Fold away x === null comparisons when propagated cid of x is not kDynamicCid.

Fold away x === null comparisons when propagated cid of x is not kDynamicCid.

Eliminate single operand phis that appear in the graph after constant propagation.

Recognize constructors for _ObjectArray and _GrowableObjectArray.

Fix bug in result cid recognition for List. constructor call. A call with an argument does not guarantee that fixed size array (kArrayCid) is returned.

These changes together allow us to produce better code after inlining of List constructor, otherwise we lose information due to non-specialized control-flow that chooses between _GrowableObjectArray and _ObjectArray.

R=kmillikin@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=14258

[Vyacheslav Egorov (Google), 2012-10-29 19:24:53]

+srdjan 

Additionally I realized that we have a bug in result cid recognition for List.
constructor call. A call with an argument does not guarantee that a fixed size
array (kArrayCid) is returned because an argument can be null and this will be
treated internally as a no argument call.

[Kevin Millikin (Google), 2012-10-30 09:13:59]

lgtm