bool LoopReroll::DAGRootTracker::collectUsedInstructions(SmallInstructionSet &PossibleRedSet) {
// Populate the MapVector with all instructions in the block, in order first,
// so we can iterate over the contents later in perfect order.
for (auto &I : *L->getHeader()) {
Uses[&I].resize(IL_End);
}
SmallInstructionSet Exclude;
Exclude.insert(Roots.begin(), Roots.end());
Exclude.insert(LoopIncs.begin(), LoopIncs.end());
DenseSet<Instruction*> VBase;
collectInLoopUserSet(IV, Exclude, PossibleRedSet, VBase);
for (auto *I : VBase) {
Uses[I].set(0);
}
unsigned Idx = 1;
for (auto *Root : Roots) {
DenseSet<Instruction*> V;
collectInLoopUserSet(Root, Exclude, PossibleRedSet, V);
// While we're here, check the use sets are the same size.
if (V.size() != VBase.size()) {
DEBUG(dbgs() << "LRR: Aborting - use sets are different sizes\n");
return false;
}
for (auto *I : V) {
Uses[I].set(Idx);
}
++Idx;
}
// Make sure the loop increments are also accounted for.
Exclude.clear();
Exclude.insert(Roots.begin(), Roots.end());
DenseSet<Instruction*> V;
collectInLoopUserSet(LoopIncs, Exclude, PossibleRedSet, V);
for (auto *I : V) {
Uses[I].set(IL_LoopIncIdx);
}
if (IV != RealIV)
Uses[RealIV].set(IL_LoopIncIdx);
return true;
}
// Collect all root increments with respect to the provided induction variable
// (normally the PHI, but sometimes a multiply). A root increment is an
// instruction, normally an add, with a positive constant less than Scale. In a
// rerollable loop, each of these increments is the root of an instruction
// graph isomorphic to the others. Also, we collect the final induction
// increment (the increment equal to the Scale), and its users in LoopIncs.
bool LoopReroll::collectAllRoots(Loop *L, uint64_t Inc, uint64_t Scale,
Instruction *IV,
SmallVector<SmallInstructionVector, 32> &Roots,
SmallInstructionSet &AllRoots,
SmallInstructionVector &LoopIncs) {
for (Value::use_iterator UI = IV->use_begin(),
UIE = IV->use_end(); UI != UIE; ++UI) {
Instruction *User = cast<Instruction>(*UI);
if (!SE->isSCEVable(User->getType()))
continue;
if (User->getType() != IV->getType())
continue;
if (!L->contains(User))
continue;
if (hasUsesOutsideLoop(User, L))
continue;
if (const SCEVConstant *Diff = dyn_cast<SCEVConstant>(SE->getMinusSCEV(
SE->getSCEV(User), SE->getSCEV(IV)))) {
uint64_t Idx = Diff->getValue()->getValue().getZExtValue();
if (Idx > 0 && Idx < Scale) {
Roots[Idx-1].push_back(User);
AllRoots.insert(User);
} else if (Idx == Scale && Inc > 1) {
LoopIncs.push_back(User);
}
}
}
if (Roots[0].empty())
return false;
bool AllSame = true;
for (unsigned i = 1; i < Scale-1; ++i)
if (Roots[i].size() != Roots[0].size()) {
AllSame = false;
break;
}
if (!AllSame)
return false;
return true;
}
