On Fri, 16 Jan 2026 13:31:16 GMT, Marc Chevalier <[email protected]> wrote:
> Some code added by [JDK-8372700](https://bugs.openjdk.org/browse/JDK-8372700) > can compute the constant value of a field of a (flatten) element in a flat > array. We get a crash when the element of the array is known to be `null`, > and so the field doesn't exist. > > So, let's just check in `ciConstant ciFlatArray::field_value(int index, > ciField* field)` whether we get a null constant before interpreting it as a > `ciInstance` and trying to retrieve a field from there. This should be enough > since a `ciObject` is (directly) derived by `ciNullObject`, `ciInstance` and > `ciArray`. Since we are looking up a value of a flat array, an element cannot > be a `ciArray` (arrays have identities and can't be contained in a flat > array). After looking up whether the flat array element is null, the > `obj->as_instance()` cast acts as an assert, should we ever add another > derived class from `ciObject`. > > In case of a null array element, `field_value` simply returns an invalid > `ciConstant`. > > Tested with > tier1,tier2,tier3,hs-precheckin-comp,hs-comp-stress,valhalla-comp-stress. > Looks good. > > Thanks, > Marc src/hotspot/share/ci/ciFlatArray.cpp line 136: > 134: > 135: ciConstant ciFlatArray::field_value(int index, ciField* field) { > 136: auto get_field_from_object_constant = [field](const ciConstant& v) -> > ciConstant { I don't really agree with this fix, `ciFlatArray::field_value` should be dumber, it is the caller who knows that we do not fold the load if the element is `null`, the callee should just return the field as it is. src/hotspot/share/opto/type.cpp line 414: > 412: > 413: if (con.is_valid() && // not a mismatched access > 414: !con.is_null_or_zero()) { // not a default value This is incorrect, the value is not constant if the element of the array is `null`, not if the field we retrieved is `null`. ------------- PR Review Comment: https://git.openjdk.org/valhalla/pull/1923#discussion_r2707955712 PR Review Comment: https://git.openjdk.org/valhalla/pull/1923#discussion_r2707940249
