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Clemens Backes authored
This reverts commit c4a062a9. Reason for revert: TSan issues: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20TSAN/33504 Original change's description: > Reland^2 "[serializer] Allocate during deserialization" > > This is a reland of 28a30c57 > which was a reland of 5d7a29c9 > > The crashes were from calling RegisterDeserializerFinished on a null > Isolate pointer, for a deserializer that was never initialised > (specifically, ReadOnlyDeserializer when ROHeap is shared). > > Original change's description: > > Reland "[serializer] Allocate during deserialization" > > > > This is a reland of 5d7a29c9 > > > > This reland shuffles around the order of checks in Heap::AllocateRawWith > > to not check the new space addresses until it's known that this is a new > > space allocation. This fixes an UBSan failure during read-only space > > deserialization, which happens before the new space is initialized. > > > > It also fixes some issues discovered by --stress-snapshot, around > > serializing ThinStrings (which are now elided as part of serialization), > > handle counts (I bumped the maximum handle count in that check), and > > clearing map transitions (the map backpointer field needed a Smi > > uninitialized value check). > > > > Original change's description: > > > [serializer] Allocate during deserialization > > > > > > This patch removes the concept of reservations and a specialized > > > deserializer allocator, and instead makes the deserializer allocate > > > directly with the Heap's Allocate method. > > > > > > The major consequence of this is that the GC can now run during > > > deserialization, which means that: > > > > > > a) Deserialized objects are visible to the GC, and > > > b) Objects that the deserializer/deserialized objects point to can > > > move. > > > > > > Point a) is mostly not a problem due to previous work in making > > > deserialized objects "GC valid", i.e. making sure that they have a valid > > > size before any subsequent allocation/safepoint. We now additionally > > > have to initialize the allocated space with a valid tagged value -- this > > > is a magic Smi value to keep "uninitialized" checks simple. > > > > > > Point b) is solved by Handlifying the deserializer. This involves > > > changing any vectors of objects into vectors of Handles, and any object > > > keyed map into an IdentityMap (we can't use Handles as keys because > > > the object's address is no longer a stable hash). > > > > > > Back-references can no longer be direct chunk offsets, so instead the > > > deserializer stores a Handle to each deserialized object, and the > > > backreference is an index into this handle array. This encoding could > > > be optimized in the future with e.g. a second pass over the serialized > > > array which emits a different bytecode for objects that are and aren't > > > back-referenced. > > > > > > Additionally, the slot-walk over objects to initialize them can no > > > longer use absolute slot offsets, as again an object may move and its > > > slot address would become invalid. Now, slots are walked as relative > > > offsets to a Handle to the object, or as absolute slots for the case of > > > root pointers. A concept of "slot accessor" is introduced to share the > > > code between these two modes, and writing the slot (including write > > > barriers) is abstracted into this accessor. > > > > > > Finally, the Code body walk is modified to deserialize all objects > > > referred to by RelocInfos before doing the RelocInfo walk itself. This > > > is because RelocInfoIterator uses raw pointers, so we cannot allocate > > > during a RelocInfo walk. > > > > > > As a drive-by, the VariableRawData bytecode is tweaked to use tagged > > > size rather than byte size -- the size is expected to be tagged-aligned > > > anyway, so now we get an extra few bits in the size encoding. > > > > > > Bug: chromium:1075999 > > > Change-Id: I672c42f553f2669888cc5e35d692c1b8ece1845e > > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2404451 > > > Commit-Queue: Leszek Swirski <leszeks@chromium.org> > > > Reviewed-by: Jakob Gruber <jgruber@chromium.org> > > > Reviewed-by: Ulan Degenbaev <ulan@chromium.org> > > > Cr-Commit-Position: refs/heads/master@{#70229} > > > > Bug: chromium:1075999 > > Change-Id: Ibc77cc48b3440b4a28b09746cfc47e50c340ce54 > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2440828 > > Commit-Queue: Leszek Swirski <leszeks@chromium.org> > > Auto-Submit: Leszek Swirski <leszeks@chromium.org> > > Reviewed-by: Ulan Degenbaev <ulan@chromium.org> > > Reviewed-by: Jakob Gruber <jgruber@chromium.org> > > Cr-Commit-Position: refs/heads/master@{#70267} > > Tbr: jgruber@chromium.org,ulan@chromium.org > Bug: chromium:1075999 > Change-Id: Iaa8dc54895866ada0e34a7c9e8fff9ae1cb13f2d > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2444991 > Reviewed-by: Ulan Degenbaev <ulan@chromium.org> > Commit-Queue: Leszek Swirski <leszeks@chromium.org> > Cr-Commit-Position: refs/heads/master@{#70279} TBR=ulan@chromium.org,jgruber@chromium.org,leszeks@chromium.org Change-Id: Ib2f01db4cd9b55639d6a4af971bda865edb45e84 No-Presubmit: true No-Tree-Checks: true No-Try: true Bug: chromium:1075999 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2445250Reviewed-by: Clemens Backes <clemensb@chromium.org> Commit-Queue: Clemens Backes <clemensb@chromium.org> Cr-Commit-Position: refs/heads/master@{#70280}
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