Revert "cppgc-js: Add snapshot for C++ objects"
This reverts commit 02849fd9. Reason for revert: Breaks Win64 MSVC bot and closes the tree - https://ci.chromium.org/p/v8/builders/ci/V8%20Win64%20-%20msvc/15416 Original change's description: > cppgc-js: Add snapshot for C++ objects > > The following implements a snapshotting algorithm for C++ objects that > also filters strongly-connected components (SCCs) of only "hidden" > objects that are not (transitively) referencing any non-hidden > objects. > > C++ objects come in two versions. > a. Named objects that have been assigned a name through NameProvider. > b. Unnamed objects, that are potentially hidden if the build > configuration requires Oilpan to hide such names. Hidden objects have > their name set to NameProvider::kHiddenName. > > The main challenge for the algorithm is to avoid blowing up the final > object graph with hidden nodes that do not carry information. For that > reason, the algorithm filters SCCs of only hidden objects, e.g.: > ... -> (object) -> (object) -> (hidden) -> (hidden) > In this case the (hidden) objects are filtered from the graph. The > trickiest part is maintaining visibility state for objects referencing > other objects that are currently being processed. > > Main algorithm idea (two passes): > 1. First pass marks all non-hidden objects and those that transitively > reach non-hidden objects as visible. Details: > - Iterate over all objects. > - If object is non-hidden mark it as visible and also mark parent > as visible if needed. > - If object is hidden, traverse children as DFS to find non-hidden > objects. Post-order process the objects and mark those objects as > visible that have child nodes that are visible themselves. > - Maintain an epoch counter (StateStorage::state_count_) to allow > deferring the visibility decision to other objects in the same > SCC. This is similar to the "lowlink" value in Tarjan's algorithm > for SCC. > - After the first pass it is guaranteed that all deferred > visibility decisions can be resolved. > 2. Second pass adds nodes and edges for all visible objects. > - Upon first checking the visibility state of an object, all deferred > visibility states are resolved. > > For practical reasons, the recursion is transformed into an iteration. > We do not use plain Tarjan's algorithm to avoid another pass over > all nodes to create SCCs. > > Follow ups: > 1. Adding wrapper nodes for cpp objects that are wrappables for V8 > wrappers. > 2. Adding detachedness information. > > Change-Id: I6e127d2c6d65e77defe08e39295a2594f463b962 > Bug: chromium:1056170 > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2467854 > Commit-Queue: Michael Lippautz <mlippautz@chromium.org> > Reviewed-by: Ulan Degenbaev <ulan@chromium.org> > Reviewed-by: Omer Katz <omerkatz@chromium.org> > Cr-Commit-Position: refs/heads/master@{#70567} TBR=ulan@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,omerkatz@chromium.org Change-Id: I64a2cf2259bdaed81f6e0f92bdcc7a1f0df4d197 No-Presubmit: true No-Tree-Checks: true No-Try: true Bug: chromium:1056170 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2479471Reviewed-by:Maya Lekova <mslekova@chromium.org> Commit-Queue: Maya Lekova <mslekova@chromium.org> Cr-Commit-Position: refs/heads/master@{#70571}
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