• Leszek Swirski's avatar
    [compiler] Remove disallow scopes · a6f465d4
    Leszek Swirski authored
    TurboFan creates DisallowHeapAccess scopes, to prevent heap access in
    the concurrent parts of the compiler. Then, for parts of the compiler
    that do want to access the heap, it either creates Allow* scopes (which
    should be avoided since they "punch a hole" in the Disallow* scopes), or
    relies on a weakening of Handle::IsDereferenceAllowed which allows
    handles owned by a LocalHeap to be dereferenced even if there is a
    DisallowHeapDereference scope.
    
    This patch:
    
      a) Strengthens the implicit requirements around handle dereferencing
         to require a running heap on this thread (either main-thread heap
         or an un-parked, un-safepointed LocalHeap).
      b) Removes the overly strict Disallow scopes in TurboFan, relying
         instead on implicit requirements for allocation/handle
         dereferencing in off-thread code.
      c) Cleans up the "should_disallow_heap_access" predicate to be more
         explicit about what should be disallowed (e.g. property accesses
         can't be computed concurrently)
    
    Change-Id: Icb56b7764913ac17e2db197a70bb189af88a6978
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2554617
    Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    Auto-Submit: Leszek Swirski <leszeks@chromium.org>
    Reviewed-by: 's avatarDominik Inführ <dinfuehr@chromium.org>
    Reviewed-by: 's avatarGeorg Neis <neis@chromium.org>
    Reviewed-by: 's avatarSantiago Aboy Solanes <solanes@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#71600}
    a6f465d4
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