This is a reland of commit 23b2d571a7
When updating pointers during a full GC, a page might not be swept
already. In such cases there might be invalid objects and slots
recorded in free memory. Updating tagged slots in free memory is fine
even though not strictly necessary.
However, the GC also needs to calculate the size of potentially dead
invalid objects in order to be able to check whether a slot is within
that object. But since that object is dead, its map might be dead as
well which makes size calculation impossible on such objects. The CL
changes this to cache the size of invalid objects. A follow-up CL will
also check the marking bit of invalid objects.
Reason for reverts:
Revert #2: In-object slack tracking on JSObjects doesn't update the
cached size of invalidated objects. The fix here was to stop
invalidating recorded slots on JSObjects at all and avoid that problem
completely (see https://crrev.com/c/3620274).
Revert #1: Not all size changes go through NotifyObjectLayoutChange, so
https://crrev.com/c/3607992 introduced NotifyObjectSizeChange as a
bottleneck for object size changes/right-trimming. This method is
now used to update the size of invalidated objects.
Bug: v8:12578, chromium:1316289
Change-Id: I0478d04601c0270ddb39419ca6cf98719951eb4d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3623542
Reviewed-by: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Patrick Thier <pthier@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80344}
2b79eefed3