Generate something sensible for an [SU]ADDO op when the overflow/carry flag is

the conditional for the BRCOND statement. For instance, it will generate:

    addl %eax, %ecx
    jo LOF

instead of

    addl %eax, %ecx
    ; About 10 instructions to compare the signs of LHS, RHS, and sum.
    jl LOF

llvm-svn: 60123