MOD_IGNORE
*modp = mod & ~MOD_IGNORE;
if ((mod1 ^ mod2) & ~MOD_IGNORE & ~MOD_SPECIFIER)
if ((mod1 ^ mod2) & ~MOD_IGNORE & ~MOD_SIGNEDNESS)
diff = (mod1 ^ mod2) & ~MOD_IGNORE;
if ((mod1 ^ mod2) & ~MOD_IGNORE & ~MOD_SIGNEDNESS)