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- Mark last use of a split interval as kill instead of letting spiller track it.

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This allows an important optimization to be re-enabled.
- If all uses / defs of a split interval can be folded, give the interval a
  low spill weight so it would not be picked in case spilling is needed (avoid
  pushing other intervals in the same BB to be spilled).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44601 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-12-05 03:22:34 +00:00
parent d64b5c82b9
commit 018f9b020b
3 changed files with 75 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/llvm/CodeGen/LiveIntervalAnalysis.h
View File

@ -278,6 +278,8 @@ namespace llvm {
SmallVector<unsigned, 2> &Ops,
bool isSS, int Slot, unsigned Reg);
/// canFoldMemoryOperand - Returns true if the specified load / store
/// folding is possible.
bool canFoldMemoryOperand(MachineInstr *MI,
SmallVector<unsigned, 2> &Ops) const;

99
lib/CodeGen/LiveIntervalAnalysis.cpp
View File

@ -691,6 +691,22 @@ bool LiveIntervals::tryFoldMemoryOperand(MachineInstr* &MI,
return false;
}
/// canFoldMemoryOperand - Returns true if the specified load / store
/// folding is possible.
bool LiveIntervals::canFoldMemoryOperand(MachineInstr *MI,
SmallVector<unsigned, 2> &Ops) const {
SmallVector<unsigned, 2> FoldOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
unsigned OpIdx = Ops[i];
// FIXME: fold subreg use.
if (MI->getOperand(OpIdx).getSubReg())
return false;
FoldOps.push_back(OpIdx);
}
return mri_->canFoldMemoryOperand(MI, FoldOps);
}
bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const {
SmallPtrSet<MachineBasicBlock*, 4> MBBs;
for (LiveInterval::Ranges::const_iterator
@ -710,7 +726,7 @@ bool LiveIntervals::intervalIsInOneMBB(const LiveInterval &li) const {
/// rewriteInstructionForSpills, rewriteInstructionsForSpills - Helper functions
/// for addIntervalsForSpills to rewrite uses / defs for the given live range.
void LiveIntervals::
bool LiveIntervals::
rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
unsigned id, unsigned index, unsigned end, MachineInstr *MI,
MachineInstr *ReMatOrigDefMI, MachineInstr *ReMatDefMI,
@ -723,6 +739,7 @@ rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
const LoopInfo *loopInfo,
std::map<unsigned,unsigned> &MBBVRegsMap,
std::vector<LiveInterval*> &NewLIs) {
bool CanFold = false;
RestartInstruction:
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& mop = MI->getOperand(i);
@ -760,11 +777,6 @@ rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
}
}
// Do not fold load / store here if we are splitting. We'll find an
// optimal point to insert a load / store later.
if (TryFold)
TryFold = !TrySplit && NewVReg == 0;
// Scan all of the operands of this instruction rewriting operands
// to use NewVReg instead of li.reg as appropriate. We do this for
// two reasons:
@ -795,15 +807,23 @@ rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
}
}
if (TryFold &&
tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index,
Ops, FoldSS, FoldSlot, Reg)) {
// Folding the load/store can completely change the instruction in
// unpredictable ways, rescan it from the beginning.
HasUse = false;
HasDef = false;
goto RestartInstruction;
}
if (TryFold) {
// Do not fold load / store here if we are splitting. We'll find an
// optimal point to insert a load / store later.
if (!TrySplit) {
if (tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index,
Ops, FoldSS, FoldSlot, Reg)) {
// Folding the load/store can completely change the instruction in
// unpredictable ways, rescan it from the beginning.
HasUse = false;
HasDef = false;
CanFold = false;
goto RestartInstruction;
}
} else {
CanFold = canFoldMemoryOperand(MI, Ops);
