void Liveness::traverse(MachineBasicBlock *B, RefMap &LiveIn) {
// The LiveIn map, for each (physical) register, contains the set of live
// reaching defs of that register that are live on entry to the associated
// block.
// The summary of the traversal algorithm:
//
// R is live-in in B, if there exists a U(R), such that rdef(R) dom B
// and (U \in IDF(B) or B dom U).
//
// for (C : children) {
// LU = {}
// traverse(C, LU)
// LiveUses += LU
// }
//
// LiveUses -= Defs(B);
// LiveUses += UpwardExposedUses(B);
// for (C : IIDF[B])
// for (U : LiveUses)
// if (Rdef(U) dom C)
// C.addLiveIn(U)
//
// Go up the dominator tree (depth-first).
MachineDomTreeNode *N = MDT.getNode(B);
for (auto I : *N) {
RefMap L;
MachineBasicBlock *SB = I->getBlock();
traverse(SB, L);
for (auto S : L)
LiveIn[S.first].insert(S.second.begin(), S.second.end());
}
if (Trace) {
dbgs() << LLVM_FUNCTION_NAME << " in BB#" << B->getNumber()
<< " after recursion into";
for (auto I : *N)
dbgs() << ' ' << I->getBlock()->getNumber();
dbgs() << "\n LiveIn: " << Print<RefMap>(LiveIn, DFG);
dbgs() << "\n Local: " << Print<RegisterSet>(LiveMap[B], DFG) << '\n';
}
// Add phi uses that are live on exit from this block.
RefMap &PUs = PhiLOX[B];
for (auto S : PUs)
LiveIn[S.first].insert(S.second.begin(), S.second.end());
if (Trace) {
dbgs() << "after LOX\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterSet>(LiveMap[B], DFG) << '\n';
}
// Stop tracking all uses defined in this block: erase those records
// where the reaching def is located in B and which cover all reached
// uses.
auto Copy = LiveIn;
LiveIn.clear();
for (auto I : Copy) {
auto &Defs = LiveIn[I.first];
NodeSet Rest;
for (auto R : I.second) {
auto DA = DFG.addr<DefNode*>(R);
RegisterRef DDR = DA.Addr->getRegRef();
NodeAddr<InstrNode*> IA = DA.Addr->getOwner(DFG);
NodeAddr<BlockNode*> BA = IA.Addr->getOwner(DFG);
// Defs from a different block need to be preserved. Defs from this
// block will need to be processed further, except for phi defs, the
// liveness of which is handled through the PhiLON/PhiLOX maps.
if (B != BA.Addr->getCode())
Defs.insert(R);
else {
bool IsPreserving = DA.Addr->getFlags() & NodeAttrs::Preserving;
if (IA.Addr->getKind() != NodeAttrs::Phi && !IsPreserving) {
bool Covering = RAI.covers(DDR, I.first);
NodeId U = DA.Addr->getReachedUse();
while (U && Covering) {
auto DUA = DFG.addr<UseNode*>(U);
RegisterRef Q = DUA.Addr->getRegRef();
Covering = RAI.covers(DA.Addr->getRegRef(), Q);
U = DUA.Addr->getSibling();
}
if (!Covering)
Rest.insert(R);
}
}
}
// Non-covering defs from B.
for (auto R : Rest) {
auto DA = DFG.addr<DefNode*>(R);
RegisterRef DRR = DA.Addr->getRegRef();
RegisterSet RRs;
for (NodeAddr<DefNode*> TA : getAllReachingDefs(DA)) {
NodeAddr<InstrNode*> IA = TA.Addr->getOwner(DFG);
NodeAddr<BlockNode*> BA = IA.Addr->getOwner(DFG);
// Preserving defs do not count towards covering.
if (!(TA.Addr->getFlags() & NodeAttrs::Preserving))
RRs.insert(TA.Addr->getRegRef());
if (BA.Addr->getCode() == B)
continue;
if (RAI.covers(RRs, DRR))
break;
Defs.insert(TA.Id);
}
}
}
emptify(LiveIn);
if (Trace) {
dbgs() << "after defs in block\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterSet>(LiveMap[B], DFG) << '\n';
}
// Scan the block for upward-exposed uses and add them to the tracking set.
