https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65162
--- Comment #13 from Oleg Endo <olegendo at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #1)
> (In reply to Oleg Endo from comment #0)
> > The following example is taken from libav, which contains quite some uses of
> > this code pattern.
> >
> > typedef unsigned short int uint16_t;
> > union unaligned_16 { uint16_t l; } __attribute__((packed));
> >
> > int
> > test (unsigned char* buf, int bits_per_component)
> > {
> > (((union unaligned_16 *)(buf))->l) =
> > __builtin_bswap16 (bits_per_component == 10 ? 1 : 0);
> >
> > return 0;
> > }
> >
>
> BTW, it should actually translate to something like:
>
> mov r6,r0
> cmp/eq #10,r0
> movt r0
> mov.b r0,@(1,r4)
> mov #0,r0
> rts
> mov.b r0,@r4
>
It's pretty much what GCC 13 produces (with -mlra -ml)
mov r5,r0 ! 51 [c=4 l=2] movsi_i/1
cmp/eq #10,r0 ! 48 [c=4 l=2] cmpeqsi_t/1
movt r0 ! 49 [c=4 l=2] movt
mov #0,r1 ! 11 [c=4 l=2] movsi_i/2
mov.b r0,@(1,r4) ! 29 [c=4 l=2] *movqi_store_mem_disp04/0
mov #0,r0 ! 34 [c=4 l=2] movsi_i/2
rts ! 55 [c=0 l=2] *return_i
mov.b r1,@r4 ! 18 [c=4 l=2] *movqi/5
