//===--- RDFLiveness.cpp --------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Computation of the liveness information from the data-flow graph.
//
// The main functionality of this code is to compute block live-in
// information. With the live-in information in place, the placement
// of kill flags can also be recalculated.
//
// The block live-in calculation is based on the ideas from the following
// publication:
//
// Dibyendu Das, Ramakrishna Upadrasta, Benoit Dupont de Dinechin.
// "Efficient Liveness Computation Using Merge Sets and DJ-Graphs."
// ACM Transactions on Architecture and Code Optimization, Association for
// Computing Machinery, 2012, ACM TACO Special Issue on "High-Performance
// and Embedded Architectures and Compilers", 8 (4),
// <10.1145/2086696.2086706>. <hal-00647369>
//
#include "RDFGraph.h"
#include "RDFLiveness.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineDominanceFrontier.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
using namespace rdf;
namespace llvm {
namespace rdf {
template<>
raw_ostream &operator<< (raw_ostream &OS, const Print<Liveness::RefMap> &P) {
OS << '{';
for (auto I : P.Obj) {
OS << ' ' << Print<RegisterRef>(I.first, P.G) << '{';
for (auto J = I.second.begin(), E = I.second.end(); J != E; ) {
OS << Print<NodeId>(*J, P.G);
if (++J != E)
OS << ',';
}
OS << '}';
}
OS << " }";
return OS;
}
} // namespace rdf
} // namespace llvm
// The order in the returned sequence is the order of reaching defs in the
// upward traversal: the first def is the closest to the given reference RefA,
// the next one is further up, and so on.
// The list ends at a reaching phi def, or when the reference from RefA is
// covered by the defs in the list (see FullChain).
// This function provides two modes of operation:
// (1) Returning the sequence of reaching defs for a particular reference
// node. This sequence will terminate at the first phi node [1].
// (2) Returning a partial sequence of reaching defs, where the final goal
// is to traverse past phi nodes to the actual defs arising from the code
// itself.
// In mode (2), the register reference for which the search was started
// may be different from the reference node RefA, for which this call was
// made, hence the argument RefRR, which holds the original register.
// Also, some definitions may have already been encountered in a previous
// call that will influence register covering. The register references
// already defined are passed in through DefRRs.
// In mode (1), the "continuation" considerations do not apply, and the
// RefRR is the same as the register in RefA, and the set DefRRs is empty.
//
// [1] It is possible for multiple phi nodes to be included in the returned
// sequence:
// SubA = phi ...
// SubB = phi ...
// ... = SuperAB(rdef:SubA), SuperAB"(rdef:SubB)
// However, these phi nodes are independent from one another in terms of
// the data-flow.
NodeList Liveness::getAllReachingDefs(RegisterRef RefRR,
NodeAddr<RefNode*> RefA, bool FullChain, const RegisterSet &DefRRs) {
SetVector<NodeId> DefQ;
SetVector<NodeId> Owners;
// The initial queue should not have reaching defs for shadows. The
// whole point of a shadow is that it will have a reaching def that
// is not aliased to the reaching defs of the related shadows.
NodeId Start = RefA.Id;
auto SNA = DFG.addr<RefNode*>(Start);
if (NodeId RD = SNA.Addr->getReachingDef())
DefQ.insert(RD);
// Collect all the reaching defs, going up until a phi node is encountered,
// or there are no more reaching defs. From this set, the actual set of
// reaching defs will be selected.
// The traversal upwards must go on until a covering def is encountered.
// It is possible that a collection of non-covering (individually) defs
// will be sufficient, but keep going until a covering one is found.
for (unsigned i = 0; i < DefQ.size(); ++i) {
auto TA = DFG.addr<DefNode*>(DefQ[i]);
if (TA.Addr->getFlags() & NodeAttrs::PhiRef)
continue;
// Stop at the covering/overwriting def of the initial register reference.
RegisterRef RR = TA.Addr->getRegRef();
if (RAI.covers(RR, RefRR)) {
uint16_t Flags = TA.Addr->getFlags();
if (!(Flags & NodeAttrs::Preserving))
continue;
}
// Get the next level of reaching defs. This will include multiple
// reaching defs for shadows.
for (auto S : DFG.getRelatedRefs(TA.Addr->getOwner(DFG), TA))
if (auto RD = NodeAddr<RefNode*>(S).Addr->getReachingDef())
DefQ.insert(RD);
}
// Remove all non-phi defs that are not aliased to RefRR, and collect
// the owners of the remaining defs.
