[PATCH] [SCEV] make SCEV smarter about proving no-wrap.

[Andrew Trick]

> On Mar 3, 2015, at 2:44 PM, Sanjoy Das <sanjoy at playingwithpointers.com> wrote:
> 
> In http://reviews.llvm.org/D7980#133867, @atrick wrote:
> 
>> The logic is great. But we really need to determine whether computing SCEV for each recurrence 5 times is worthwhile. Please do some compile time experiments where SCEV is taking more time than usual to find out how much worse this makes it.
> 
> 
> Sure, I'll run some experiments and measure the compile time.
> 
>> Why did you do this rather than checking SCEV's for existing phis?
> 
> 
> Do you mean just checking the folding set for an _existing_ SCEVAddRec instead of `SE.getAddRecExpr(PreStart, Step, AR->getLoop(), SCEV::FlagAnyWrap)`?  That sounds like a very good idea, I'll try that.

If you can do that, it would be ideal, and you would not need to worry about compile time.

Andy

> http://reviews.llvm.org/D7980
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