1: The second xor instruction will clear carry flag which
is necessary for following sbb instruction.
2: The select coding for sbb instruction is wrong, the coding
is "sbb dreg_hi,ecx", but what we need is "sbb ecx,dreg_hi".
This patch rewrites the implementation and fixes the errors.
This patch fixes below errors reported by bpf/test_verifier in x32
platform when the jit is enabled: