[PATCH] [AArch64] Lower sdiv x, pow2 using add + select + shift.

[Chad Rosier]

Tim,
I gave this a little more thought and I don't think we want to move the BuildSDIV call above the pow2 block.  How would you feel about adding a BuildSDivPow2 function?  The problem is that the pow2 block will never be hit unless I add some ugly logic in both the target-independent and target-dependent (i.e., AArch64) implementations of BuildSDIV to bail when we should perform the pow2 combine.  If I had a BuildSDivPow2 function I would just put it inside the pow2 block before the target-independent implementation.  Please let me know what you think.

 Chad

http://reviews.llvm.org/D4438