Disable hoisting CheckClass due to excessive deoptimization.

Disable hoisting CheckClass due to excessive deoptimization (issue 16285). Detect that a deoptimization was caused by hoisted check class instruction and disable hoisting of CheckClassInstr for that function. This is a short-term solution to fix excessive deoptimization causing slow start-ups.

R=johnmccutchan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=32460

[Cutch, 2014-02-07 23:07:14]

lgtm

[srdjan, 2014-02-07 23:27:40]

On 2014/02/07 23:07:14, Cutch wrote:
> lgtm

Thee VM crashes unless I disable all LICM. Changed.

[srdjan, 2014-02-08 00:02:31]

Committed patchset #5 manually as r32460 (presubmit successful).

[Florian Schneider, 2014-02-10 09:22:58]

On 2014/02/07 23:27:40, srdjan wrote:
> On 2014/02/07 23:07:14, Cutch wrote:
> > lgtm
> 
> Thee VM crashes unless I disable all LICM. Changed.

This is a known problem. The problem is as follows: Right now, we don't know
which instructions depend on a CheckClass. There is no explicit dependency.
Therefore, you can't selectively disable hoisting for CheckClass only, because
the instructions depending on the CheckClass must not be hoisted as well.

To solve this problem for good we need explicit dependencies in the IL. I think
this would be a good idea in general even though it adds additional overhead to
the IL.