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Optimize ScheduleDAGRRList's topological sort to use one pass instead

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of two, and to not need a scratch std::vector. Also, compute the ordering
immediately in the result array, instead of in another scratch std::vector
that is copied to the result array.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55421 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2008-08-27 16:29:48 +00:00
parent 3a09d891a4
commit e5a8dc5cc4
1 changed files with 8 additions and 19 deletions
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27
lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
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@ -448,18 +448,19 @@ inline void ScheduleDAGRRList::Allocate(int n, int index) {
/// immediately after X in Index2Node.
void ScheduleDAGRRList::InitDAGTopologicalSorting() {
unsigned DAGSize = SUnits.size();
std::vector<unsigned> InDegree(DAGSize);
std::vector<SUnit*> WorkList;
WorkList.reserve(DAGSize);
std::vector<SUnit*> TopOrder;
TopOrder.reserve(DAGSize);
Index2Node.resize(DAGSize);
Node2Index.resize(DAGSize);
// Initialize the data structures.
for (unsigned i = 0, e = DAGSize; i != e; ++i) {
SUnit *SU = &SUnits[i];
int NodeNum = SU->NodeNum;
unsigned Degree = SU->Succs.size();
InDegree[NodeNum] = Degree;
// Temporarily use the Node2Index array as scratch space for degree counts.
Node2Index[NodeNum] = Degree;
// Is it a node without dependencies?
if (Degree == 0) {
@ -469,35 +470,23 @@ void ScheduleDAGRRList::InitDAGTopologicalSorting() {
}
}
int Id = DAGSize;
while (!WorkList.empty()) {
SUnit *SU = WorkList.back();
WorkList.pop_back();
TopOrder.push_back(SU);
Allocate(SU->NodeNum, --Id);
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
SUnit *SU = I->Dep;
if (!--InDegree[SU->NodeNum])
if (!--Node2Index[SU->NodeNum])
// If all dependencies of the node are processed already,
// then the node can be computed now.
WorkList.push_back(SU);
}
}
// Second pass, assign the actual topological order as node ids.
int Id = 0;
Index2Node.clear();
Node2Index.clear();
Index2Node.resize(DAGSize);
Node2Index.resize(DAGSize);
Visited.resize(DAGSize);
for (std::vector<SUnit*>::reverse_iterator TI = TopOrder.rbegin(),
TE = TopOrder.rend();TI != TE; ++TI) {
Allocate((*TI)->NodeNum, Id);
Id++;
}
#ifndef NDEBUG
// Check correctness of the ordering
for (unsigned i = 0, e = DAGSize; i != e; ++i) {