Re: [AArch64][testsuite] Adjust vect_copy_lane_1.c for new code-gen

[Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>]

On Sun, 17 Sept 2023 at 20:11, Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
> > Hi,
> > After 27de9aa152141e7f3ee66372647d0f2cd94c4b90, there's a following regression:
> > FAIL: gcc.target/aarch64/vect_copy_lane_1.c scan-assembler-times
> > ins\\tv0.s\\[1\\], v1.s\\[0\\] 3
> >
> > This happens because for the following function from vect_copy_lane_1.c:
> > float32x2_t
> > __attribute__((noinline, noclone)) test_copy_lane_f32 (float32x2_t a,
> > float32x2_t b)
> > {
> >   return vcopy_lane_f32 (a, 1, b, 0);
> > }
> >
> > Before 27de9aa152141e7f3ee66372647d0f2cd94c4b90,
> > it got lowered to following sequence in .optimized dump:
> >   <bb 2> [local count: 1073741824]:
> >   _4 = BIT_FIELD_REF <b_3(D), 32, 0>;
> >   __a_5 = BIT_INSERT_EXPR <a_2(D), _4, 32>;
> >   return __a_5;
> >
> > The above commit simplifies BIT_FIELD_REF + BIT_INSERT_EXPR
> > to vector permutation and now thus gets lowered to:
> >
> >   <bb 2> [local count: 1073741824]:
> >   __a_4 = VEC_PERM_EXPR <a_2(D), b_3(D), { 0, 2 }>;
> >   return __a_4;
> >
> > Since we give higher priority to aarch64_evpc_zip over aarch64_evpc_ins
> > in aarch64_expand_vec_perm_const_1, it now generates:
> >
> > test_copy_lane_f32:
> >         zip1    v0.2s, v0.2s, v1.2s
> >         ret
> >
> > Similarly for test_copy_lane_[us]32.
>
> Yeah, I suppose this choice is at least as good as INS.  It has the advantage
> that the source and destination don't need to be tied.  For example:
>
> int32x2_t f(int32x2_t a, int32x2_t b, int32x2_t c) {
>     return vcopy_lane_s32 (b, 1, c, 0);
> }
>
> used to be:
>
> f:
>         mov     v0.8b, v1.8b
>         ins     v0.s[1], v2.s[0]
>         ret
>
> but is now:
>
> f:
>         zip1    v0.2s, v1.2s, v2.2s
>         ret
>
> > The attached patch adjusts the tests to reflect the change in code-gen
> > and the tests pass.
> > OK to commit ?
> >
> > Thanks,
> > Prathamesh
> >
> > diff --git a/gcc/testsuite/gcc.target/aarch64/vect_copy_lane_1.c b/gcc/testsuite/gcc.target/aarch64/vect_copy_lane_1.c
> > index 2848be564d5..811dc678b92 100644
> > --- a/gcc/testsuite/gcc.target/aarch64/vect_copy_lane_1.c
> > +++ b/gcc/testsuite/gcc.target/aarch64/vect_copy_lane_1.c
> > @@ -22,7 +22,7 @@ BUILD_TEST (uint16x4_t, uint16x4_t, , , u16, 3, 2)
> >  BUILD_TEST (float32x2_t, float32x2_t, , , f32, 1, 0)
> >  BUILD_TEST (int32x2_t,   int32x2_t,   , , s32, 1, 0)
> >  BUILD_TEST (uint32x2_t,  uint32x2_t,  , , u32, 1, 0)
> > -/* { dg-final { scan-assembler-times "ins\\tv0.s\\\[1\\\], v1.s\\\[0\\\]" 3 } } */
> > +/* { dg-final { scan-assembler-times "zip1\\tv0.2s, v0.2s, v1.2s" 3 } } */
> >  BUILD_TEST (int64x1_t,   int64x1_t,   , , s64, 0, 0)
> >  BUILD_TEST (uint64x1_t,  uint64x1_t,  , , u64, 0, 0)
> >  BUILD_TEST (float64x1_t, float64x1_t, , , f64, 0, 0)
>
> OK, thanks.
Thanks, committed to trunk in 98c25cfc79a21886de7342fb563c4eb3c3d5f4e9.

Thanks,
Prathamesh
>
> Richard