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util/irep: O(1) SHARING fast-path for irept::compare #9130

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util/irep: O(1) SHARING fast-path for irept::compare #9130

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10 changes: 10 additions & 0 deletions src/util/irep.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -300,6 +300,16 @@ bool irept::ordering(const irept &other) const
/// comments are ignored
int irept::compare(const irept &i) const
{
// Fast path: structurally-shared instances compare equal in O(1).
// Without this, dictionaries / std::map<exprt> walk the entire
// sub-tree even when both keys point to the same node — this is
// a hot path under heavy SMT struct flattening (smt2_convt's
// defined_expressions / datatype_map lookups).
#ifdef SHARING
if(data == i.data)
return 0;
#endif

int r;

r=id().compare(i.id());
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