[llvm] r179111 - Revert r176408 and r176407 to address PR15540.

[Shuxin Yang]

On 4/13/13 11:33 PM, Nuno Lopes wrote:
> Shuxin,
>
> My vision of the events is slightly different than yours.
> It's true that I introduced the bug in the first place. I then 
> acknowledged your work in tracking the underlying root cause of it, 
> which was a misinterpretation on my end of the required semantics of 
> Basic AA.
> You committed a fix, but in my understanding that was a hack, and not 
> a real solution.  I then introduced getUnderlyingObjectSize(), which 
> has the semantics that BasicAA requires. It's a superior solution than 
> your patch that tries to work around the mismatch in the semantics of 
> getObjectSize() and what Basic AA requires.
> And btw, r176407 is not at fault in the compile time regression.
>
> So far so good. The problem is that you kept insisting my solution was 
> wrong without giving any technical explanation. You became extremely 
> aggressive, and therefore I stop paying attention.
> If you give me a technical reason why r176407 is wrong, then I'll 
> surely back off and apologize.  Otherwise I'll keep insisting that 
> r176407 is the real fix.

I think your wording is bit interesting. When did I say r176407 is 
wrong? Please paste my mail to the list.

I did have some little concern about the 176407 at the beginning you 
commit your change. As it, combined with your next revision,
it walk along the SSA, each time alias is queried.  Yi's report prove my 
concerns.

It seems you are insist on the 176407. You state it is "required" in 
your previous mail.
Now that you are so sure about your change, why not show us some data 
proving how much
speedup you achieve at what cost?