MIPS: Support fast case for-in in Crankshaft.

MIPS: Support fast case for-in in Crankshaft.

Port r10794 (654fe910).

Original commit message:

Only JSObject enumerables with enum cache (fast case properties, no interceptors, no enumerable properties on the prototype) are supported.

HLoadKeyedGeneric with keys produced by for-in enumeration are recognized and rewritten into direct property load by index. For this enum-cache was extended to store property indices in a separate array (see handles.cc).

New hydrogen instructions:

- HForInPrepareMap: checks for-in fast case preconditions and returns map that contains enum-cache;
- HForInCacheArray: extracts enum-cache array from the map;
- HCheckMapValue: map check with HValue map instead of immediate;
- HLoadFieldByIndex: load fast property by it's index, positive indexes denote in-object properties, negative - out of object properties;

Changed hydrogen instructions:

- HLoadKeyedFastElement: added hole check suppression for loads from internal FixedArrays that are knows to have no holes inside.

BUG=
TEST=

Committed: https://code.google.com/p/v8/source/detail?r=10865

[kalmard, 2012-02-25 10:07:53]

rebased on r10833.

[kalmard, 2012-02-28 14:32:57]

rebased on r10858.

[Vyacheslav Egorov (Chromium), 2012-02-29 11:58:49]

lgtm

[Vyacheslav Egorov (Chromium), 2012-02-29 12:06:16]

landed