tree 800f02944dcba7cd176b7e51d10f955811f44fc4
parent 99928fc00d95803edd307716b66fd705954ca006
author Evan Brown CA <ezb@google.com> 1793298042 -0700
committer Copybara-Service <copybara-worker@google.com> 1793374905 -0700

Use `AddConstRefIfExpensiveToCopy` and `ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS` for hash/eq functor members in SwissTable helpers.

HashElement, HashKey, and EqualElement previously stored `const Hash&` and `const KeyEqual&` references. Even for empty stateless functors (such as absl::Hash) or small trivially copyable stateful functors, those reference members occupied 8 bytes, forced callers like find_or_prepare_insert_small() to materialize and store `&this->hash_` on the stack inside HashKey, and placed HashKey::key at offset 8 instead of offset 0 in HashKey::GetHash().

Store hash/eq as `ABSL_ATTRIBUTE_NO_UNIQUE_ADDRESS type_traits_internal::AddConstRefIfExpensiveToCopy` so empty functors occupy no space and small trivial functors are passed and stored by value without pointer indirection.

PiperOrigin-RevId: 1009828336