https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55906
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Known to work| |10.1.0, 9.1.0
Known to fail| |8.5.0
Status|NEW |RESOLVED
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
In GCC 9+:
ffs:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
movs r3, r0
movs r0, #0
push {r4, lr}
cmp r3, r0
beq .L1
movs r1, #1
.L3:
movs r4, r3
asrs r4, r4, r0
adds r0, r0, #1
tst r4, r1
beq .L3
.L1:
@ sp needed
pop {r4, pc}
So no move after inbetween the loop and the return.
GCC 5-8 produces:
ffs:
movs r3, #0
cmp r0, r3
beq .L2
movs r2, #1
.L3:
movs r1, r0
asrs r1, r1, r3
adds r3, r3, #1
tst r1, r2
beq .L3
.L2:
movs r0, r3
@ sp needed
bx lr
So no extra move there either but GCC 9+ seems better, though using one extra
register.
