bool RenameIndependentSubregs::renameComponents(LiveInterval &LI) const {
// Shortcut: We cannot have split components with a single definition.
if (LI.valnos.size() < 2)
return false;
SmallVector<SubRangeInfo, 4> SubRangeInfos;
IntEqClasses Classes;
if (!findComponents(Classes, SubRangeInfos, LI))
return false;
// Create a new VReg for each class.
unsigned Reg = LI.reg;
const TargetRegisterClass *RegClass = MRI->getRegClass(Reg);
SmallVector<LiveInterval*, 4> Intervals;
Intervals.push_back(&LI);
DEBUG(dbgs() << PrintReg(Reg) << ": Found " << Classes.getNumClasses()
<< " equivalence classes.\n");
DEBUG(dbgs() << PrintReg(Reg) << ": Splitting into newly created:");
for (unsigned I = 1, NumClasses = Classes.getNumClasses(); I < NumClasses;
++I) {
unsigned NewVReg = MRI->createVirtualRegister(RegClass);
LiveInterval &NewLI = LIS->createEmptyInterval(NewVReg);
Intervals.push_back(&NewLI);
DEBUG(dbgs() << ' ' << PrintReg(NewVReg));
}
DEBUG(dbgs() << '\n');
rewriteOperands(Classes, SubRangeInfos, Intervals);
distribute(Classes, SubRangeInfos, Intervals);
computeMainRangesFixFlags(Classes, SubRangeInfos, Intervals);
return true;
}
bool RenameIndependentSubregs::findComponents(IntEqClasses &Classes,
SmallVectorImpl<RenameIndependentSubregs::SubRangeInfo> &SubRangeInfos,
LiveInterval &LI) const {
// First step: Create connected components for the VNInfos inside the
// subranges and count the global number of such components.
unsigned NumComponents = 0;
for (LiveInterval::SubRange &SR : LI.subranges()) {
SubRangeInfos.push_back(SubRangeInfo(*LIS, SR, NumComponents));
ConnectedVNInfoEqClasses &ConEQ = SubRangeInfos.back().ConEQ;
unsigned NumSubComponents = ConEQ.Classify(SR);
NumComponents += NumSubComponents;
}
// Shortcut: With only 1 subrange, the normal separate component tests are
// enough and we do not need to perform the union-find on the subregister
// segments.
if (SubRangeInfos.size() < 2)
return false;
// Next step: Build union-find structure over all subranges and merge classes
// across subranges when they are affected by the same MachineOperand.
const TargetRegisterInfo &TRI = *MRI->getTargetRegisterInfo();
Classes.grow(NumComponents);
unsigned Reg = LI.reg;
for (const MachineOperand &MO : MRI->reg_nodbg_operands(Reg)) {
if (!MO.isDef() && !MO.readsReg())
continue;
unsigned SubRegIdx = MO.getSubReg();
LaneBitmask LaneMask = TRI.getSubRegIndexLaneMask(SubRegIdx);
unsigned MergedID = ~0u;
for (RenameIndependentSubregs::SubRangeInfo &SRInfo : SubRangeInfos) {
const LiveInterval::SubRange &SR = *SRInfo.SR;
if ((SR.LaneMask & LaneMask) == 0)
continue;
SlotIndex Pos = LIS->getInstructionIndex(*MO.getParent());
Pos = MO.isDef() ? Pos.getRegSlot(MO.isEarlyClobber())
: Pos.getBaseIndex();
const VNInfo *VNI = SR.getVNInfoAt(Pos);
if (VNI == nullptr)
continue;
// Map to local representant ID.
unsigned LocalID = SRInfo.ConEQ.getEqClass(VNI);
// Global ID
unsigned ID = LocalID + SRInfo.Index;
// Merge other sets
MergedID = MergedID == ~0u ? ID : Classes.join(MergedID, ID);
}
}
// Early exit if we ended up with a single equivalence class.
