MachineInstr*, VNInfo*>& NewVNs,
DenseMap<MachineBasicBlock*, VNInfo*>& LiveOut,
DenseMap<MachineBasicBlock*, VNInfo*>& Phis,
bool IsTopLevel, bool IsIntraBlock);
VNInfo* PerformPHIConstructionFallBack(MachineBasicBlock::iterator Use,
MachineBasicBlock* MBB, LiveInterval* LI,
SmallPtrSet<MachineInstr*, 4>& Visited,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
DenseMap<MachineInstr*, VNInfo*>& NewVNs,
DenseMap<MachineBasicBlock*, VNInfo*>& LiveOut,
DenseMap<MachineBasicBlock*, VNInfo*>& Phis,
bool IsTopLevel, bool IsIntraBlock);
};
} // 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();
MachineBasicBlock::iterator MII = MI;
MachineBasicBlock::iterator EndPt = DefMI
? MachineBasicBlock::iterator(DefMI) : MBB->begin();
while (MII != EndPt && !RefsInMBB.count(MII) &&
MII->getOpcode() != TRI->getCallFrameSetupOpcode())
--MII;
if (MII == EndPt || RefsInMBB.count(MII)) return Pt;
while (MII != EndPt && !RefsInMBB.count(MII)) {
unsigned Index = LIs->getInstructionIndex(MII);
// We can't insert the spill between the barrier (a call), and its
// corresponding call frame setup.
if (MII->getOpcode() == TRI->getCallFrameDestroyOpcode()) {
while (MII->getOpcode() != TRI->getCallFrameSetupOpcode()) {
--MII;
if (MII == EndPt) {
return Pt;
}
}
continue;
} else if (LIs->hasGapBeforeInstr(Index)) {
Pt = MII;
SpillIndex = LIs->findGapBeforeInstr(Index, true);
}
if (RefsInMBB.count(MII))
return Pt;
--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();
MachineBasicBlock::iterator EndPt = MBB->getFirstTerminator();
// We start at the call, so walk forward until we find the call frame teardown
// since we can't insert restores before that. Bail if we encounter a use
// during this time.
MachineBasicBlock::iterator MII = MI;
if (MII == EndPt) return Pt;
while (MII != EndPt && !RefsInMBB.count(MII) &&
MII->getOpcode() != TRI->getCallFrameDestroyOpcode())
++MII;
if (MII == EndPt || RefsInMBB.count(MII)) return Pt;
++MII;
// FIXME: Limit the number of instructions to examine to reduce
// compile time?
while (MII != EndPt) {
unsigned Index = LIs->getInstructionIndex(MII);
if (Index > LastIdx)
break;
unsigned Gap = LIs->findGapBeforeInstr(Index);
// We can't insert a restore between the barrier (a call) and its
// corresponding call frame teardown.
if (MII->getOpcode() == TRI->getCallFrameSetupOpcode()) {
do {
if (MII == EndPt || RefsInMBB.count(MII)) return Pt;
++MII;
} while (MII->getOpcode() != TRI->getCallFrameDestroyOpcode());
} else if (Gap) {
Pt = MII;
RestoreIndex = Gap;
}
if (RefsInMBB.count(MII))
return Pt;
++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, RC);
if (CurrSLI->hasAtLeastOneValue())
CurrSValNo = CurrSLI->getValNumInfo(0);
else
CurrSValNo = CurrSLI->getNextValue(0, 0, false, 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);
}
}
}
/// PerformPHIConstruction - From properly set up use and def lists, use a PHI
/// construction algorithm to compute the ranges and valnos for an interval.
VNInfo*
PreAllocSplitting::PerformPHIConstruction(MachineBasicBlock::iterator UseI,
MachineBasicBlock* MBB, LiveInterval* LI,
SmallPtrSet<MachineInstr*, 4>& Visited,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
DenseMap<MachineInstr*, VNInfo*>& NewVNs,
DenseMap<MachineBasicBlock*, VNInfo*>& LiveOut,
DenseMap<MachineBasicBlock*, VNInfo*>& Phis,
bool IsTopLevel, bool IsIntraBlock) {
// Return memoized result if it's available.
if (IsTopLevel && Visited.count(UseI) && NewVNs.count(UseI))
return NewVNs[UseI];
else if (!IsTopLevel && IsIntraBlock && NewVNs.count(UseI))
return NewVNs[UseI];
else if (!IsIntraBlock && LiveOut.count(MBB))
return LiveOut[MBB];
// Check if our block contains any uses or defs.
bool ContainsDefs = Defs.count(MBB);
bool ContainsUses = Uses.count(MBB);
VNInfo* RetVNI = 0;
// Enumerate the cases of use/def contaning blocks.
