Clang 4.0 trunk warns:

warning: logical not is only applied to the left hand side of this bitwise operator [-Wlogical-not-parentheses]

This points to a potential bug if the code really wants to check if the single bit is not set: If for example `(buf.edx >> 9) = 2` (has any bit set except the

least significant one), 'logical not' will return 0 which stays 0 after the 'bitwise and'.

To do this correctly we first need to evaluate the 'bitwise and'. In that case it returns `2 & 1 = 0` which after the 'logical not' evaluates to 1.