[PATCH] Improve Cost model for SLPVectorizer when we have a vector division by power of 2

[Andrea Di Biagio]

Patch LGTM. Thanks!

>>! In D4971#33, @karthikthecool wrote:
> Hi Andrea,Sanjay,
> It seems like i missed out on some intresting discussion yesterday.
> Updating the patch addressing Andrea and Sanjay's comments.
> 
> Intrestingly yes UDIV by power of 2 is actually coverted into SRL before it reaches vectorization code so i think checking for UDIV with power of 2 is as good as dead code here. Removed the same.
> 
> Opd1PropInfo,Opd2PropInfo actually doesn't effect cost of Instruction::AShr,Instruction::LShr,Instruction::Add as it is used only by SDIV. Having said that i agree it is incorrect to pass old property while getting the cost although they are not used as of now. So updated it to use OP_None.
> 
> Updated formatting comments given by Sanjay.
> Since now we are only checking for signed division by power of 2 the existing test cases should suffice?
> 
> Thanks again for your interest in the patch. Does this now look good to commit?
> 
> Thanks and Regards
> Karthik Bhat

http://reviews.llvm.org/D4971