(For X86) Enhancement to add-carray/sub-borrow (adc/sbb) optimization.

(For X86) Enhancement to add-carray/sub-borrow (adc/sbb) optimization.

  The adc/sbb optimization is to able to convert following expression
into a single adc/sbb instruction:
  (ult) ... = x + 1 // where the ult is unsigned-less-than comparison
  (ult) ... = x - 1

  This change is to flip the "x >u y" (i.e. ugt comparison) in order
to expose the adc/sbb opportunity.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167180 91177308-0d34-0410-b5e6-96231b3b80d8