SetVector<NodeId> Defs;
for (auto N : DefQ) {
auto TA = DFG.addr<DefNode*>(N);
bool IsPhi = TA.Addr->getFlags() & NodeAttrs::PhiRef;
if (!IsPhi && !RAI.alias(RefRR, TA.Addr->getRegRef()))
continue;
Defs.insert(TA.Id);
Owners.insert(TA.Addr->getOwner(DFG).Id);
}
// Return the MachineBasicBlock containing a given instruction.
auto Block = [this] (NodeAddr<InstrNode*> IA) -> MachineBasicBlock* {
if (IA.Addr->getKind() == NodeAttrs::Stmt)
return NodeAddr<StmtNode*>(IA).Addr->getCode()->getParent();
assert(IA.Addr->getKind() == NodeAttrs::Phi);
NodeAddr<PhiNode*> PA = IA;
NodeAddr<BlockNode*> BA = PA.Addr->getOwner(DFG);
return BA.Addr->getCode();
};
// Less(A,B) iff instruction A is further down in the dominator tree than B.
auto Less = [&Block,this] (NodeId A, NodeId B) -> bool {
if (A == B)
return false;
auto OA = DFG.addr<InstrNode*>(A), OB = DFG.addr<InstrNode*>(B);
MachineBasicBlock *BA = Block(OA), *BB = Block(OB);
if (BA != BB)
return MDT.dominates(BB, BA);
// They are in the same block.
bool StmtA = OA.Addr->getKind() == NodeAttrs::Stmt;
bool StmtB = OB.Addr->getKind() == NodeAttrs::Stmt;
if (StmtA) {
if (!StmtB) // OB is a phi and phis dominate statements.
return true;
auto CA = NodeAddr<StmtNode*>(OA).Addr->getCode();
auto CB = NodeAddr<StmtNode*>(OB).Addr->getCode();
// The order must be linear, so tie-break such equalities.
if (CA == CB)
return A < B;
return MDT.dominates(CB, CA);
} else {
// OA is a phi.
if (StmtB)
return false;
// Both are phis. There is no ordering between phis (in terms of
// the data-flow), so tie-break this via node id comparison.
return A < B;
}
};
std::vector<NodeId> Tmp(Owners.begin(), Owners.end());
std::sort(Tmp.begin(), Tmp.end(), Less);
// The vector is a list of instructions, so that defs coming from
// the same instruction don't need to be artificially ordered.
// Then, when computing the initial segment, and iterating over an
// instruction, pick the defs that contribute to the covering (i.e. is
// not covered by previously added defs). Check the defs individually,
// i.e. first check each def if is covered or not (without adding them
// to the tracking set), and then add all the selected ones.
// The reason for this is this example:
// *d1<A>, *d2<B>, ... Assume A and B are aliased (can happen in phi nodes).
// *d3<C> If A \incl BuC, and B \incl AuC, then *d2 would be
// covered if we added A first, and A would be covered
// if we added B first.
NodeList RDefs;
RegisterSet RRs = DefRRs;
auto DefInSet = [&Defs] (NodeAddr<RefNode*> TA) -> bool {
return TA.Addr->getKind() == NodeAttrs::Def &&
Defs.count(TA.Id);
};
for (auto T : Tmp) {
if (!FullChain && RAI.covers(RRs, RefRR))
break;
auto TA = DFG.addr<InstrNode*>(T);
bool IsPhi = DFG.IsCode<NodeAttrs::Phi>(TA);
NodeList Ds;
for (NodeAddr<DefNode*> DA : TA.Addr->members_if(DefInSet, DFG)) {
auto QR = DA.Addr->getRegRef();
// Add phi defs even if they are covered by subsequent defs. This is
// for cases where the reached use is not covered by any of the defs
// encountered so far: the phi def is needed to expose the liveness
// of that use to the entry of the block.
// Example:
// phi d1<R3>(,d2,), ... Phi def d1 is covered by d2.
// d2<R3>(d1,,u3), ...
