My commit bdb0c43c7 optimized the encoding of instructions to test
tag bits, but it did not always set exactly the same condition codes
since the testb instruction does a single-byte comparison, rather
than a full-word comparison.
It would be correct to optimize the expression x .&. 128 > 0 to
testb $128, %al seta %al ; note: 'a' for unsigned comparison, ; not 'g' for signed comparison
but the pretty-printer is not the right place to make this kind of