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Optimize array length handling in ArraySetLength and array_unshift by caching property and argument counts

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wuggy 2026-04-22 07:45:40 -07:00
commit bd8939adb7
1 changed files with 10 additions and 8 deletions
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18
js/src/jsarray.cpp
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@ -705,7 +705,8 @@ js::ArraySetLength(JSContext* cx, Handle<ArrayObject*> arr, HandleId id,
if (!GetPropertyKeys(cx, arr, JSITER_OWNONLY | JSITER_HIDDEN, &props))
return false;
for (size_t i = 0; i < props.length(); i++) {
const size_t propCount = props.length();
for (size_t i = 0; i < propCount; i++) {
if (!CheckForInterrupt(cx))
return false;
@ -2316,8 +2317,9 @@ js::array_unshift(JSContext* cx, unsigned argc, Value* vp)
if (!GetLengthProperty(cx, obj, &length))
return false;
const unsigned argCount = args.length();
double newlen = length;
if (args.length() > 0) {
if (argCount > 0) {
/* Slide up the array to make room for all args at the bottom. */
if (length > 0) {
// Only include a fast path for boxed arrays. Unboxed arrays can'nt
@ -2332,22 +2334,22 @@ js::array_unshift(JSContext* cx, unsigned argc, Value* vp)
ArrayObject* aobj = &obj->as<ArrayObject>();
if (!aobj->lengthIsWritable())
break;
DenseElementResult result = aobj->ensureDenseElements(cx, length, args.length());
DenseElementResult result = aobj->ensureDenseElements(cx, length, argCount);
if (result != DenseElementResult::Success) {
if (result == DenseElementResult::Failure)
return false;
MOZ_ASSERT(result == DenseElementResult::Incomplete);
break;
}
aobj->moveDenseElements(args.length(), 0, length);
for (uint32_t i = 0; i < args.length(); i++)
aobj->moveDenseElements(argCount, 0, length);
for (uint32_t i = 0; i < argCount; i++)
aobj->setDenseElement(i, MagicValue(JS_ELEMENTS_HOLE));
optimized = true;
} while (false);
if (!optimized) {
double last = length;
double upperIndex = last + args.length();
double upperIndex = last + argCount;
RootedValue value(cx);
do {
--last, --upperIndex;
@ -2368,10 +2370,10 @@ js::array_unshift(JSContext* cx, unsigned argc, Value* vp)
}
/* Copy from args to the bottom of the array. */
if (!InitArrayElements(cx, obj, 0, args.length(), args.array()))
if (!InitArrayElements(cx, obj, 0, argCount, args.array()))
return false;
newlen += args.length();
newlen += argCount;
}
if (!SetLengthProperty(cx, obj, newlen))
return false;