// ..., u3<D1>(d2) This use needs to be live on entry.
if (FullChain || IsPhi || !RAI.covers(RRs, QR))
Ds.push_back(DA);
}
RDefs.insert(RDefs.end(), Ds.begin(), Ds.end());
for (NodeAddr<DefNode*> DA : Ds) {
// When collecting a full chain of definitions, do not consider phi
// defs to actually define a register.
uint16_t Flags = DA.Addr->getFlags();
if (!FullChain || !(Flags & NodeAttrs::PhiRef))
if (!(Flags & NodeAttrs::Preserving))
RRs.insert(DA.Addr->getRegRef());
}
}
return RDefs;
}
static const RegisterSet NoRegs;
NodeList Liveness::getAllReachingDefs(NodeAddr<RefNode*> RefA) {
return getAllReachingDefs(RefA.Addr->getRegRef(), RefA, false, NoRegs);
}
NodeSet Liveness::getAllReachingDefsRec(RegisterRef RefRR,
NodeAddr<RefNode*> RefA, NodeSet &Visited, const NodeSet &Defs) {
// Collect all defined registers. Do not consider phis to be defining
// anything, only collect "real" definitions.
RegisterSet DefRRs;
for (const auto D : Defs) {
const auto DA = DFG.addr<const DefNode*>(D);
if (!(DA.Addr->getFlags() & NodeAttrs::PhiRef))
DefRRs.insert(DA.Addr->getRegRef());
}
auto RDs = getAllReachingDefs(RefRR, RefA, true, DefRRs);
if (RDs.empty())
return Defs;
// Make a copy of the preexisting definitions and add the newly found ones.
NodeSet TmpDefs = Defs;
for (auto R : RDs)
TmpDefs.insert(R.Id);
NodeSet Result = Defs;
for (NodeAddr<DefNode*> DA : RDs) {
Result.insert(DA.Id);
if (!(DA.Addr->getFlags() & NodeAttrs::PhiRef))
continue;
NodeAddr<PhiNode*> PA = DA.Addr->getOwner(DFG);
if (Visited.count(PA.Id))
continue;
Visited.insert(PA.Id);
// Go over all phi uses and get the reaching defs for each use.
for (auto U : PA.Addr->members_if(DFG.IsRef<NodeAttrs::Use>, DFG)) {
const auto &T = getAllReachingDefsRec(RefRR, U, Visited, TmpDefs);
Result.insert(T.begin(), T.end());
}
}
return Result;
}
NodeSet Liveness::getAllReachedUses(RegisterRef RefRR,
NodeAddr<DefNode*> DefA, const RegisterSet &DefRRs) {
NodeSet Uses;
// If the original register is already covered by all the intervening
// defs, no more uses can be reached.
if (RAI.covers(DefRRs, RefRR))
return Uses;
// Add all directly reached uses.
NodeId U = DefA.Addr->getReachedUse();
while (U != 0) {
auto UA = DFG.addr<UseNode*>(U);
auto UR = UA.Addr->getRegRef();
if (RAI.alias(RefRR, UR) && !RAI.covers(DefRRs, UR))
Uses.insert(U);
U = UA.Addr->getSibling();
}
// Traverse all reached defs.
for (NodeId D = DefA.Addr->getReachedDef(), NextD; D != 0; D = NextD) {
auto DA = DFG.addr<DefNode*>(D);
NextD = DA.Addr->getSibling();
auto DR = DA.Addr->getRegRef();
// If this def is already covered, it cannot reach anything new.
// Similarly, skip it if it is not aliased to the interesting register.
if (RAI.covers(DefRRs, DR) || !RAI.alias(RefRR, DR))
continue;
NodeSet T;
if (DA.Addr->getFlags() & NodeAttrs::Preserving) {
// If it is a preserving def, do not update the set of intervening defs.
T = getAllReachedUses(RefRR, DA, DefRRs);
} else {
RegisterSet NewDefRRs = DefRRs;
NewDefRRs.insert(DR);
T = getAllReachedUses(RefRR, DA, NewDefRRs);
}
Uses.insert(T.begin(), T.end());
}
return Uses;
}
void Liveness::computePhiInfo() {
RealUseMap.clear();
NodeList Phis;
NodeAddr<FuncNode*> FA = DFG.getFunc();
auto Blocks = FA.Addr->members(DFG);
for (NodeAddr<BlockNode*> BA : Blocks) {
auto Ps = BA.Addr->members_if(DFG.IsCode<NodeAttrs::Phi>, DFG);
Phis.insert(Phis.end(), Ps.begin(), Ps.end());
}
// phi use -> (map: reaching phi -> set of registers defined in between)
std::map<NodeId,std::map<NodeId,RegisterSet>> PhiUp;
std::vector<NodeId> PhiUQ; // Work list of phis for upward propagation.
