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Add an initial pass at dead spill/restore removal for pre alloc splitting.

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llvm-svn: 62821
This commit is contained in:
Owen Anderson 2009-01-23 00:23:32 +00:00
parent c843f0f484
commit b9426381f3
1 changed files with 56 additions and 4 deletions
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60
lib/CodeGen/PreAllocSplitting.cpp
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@ -42,6 +42,7 @@ STATISTIC(NumSplits, "Number of intervals split");
STATISTIC(NumRemats, "Number of intervals split by rematerialization");
STATISTIC(NumFolds, "Number of intervals split with spill folding");
STATISTIC(NumRenumbers, "Number of intervals renumbered into new registers");
STATISTIC(NumDeadSpills, "Number of dead spills removed");
namespace {
class VISIBILITY_HIDDEN PreAllocSplitting : public MachineFunctionPass {
@ -152,7 +153,8 @@ namespace {
bool SplitRegLiveInterval(LiveInterval*);
bool SplitRegLiveIntervals(const TargetRegisterClass **);
bool SplitRegLiveIntervals(const TargetRegisterClass **,
SmallPtrSet<LiveInterval*, 8>&);
void RepairLiveInterval(LiveInterval* CurrLI, VNInfo* ValNo,
MachineInstr* DefMI, unsigned RestoreIdx);
@ -172,6 +174,7 @@ namespace {
SmallPtrSet<MachineInstr*, 4>& RefsInMBB);
void RenumberValno(VNInfo* VN);
void ReconstructLiveInterval(LiveInterval* LI);
bool removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split);
VNInfo* PerformPHIConstruction(MachineBasicBlock::iterator use,
MachineBasicBlock* MBB,
LiveInterval* LI,
@ -1340,7 +1343,8 @@ bool PreAllocSplitting::SplitRegLiveInterval(LiveInterval *LI) {
/// SplitRegLiveIntervals - Split all register live intervals that cross the
/// barrier that's being processed.
bool
PreAllocSplitting::SplitRegLiveIntervals(const TargetRegisterClass **RCs) {
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;
@ -1369,12 +1373,56 @@ PreAllocSplitting::SplitRegLiveIntervals(const TargetRegisterClass **RCs) {
Change |= Change;
LiveInterval *LI = Intervals.back();
Intervals.pop_back();
Change |= SplitRegLiveInterval(LI);
bool result = SplitRegLiveInterval(LI);
if (result) Split.insert(LI);
Change |= result;
}
return Change;
}
/// 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;
for (SmallPtrSet<LiveInterval*, 8>::iterator LI = split.begin(),
LE = split.end(); LI != LE; ++LI) {
DenseMap<VNInfo*, unsigned > VNUseCount;
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]++;
}
for (LiveInterval::vni_iterator VI = (*LI)->vni_begin(),
VE = (*LI)->vni_end(); VI != VE; ++VI) {
VNInfo* CurrVN = *VI;
if (CurrVN->hasPHIKill) continue;
if (VNUseCount[CurrVN] > 0) continue;
unsigned DefIdx = CurrVN->def;
if (DefIdx == ~0U || DefIdx == ~1U) continue;
MachineInstr* DefMI = LIs->getInstructionFromIndex(DefIdx);
int FrameIndex;
if (!TII->isLoadFromStackSlot(DefMI, FrameIndex)) continue;
LIs->RemoveMachineInstrFromMaps(DefMI);
(*LI)->removeValNo(CurrVN);
DefMI->eraseFromParent();
NumDeadSpills++;
changed = true;
}
}
return changed;
}
bool PreAllocSplitting::createsNewJoin(LiveRange* LR,
MachineBasicBlock* DefMBB,
MachineBasicBlock* BarrierMBB) {
@ -1457,6 +1505,8 @@ bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
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) {
@ -1469,9 +1519,11 @@ bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
if (!BarrierRCs)
continue;
BarrierIdx = LIs->getInstructionIndex(Barrier);
MadeChange |= SplitRegLiveIntervals(BarrierRCs);
MadeChange |= SplitRegLiveIntervals(BarrierRCs, Split);
}
}
MadeChange |= removeDeadSpills(Split);
return MadeChange;
}