On Fri, 4 Jun 2021 at 13:15, Christophe Lyon <christophe.l...@linaro.org> wrote:
>
> On Fri, 4 Jun 2021 at 09:27, Prathamesh Kulkarni via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > Hi,
> > As mentioned in PR, for the following test-case:
> >
> > #include <arm_neon.h>
> >
> > bfloat16x4_t f1 (bfloat16_t a)
> > {
> > return vdup_n_bf16 (a);
> > }
> >
> > bfloat16x4_t f2 (bfloat16_t a)
> > {
> > return (bfloat16x4_t) {a, a, a, a};
> > }
> >
> > Compiling with arm-linux-gnueabi -O3 -mfpu=neon -mfloat-abi=softfp
> > -march=armv8.2-a+bf16+fp16 results in f2 not being vectorized:
> >
> > f1:
> > vdup.16 d16, r0
> > vmov r0, r1, d16 @ v4bf
> > bx lr
> >
> > f2:
> > mov r3, r0 @ __bf16
> > adr r1, .L4
> > ldrd r0, [r1]
> > mov r2, r3 @ __bf16
> > mov ip, r3 @ __bf16
> > bfi r1, r2, #0, #16
> > bfi r0, ip, #0, #16
> > bfi r1, r3, #16, #16
> > bfi r0, r2, #16, #16
> > bx lr
> >
> > This seems to happen because vec_init pattern in neon.md has VDQ mode
> > iterator, which doesn't include V4BF. In attached patch, I changed
> > mode
> > to VDQX which seems to work for the test-case, and the compiler now
> > generates:
> >
> > f2:
> > vdup.16 d16, r0
> > vmov r0, r1, d16 @ v4bf
> > bx lr
> >
> > However, the pattern is also gated on TARGET_HAVE_MVE and I am not
> > sure if either VDQ or VDQX are correct modes for MVE since MVE has
> > only 128-bit vectors ?
> >
>
> I think patterns common to both Neon and MVE should be moved to
> vec-common.md, I don't know why such patterns were left in neon.md.
Since we end up calling neon_expand_vector_init for both NEON and MVE,
I am not sure if we should separate the pattern ?
Would it make sense to FAIL if the mode size isn't 16 bytes for MVE as
in attached patch so
it will call neon_expand_vector_init only for 128-bit vectors ?
Altho hard-coding 16 in the pattern doesn't seem a good idea to me either.Thanks, Prathamesh > > That being said, I suggest you look at other similar patterns in > vec-common.md, most of which are gated on > ARM_HAVE_<MODE>_ARITH > and possibly beware of issues with iwmmxt :-) > > Christophe > > > Thanks, > > Prathamesh
pr98435-2.diff
Description: Binary data
