stdlib: Add some inlining attributes to help the optimizer getting the right inlining decisions.

This is more or less a workaround for some optimizations (mainly ARC opt) to avoid performance degradation with the upcoming inliner changes
In some situations it makes a big difference for ARC opt if a function is inlined or not, althought this shouldn't be the case.

stdlib/public/core/HashedCollections.swift.gyb

@@ -419,6 +419,7 @@ public struct Set<Element : Hashable> :
   /// Returns an iterator over the members.
   ///
   /// - Complexity: O(1).
+  @inline(__always)
   public func makeIterator() -> SetIterator<Element> {
     return _variantStorage.makeIterator()
   }
@@ -1038,6 +1039,7 @@ public struct Dictionary<Key : Hashable, Value> :
   /// Returns the `Index` for the given key, or `nil` if the key is not
   /// present in the dictionary.
   @warn_unused_result
+  @inline(__always)
   public func index(forKey key: Key) -> Index? {
     // Complexity: amortized O(1) for native storage, O(N) when wrapping an
     // NSDictionary.
@@ -1057,6 +1059,7 @@ public struct Dictionary<Key : Hashable, Value> :
   /// Writing `nil` as the value for a given key erases that key from
   /// `self`.
   public subscript(key: Key) -> Value? {
+    @inline(__always)
     get {
       return _variantStorage.maybeGet(key)
     }
@@ -1132,6 +1135,7 @@ public struct Dictionary<Key : Hashable, Value> :
   /// Returns an iterator over the `(Key, Value)` pairs.
   ///
   /// - Complexity: O(1).
+  @inline(__always)
   public func makeIterator() -> DictionaryIterator<Key, Value> {
     return _variantStorage.makeIterator()
   }
@@ -1950,6 +1954,7 @@ struct _Native${Self}Storage<${TypeParametersDecl}> :
   }
 
   @warn_unused_result
+  @inline(__always)
   internal func key(at i: Int) -> Key {
     _precondition(i >= 0 && i < capacity)
     _sanityCheck(isInitializedEntry(at: i))
@@ -2077,6 +2082,7 @@ struct _Native${Self}Storage<${TypeParametersDecl}> :
   /// If the key is not present, returns the position where it could be
   /// inserted.
   @warn_unused_result
+  @inline(__always)
   internal func _find(key: Key, startBucket: Int)
     -> (pos: Index, found: Bool) {
 
@@ -2163,6 +2169,7 @@ struct _Native${Self}Storage<${TypeParametersDecl}> :
   }
 
   @warn_unused_result
+  @inline(__always)
   internal func index(forKey key: Key) -> Index? {
     if count == 0 {
       // Fast path that avoids computing the hash of the key.
@@ -2198,6 +2205,7 @@ struct _Native${Self}Storage<${TypeParametersDecl}> :
   }
 
   @warn_unused_result
+  @inline(__always)
   internal func maybeGet(key: Key) -> Value? {
     if count == 0 {
       // Fast path that avoids computing the hash of the key.
@@ -2879,6 +2887,7 @@ internal struct _Cocoa${Self}Storage : _HashStorage {
   }
 
   @warn_unused_result
+  @inline(__always)
   internal func maybeGet(key: Key) -> Value? {
 
 %if Self == 'Set':
@@ -3117,6 +3126,7 @@ internal enum _Variant${Self}Storage<${TypeParametersDecl}> : _HashStorage {
   }
 
   @warn_unused_result
+  @inline(__always)
   internal func index(forKey key: Key) -> Index? {
     if _fastPath(guaranteedNative) {
       if let nativeIndex = asNative.index(forKey: key) {
@@ -3207,6 +3217,7 @@ internal enum _Variant${Self}Storage<${TypeParametersDecl}> : _HashStorage {
 #endif
 
   @warn_unused_result
+  @inline(__always)
   internal func maybeGet(key: Key) -> Value? {
     if _fastPath(guaranteedNative) {
       return asNative.maybeGet(key)
@@ -3527,6 +3538,7 @@ internal enum _Variant${Self}Storage<${TypeParametersDecl}> : _HashStorage {
   /// Returns an iterator over the `(Key, Value)` pairs.
   ///
   /// - Complexity: O(1).
+  @inline(__always)
   internal func makeIterator() -> ${Self}Iterator<${TypeParameters}> {
     switch self {
     case .native(let owner):
@@ -3987,6 +3999,7 @@ public struct ${Self}Iterator<${TypeParametersDecl}> : IteratorProtocol {
   /// element exists.
   ///
   /// - Precondition: No preceding call to `self.next()` has returned `nil`.
+  @inline(__always)
   public mutating func next() -> ${Sequence}? {
     if _fastPath(_guaranteedNative) {
       return _nativeNext()