When adding the carry bit to another value on X86, exploit the fact that the carry...

When adding the carry bit to another value on X86, exploit the fact that the carry-materialization
(sbbl x, x) sets the registers to 0 or ~0.  Combined with two's complement arithmetic, we can fold
the intermediate AND and the ADD into a single SUB.

This fixes <rdar://problem/8449754>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114460 91177308-0d34-0410-b5e6-96231b3b80d8