https://gcc.gnu.org/bugzilla/show_bug.cgi?id=17935
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
Target Milestone|--- |4.4.0
--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC 4.4.0 produces (which is like future versions of GCC):
bar:
movl 4(%esp), %eax
testb $1, (%eax)
je .L2
xorl %eax, %eax
ret
.L2:
movl 8(%esp), %eax
movb (%eax), %al
xorl $1, %eax
andl $1, %eax
ret
So GCC 4.5.0 and 4.6.0 produces:
bar:
movl 4(%esp), %eax
testb $1, (%eax)
jne .L3
movl 8(%esp), %eax
testb $1, (%eax)
sete %al
ret
.L3:
xorl %eax, %eax
ret
Which is what we want.
GCC 4.7-8.5.0 changed the testb to movb, xor and and:
bar:
.LFB0:
movl 4(%esp), %eax
testb $1, (%eax)
jne .L3
movl 8(%esp), %eax
movb (%eax), %al
xorl $1, %eax
andl $1, %eax
ret
.L3:
xorl %eax, %eax
ret
GCC 9+ changes the xorl to a not:
bar:
movl 4(%esp), %eax
testb $1, (%eax)
jne .L3
movl 8(%esp), %eax
movb (%eax), %al
notl %eax
andl $1, %eax
ret
.L3:
xorl %eax, %eax
ret
So this was fixed back in GCC 4.4.0.
I am not going to look what fixed it either.
