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Add support for aggressive load-use-store folding. This takes care of the 

vast majority of code size regressions introduced by pre-alloc-splitting.

llvm-svn: 63274
This commit is contained in:
Owen Anderson 2009-01-29 05:28:55 +00:00
parent 50338007b9
commit b05ce78c51
1 changed files with 85 additions and 19 deletions
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104
llvm/lib/CodeGen/PreAllocSplitting.cpp
View File

@ -37,8 +37,9 @@
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);
STATISTIC(NumTotalSplits, "Number of intervals split");
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");
@ -77,8 +78,6 @@ namespace {
// Def2SpillMap - A map from a def instruction index to spill index.
DenseMap<unsigned, unsigned> Def2SpillMap;
unsigned NumSplits;
public:
static char ID;
@ -162,8 +161,8 @@ namespace {
void RenumberValno(VNInfo* VN);
void ReconstructLiveInterval(LiveInterval* LI);
bool removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split);
unsigned getNumberOfSpills(SmallPtrSet<MachineInstr*, 4>& MIs,
unsigned Reg, int FrameIndex);
unsigned getNumberOfNonSpills(SmallPtrSet<MachineInstr*, 4>& MIs,
unsigned Reg, int FrameIndex, bool& TwoAddr);
VNInfo* PerformPHIConstruction(MachineBasicBlock::iterator use,
MachineBasicBlock* MBB,
LiveInterval* LI,
@ -789,6 +788,10 @@ void PreAllocSplitting::RenumberValno(VNInfo* VN) {
MO.setReg(NewVReg);
}
// The renumbered vreg shares a stack slot with the old register.
if (IntervalSSMap.count(CurrLI->reg))
IntervalSSMap[NewVReg] = IntervalSSMap[CurrLI->reg];
NumRenumbers++;
}
@ -1042,19 +1045,24 @@ PreAllocSplitting::SplitRegLiveIntervals(const TargetRegisterClass **RCs,
return Change;
}
unsigned PreAllocSplitting::getNumberOfSpills(
unsigned PreAllocSplitting::getNumberOfNonSpills(
SmallPtrSet<MachineInstr*, 4>& MIs,
unsigned Reg, int FrameIndex) {
unsigned Spills = 0;
unsigned Reg, int FrameIndex,
bool& FeedsTwoAddr) {
unsigned NonSpills = 0;
for (SmallPtrSet<MachineInstr*, 4>::iterator UI = MIs.begin(), UE = MIs.end();
UI != UI; ++UI) {
UI != UE; ++UI) {
int StoreFrameIndex;
unsigned StoreVReg = TII->isStoreToStackSlot(*UI, StoreFrameIndex);
if (StoreVReg == Reg && StoreFrameIndex == FrameIndex)
Spills++;
if (StoreVReg != Reg || StoreFrameIndex != FrameIndex)
NonSpills++;
int DefIdx = (*UI)->findRegisterDefOperandIdx(Reg);
if (DefIdx != -1 && (*UI)->isRegReDefinedByTwoAddr(DefIdx))
FeedsTwoAddr = true;
}
return Spills;
return NonSpills;
}
/// removeDeadSpills - After doing splitting, filter through all intervals we've
@ -1077,6 +1085,10 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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;
if (CurrVN->hasPHIKill) continue;
@ -1096,9 +1108,67 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
continue;
}
unsigned SpillCount = getNumberOfSpills(VNUseCount[CurrVN],
(*LI)->reg, FrameIndex);
if (SpillCount != VNUseCount[CurrVN].size()) continue;
bool FeedsTwoAddr = false;
unsigned NonSpillCount = getNumberOfNonSpills(VNUseCount[CurrVN],
(*LI)->reg, FrameIndex,
FeedsTwoAddr);
if (NonSpillCount == 1 && !FeedsTwoAddr) {
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;
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;
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);
for (SmallPtrSet<MachineInstr*, 4>::iterator II =
VNUseCount[CurrVN].begin(), IE = VNUseCount[CurrVN].end();
II != IE; ++II) {
LIs->RemoveMachineInstrFromMaps(*II);
(*II)->eraseFromParent();
}
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 (NonSpillCount) continue;
for (SmallPtrSet<MachineInstr*, 4>::iterator UI =
VNUseCount[CurrVN].begin(), UE = VNUseCount[CurrVN].end();
@ -1193,7 +1263,6 @@ bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
LSs = &getAnalysis<LiveStacks>();
bool MadeChange = false;
NumSplits = 0;
// Make sure blocks are numbered in order.
MF.RenumberBlocks();
@ -1220,9 +1289,6 @@ bool PreAllocSplitting::runOnMachineFunction(MachineFunction &MF) {
}
MadeChange |= removeDeadSpills(Split);
if (NumSplits)
NumTotalSplits += NumSplits;
return MadeChange;
}