if (!ContainsDefs && !ContainsUses) {
return PerformPHIConstructionFallBack(UseI, MBB, LI, Visited, Defs, Uses,
NewVNs, LiveOut, Phis,
IsTopLevel, IsIntraBlock);
} else if (ContainsDefs && !ContainsUses) {
SmallPtrSet<MachineInstr*, 2>& BlockDefs = Defs[MBB];
// Search for the def in this block. If we don't find it before the
// instruction we care about, go to the fallback case. Note that that
// should never happen: this cannot be intrablock, so use should
// always be an end() iterator.
assert(UseI == MBB->end() && "No use marked in intrablock");
MachineBasicBlock::iterator Walker = UseI;
--Walker;
while (Walker != MBB->begin()) {
if (BlockDefs.count(Walker))
break;
--Walker;
}
// Once we've found it, extend its VNInfo to our instruction.
unsigned DefIndex = LIs->getInstructionIndex(Walker);
DefIndex = LiveIntervals::getDefIndex(DefIndex);
unsigned EndIndex = LIs->getMBBEndIdx(MBB);
RetVNI = NewVNs[Walker];
LI->addRange(LiveRange(DefIndex, EndIndex+1, RetVNI));
} else if (!ContainsDefs && ContainsUses) {
SmallPtrSet<MachineInstr*, 2>& BlockUses = Uses[MBB];
// Search for the use in this block that precedes the instruction we care
// about, going to the fallback case if we don't find it.
if (UseI == MBB->begin())
return PerformPHIConstructionFallBack(UseI, MBB, LI, Visited, Defs,
Uses, NewVNs, LiveOut, Phis,
IsTopLevel, IsIntraBlock);
MachineBasicBlock::iterator Walker = UseI;
--Walker;
bool found = false;
while (Walker != MBB->begin()) {
if (BlockUses.count(Walker)) {
found = true;
break;
}
--Walker;
}
// Must check begin() too.
if (!found) {
if (BlockUses.count(Walker))
found = true;
else
return PerformPHIConstructionFallBack(UseI, MBB, LI, Visited, Defs,
Uses, NewVNs, LiveOut, Phis,
IsTopLevel, IsIntraBlock);
}
unsigned UseIndex = LIs->getInstructionIndex(Walker);
UseIndex = LiveIntervals::getUseIndex(UseIndex);
unsigned EndIndex = 0;
if (IsIntraBlock) {
EndIndex = LIs->getInstructionIndex(UseI);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(MBB);
// Now, recursively phi construct the VNInfo for the use we found,
// and then extend it to include the instruction we care about
RetVNI = PerformPHIConstruction(Walker, MBB, LI, Visited, Defs, Uses,
NewVNs, LiveOut, Phis, false, true);
LI->addRange(LiveRange(UseIndex, EndIndex+1, RetVNI));
// FIXME: Need to set kills properly for inter-block stuff.
if (LI->isKill(RetVNI, UseIndex)) LI->removeKill(RetVNI, UseIndex);
if (IsIntraBlock)
LI->addKill(RetVNI, EndIndex, false);
} else if (ContainsDefs && ContainsUses) {
SmallPtrSet<MachineInstr*, 2>& BlockDefs = Defs[MBB];
SmallPtrSet<MachineInstr*, 2>& BlockUses = Uses[MBB];
// This case is basically a merging of the two preceding case, with the
// special note that checking for defs must take precedence over checking
// for uses, because of two-address instructions.
if (UseI == MBB->begin())
return PerformPHIConstructionFallBack(UseI, MBB, LI, Visited, Defs, Uses,
NewVNs, LiveOut, Phis,
IsTopLevel, IsIntraBlock);
MachineBasicBlock::iterator Walker = UseI;
--Walker;
bool foundDef = false;
bool foundUse = false;
while (Walker != MBB->begin()) {
if (BlockDefs.count(Walker)) {
foundDef = true;
break;
} else if (BlockUses.count(Walker)) {
foundUse = true;
break;
}
--Walker;
}
// Must check begin() too.
