tree 3f5159f03c4898ebd70b4ef0bb5adde07efd9bad
parent f41ecbe01e51da1c1770d4cc361584a44cf2fb3c
author Vyacheslav Egorov <vegorov@google.com> 1546878302 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> 1546878302 +0000

[vm/compiler] Ensure that field is added to guarded fields when Slot::Get uses its guarded properties.

There might be a race between background compiler and mutator where
mutator changes guarded state of the field after Slot was created from
it.

A situation is possible where we have a clone of a field with its
guarded state set to unknown, however Slot::Get for this field returns
a Slot created from the previous clone of the same field with a known
guarded state. In this case we must add *old* clone from which the Slot
was created to guarded fields and not the new clone, because new clone
has no guarded state to begin with and thus
ParsedFunction::AddToGuardedFields(...) would simply ignore it.

Such slots with inconsistent guarded state that are not in the current
list of guarded fields arise due to unsuccessful inlining attempts.
If we built and discard the graph, then guarded fields associated with
that graph are also discarded. However the slot itself stays behind in
the compilation global cache.

TEST=vm/cc/SlotFromGuardedField

Bug: b/121271056
Change-Id: Ib6ee5ec4922c033c3a71bdc46da74ead47b1edd0
Reviewed-on: https://dart-review.googlesource.com/c/88575
Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>