RFR: 8340012: [C2] assert(KlassEncodingMetaspaceMax > pd) failed: change encoding max if new encoding after 8338526 [v2]

[Thomas Stuefe]

On Fri, 13 Sep 2024 15:40:56 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> After JDK-8338526, the transformation can only be done if the Klass* is in the encoding range (also see JBS issue for more details). I've also enhanced the assertion message.
>
> Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add sanity check.

Good catch. I was afraid we would hit things like this. I hope there are not more.

src/hotspot/share/oops/compressedKlass.inline.hpp line 54:

> 52:   assert(check_alignment(v), "Address not aligned");
> 53:   uint64_t pd = (uint64_t)(pointer_delta(v, narrow_base, 1));
> 54:   assert(KlassEncodingMetaspaceMax > pd, "change encoding max if new encoding (Klass " PTR_FORMAT ", Base " PTR_FORMAT ")", p2i(v), p2i(narrow_base));

Would it be possible to leave this hunk out? I am in the process of rewriting large parts of this for Lilliput, so it won't survive in this current form. These things will be a lot better tested, and the assertion messages make more sense, too)

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PR Review: https://git.openjdk.org/jdk/pull/20971#pullrequestreview-2303454203
PR Review Comment: https://git.openjdk.org/jdk/pull/20971#discussion_r1759082597