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[LLD][ELF] - Simplify Call-Chain Clustering implementation a bit. 

Looking at the current implementation and algorithm description,
it does not seem we need to keep vector with all edges for
each cluster and can just remember the best one. This is NFC change.

Differential revision: https://reviews.llvm.org/D50609

llvm-svn: 340806
This commit is contained in:
George Rimar 2018-08-28 08:49:40 +00:00
parent 2cfbe933a1
commit f0eedbce44
1 changed files with 10 additions and 16 deletions
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26
lld/ELF/CallGraphSort.cpp
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@ -72,7 +72,7 @@ struct Cluster {
size_t Size = 0;
uint64_t Weight = 0;
uint64_t InitialWeight = 0;
std::vector<Edge> Preds;
Edge BestPred = {-1, 0};
};
class CallGraphSort {
@ -136,8 +136,12 @@ CallGraphSort::CallGraphSort() {
if (From == To)
continue;
// Add an edge
Clusters[To].Preds.push_back({From, Weight});
// Remember the best edge.
Cluster &ToC = Clusters[To];
if (ToC.BestPred.From == -1 || ToC.BestPred.Weight < Weight) {
ToC.BestPred.From = From;
ToC.BestPred.Weight = Weight;
}
}
for (Cluster &C : Clusters)
C.InitialWeight = C.Weight;
@ -181,21 +185,11 @@ void CallGraphSort::groupClusters() {
// been merged into another cluster yet.
Cluster &C = Clusters[SI];
int BestPred = -1;
uint64_t BestWeight = 0;
for (Edge &E : C.Preds) {
if (BestPred == -1 || E.Weight > BestWeight) {
BestPred = E.From;
BestWeight = E.Weight;
}
}
// don't consider merging if the edge is unlikely.
if (BestWeight * 10 <= C.InitialWeight)
// Don't consider merging if the edge is unlikely.
if (C.BestPred.From == -1 || C.BestPred.Weight * 10 <= C.InitialWeight)
continue;
Cluster *PredC = SecToCluster[BestPred];
Cluster *PredC = SecToCluster[C.BestPred.From];
if (PredC == &C)
continue;