[PATCH] Add support to vectorize ctlz, cttz and powi intrinsics in SLPVectorizer

[Karthik Bhat]

Hi Arnold, Thanks for the review. 
I will update the patch.
Can you also have a look at http://reviews.llvm.org/D3937 which implements vectorization of these intrinsics in Loopvectorizer?

I feel we should commit these 2 as a single revision or alteast one after another. 
isTriviallyVectorizable function in VectorUtils is a common function and used by both SLP and Loop Vectorizer commiting just this patch without handling the intrinsics in LoopVectorizer will result in miscompilation when we try to vectorize these intrinsics inside a loop.

Thanks for your time and inputs.
Regards
Karthik Bhat

http://reviews.llvm.org/D3851