if (!foundDef && !foundUse) {
if (BlockDefs.count(Walker))
foundDef = true;
else if (BlockUses.count(Walker))
foundUse = true;
else
return PerformPHIConstructionFallBack(UseI, MBB, LI, Visited, Defs,
Uses, NewVNs, LiveOut, Phis,
IsTopLevel, IsIntraBlock);
}
unsigned StartIndex = LIs->getInstructionIndex(Walker);
StartIndex = foundDef ? LiveIntervals::getDefIndex(StartIndex) :
LiveIntervals::getUseIndex(StartIndex);
unsigned EndIndex = 0;
if (IsIntraBlock) {
EndIndex = LIs->getInstructionIndex(UseI);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(MBB);
if (foundDef)
RetVNI = NewVNs[Walker];
else
RetVNI = PerformPHIConstruction(Walker, MBB, LI, Visited, Defs, Uses,
NewVNs, LiveOut, Phis, false, true);
LI->addRange(LiveRange(StartIndex, EndIndex+1, RetVNI));
if (foundUse && LI->isKill(RetVNI, StartIndex))
LI->removeKill(RetVNI, StartIndex);
if (IsIntraBlock) {
LI->addKill(RetVNI, EndIndex, false);
}
}
// Memoize results so we don't have to recompute them.
if (!IsIntraBlock) LiveOut[MBB] = RetVNI;
else {
if (!NewVNs.count(UseI))
NewVNs[UseI] = RetVNI;
Visited.insert(UseI);
}
return RetVNI;
}
/// PerformPHIConstructionFallBack - PerformPHIConstruction fall back path.
///
VNInfo*
PreAllocSplitting::PerformPHIConstructionFallBack(MachineBasicBlock::iterator UseI,
MachineBasicBlock* MBB, LiveInterval* LI,
SmallPtrSet<MachineInstr*, 4>& Visited,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
DenseMap<MachineInstr*, VNInfo*>& NewVNs,
DenseMap<MachineBasicBlock*, VNInfo*>& LiveOut,
DenseMap<MachineBasicBlock*, VNInfo*>& Phis,
bool IsTopLevel, bool IsIntraBlock) {
// NOTE: Because this is the fallback case from other cases, we do NOT
// assume that we are not intrablock here.
if (Phis.count(MBB)) return Phis[MBB];
unsigned StartIndex = LIs->getMBBStartIdx(MBB);
VNInfo *RetVNI = Phis[MBB] =
LI->getNextValue(0, /*FIXME*/ 0, false, LIs->getVNInfoAllocator());
if (!IsIntraBlock) LiveOut[MBB] = RetVNI;
// If there are no uses or defs between our starting point and the
// beginning of the block, then recursive perform phi construction
// on our predecessors.
DenseMap<MachineBasicBlock*, VNInfo*> IncomingVNs;
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
VNInfo* Incoming = PerformPHIConstruction((*PI)->end(), *PI, LI,
Visited, Defs, Uses, NewVNs,
LiveOut, Phis, false, false);
if (Incoming != 0)
IncomingVNs[*PI] = Incoming;
}
if (MBB->pred_size() == 1 && !RetVNI->hasPHIKill()) {
VNInfo* OldVN = RetVNI;
VNInfo* NewVN = IncomingVNs.begin()->second;
VNInfo* MergedVN = LI->MergeValueNumberInto(OldVN, NewVN);
if (MergedVN == OldVN) std::swap(OldVN, NewVN);
for (DenseMap<MachineBasicBlock*, VNInfo*>::iterator LOI = LiveOut.begin(),
LOE = LiveOut.end(); LOI != LOE; ++LOI)
if (LOI->second == OldVN)
LOI->second = MergedVN;
for (DenseMap<MachineInstr*, VNInfo*>::iterator NVI = NewVNs.begin(),
NVE = NewVNs.end(); NVI != NVE; ++NVI)
if (NVI->second == OldVN)
NVI->second = MergedVN;
for (DenseMap<MachineBasicBlock*, VNInfo*>::iterator PI = Phis.begin(),
PE = Phis.end(); PI != PE; ++PI)
if (PI->second == OldVN)
PI->second = MergedVN;
RetVNI = MergedVN;
} else {
// Otherwise, merge the incoming VNInfos with a phi join. Create a new
// VNInfo to represent the joined value.
for (DenseMap<MachineBasicBlock*, VNInfo*>::iterator I =
IncomingVNs.begin(), E = IncomingVNs.end(); I != E; ++I) {
I->second->setHasPHIKill(true);
unsigned KillIndex = LIs->getMBBEndIdx(I->first);
if (!LiveInterval::isKill(I->second, KillIndex))
LI->addKill(I->second, KillIndex, false);
}
}
unsigned EndIndex = 0;
if (IsIntraBlock) {
EndIndex = LIs->getInstructionIndex(UseI);
EndIndex = LiveIntervals::getUseIndex(EndIndex);
} else
EndIndex = LIs->getMBBEndIdx(MBB);
LI->addRange(LiveRange(StartIndex, EndIndex+1, RetVNI));
if (IsIntraBlock)
LI->addKill(RetVNI, EndIndex, false);
// Memoize results so we don't have to recompute them.
if (!IsIntraBlock)
LiveOut[MBB] = RetVNI;
else {
if (!NewVNs.count(UseI))
NewVNs[UseI] = RetVNI;
Visited.insert(UseI);
}
return RetVNI;
}
/// ReconstructLiveInterval - Recompute a live interval from scratch.
void PreAllocSplitting::ReconstructLiveInterval(LiveInterval* LI) {
BumpPtrAllocator& Alloc = LIs->getVNInfoAllocator();
// Clear the old ranges and valnos;
LI->clear();
// Cache the uses and defs of the register
typedef DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> > RegMap;
RegMap Defs, Uses;
// Keep track of the new VNs we're creating.
