[PATCH] Use rsqrt (X86) to speed up reciprocal square root calcs (PR20900)

[Andrea Di Biagio]

Hi Sanjay,

The changes to the dag combiner and all the x86 specific changes look good to me.
FWIW, the rest of the patch looks good to me too. But you might want to wait to see what Hal thinks.

http://reviews.llvm.org/D5658