On Wed, 30 Oct 2024 19:07:50 GMT, Jiangli Zhou <jian...@openjdk.org> wrote:
>> I don't think I understand. The whole point is to make sure the runtime
>> cache instances are the same as archive cache instances, right? Using both
>> archived and runtime caches leads to identity inconsistencies: if we `==`
>> compare the archived `Integer` box and the runtime `Integer` box of the same
>> value in [-128; 127], they should equal each other. So we have to make sure
>> we use the parts we have already committed to use (from the archive), and
>> add whatever cache elements are missing at runtime. I don't see how it works
>> otherwise.
>
> The runtime cache would only store the additional boxed Integers not in the
> archived cache, without affecting the archived boxed Integers. Something like
> the following would work (I didn't test all corner cases):
>
>
> static final int archivedSize;
> ...
> archivedSize = archivedCache == null ? 0 : archivedCache.length;
> if (archivedCache == null || size > archivedCache.length) {
> int runtimeCacheSize = size - archivedSize;
> Integer[] c = new Integer[runtimeCacheSize];
> int j = low + archivedSize;
> for(int i = 0; i < runtimeCacheSize; i++) {
> c[i] = new Integer(j++);
> }
>
> cache = c;
> if (archivedCache == null) {
> archivedCache = c;
> }
> } else {
> cache = null;
> }
>
>
> `Integer.valueOf()` would retrieve the cached boxed Integer either from the
> archived cache or the runtime created cache, if the value is within the
> runtime [low, high].
>
>
> public static Integer valueOf(int i) {
> if (i >= IntegerCache.low && i <= IntegerCache.high) {
> int index = i + (-IntegerCache.low);
> if (IntegerCache.archivedSize != 0 && IntegerCache.archivedSize
> >= index) {
> return IntegerCache.archivedCache[index];
> } else {
> return IntegerCache.cache[index - IntegerCache.archivedSize];
> }
> }
> return new Integer(i);
> }
Ah, I see. I don't think we want to do this, though. I vaguely remember
`Integer.valueOf` code shape being important for things like C2 optimizations
around EA and autoboxing elimination. The beauty of staying within a single
array is avoiding a whole class of these issues.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/21737#discussion_r1823971473
