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[ADT] Make set_subtract more efficient when subtrahend is larger (NFC) #98702

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Merged
merged 3 commits into from
Jul 17, 2024
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[ADT] Make set_subtract more efficient when subtrahend is larger (NFC) #98702

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0d947a2
[ADT] Make set_subtract more efficient when subtrahend is larger (NFC)
teresajohnson Jul 12, 2024
bc03353
Address comments
teresajohnson Jul 15, 2024
0554956
Just check/use contains
teresajohnson Jul 15, 2024
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15 changes: 15 additions & 0 deletions llvm/include/llvm/ADT/SetOperations.h
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,22 @@ S1Ty set_difference(const S1Ty &S1, const S2Ty &S2) {

/// set_subtract(A, B) - Compute A := A - B
///
/// Selects the set to iterate based on the relative sizes of A and B for better
/// efficiency.
///
template <class S1Ty, class S2Ty> void set_subtract(S1Ty &S1, const S2Ty &S2) {
using ElemTy = decltype(*S1.begin());
// A couple callers pass a vector for S2, which doesn't support contains(),
// and wouldn't be efficient if it did.
if constexpr (detail::HasMemberContains<S2Ty, ElemTy>) {
if (S1.size() < S2.size()) {
for (typename S1Ty::iterator SI = S1.begin(), SE = S1.end(); SI != SE;
++SI)
if (S2.contains(*SI))
S1.erase(SI);
return;
}
}
for (typename S2Ty::const_iterator SI = S2.begin(), SE = S2.end(); SI != SE;
++SI)
S1.erase(*SI);
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