Refactor register allocator a little bit

Refactor register allocator a little bit

R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16998

[haitao.feng, 2013-09-25 07:38:17]

Replaced is_double_(bool) with kind_(enum) in LiveRange.

We are prototyping SIMD  proposal
(https://github.com/johnmccutchan/ecmascript_simd) in V8 and need allocating XMM
registers for SIMD operands. Basically we need to add XMM_REGISTERS kind and
allocate them with DOUBLE_REGISTERS together in the register allocation. When
XMM_REGISTERS spill, we need 16 bytes in the stack and we use LiveRange.Kind()
to distinguish DOUBLE_REGISTER and XMM_REGISTER.

GetNextSpillSlot will be modified to use RegisterKind in the next patchset.

[Jakob Kummerow, 2013-09-25 12:57:32]

lgtm

[haitao.feng, 2013-09-25 14:00:39]

Jakob, thanks for the review.

Patchset 2 is uploaded to change GetNextSpillSlot to use RegisterKind instead of
bool.

[haitao.feng, 2013-09-26 02:48:55]

The git cl said: 

"
The following errors occured:
Base files missing.
Try to upload the changeset again.
"

but I have no problem to see the patches and all the changes are here. Please
let me know if you have issues to review the patchset 3.

[Jakob Kummerow, 2013-09-27 13:19:49]

Patch set 3 LGTM.

[haitao.feng, 2013-09-28 00:48:27]

Committed patchset #3 manually as r16998 (presubmit successful).