------- Additional Comments From uros at kss-loka dot si 2005-05-13 10:07
-------
I think there is another optimization opportunity regarding movzbl following
andl.
Consider this part:
movb (%eax), %al EAX = x...xbbbbbbbb
andl $1, %eax EAX = 0...00000000b
movzbl %al, %eax (not needed)
ret
If the value of the constant to andl operator is less than 2 ^ bit width of the
register we would like to extend, then andl instruction inherently performs
zero-extension.
So if the xorl in comment #5 is moved before andl, we could apply above
simplification to get:
movb (%eax), %al
xorl $1, %eax
andl $1, %eax
ret
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17935