// Go over all phis.
for (NodeAddr<PhiNode*> PhiA : Phis) {
// Go over all defs and collect the reached uses that are non-phi uses
// (i.e. the "real uses").
auto &RealUses = RealUseMap[PhiA.Id];
auto PhiRefs = PhiA.Addr->members(DFG);
// Have a work queue of defs whose reached uses need to be found.
// For each def, add to the queue all reached (non-phi) defs.
SetVector<NodeId> DefQ;
NodeSet PhiDefs;
for (auto R : PhiRefs) {
if (!DFG.IsRef<NodeAttrs::Def>(R))
continue;
DefQ.insert(R.Id);
PhiDefs.insert(R.Id);
}
for (unsigned i = 0; i < DefQ.size(); ++i) {
NodeAddr<DefNode*> DA = DFG.addr<DefNode*>(DefQ[i]);
NodeId UN = DA.Addr->getReachedUse();
while (UN != 0) {
NodeAddr<UseNode*> A = DFG.addr<UseNode*>(UN);
if (!(A.Addr->getFlags() & NodeAttrs::PhiRef))
RealUses[getRestrictedRegRef(A)].insert(A.Id);
UN = A.Addr->getSibling();
}
NodeId DN = DA.Addr->getReachedDef();
while (DN != 0) {
NodeAddr<DefNode*> A = DFG.addr<DefNode*>(DN);
for (auto T : DFG.getRelatedRefs(A.Addr->getOwner(DFG), A)) {
uint16_t Flags = NodeAddr<DefNode*>(T).Addr->getFlags();
// Must traverse the reached-def chain. Consider:
// def(D0) -> def(R0) -> def(R0) -> use(D0)
// The reachable use of D0 passes through a def of R0.
if (!(Flags & NodeAttrs::PhiRef))
DefQ.insert(T.Id);
}
DN = A.Addr->getSibling();
}
}
// Filter out these uses that appear to be reachable, but really
// are not. For example:
//
// R1:0 = d1
// = R1:0 u2 Reached by d1.
// R0 = d3
// = R1:0 u4 Still reached by d1: indirectly through
// the def d3.
// R1 = d5
// = R1:0 u6 Not reached by d1 (covered collectively
// by d3 and d5), but following reached
// defs and uses from d1 will lead here.
auto HasDef = [&PhiDefs] (NodeAddr<DefNode*> DA) -> bool {
return PhiDefs.count(DA.Id);
};
for (auto UI = RealUses.begin(), UE = RealUses.end(); UI != UE; ) {
// For each reached register UI->first, there is a set UI->second, of
// uses of it. For each such use, check if it is reached by this phi,
// i.e. check if the set of its reaching uses intersects the set of
// this phi's defs.
auto &Uses = UI->second;
for (auto I = Uses.begin(), E = Uses.end(); I != E; ) {
auto UA = DFG.addr<UseNode*>(*I);
NodeList RDs = getAllReachingDefs(UI->first, UA);
if (std::any_of(RDs.begin(), RDs.end(), HasDef))
++I;
else
I = Uses.erase(I);
}
if (Uses.empty())
UI = RealUses.erase(UI);
else
++UI;
}
// If this phi reaches some "real" uses, add it to the queue for upward
// propagation.
if (!RealUses.empty())
PhiUQ.push_back(PhiA.Id);
// Go over all phi uses and check if the reaching def is another phi.
// Collect the phis that are among the reaching defs of these uses.
