Avoid redundant smi check for Math.abs

Avoid redundant smi check for Math.abs

R=jkummerow@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=16021

[weiliang.lin2, 2013-07-31 14:27:51]

The original commit is https://codereview.chromium.org/21210002/

Hi Jakob, 
Sorry for using another commit entry because I just deleted previous change
list. So when I generate a new change list, it uploads to a new entry. 

The comments are addressed.Thanks a lot for your review and pointed out my
fault. I made a mistake on X64 case and now the new solution is to use a new
function "EmitInteger64MathAbs()" to do it which could avoid SMI tag/untag. And
I also append your test case into the math-abs.js file.

[Jakob Kummerow, 2013-08-01 11:33:38]

LGTM, I'll land.

Next time, when you accidentally delete a local git branch, you can create a new
one and use "git cl issue 21210002" to associate it with an existing code review
issue. Or even easier: you'll probably want to do "git cl patch 21210002" on
that new branch instead, which automatically fetches the last patch set from
that issue, applies it, commits locally, and associates the git branch with that
review issue, so future calls to "git cl upload" will create new patch sets.

[weiliang.lin2, 2013-08-01 13:11:57]

On 2013/08/01 11:33:38, Jakob wrote:
> LGTM, I'll land.
> 
> Next time, when you accidentally delete a local git branch, you can create a
new
> one and use "git cl issue 21210002" to associate it with an existing code
review
> issue. Or even easier: you'll probably want to do "git cl patch 21210002" on
> that new branch instead, which automatically fetches the last patch set from
> that issue, applies it, commits locally, and associates the git branch with
that
> review issue, so future calls to "git cl upload" will create new patch sets.

[weiliang.lin2, 2013-08-01 13:21:53]

On 2013/08/01 11:33:38, Jakob wrote:
> LGTM, I'll land.
> 
> Next time, when you accidentally delete a local git branch, you can create a
new
> one and use "git cl issue 21210002" to associate it with an existing code
review
> issue. Or even easier: you'll probably want to do "git cl patch 21210002" on
> that new branch instead, which automatically fetches the last patch set from
> that issue, applies it, commits locally, and associates the git branch with
that
> review issue, so future calls to "git cl upload" will create new patch sets.

Thanks a lot for your instructions, that is very helpful~

[Jakob Kummerow, 2013-08-02 08:59:10]

Committed patchset #1 manually as r16021 (presubmit successful).