stdlib: rewrite optional-check to improve performance

eeckstein · eeckstein · commit 31234f64b034 · 2016-05-25T14:27:27.000-07:00
The statement "if x == nil { }" involves creating an Optional.none for the RHS and calling the == function.
diff --git a/stdlib/public/core/UnsafeBufferPointer.swift.gyb b/stdlib/public/core/UnsafeBufferPointer.swift.gyb
@@ -126,11 +126,10 @@ public struct Unsafe${Mutable}BufferPointer<Element>
 
   /// The number of elements in the buffer.
   public var count: Int {
-    if _position == nil {
-      _sanityCheck(_end == nil)
-      return 0
+    if let pos = _position {
+      return _end! - pos
     }
-    return _end! - _position!
+    return 0
   }
 
   let _position, _end: Unsafe${Mutable}Pointer<Element>?

Original file line number	Diff line number	Diff line change
`@@ -126,11 +126,10 @@ public struct Unsafe${Mutable}BufferPointer<Element>`
`126`	`126`
`127`	`127`	`/// The number of elements in the buffer.`
`128`	`128`	`public var count: Int {`
`129`		`- if _position == nil {`
`130`		`- _sanityCheck(_end == nil)`
`131`		`- return 0`
	`129`	`+ if let pos = _position {`
	`130`	`+ return _end! - pos`
`132`	`131`	`}`
`133`		`- return _end! - _position!`
	`132`	`+ return 0`
`134`	`133`	`}`
`135`	`134`
`136`	`135`	`let _position, _end: Unsafe${Mutable}Pointer<Element>?`