DenseMap<MachineInstr*, VNInfo*> NewVNs;
SmallPtrSet<VNInfo*, 2> PhiVNs;
// Cache defs, and create a new VNInfo for each def.
for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(LI->reg),
DE = MRI->def_end(); DI != DE; ++DI) {
Defs[(*DI).getParent()].insert(&*DI);
unsigned DefIdx = LIs->getInstructionIndex(&*DI);
DefIdx = LiveIntervals::getDefIndex(DefIdx);
assert(DI->getOpcode() != TargetInstrInfo::PHI &&
"Following NewVN isPHIDef flag incorrect. Fix me!");
VNInfo* NewVN = LI->getNextValue(DefIdx, 0, true, Alloc);
// If the def is a move, set the copy field.
unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
if (TII->isMoveInstr(*DI, SrcReg, DstReg, SrcSubIdx, DstSubIdx))
if (DstReg == LI->reg)
NewVN->copy = &*DI;
NewVNs[&*DI] = NewVN;
}
// Cache uses as a separate pass from actually processing them.
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(LI->reg),
UE = MRI->use_end(); UI != UE; ++UI)
Uses[(*UI).getParent()].insert(&*UI);
// Now, actually process every use and use a phi construction algorithm
// to walk from it to its reaching definitions, building VNInfos along
// the way.
DenseMap<MachineBasicBlock*, VNInfo*> LiveOut;
DenseMap<MachineBasicBlock*, VNInfo*> Phis;
SmallPtrSet<MachineInstr*, 4> Visited;
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(LI->reg),
UE = MRI->use_end(); UI != UE; ++UI) {
PerformPHIConstruction(&*UI, UI->getParent(), LI, Visited, Defs,
Uses, NewVNs, LiveOut, Phis, true, true);
}
// Add ranges for dead defs
for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(LI->reg),
DE = MRI->def_end(); DI != DE; ++DI) {
unsigned DefIdx = LIs->getInstructionIndex(&*DI);
DefIdx = LiveIntervals::getDefIndex(DefIdx);
if (LI->liveAt(DefIdx)) continue;
VNInfo* DeadVN = NewVNs[&*DI];
LI->addRange(LiveRange(DefIdx, DefIdx+1, DeadVN));
LI->addKill(DeadVN, DefIdx, false);
}
}
/// RenumberValno - Split the given valno out into a new vreg, allowing it to
/// be allocated to a different register. This function creates a new vreg,
/// copies the valno and its live ranges over to the new vreg's interval,
/// removes them from the old interval, and rewrites all uses and defs of
/// the original reg to the new vreg within those ranges.
void PreAllocSplitting::RenumberValno(VNInfo* VN) {
SmallVector<VNInfo*, 4> Stack;
SmallVector<VNInfo*, 4> VNsToCopy;
Stack.push_back(VN);
// Walk through and copy the valno we care about, and any other valnos
// that are two-address redefinitions of the one we care about. These
// will need to be rewritten as well. We also check for safety of the
// renumbering here, by making sure that none of the valno involved has
// phi kills.
while (!Stack.empty()) {
VNInfo* OldVN = Stack.back();
Stack.pop_back();
// Bail out if we ever encounter a valno that has a PHI kill. We can't
// renumber these.
