• Omer Katz's avatar
    Reland "cppgc: Stack scanning using ObjectStartBitmap" · 93059842
    Omer Katz authored
    This reverts commit 580917d2.
    
    Reason for revert: fix in patchset 2
    
    Original change's description:
    > Revert "cppgc: Stack scanning using ObjectStartBitmap"
    > 
    > This reverts commit d3a72e3c.
    > 
    > Reason for revert: MSAN failures (https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20arm64%20-%20sim%20-%20MSAN/32360)
    > 
    > Original change's description:
    > > cppgc: Stack scanning using ObjectStartBitmap
    > > 
    > > This CL implements stack scanning for cppgc.
    > > Given a value on the stack, the MarkingVisitor uses
    > > PageBackend::Lookup to checks whether that address is on
    > > the heap. If it is, BasePage::TryObjectHeaderFromInnerAddress
    > > (introduced in this CL) is used to get the relevant object
    > > header. Note that random addresses on the heap might point to
    > > free memory, object-start-bitmap, etc.
    > > 
    > > If a valid object header is found:
    > > * If the object is not in construction, the GCInfoIndex is used
    > > the get the relevant Trace method and the object is traced.
    > > * Otherwise, the object is conservatively scanned - i.e. the
    > > payload of the object is iterated word by word and each word is
    > > treated as a possible pointer.
    > > 
    > > Only addresses pointing to the payload on non-free objects are
    > > traced.
    > > 
    > > BasePage::TryObjectHeaderFromInnerAddress assumes on LAB on the
    > > relevant space, thus all LABs are reset before scanning the stack.
    > > 
    > > Bug: chromium:1056170
    > > Change-Id: I172850f6f1bbb6f0efca8e44ad8fdfe222977b9f
    > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2190426
    > > Commit-Queue: Omer Katz <omerkatz@chromium.org>
    > > Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
    > > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
    > > Reviewed-by: Anton Bikineev <bikineev@chromium.org>
    > > Cr-Commit-Position: refs/heads/master@{#67795}
    > 
    > TBR=ulan@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,omerkatz@chromium.org
    > 
    > Change-Id: I3caef6f9f55911fd1a86e895c3495d1b98b1eac2
    > No-Presubmit: true
    > No-Tree-Checks: true
    > No-Try: true
    > Bug: chromium:1056170
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2201136
    > Reviewed-by: Leszek Swirski <leszeks@chromium.org>
    > Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#67796}
    
    TBR=ulan@chromium.org,mlippautz@chromium.org,leszeks@chromium.org,bikineev@chromium.org,omerkatz@chromium.org
    
    # Not skipping CQ checks because this is a reland.
    
    Bug: chromium:1056170
    Change-Id: If7ea4fe5cb794c07544d5545f5d6548e3375d3ae
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2201137Reviewed-by: 's avatarOmer Katz <omerkatz@chromium.org>
    Reviewed-by: 's avatarUlan Degenbaev <ulan@chromium.org>
    Reviewed-by: 's avatarAnton Bikineev <bikineev@chromium.org>
    Reviewed-by: 's avatarMichael Lippautz <mlippautz@chromium.org>
    Commit-Queue: Omer Katz <omerkatz@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#67803}
    93059842
page-memory-inl.h 2.04 KB