Classes.compress();
unsigned NumClasses = Classes.getNumClasses();
return NumClasses > 1;
}
void RenameIndependentSubregs::distribute(const IntEqClasses &Classes,
const SmallVectorImpl<SubRangeInfo> &SubRangeInfos,
const SmallVectorImpl<LiveInterval*> &Intervals) const {
unsigned NumClasses = Classes.getNumClasses();
SmallVector<unsigned, 8> VNIMapping;
SmallVector<LiveInterval::SubRange*, 8> SubRanges;
BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
for (const SubRangeInfo &SRInfo : SubRangeInfos) {
LiveInterval::SubRange &SR = *SRInfo.SR;
unsigned NumValNos = SR.valnos.size();
VNIMapping.clear();
VNIMapping.reserve(NumValNos);
SubRanges.clear();
SubRanges.resize(NumClasses-1, nullptr);
for (unsigned I = 0; I < NumValNos; ++I) {
const VNInfo &VNI = *SR.valnos[I];
unsigned LocalID = SRInfo.ConEQ.getEqClass(&VNI);
unsigned ID = Classes[LocalID + SRInfo.Index];
VNIMapping.push_back(ID);
if (ID > 0 && SubRanges[ID-1] == nullptr)
SubRanges[ID-1] = Intervals[ID]->createSubRange(Allocator, SR.LaneMask);
}
DistributeRange(SR, SubRanges.data(), VNIMapping);
}
}
/// Set each node's subtree ID to the representative ID and record connections
/// between trees.
void finalize() {
SubtreeClasses.compress();
R.SubtreeConnections.resize(SubtreeClasses.getNumClasses());
R.SubtreeConnectLevels.resize(SubtreeClasses.getNumClasses());
DEBUG(dbgs() << R.getNumSubtrees() << " subtrees:\n");
for (unsigned Idx = 0, End = R.DFSData.size(); Idx != End; ++Idx) {
R.DFSData[Idx].SubtreeID = SubtreeClasses[Idx];
DEBUG(dbgs() << " SU(" << Idx << ") in tree "
<< R.DFSData[Idx].SubtreeID << '\n');
}
for (std::vector<std::pair<const SUnit*, const SUnit*> >::const_iterator
I = ConnectionPairs.begin(), E = ConnectionPairs.end();
I != E; ++I) {
unsigned PredTree = SubtreeClasses[I->first->NodeNum];
unsigned SuccTree = SubtreeClasses[I->second->NodeNum];
if (PredTree == SuccTree)
continue;
unsigned Depth = I->first->getDepth();
addConnection(PredTree, SuccTree, Depth);
addConnection(SuccTree, PredTree, Depth);
}
}
/// Determine whether the DFS cross edge should be considered a subtree edge
/// or a connection between subtrees.
void visitCross(const SDep &PredDep, const SUnit *Succ) {
if (PredDep.getKind() == SDep::Data) {
// If this is a cross edge to a root, join the subtrees. This happens when
// the root was first reached by a non-data dependence.
unsigned NodeNum = PredDep.getSUnit()->NodeNum;
unsigned PredCnt = R.DFSData[NodeNum].InstrCount;
if (R.DFSData[NodeNum].SubtreeID == NodeNum && PredCnt < R.SubtreeLimit) {
R.DFSData[NodeNum].SubtreeID = Succ->NodeNum;
R.DFSData[Succ->NodeNum].InstrCount += PredCnt;
SubtreeClasses.join(Succ->NodeNum, NodeNum);
return;
}
}
ConnectionPairs.push_back(std::make_pair(PredDep.getSUnit(), Succ));
}
/// Mark this node as either the root of a subtree or an interior
/// node. Increment the parent node's instruction count.
void visitPostorder(const SUnit *SU, const SDep *PredDep, const SUnit *Parent) {
R.DFSData[SU->NodeNum].SubtreeID = SU->NodeNum;
// Join the child to its parent if they are connected via data dependence
// and do not exceed the limit.
if (!Parent || PredDep->getKind() != SDep::Data)
return;
unsigned PredCnt = R.DFSData[SU->NodeNum].InstrCount;
if (PredCnt > R.SubtreeLimit)
return;
R.DFSData[SU->NodeNum].SubtreeID = Parent->NodeNum;
// Add the recently finished predecessor's bottom-up descendent count.
R.DFSData[Parent->NodeNum].InstrCount += PredCnt;
SubtreeClasses.join(Parent->NodeNum, SU->NodeNum);
}
