Optimize SwissTable slot lifecycle and resize transfers with restrict qualifiers.

In raw_hash_set, constructing, destroying, or transferring slots writes subobjects (such as moved-from SSO string tags, vector end pointers, map values, or control bytes) through one pointer while reading from another, preventing the compiler from proving non-aliasing across slot-lifecycle operations and table growth.

Add __restrict qualifiers to the slot pointer parameters of the slot-lifecycle helpers (construct, destroy, transfer) and type-erased slot callbacks (transfer_n_slots_fn, destroy_slot_fn_impl, and transfer_unprobed_elements_to_next_capacity_fn, along with CommonFields& __restrict common) in raw_hash_set.h.

PiperOrigin-RevId: 996076967

absl/container/internal/raw_hash_set.h

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index ce8a1e4..2cd1784 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -3593,17 +3593,17 @@
   };
 
   template <typename... Args>
-  void construct(slot_type* slot, Args&&... args) {
+  void construct(slot_type* __restrict slot, Args&&... args) {
     ReentranceGuard guard(common());
     allocator_type alloc(char_alloc_ref());
     PolicyTraits::construct(&alloc, slot, std::forward<Args>(args)...);
   }
-  void destroy(slot_type* slot) {
+  void destroy(slot_type* __restrict slot) {
     ReentranceGuard guard(common());
     allocator_type alloc(char_alloc_ref());
     PolicyTraits::destroy(&alloc, slot);
   }
-  void transfer(slot_type* to, slot_type* from) {
+  void transfer(slot_type* __restrict to, slot_type* __restrict from) {
     ReentranceGuard guard(common());
     allocator_type alloc(char_alloc_ref());
     PolicyTraits::transfer(&alloc, to, from);
@@ -4170,8 +4170,8 @@
                                                    kSeedShift>();
   }
 
-  static void transfer_n_slots_fn(void* set, void* dst, void* src,
-                                  size_t count) {
+  static void transfer_n_slots_fn(void* set, void* __restrict dst,
+                                  void* __restrict src, size_t count) {
     auto* src_slot = to_slot(src);
     auto* dst_slot = to_slot(dst);
 
@@ -4189,7 +4189,7 @@
         PolicyTraits::element(static_cast<slot_type*>(const_cast<void*>(src))));
   }
 
-  static void destroy_slot_fn_impl(void* set, void* slot) {
+  static void destroy_slot_fn_impl(void* set, void* __restrict slot) {
     auto* h = static_cast<raw_hash_set*>(set);
     h->destroy(to_slot(slot));
   }
@@ -4203,8 +4203,8 @@
   // by GetKey + Hash for memcpyable types.
   // TODO(b/382423690): Try to type erase for big slots: sizeof(slot_type) > 16.
   static void transfer_unprobed_elements_to_next_capacity_fn(
-      CommonFields& common, const ctrl_t* old_ctrl, void* probed_storage,
-      void* old_slots, size_t old_capacity,
+      CommonFields& __restrict common, const ctrl_t* old_ctrl,
+      void* probed_storage, void* __restrict old_slots, size_t old_capacity,
       void (*encode_probed_element)(void* probed_storage, size_t hash,
                                     size_t source_offset)) {
     ABSL_ASSUME(old_capacity + 1 >= Group::kWidth);