On Wed, 16 Apr 2025 05:38:59 GMT, Chen Liang <li...@openjdk.org> wrote:
>> yes ! I would write >> "given the current implementation of hashCode(), marking hasIsZero @Stable >> is not useful for constant folding, as the field `hash` of value '0' is read >> first." > > Yep. To be more exact, JIT anticipates a read of `hash` to be non-zero at any > future point instead of trusting it to be zero when it observes `hashIsZero > == 1`. >From a theoretical point of view, there is nothing that prevents the VM from >constant folding the case where `hash = 0` as the two sub-conditions in `(h >== 0 && !hashIsZero)` do not have any side effect. In theory, the VM could >check both conditions and determine that `h = 0` is not trusted (as `hash` is >not trusted because it is the default value) but `!hashIsZero` is trusted and >`false` which means the entire expression is trusted to be `false`. However, >the VM logic is not implemented in such a way. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/24625#discussion_r2046225943
