Integrated: 8290833: Remove ConstantPoolCache::walk_entries_for_initialization()

[Ioi Lam]

On Thu, 4 Aug 2022 23:22:25 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> **Background:**
> 
> `ConstantPoolCache::walk_entries_for_initialization()` is called by `ConstantPoolCache::remove_unshareable_info()` to restore the CpCache to the state immediately after the class has been rewritten by the Rewriter (which happens during the class linking phase). In most part, this means the `ConstantPoolCacheEntry`'s need to be zeroed. However, the `_f2` fields of some of the entries are initialized to be non-zero by the Rewriter and must be preserved.
> 
> The reason `walk_entries_for_initialization()` exists is that after `Rewriter::rewrite()` has finished, some information about what is stored inside the CpCache is discarded (e.g., `Rewriter::_invokedynamic_references_map`). As a result, we cannot easily determine which entries has a `_f2` field that need to be preserved. We must walk all the bytecodes in all the methods of this class to recompute this information.
> 
> This is awkward and time consuming. It also needs to be updated if the `Rewriter` ever changes.
> 
> Also, for future optimizations, we may need to pre-resolve a subset of the CpCache entries during CDS dump time. Trying to make that work alongside `walk_entries_for_initialization()` seems too complicated.
> 
> **Fix:**
> 
> Store a copy of the CpCache after rewritting. Use this to revert the CpCache's state inside  `ConstantPoolCache::remove_unshareable_info()`.

This pull request has now been integrated.

Changeset: bd585533
Author:    Ioi Lam <iklam at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/bd5855337c9eebc0044fd467fa39a671e260f891
Stats:     187 lines in 9 files changed: 102 ins; 63 del; 22 mod

8290833: Remove ConstantPoolCache::walk_entries_for_initialization()

Reviewed-by: coleenp, ccheung

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PR: https://git.openjdk.org/jdk/pull/9759