for (auto I : DFG.getFunc().Addr->findBlock(B, DFG).Addr->members(DFG)) {
NodeAddr<InstrNode*> IA = I;
if (IA.Addr->getKind() != NodeAttrs::Stmt)
continue;
for (NodeAddr<UseNode*> UA : IA.Addr->members_if(DFG.IsUse, DFG)) {
RegisterRef RR = UA.Addr->getRegRef();
for (auto D : getAllReachingDefs(UA))
if (getBlockWithRef(D.Id) != B)
LiveIn[RR].insert(D.Id);
}
}
if (Trace) {
dbgs() << "after uses in block\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterSet>(LiveMap[B], DFG) << '\n';
}
// Phi uses should not be propagated up the dominator tree, since they
// are not dominated by their corresponding reaching defs.
auto &Local = LiveMap[B];
auto &LON = PhiLON[B];
for (auto R : LON)
Local.insert(R.first);
if (Trace) {
dbgs() << "after phi uses in block\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterSet>(Local, DFG) << '\n';
}
for (auto C : IIDF[B]) {
auto &LiveC = LiveMap[C];
for (auto S : LiveIn)
for (auto R : S.second)
if (MDT.properlyDominates(getBlockWithRef(R), C))
LiveC.insert(S.first);
}
}
void Liveness::traverse(MachineBasicBlock *B, RefMap &LiveIn) {
// The LiveIn map, for each (physical) register, contains the set of live
// reaching defs of that register that are live on entry to the associated
// block.
// The summary of the traversal algorithm:
//
// R is live-in in B, if there exists a U(R), such that rdef(R) dom B
// and (U \in IDF(B) or B dom U).
//
// for (C : children) {
// LU = {}
// traverse(C, LU)
// LiveUses += LU
// }
//
// LiveUses -= Defs(B);
// LiveUses += UpwardExposedUses(B);
// for (C : IIDF[B])
// for (U : LiveUses)
// if (Rdef(U) dom C)
// C.addLiveIn(U)
//
// Go up the dominator tree (depth-first).
MachineDomTreeNode *N = MDT.getNode(B);
for (auto I : *N) {
RefMap L;
MachineBasicBlock *SB = I->getBlock();
traverse(SB, L);
for (auto S : L)
LiveIn[S.first].insert(S.second.begin(), S.second.end());
}
if (Trace) {
dbgs() << "\n-- BB#" << B->getNumber() << ": " << __func__
<< " after recursion into: {";
for (auto I : *N)
dbgs() << ' ' << I->getBlock()->getNumber();
dbgs() << " }\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterAggr>(LiveMap[B], DFG) << '\n';
}
// Add reaching defs of phi uses that are live on exit from this block.
RefMap &PUs = PhiLOX[B];
for (auto &S : PUs)
LiveIn[S.first].insert(S.second.begin(), S.second.end());
if (Trace) {
dbgs() << "after LOX\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterAggr>(LiveMap[B], DFG) << '\n';
}
// The LiveIn map at this point has all defs that are live-on-exit from B,
// as if they were live-on-entry to B. First, we need to filter out all
// defs that are present in this block. Then we will add reaching defs of
// all upward-exposed uses.
// To filter out the defs, first make a copy of LiveIn, and then re-populate
// LiveIn with the defs that should remain.
RefMap LiveInCopy = LiveIn;
LiveIn.clear();
for (const std::pair<RegisterId,NodeRefSet> &LE : LiveInCopy) {
RegisterRef LRef(LE.first);
NodeRefSet &NewDefs = LiveIn[LRef.Reg]; // To be filled.
const NodeRefSet &OldDefs = LE.second;
for (NodeRef OR : OldDefs) {
// R is a def node that was live-on-exit
auto DA = DFG.addr<DefNode*>(OR.first);
NodeAddr<InstrNode*> IA = DA.Addr->getOwner(DFG);
NodeAddr<BlockNode*> BA = IA.Addr->getOwner(DFG);
if (B != BA.Addr->getCode()) {
// Defs from a different block need to be preserved. Defs from this
// block will need to be processed further, except for phi defs, the
// liveness of which is handled through the PhiLON/PhiLOX maps.
