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[MCA] Do not allocate space for DependenceEdge by default in DependencyGraphNode (NFC) #125080

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Merged
merged 2 commits into from
Jan 31, 2025
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[MCA] Do not allocate space for DependenceEdge by default in DependencyGraphNode (NFC) #125080

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[MCA] Do not allocate space for DependenceEdge by default in Dependen…
asi-sc Jan 16, 2025
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fixup! [MCA] Do not allocate space for DependenceEdge by default in D…
asi-sc Jan 31, 2025
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5 changes: 4 additions & 1 deletion llvm/tools/llvm-mca/Views/BottleneckAnalysis.h
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Original file line number Diff line number Diff line change
Expand Up @@ -228,7 +228,10 @@ class DependencyGraph {
unsigned Depth;

DependencyEdge CriticalPredecessor;
SmallVector<DependencyEdge, 8> OutgoingEdges;
// Measurements show that more than 90% of nodes have no outgoing edges. To
// minimize memory consumption we use SmallVector with zero inline elements
// that is preferred version of std::vector.
SmallVector<DependencyEdge, 0> OutgoingEdges;
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I think it is useful to have a comment (not more than a couple of lines) explaining why zero was used for the number of inline elements. Otherwise it would be unclear for the reader why we chose that number in this case.

};
SmallVector<DGNode, 16> Nodes;

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