if (OldVN->hasPHIKill()) return;
VNsToCopy.push_back(OldVN);
// Locate two-address redefinitions
for (VNInfo::KillSet::iterator KI = OldVN->kills.begin(),
KE = OldVN->kills.end(); KI != KE; ++KI) {
assert(!KI->isPHIKill && "VN previously reported having no PHI kills.");
MachineInstr* MI = LIs->getInstructionFromIndex(KI->killIdx);
unsigned DefIdx = MI->findRegisterDefOperandIdx(CurrLI->reg);
if (DefIdx == ~0U) continue;
if (MI->isRegTiedToUseOperand(DefIdx)) {
VNInfo* NextVN =
CurrLI->findDefinedVNInfo(LiveIntervals::getDefIndex(KI->killIdx));
if (NextVN == OldVN) continue;
Stack.push_back(NextVN);
}
}
}
// Create the new vreg
unsigned NewVReg = MRI->createVirtualRegister(MRI->getRegClass(CurrLI->reg));
// Create the new live interval
LiveInterval& NewLI = LIs->getOrCreateInterval(NewVReg);
for (SmallVector<VNInfo*, 4>::iterator OI = VNsToCopy.begin(), OE =
VNsToCopy.end(); OI != OE; ++OI) {
VNInfo* OldVN = *OI;
// Copy the valno over
VNInfo* NewVN = NewLI.createValueCopy(OldVN, LIs->getVNInfoAllocator());
NewLI.MergeValueInAsValue(*CurrLI, OldVN, NewVN);
// Remove the valno from the old interval
CurrLI->removeValNo(OldVN);
}
// Rewrite defs and uses. This is done in two stages to avoid invalidating
// the reg_iterator.
SmallVector<std::pair<MachineInstr*, unsigned>, 8> OpsToChange;
for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(CurrLI->reg),
E = MRI->reg_end(); I != E; ++I) {
MachineOperand& MO = I.getOperand();
unsigned InstrIdx = LIs->getInstructionIndex(&*I);
if ((MO.isUse() && NewLI.liveAt(LiveIntervals::getUseIndex(InstrIdx))) ||
(MO.isDef() && NewLI.liveAt(LiveIntervals::getDefIndex(InstrIdx))))
OpsToChange.push_back(std::make_pair(&*I, I.getOperandNo()));
}
for (SmallVector<std::pair<MachineInstr*, unsigned>, 8>::iterator I =
OpsToChange.begin(), E = OpsToChange.end(); I != E; ++I) {
MachineInstr* Inst = I->first;
unsigned OpIdx = I->second;
MachineOperand& MO = Inst->getOperand(OpIdx);
MO.setReg(NewVReg);
}
// Grow the VirtRegMap, since we've created a new vreg.
VRM->grow();
// The renumbered vreg shares a stack slot with the old register.
if (IntervalSSMap.count(CurrLI->reg))
IntervalSSMap[NewVReg] = IntervalSSMap[CurrLI->reg];
NumRenumbers++;
}
bool PreAllocSplitting::Rematerialize(unsigned vreg, VNInfo* ValNo,
MachineInstr* DefMI,
MachineBasicBlock::iterator RestorePt,
unsigned RestoreIdx,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB) {
MachineBasicBlock& MBB = *RestorePt->getParent();
MachineBasicBlock::iterator KillPt = BarrierMBB->end();
unsigned KillIdx = 0;
if (!ValNo->isDefAccurate() || DefMI->getParent() == BarrierMBB)
KillPt = findSpillPoint(BarrierMBB, Barrier, NULL, RefsInMBB, KillIdx);
else
KillPt = findNextEmptySlot(DefMI->getParent(), DefMI, KillIdx);
if (KillPt == DefMI->getParent()->end())
return false;
TII->reMaterialize(MBB, RestorePt, vreg, DefMI);
LIs->InsertMachineInstrInMaps(prior(RestorePt), RestoreIdx);
ReconstructLiveInterval(CurrLI);
unsigned RematIdx = LIs->getInstructionIndex(prior(RestorePt));
RematIdx = LiveIntervals::getDefIndex(RematIdx);
RenumberValno(CurrLI->findDefinedVNInfo(RematIdx));
++NumSplits;
++NumRemats;
return true;
}
MachineInstr* PreAllocSplitting::FoldSpill(unsigned vreg,
const TargetRegisterClass* RC,
MachineInstr* DefMI,
MachineInstr* Barrier,
MachineBasicBlock* MBB,
int& SS,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB) {
MachineBasicBlock::iterator Pt = MBB->begin();
// Go top down if RefsInMBB is empty.
