VM background optimization: Fix another use of the original IC data.

VM background optimization: Fix another use of the original IC data.

The original IC data are only needed when we reference them from the generated code.
EmitMegamorphicInstanceCall does not emit them into the code, but calls
EmitMegamorphicInstanceCall -> ShouldInlineSmiStringHashCode -> NumberOfChecks,
which fails if the mutator thread grows the IC data concurrently.

BUG=
R=vegorov@google.com

Committed: https://github.com/dart-lang/sdk/commit/a8ba557dc96b06f6a479371af32635c783c41e35

[Florian Schneider, 2016-05-19 14:43:07]

fschneider@google.com changed reviewers:
+ vegorov@google.com

[Vyacheslav Egorov (Google), 2016-05-19 14:48:19]

lgtm

[Florian Schneider, 2016-05-19 14:54:58]

Description was changed from

==========
VM background optimization: Fix another use of the original IC data.

The original IC data are only needed when we reference them from the generated
code.
EmitMegamorphicInstanceCall does not emit them into the code, but calls
EmitMegamorphicInstanceCall -> ShouldInlineSmiStringHashCode -> NumberOfChecks,
which fails if the mutator thread grows the IC data concurrently.

BUG=
==========

to

==========
VM background optimization: Fix another use of the original IC data.

The original IC data are only needed when we reference them from the generated
code.
EmitMegamorphicInstanceCall does not emit them into the code, but calls
EmitMegamorphicInstanceCall -> ShouldInlineSmiStringHashCode -> NumberOfChecks,
which fails if the mutator thread grows the IC data concurrently.

BUG=
R=vegorov@google.com

Committed:
https://github.com/dart-lang/sdk/commit/a8ba557dc96b06f6a479371af32635c783c41e35
==========

[Florian Schneider, 2016-05-19 14:55:00]

Committed patchset #1 (id:1) manually as
a8ba557dc96b06f6a479371af32635c783c41e35 (presubmit successful).

[siva, 2016-05-19 15:57:23]

asiva@google.com changed reviewers:
+ asiva@google.com

[siva, 2016-05-19 15:57:23]

I am wondering if we should add a state in these objects that are copied for use
by the back ground compiler and assert that the original objects can only be
accessed by the Mutator thread.