NewDefs.insert(OR);
continue;
}
// Defs from this block need to stop the liveness from being
// propagated upwards. This only applies to non-preserving defs,
// and to the parts of the register actually covered by those defs.
// (Note that phi defs should always be preserving.)
RegisterAggr RRs(PRI);
LRef.Mask = OR.second;
if (!DFG.IsPreservingDef(DA)) {
assert(!(IA.Addr->getFlags() & NodeAttrs::Phi));
// DA is a non-phi def that is live-on-exit from this block, and
// that is also located in this block. LRef is a register ref
// whose use this def reaches. If DA covers LRef, then no part
// of LRef is exposed upwards.A
if (RRs.insert(DA.Addr->getRegRef(DFG)).hasCoverOf(LRef))
continue;
}
// DA itself was not sufficient to cover LRef. In general, it is
// the last in a chain of aliased defs before the exit from this block.
// There could be other defs in this block that are a part of that
// chain. Check that now: accumulate the registers from these defs,
// and if they all together cover LRef, it is not live-on-entry.
for (NodeAddr<DefNode*> TA : getAllReachingDefs(DA)) {
// DefNode -> InstrNode -> BlockNode.
NodeAddr<InstrNode*> ITA = TA.Addr->getOwner(DFG);
NodeAddr<BlockNode*> BTA = ITA.Addr->getOwner(DFG);
// Reaching defs are ordered in the upward direction.
if (BTA.Addr->getCode() != B) {
// We have reached past the beginning of B, and the accumulated
// registers are not covering LRef. The first def from the
// upward chain will be live.
// Subtract all accumulated defs (RRs) from LRef.
RegisterAggr L(PRI);
L.insert(LRef).clear(RRs);
assert(!L.empty());
NewDefs.insert({TA.Id,L.begin()->second});
break;
}
// TA is in B. Only add this def to the accumulated cover if it is
// not preserving.
if (!(TA.Addr->getFlags() & NodeAttrs::Preserving))
RRs.insert(TA.Addr->getRegRef(DFG));
// If this is enough to cover LRef, then stop.
if (RRs.hasCoverOf(LRef))
break;
}
}
}
emptify(LiveIn);
if (Trace) {
dbgs() << "after defs in block\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterAggr>(LiveMap[B], DFG) << '\n';
}
// Scan the block for upward-exposed uses and add them to the tracking set.
for (auto I : DFG.getFunc().Addr->findBlock(B, DFG).Addr->members(DFG)) {
NodeAddr<InstrNode*> IA = I;
if (IA.Addr->getKind() != NodeAttrs::Stmt)
continue;
for (NodeAddr<UseNode*> UA : IA.Addr->members_if(DFG.IsUse, DFG)) {
if (UA.Addr->getFlags() & NodeAttrs::Undef)
continue;
RegisterRef RR = PRI.normalize(UA.Addr->getRegRef(DFG));
for (NodeAddr<DefNode*> D : getAllReachingDefs(UA))
if (getBlockWithRef(D.Id) != B)
LiveIn[RR.Reg].insert({D.Id,RR.Mask});
}
}
if (Trace) {
dbgs() << "after uses in block\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterAggr>(LiveMap[B], DFG) << '\n';
}
// Phi uses should not be propagated up the dominator tree, since they
// are not dominated by their corresponding reaching defs.
RegisterAggr &Local = LiveMap[B];
RefMap &LON = PhiLON[B];
for (auto &R : LON) {
LaneBitmask M;
for (auto P : R.second)
M |= P.second;
Local.insert(RegisterRef(R.first,M));
}
if (Trace) {
dbgs() << "after phi uses in block\n";
dbgs() << " LiveIn: " << Print<RefMap>(LiveIn, DFG) << '\n';
dbgs() << " Local: " << Print<RegisterAggr>(Local, DFG) << '\n';
}
for (auto C : IIDF[B]) {
RegisterAggr &LiveC = LiveMap[C];
for (const std::pair<RegisterId,NodeRefSet> &S : LiveIn)
for (auto R : S.second)
if (MDT.properlyDominates(getBlockWithRef(R.first), C))
LiveC.insert(RegisterRef(S.first, R.second));
}
}