if (RefsInMBB.empty())
return 0;
MachineBasicBlock::iterator FoldPt = Barrier;
while (&*FoldPt != DefMI && FoldPt != MBB->begin() &&
!RefsInMBB.count(FoldPt))
--FoldPt;
int OpIdx = FoldPt->findRegisterDefOperandIdx(vreg, false);
if (OpIdx == -1)
return 0;
SmallVector<unsigned, 1> Ops;
Ops.push_back(OpIdx);
if (!TII->canFoldMemoryOperand(FoldPt, Ops))
return 0;
DenseMap<unsigned, int>::iterator I = IntervalSSMap.find(vreg);
if (I != IntervalSSMap.end()) {
SS = I->second;
} else {
SS = MFI->CreateStackObject(RC->getSize(), RC->getAlignment());
}
MachineInstr* FMI = TII->foldMemoryOperand(*MBB->getParent(),
FoldPt, Ops, SS);
if (FMI) {
LIs->ReplaceMachineInstrInMaps(FoldPt, FMI);
FMI = MBB->insert(MBB->erase(FoldPt), FMI);
++NumFolds;
IntervalSSMap[vreg] = SS;
CurrSLI = &LSs->getOrCreateInterval(SS, RC);
if (CurrSLI->hasAtLeastOneValue())
CurrSValNo = CurrSLI->getValNumInfo(0);
else
CurrSValNo = CurrSLI->getNextValue(0, 0, false, LSs->getVNInfoAllocator());
}
return FMI;
}
MachineInstr* PreAllocSplitting::FoldRestore(unsigned vreg,
const TargetRegisterClass* RC,
MachineInstr* Barrier,
MachineBasicBlock* MBB,
int SS,
SmallPtrSet<MachineInstr*, 4>& RefsInMBB) {
if ((int)RestoreFoldLimit != -1 && RestoreFoldLimit == (int)NumRestoreFolds)
return 0;
// Go top down if RefsInMBB is empty.
if (RefsInMBB.empty())
return 0;
// Can't fold a restore between a call stack setup and teardown.
MachineBasicBlock::iterator FoldPt = Barrier;
// Advance from barrier to call frame teardown.
while (FoldPt != MBB->getFirstTerminator() &&
FoldPt->getOpcode() != TRI->getCallFrameDestroyOpcode()) {
if (RefsInMBB.count(FoldPt))
return 0;
++FoldPt;
}
if (FoldPt == MBB->getFirstTerminator())
return 0;
else
++FoldPt;
// Now find the restore point.
while (FoldPt != MBB->getFirstTerminator() && !RefsInMBB.count(FoldPt)) {
if (FoldPt->getOpcode() == TRI->getCallFrameSetupOpcode()) {
while (FoldPt != MBB->getFirstTerminator() &&
FoldPt->getOpcode() != TRI->getCallFrameDestroyOpcode()) {
if (RefsInMBB.count(FoldPt))
return 0;
++FoldPt;
}
if (FoldPt == MBB->getFirstTerminator())
return 0;
}
++FoldPt;
}
if (FoldPt == MBB->getFirstTerminator())
return 0;
int OpIdx = FoldPt->findRegisterUseOperandIdx(vreg, true);
if (OpIdx == -1)
return 0;
SmallVector<unsigned, 1> Ops;
Ops.push_back(OpIdx);
if (!TII->canFoldMemoryOperand(FoldPt, Ops))
return 0;
MachineInstr* FMI = TII->foldMemoryOperand(*MBB->getParent(),
FoldPt, Ops, SS);
if (FMI) {
LIs->ReplaceMachineInstrInMaps(FoldPt, FMI);
FMI = MBB->insert(MBB->erase(FoldPt), FMI);
++NumRestoreFolds;
}
return FMI;
}
/// 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->isUnused()) {
// Defined by a dead def? How can this be?
assert(0 && "Val# is defined by a dead def?");
abort();
}
MachineInstr *DefMI = ValNo->isDefAccurate()
? LIs->getInstructionFromIndex(ValNo->def) : NULL;
// 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 = 0;
MachineBasicBlock::iterator RestorePt =
findRestorePoint(BarrierMBB, Barrier, LR->end, RefsInMBB, RestoreIndex);
if (RestorePt == BarrierMBB->end())
return false;
if (DefMI && LIs->isReMaterializable(*LI, ValNo, DefMI))
if (Rematerialize(LI->reg, ValNo, DefMI, RestorePt,
RestoreIndex, RefsInMBB))
return true;
// 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->isDefAccurate()) {
// If we don't know where the def is we must split just before the barrier.
if ((SpillMI = FoldSpill(LI->reg, RC, 0, Barrier,
BarrierMBB, SS, RefsInMBB))) {
SpillIndex = LIs->getInstructionIndex(SpillMI);
} else {
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.
if ((SpillMI = FoldSpill(LI->reg, RC, DefMI, Barrier,
BarrierMBB, SS, RefsInMBB))) {
SpillIndex = LIs->getInstructionIndex(SpillMI);
} else {
// 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.
bool FoldedRestore = false;
if (MachineInstr* LMI = FoldRestore(CurrLI->reg, RC, Barrier,
BarrierMBB, SS, RefsInMBB)) {
RestorePt = LMI;
RestoreIndex = LIs->getInstructionIndex(RestorePt);
FoldedRestore = true;
} else {
TII->loadRegFromStackSlot(*BarrierMBB, RestorePt, CurrLI->reg, SS, RC);
MachineInstr *LoadMI = prior(RestorePt);
LIs->InsertMachineInstrInMaps(LoadMI, RestoreIndex);
}
// Update spill stack slot live interval.