// While traversing the list of reaching defs for each phi use, collect
// the set of registers defined between this phi (Phi) and the owner phi
// of the reaching def.
for (auto I : PhiRefs) {
if (!DFG.IsRef<NodeAttrs::Use>(I))
continue;
NodeAddr<UseNode*> UA = I;
auto &UpMap = PhiUp[UA.Id];
RegisterSet DefRRs;
for (NodeAddr<DefNode*> DA : getAllReachingDefs(UA)) {
if (DA.Addr->getFlags() & NodeAttrs::PhiRef)
UpMap[DA.Addr->getOwner(DFG).Id] = DefRRs;
else
DefRRs.insert(DA.Addr->getRegRef());
}
}
}
if (Trace) {
dbgs() << "Phi-up-to-phi map:\n";
for (auto I : PhiUp) {
dbgs() << "phi " << Print<NodeId>(I.first, DFG) << " -> {";
for (auto R : I.second)
dbgs() << ' ' << Print<NodeId>(R.first, DFG)
<< Print<RegisterSet>(R.second, DFG);
dbgs() << " }\n";
}
}
// Propagate the reached registers up in the phi chain.
//
// The following type of situation needs careful handling:
//
// phi d1<R1:0> (1)
// |
// ... d2<R1>
// |
// phi u3<R1:0> (2)
// |
// ... u4<R1>
//
// The phi node (2) defines a register pair R1:0, and reaches a "real"
// use u4 of just R1. The same phi node is also known to reach (upwards)
// the phi node (1). However, the use u4 is not reached by phi (1),
// because of the intervening definition d2 of R1. The data flow between
// phis (1) and (2) is restricted to R1:0 minus R1, i.e. R0.
//
// When propagating uses up the phi chains, get the all reaching defs
// for a given phi use, and traverse the list until the propagated ref
// is covered, or until or until reaching the final phi. Only assume
// that the reference reaches the phi in the latter case.
for (unsigned i = 0; i < PhiUQ.size(); ++i) {
auto PA = DFG.addr<PhiNode*>(PhiUQ[i]);
auto &RealUses = RealUseMap[PA.Id];
for (auto U : PA.Addr->members_if(DFG.IsRef<NodeAttrs::Use>, DFG)) {
NodeAddr<UseNode*> UA = U;
auto &UpPhis = PhiUp[UA.Id];
for (auto UP : UpPhis) {
bool Changed = false;
auto &MidDefs = UP.second;
// Collect the set UpReached of uses that are reached by the current
// phi PA, and are not covered by any intervening def between PA and
// the upward phi UP.
RegisterSet UpReached;
for (auto T : RealUses) {
if (!isRestricted(PA, UA, T.first))
continue;
if (!RAI.covers(MidDefs, T.first))
UpReached.insert(T.first);
}
if (UpReached.empty())
continue;
// Update the set PRUs of real uses reached by the upward phi UP with
// the actual set of uses (UpReached) that the UP phi reaches.
auto &PRUs = RealUseMap[UP.first];
for (auto R : UpReached) {
unsigned Z = PRUs[R].size();
PRUs[R].insert(RealUses[R].begin(), RealUses[R].end());
Changed |= (PRUs[R].size() != Z);
}
if (Changed)
PhiUQ.push_back(UP.first);
}
}
}
if (Trace) {
dbgs() << "Real use map:\n";
for (auto I : RealUseMap) {
dbgs() << "phi " << Print<NodeId>(I.first, DFG);
NodeAddr<PhiNode*> PA = DFG.addr<PhiNode*>(I.first);
NodeList Ds = PA.Addr->members_if(DFG.IsRef<NodeAttrs::Def>, DFG);
if (!Ds.empty()) {
RegisterRef RR = NodeAddr<DefNode*>(Ds[0]).Addr->getRegRef();
dbgs() << '<' << Print<RegisterRef>(RR, DFG) << '>';
} else {
dbgs() << "<noreg>";
}
dbgs() << " -> " << Print<RefMap>(I.second, DFG) << '\n';
}
}
}
void Liveness::computeLiveIns() {
// Populate the node-to-block map. This speeds up the calculations
// significantly.
NBMap.clear();
for (NodeAddr<BlockNode*> BA : DFG.getFunc().Addr->members(DFG)) {
MachineBasicBlock *BB = BA.Addr->getCode();
for (NodeAddr<InstrNode*> IA : BA.Addr->members(DFG)) {
for (NodeAddr<RefNode*> RA : IA.Addr->members(DFG))
NBMap.insert(std::make_pair(RA.Id, BB));
NBMap.insert(std::make_pair(IA.Id, BB));
}
}
MachineFunction &MF = DFG.getMF();
// Compute IDF first, then the inverse.
decltype(IIDF) IDF;
for (auto &B : MF) {
auto F1 = MDF.find(&B);
if (F1 == MDF.end())
continue;
SetVector<MachineBasicBlock*> IDFB(F1->second.begin(), F1->second.end());
for (unsigned i = 0; i < IDFB.size(); ++i) {
auto F2 = MDF.find(IDFB[i]);
if (F2 != MDF.end())
IDFB.insert(F2->second.begin(), F2->second.end());
}
// Add B to the IDF(B). This will put B in the IIDF(B).
