Match the InstCombine form of rotates by X+C

InstCombine converts (sub 32, (add X, C)) into (sub 32-C, X),
so a rotate left of a 32-bit Y by X+C could appear as either:

   (or (shl Y, (add X, C)), (shr Y, (sub 32, (add X, C))))

without InstCombine or:

   (or (shl Y, (add X, C)), (shr Y, (sub 32-C, X)))

with it.

We already matched the first form.  This patch handles the second too.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198860 91177308-0d34-0410-b5e6-96231b3b80d8