UpdateSpillSlotInterval(ValNo, LIs->getUseIndex(SpillIndex)+1,
LIs->getDefIndex(RestoreIndex));
ReconstructLiveInterval(CurrLI);
if (!FoldedRestore) {
unsigned RestoreIdx = LIs->getInstructionIndex(prior(RestorePt));
RestoreIdx = LiveIntervals::getDefIndex(RestoreIdx);
RenumberValno(CurrLI->findDefinedVNInfo(RestoreIdx));
}
++NumSplits;
return true;
}
/// SplitRegLiveIntervals - Split all register live intervals that cross the
/// barrier that's being processed.
bool
PreAllocSplitting::SplitRegLiveIntervals(const TargetRegisterClass **RCs,
SmallPtrSet<LiveInterval*, 8>& Split) {
// 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) {
// FIXME: If it's not safe to move any instruction that defines the barrier
// register class, then it means there are some special dependencies which
// codegen is not modelling. Ignore these barriers for now.
if (!TII->isSafeToMoveRegClassDefs(*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;
else if (NumSplits == 4)
Change |= Change;
LiveInterval *LI = Intervals.back();
Intervals.pop_back();
bool result = SplitRegLiveInterval(LI);
if (result) Split.insert(LI);
Change |= result;
}
return Change;
}
unsigned PreAllocSplitting::getNumberOfNonSpills(
SmallPtrSet<MachineInstr*, 4>& MIs,
unsigned Reg, int FrameIndex,
bool& FeedsTwoAddr) {
unsigned NonSpills = 0;
for (SmallPtrSet<MachineInstr*, 4>::iterator UI = MIs.begin(), UE = MIs.end();
UI != UE; ++UI) {
int StoreFrameIndex;
unsigned StoreVReg = TII->isStoreToStackSlot(*UI, StoreFrameIndex);
if (StoreVReg != Reg || StoreFrameIndex != FrameIndex)
NonSpills++;
int DefIdx = (*UI)->findRegisterDefOperandIdx(Reg);
if (DefIdx != -1 && (*UI)->isRegTiedToUseOperand(DefIdx))
FeedsTwoAddr = true;
}
return NonSpills;
}
/// removeDeadSpills - After doing splitting, filter through all intervals we've
/// split, and see if any of the spills are unnecessary. If so, remove them.
bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
bool changed = false;
// Walk over all of the live intervals that were touched by the splitter,
// and see if we can do any DCE and/or folding.
for (SmallPtrSet<LiveInterval*, 8>::iterator LI = split.begin(),
LE = split.end(); LI != LE; ++LI) {
DenseMap<VNInfo*, SmallPtrSet<MachineInstr*, 4> > VNUseCount;
// First, collect all the uses of the vreg, and sort them by their
// reaching definition (VNInfo).
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin((*LI)->reg),
UE = MRI->use_end(); UI != UE; ++UI) {
unsigned index = LIs->getInstructionIndex(&*UI);
index = LiveIntervals::getUseIndex(index);
const LiveRange* LR = (*LI)->getLiveRangeContaining(index);
VNUseCount[LR->valno].insert(&*UI);
}
// Now, take the definitions (VNInfo's) one at a time and try to DCE
// and/or fold them away.
for (LiveInterval::vni_iterator VI = (*LI)->vni_begin(),
VE = (*LI)->vni_end(); VI != VE; ++VI) {
if (DeadSplitLimit != -1 && (int)NumDeadSpills == DeadSplitLimit)
return changed;
VNInfo* CurrVN = *VI;
// We don't currently try to handle definitions with PHI kills, because
// it would involve processing more than one VNInfo at once.
if (CurrVN->hasPHIKill()) continue;
// We also don't try to handle the results of PHI joins, since there's
// no defining instruction to analyze.
if (!CurrVN->isDefAccurate() || CurrVN->isUnused()) continue;
// We're only interested in eliminating cruft introduced by the splitter,
// is of the form load-use or load-use-store. First, check that the
// definition is a load, and remember what stack slot we loaded it from.