IDFB.insert(&B);
IDF[&B].insert(IDFB.begin(), IDFB.end());
}
for (auto I : IDF)
for (auto S : I.second)
IIDF[S].insert(I.first);
computePhiInfo();
NodeAddr<FuncNode*> FA = DFG.getFunc();
auto Blocks = FA.Addr->members(DFG);
// Build the phi live-on-entry map.
for (NodeAddr<BlockNode*> BA : Blocks) {
MachineBasicBlock *MB = BA.Addr->getCode();
auto &LON = PhiLON[MB];
for (auto P : BA.Addr->members_if(DFG.IsCode<NodeAttrs::Phi>, DFG))
for (auto S : RealUseMap[P.Id])
LON[S.first].insert(S.second.begin(), S.second.end());
}
if (Trace) {
dbgs() << "Phi live-on-entry map:\n";
for (auto I : PhiLON)
dbgs() << "block #" << I.first->getNumber() << " -> "
<< Print<RefMap>(I.second, DFG) << '\n';
}
// Build the phi live-on-exit map. Each phi node has some set of reached
// "real" uses. Propagate this set backwards into the block predecessors
// through the reaching defs of the corresponding phi uses.
for (NodeAddr<BlockNode*> BA : Blocks) {
auto Phis = BA.Addr->members_if(DFG.IsCode<NodeAttrs::Phi>, DFG);
for (NodeAddr<PhiNode*> PA : Phis) {
auto &RUs = RealUseMap[PA.Id];
if (RUs.empty())
continue;
for (auto U : PA.Addr->members_if(DFG.IsRef<NodeAttrs::Use>, DFG)) {
NodeAddr<PhiUseNode*> UA = U;
if (UA.Addr->getReachingDef() == 0)
continue;
// Mark all reached "real" uses of P as live on exit in the
// predecessor.
// Remap all the RUs so that they have a correct reaching def.
auto PrA = DFG.addr<BlockNode*>(UA.Addr->getPredecessor());
auto &LOX = PhiLOX[PrA.Addr->getCode()];
for (auto R : RUs) {
RegisterRef RR = R.first;
if (!isRestricted(PA, UA, RR))
RR = getRestrictedRegRef(UA);
// The restricted ref may be different from the ref that was
// accessed in the "real use". This means that this phi use
// is not the one that carries this reference, so skip it.
if (!RAI.alias(R.first, RR))
continue;
for (auto D : getAllReachingDefs(RR, UA))
LOX[RR].insert(D.Id);
}
} // for U : phi uses
} // for P : Phis
} // for B : Blocks
if (Trace) {
dbgs() << "Phi live-on-exit map:\n";
for (auto I : PhiLOX)
dbgs() << "block #" << I.first->getNumber() << " -> "
<< Print<RefMap>(I.second, DFG) << '\n';
}
RefMap LiveIn;
traverse(&MF.front(), LiveIn);
// Add function live-ins to the live-in set of the function entry block.
auto &EntryIn = LiveMap[&MF.front()];
for (auto I = MRI.livein_begin(), E = MRI.livein_end(); I != E; ++I)
EntryIn.insert({I->first,0});
if (Trace) {
// Dump the liveness map
for (auto &B : MF) {
BitVector LV(TRI.getNumRegs());
for (auto I = B.livein_begin(), E = B.livein_end(); I != E; ++I)
LV.set(I->PhysReg);
dbgs() << "BB#" << B.getNumber() << "\t rec = {";
for (int x = LV.find_first(); x >= 0; x = LV.find_next(x))
dbgs() << ' ' << Print<RegisterRef>({unsigned(x),0}, DFG);
dbgs() << " }\n";
dbgs() << "\tcomp = " << Print<RegisterSet>(LiveMap[&B], DFG) << '\n';
}
}
}
void Liveness::resetLiveIns() {
for (auto &B : DFG.getMF()) {
// Remove all live-ins.
