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llvm-svn: 63276
This commit is contained in:
Owen Anderson 2009-01-29 05:41:02 +00:00
parent 607c1ea284
commit ad49be6552
1 changed files with 30 additions and 3 deletions
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33
lib/CodeGen/PreAllocSplitting.cpp
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@ -1070,10 +1070,14 @@ unsigned PreAllocSplitting::getNumberOfNonSpills(
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);
@ -1083,6 +1087,8 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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) {
@ -1090,15 +1096,24 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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.
unsigned DefIdx = CurrVN->def;
if (DefIdx == ~0U || DefIdx == ~1U) 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(DefIdx);
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);
@ -1108,12 +1123,17 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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);
@ -1123,17 +1143,15 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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 =
@ -1142,6 +1160,7 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
if (!NewMI) continue;
// Update relevant analyses.
LIs->RemoveMachineInstrFromMaps(DefMI);
LIs->ReplaceMachineInstrInMaps(use, NewMI);
(*LI)->removeValNo(CurrVN);
@ -1151,9 +1170,14 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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
VI = VNUseCount.begin(), VE = VNUseCount.end(); VI != VE; ++VI)
VI->second.erase(*II);
LIs->RemoveMachineInstrFromMaps(*II);
(*II)->eraseFromParent();
}
@ -1168,8 +1192,11 @@ bool PreAllocSplitting::removeDeadSpills(SmallPtrSet<LiveInterval*, 8>& split) {
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) {