}
} else CanFold = false;
// Create a new virtual register for the spill interval.
bool CreatedNewVReg = false;
@ -879,8 +899,8 @@ rewriteInstructionForSpills(const LiveInterval &li, bool TrySplit,
nI.print(DOUT, mri_);
DOUT << '\n';
}
return CanFold;
}
bool LiveIntervals::anyKillInMBBAfterIdx(const LiveInterval &li,
const VNInfo *VNI,
MachineBasicBlock *MBB, unsigned Idx) const {
@ -920,6 +940,7 @@ rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
std::map<unsigned, std::vector<SRInfo> > &RestoreIdxes,
std::map<unsigned,unsigned> &MBBVRegsMap,
std::vector<LiveInterval*> &NewLIs) {
bool AllCanFold = true;
unsigned NewVReg = 0;
unsigned index = getBaseIndex(I->start);
unsigned end = getBaseIndex(I->end-1) + InstrSlots::NUM;
@ -931,12 +952,12 @@ rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
MachineInstr *MI = getInstructionFromIndex(index);
MachineBasicBlock *MBB = MI->getParent();
NewVReg = 0;
unsigned ThisVReg = 0;
if (TrySplit) {
std::map<unsigned,unsigned>::const_iterator NVI =
MBBVRegsMap.find(MBB->getNumber());
if (NVI != MBBVRegsMap.end()) {
NewVReg = NVI->second;
ThisVReg = NVI->second;
// One common case:
// x = use
// ...
@ -959,21 +980,35 @@ rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
}
if (MIHasDef && !MIHasUse) {
MBBVRegsMap.erase(MBB->getNumber());
NewVReg = 0;
ThisVReg = 0;
}
}
}
bool IsNew = NewVReg == 0;
bool IsNew = ThisVReg == 0;
if (IsNew) {
// This ends the previous live interval. If all of its def / use
// can be folded, give it a low spill weight.
if (NewVReg && TrySplit && AllCanFold) {
LiveInterval &nI = getOrCreateInterval(NewVReg);
nI.weight /= 10.0F;
}
AllCanFold = true;
}
NewVReg = ThisVReg;
bool HasDef = false;
bool HasUse = false;
rewriteInstructionForSpills(li, TrySplit, I->valno->id, index, end,
MI, ReMatOrigDefMI, ReMatDefMI, Slot, LdSlot,
isLoad, isLoadSS, DefIsReMat, CanDelete, vrm,
RegMap, rc, ReMatIds, NewVReg, HasDef, HasUse,
loopInfo, MBBVRegsMap, NewLIs);
bool CanFold = rewriteInstructionForSpills(li, TrySplit, I->valno->id,
index, end, MI, ReMatOrigDefMI, ReMatDefMI,
Slot, LdSlot, isLoad, isLoadSS, DefIsReMat,
CanDelete, vrm, RegMap, rc, ReMatIds, NewVReg,
HasDef, HasUse, loopInfo, MBBVRegsMap, NewLIs);
if (!HasDef && !HasUse)
continue;
AllCanFold &= CanFold;
// Update weight of spill interval.
LiveInterval &nI = getOrCreateInterval(NewVReg);
if (!TrySplit) {
@ -1058,6 +1093,12 @@ rewriteInstructionsForSpills(const LiveInterval &li, bool TrySplit,
unsigned loopDepth = loopInfo->getLoopDepth(MBB->getBasicBlock());
nI.weight += getSpillWeight(HasDef, HasUse, loopDepth);
}
if (NewVReg && TrySplit && AllCanFold) {
// If all of its def / use can be folded, give it a low spill weight.
LiveInterval &nI = getOrCreateInterval(NewVReg);
nI.weight /= 10.0F;
}
}
bool LiveIntervals::alsoFoldARestore(int Id, int index, unsigned vr,
@ -1331,8 +1372,14 @@ addIntervalsForSpills(const LiveInterval &li,
// load / rematerialization for us.
if (Folded)
nI.removeRange(getLoadIndex(index), getUseIndex(index)+1);
else
else {
vrm.addRestorePoint(VReg, MI);
LiveRange *LR = &nI.ranges[nI.ranges.size()-1];
MachineInstr *LastUse = getInstructionFromIndex(getBaseIndex(LR->end));
int UseIdx = LastUse->findRegisterUseOperandIdx(VReg);
assert(UseIdx != -1);
LastUse->getOperand(UseIdx).setIsKill();
}
}
Id = RestoreMBBs.find_next(Id);
}

2
lib/CodeGen/VirtRegMap.cpp
View File

@ -1295,8 +1295,6 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
// the value and there isn't an earlier def that has already clobbered the
// physreg.
if (PhysReg &&
Spills.canClobberPhysReg(SS) &&
!ReusedOperands.isClobbered(PhysReg) &&
DeadStore->findRegisterUseOperandIdx(PhysReg, true) != -1 &&
MRI->unfoldMemoryOperand(MF, &MI, PhysReg, false, true, NewMIs)) {
MBB.insert(MII, NewMIs[0]);