std::vector<unsigned> T;
for (auto I = B.livein_begin(), E = B.livein_end(); I != E; ++I)
T.push_back(I->PhysReg);
for (auto I : T)
B.removeLiveIn(I);
// Add the newly computed live-ins.
auto &LiveIns = LiveMap[&B];
for (auto I : LiveIns) {
assert(I.Sub == 0);
B.addLiveIn(I.Reg);
}
}
}
void Liveness::resetKills() {
for (auto &B : DFG.getMF())
resetKills(&B);
}
void Liveness::resetKills(MachineBasicBlock *B) {
auto CopyLiveIns = [] (MachineBasicBlock *B, BitVector &LV) -> void {
for (auto I = B->livein_begin(), E = B->livein_end(); I != E; ++I)
LV.set(I->PhysReg);
};
BitVector LiveIn(TRI.getNumRegs()), Live(TRI.getNumRegs());
CopyLiveIns(B, LiveIn);
for (auto SI : B->successors())
CopyLiveIns(SI, Live);
for (auto I = B->rbegin(), E = B->rend(); I != E; ++I) {
MachineInstr *MI = &*I;
if (MI->isDebugValue())
continue;
MI->clearKillInfo();
for (auto &Op : MI->operands()) {
// An implicit def of a super-register may not necessarily start a
// live range of it, since an implicit use could be used to keep parts
// of it live. Instead of analyzing the implicit operands, ignore
// implicit defs.
if (!Op.isReg() || !Op.isDef() || Op.isImplicit())
continue;
unsigned R = Op.getReg();
if (!TargetRegisterInfo::isPhysicalRegister(R))
continue;
for (MCSubRegIterator SR(R, &TRI, true); SR.isValid(); ++SR)
Live.reset(*SR);
}
for (auto &Op : MI->operands()) {
if (!Op.isReg() || !Op.isUse())
continue;
unsigned R = Op.getReg();
if (!TargetRegisterInfo::isPhysicalRegister(R))
continue;
bool IsLive = false;
for (MCRegAliasIterator AR(R, &TRI, true); AR.isValid(); ++AR) {
if (!Live[*AR])
continue;
IsLive = true;
break;
}
if (IsLive)
continue;
Op.setIsKill(true);
for (MCSubRegIterator SR(R, &TRI, true); SR.isValid(); ++SR)
Live.set(*SR);
}
}
}
// For shadows, determine if RR is aliased to a reaching def of any other
// shadow associated with RA. If it is not, then RR is "restricted" to RA,
// and so it can be considered a value specific to RA. This is important
// for accurately determining values associated with phi uses.
// For non-shadows, this function returns "true".
bool Liveness::isRestricted(NodeAddr<InstrNode*> IA, NodeAddr<RefNode*> RA,
RegisterRef RR) const {
NodeId Start = RA.Id;
for (NodeAddr<RefNode*> TA = DFG.getNextShadow(IA, RA);
TA.Id != 0 && TA.Id != Start; TA = DFG.getNextShadow(IA, TA)) {
NodeId RD = TA.Addr->getReachingDef();
if (RD == 0)
continue;
if (RAI.alias(RR, DFG.addr<DefNode*>(RD).Addr->getRegRef()))
return false;
}
return true;
}
RegisterRef Liveness::getRestrictedRegRef(NodeAddr<RefNode*> RA) const {
assert(DFG.IsRef<NodeAttrs::Use>(RA));
if (RA.Addr->getFlags() & NodeAttrs::Shadow) {
NodeId RD = RA.Addr->getReachingDef();
assert(RD);
RA = DFG.addr<DefNode*>(RD);
}
return RA.Addr->getRegRef();
}
unsigned Liveness::getPhysReg(RegisterRef RR) const {
if (!TargetRegisterInfo::isPhysicalRegister(RR.Reg))
return 0;
return RR.Sub ? TRI.getSubReg(RR.Reg, RR.Sub) : RR.Reg;
}
// Helper function to obtain the basic block containing the reaching def
// of the given use.
MachineBasicBlock *Liveness::getBlockWithRef(NodeId RN) const {
auto F = NBMap.find(RN);
if (F != NBMap.end())
return F->second;
llvm_unreachable("Node id not in map");
}
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::emptify(RefMap &M) {
for (auto I = M.begin(), E = M.end(); I != E; )
I = I->second.empty() ? M.erase(I) : std::next(I);
}