stdlib: move Dictionary's find functions into __RawDictionaryStorage.

The find functions do not require the generic Value parameter. Moving them to __RawDictionaryStorage allows to define them with only one generic parameter: the Key.
This allows the optimizer to share specializations for dictionaries which have the same Key, but a different Value.
Also, prevent inlining of the find-functions to save some additional code size.

Author: eeckstein

stdlib/public/core/DictionaryStorage.swift

@@ -196,6 +196,35 @@ extension __RawDictionaryStorage {
     return Builtin.bridgeFromRawPointer(
       Builtin.addressof(&_swiftEmptyDictionarySingleton))
   }
+  
+  @_alwaysEmitIntoClient
+  @inline(__always)
+  internal final func uncheckedKey<Key: Hashable>(at bucket: _HashTable.Bucket) -> Key {
+    defer { _fixLifetime(self) }
+    _internalInvariant(_hashTable.isOccupied(bucket))
+    let keys = _rawKeys.assumingMemoryBound(to: Key.self)
+    return keys[bucket.offset]
+  }
+
+  @_alwaysEmitIntoClient
+  @inline(never)
+  internal final func find<Key: Hashable>(_ key: Key) -> (bucket: _HashTable.Bucket, found: Bool) {
+    return find(key, hashValue: key._rawHashValue(seed: _seed))
+  }
+
+  @_alwaysEmitIntoClient
+  @inline(never)
+  internal final func find<Key: Hashable>(_ key: Key, hashValue: Int) -> (bucket: _HashTable.Bucket, found: Bool) {
+      let hashTable = _hashTable
+      var bucket = hashTable.idealBucket(forHashValue: hashValue)
+      while hashTable._isOccupied(bucket) {
+        if uncheckedKey(at: bucket) == key {
+          return (bucket, true)
+        }
+        bucket = hashTable.bucket(wrappedAfter: bucket)
+      }
+      return (bucket, false)
+  }
 }
 
 @usableFromInline

stdlib/public/core/NativeDictionary.swift

@@ -161,7 +161,7 @@ extension _NativeDictionary { // Low-level lookup operations
   @inlinable
   @inline(__always)
   internal func find(_ key: Key) -> (bucket: Bucket, found: Bool) {
-    return find(key, hashValue: self.hashValue(for: key))
+    return _storage.find(key)
   }
 
   /// Search for a given element, assuming it has the specified hash value.
@@ -174,15 +174,7 @@ extension _NativeDictionary { // Low-level lookup operations
     _ key: Key,
     hashValue: Int
   ) -> (bucket: Bucket, found: Bool) {
-    let hashTable = self.hashTable
-    var bucket = hashTable.idealBucket(forHashValue: hashValue)
-    while hashTable._isOccupied(bucket) {
-      if uncheckedKey(at: bucket) == key {
-        return (bucket, true)
-      }
-      bucket = hashTable.bucket(wrappedAfter: bucket)
-    }
-    return (bucket, false)
+    return _storage.find(key, hashValue: hashValue)
   }
 }