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[stdlib] Array: one-element _typeCheck, for ARC

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the ARC optimizer does not handle loops well, and so can get blocked by
the presence of a loop over the range. Therefore, add a single-element
check for the common case where we're not slicing.

Swift SVN r23502
This commit is contained in:
Dave Abrahams
2014-11-21 01:39:53 +00:00
parent 3cda8c1bd3
commit b9342e5c1b
1 changed files with 22 additions and 10 deletions
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32
stdlib/core/ArrayBuffer.swift
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@@ -209,7 +209,11 @@ extension _ArrayBuffer {
_arrayNonSliceInPlaceReplace(&self, subRange, newCount, newValues)
}
func _typeCheck(subRange: Range<Int>) {
// We have two versions of type check: one that takes a range and the other
// checks one element. The reason for this is that the ARC optimizer does not
// handle loops atm. and so can get blocked by the presence of a loop (over
// the range). This loop is not necessary for a single element access.
func _typeCheck(index: Int) {
if !_isClassOrObjCExistential(T.self) {
return
}
@@ -218,14 +222,22 @@ extension _ArrayBuffer {
_sanityCheck(
!_isNative, "A native array that needs a type check?")
if !subRange.isEmpty {
let ns = _nonNative
// Could be sped up, e.g. by using
// enumerateObjectsAtIndexes:options:usingBlock:
for i in subRange {
_precondition(ns.objectAtIndex(i) is T,
"NSArray element failed to match the Swift Array Element type")
}
let ns = _nonNative
// Could be sped up, e.g. by using
// enumerateObjectsAtIndexes:options:usingBlock:
_precondition(ns.objectAtIndex(index) is T,
"NSArray element failed to match the Swift Array Element type")
}
}
func _typeCheck(subRange: Range<Int>) {
if !_isClassOrObjCExistential(T.self) {
return
}
if _slowPath(needsElementTypeCheck) {
for i in subRange {
_typeCheck(i)
}
}
}
@@ -341,7 +353,7 @@ extension _ArrayBuffer {
subscript(i: Int) -> T {
get {
if _isClassOrObjCExistential(T.self) {
_typeCheck(i...i)
_typeCheck(i)
}
if _fastPath(_isNative) {
return _native[i]