MachineInstr* DefMI = LIs->getInstructionFromIndex(CurrVN->def);
int FrameIndex;
if (!TII->isLoadFromStackSlot(DefMI, FrameIndex)) continue;
// If the definition has no uses at all, just DCE it.
if (VNUseCount[CurrVN].size() == 0) {
LIs->RemoveMachineInstrFromMaps(DefMI);
(*LI)->removeValNo(CurrVN);
DefMI->eraseFromParent();
VNUseCount.erase(CurrVN);
NumDeadSpills++;
changed = true;
continue;
}
// Second, get the number of non-store uses of the definition, as well as
// a flag indicating whether it feeds into a later two-address definition.
bool FeedsTwoAddr = false;
unsigned NonSpillCount = getNumberOfNonSpills(VNUseCount[CurrVN],
(*LI)->reg, FrameIndex,
FeedsTwoAddr);
// If there's one non-store use and it doesn't feed a two-addr, then
// this is a load-use-store case that we can try to fold.
if (NonSpillCount == 1 && !FeedsTwoAddr) {
// Start by finding the non-store use MachineInstr.
SmallPtrSet<MachineInstr*, 4>::iterator UI = VNUseCount[CurrVN].begin();
int StoreFrameIndex;
unsigned StoreVReg = TII->isStoreToStackSlot(*UI, StoreFrameIndex);
while (UI != VNUseCount[CurrVN].end() &&
(StoreVReg == (*LI)->reg && StoreFrameIndex == FrameIndex)) {
++UI;
if (UI != VNUseCount[CurrVN].end())
StoreVReg = TII->isStoreToStackSlot(*UI, StoreFrameIndex);
}
if (UI == VNUseCount[CurrVN].end()) continue;
MachineInstr* use = *UI;
// Attempt to fold it away!
int OpIdx = use->findRegisterUseOperandIdx((*LI)->reg, false);
if (OpIdx == -1) continue;
SmallVector<unsigned, 1> Ops;
Ops.push_back(OpIdx);
if (!TII->canFoldMemoryOperand(use, Ops)) continue;
MachineInstr* NewMI =
TII->foldMemoryOperand(*use->getParent()->getParent(),
use, Ops, FrameIndex);
if (!NewMI) continue;
// Update relevant analyses.
LIs->RemoveMachineInstrFromMaps(DefMI);
LIs->ReplaceMachineInstrInMaps(use, NewMI);
(*LI)->removeValNo(CurrVN);
DefMI->eraseFromParent();
MachineBasicBlock* MBB = use->getParent();
NewMI = MBB->insert(MBB->erase(use), NewMI);
VNUseCount[CurrVN].erase(use);
// Remove deleted instructions. Note that we need to remove them from
// the VNInfo->use map as well, just to be safe.
for (SmallPtrSet<MachineInstr*, 4>::iterator II =
VNUseCount[CurrVN].begin(), IE = VNUseCount[CurrVN].end();
II != IE; ++II) {
for (DenseMap<VNInfo*, SmallPtrSet<MachineInstr*, 4> >::iterator
VNI = VNUseCount.begin(), VNE = VNUseCount.end(); VNI != VNE;
++VNI)
if (VNI->first != CurrVN)
VNI->second.erase(*II);
LIs->RemoveMachineInstrFromMaps(*II);
(*II)->eraseFromParent();
}
VNUseCount.erase(CurrVN);
for (DenseMap<VNInfo*, SmallPtrSet<MachineInstr*, 4> >::iterator
VI = VNUseCount.begin(), VE = VNUseCount.end(); VI != VE; ++VI)
if (VI->second.erase(use))
VI->second.insert(NewMI);
NumDeadSpills++;
changed = true;
continue;
}
// If there's more than one non-store instruction, we can't profitably
// fold it, so bail.
if (NonSpillCount) continue;
// Otherwise, this is a load-store case, so DCE them.
for (SmallPtrSet<MachineInstr*, 4>::iterator UI =
VNUseCount[CurrVN].begin(), UE = VNUseCount[CurrVN].end();
UI != UI; ++UI) {
LIs->RemoveMachineInstrFromMaps(*UI);
(*UI)->eraseFromParent();
}
VNUseCount.erase(CurrVN);
LIs->RemoveMachineInstrFromMaps(DefMI);
(*LI)->removeValNo(CurrVN);
DefMI->eraseFromParent();
NumDeadSpills++;
changed = true;
}
}
return changed;
}
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();
TRI = TM->getRegisterInfo();
TII = TM->getInstrInfo();
MFI = MF.getFrameInfo();
MRI = &MF.getRegInfo();
LIs = &getAnalysis<LiveIntervals>();
LSs = &getAnalysis<LiveStacks>();
VRM = &getAnalysis<VirtRegMap>();
bool MadeChange = false;
// Make sure blocks are numbered in order.
MF.RenumberBlocks();
MachineBasicBlock *Entry = MF.begin();
SmallPtrSet<MachineBasicBlock*,16> Visited;
SmallPtrSet<LiveInterval*, 8> Split;
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, Split);
}
}
MadeChange |= removeDeadSpills(Split);
return MadeChange;
}
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