Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
> On Wed, 18 Jan 2023 at 19:59, Richard Sandiford
> <richard.sandif...@arm.com> wrote:
>>
>> Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
>> > On Tue, 17 Jan 2023 at 18:29, Richard Sandiford
>> > <richard.sandif...@arm.com> wrote:
>> >>
>> >> Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
>> >> > Hi Richard,
>> >> > For the following (contrived) test:
>> >> >
>> >> > void foo(int32x4_t v)
>> >> > {
>> >> > v[3] = 0;
>> >> > return v;
>> >> > }
>> >> >
>> >> > -O2 code-gen:
>> >> > foo:
>> >> > fmov s1, wzr
>> >> > ins v0.s[3], v1.s[0]
>> >> > ret
>> >> >
>> >> > I suppose we can instead emit the following code-gen ?
>> >> > foo:
>> >> > ins v0.s[3], wzr
>> >> > ret
>> >> >
>> >> > combine produces:
>> >> > Failed to match this instruction:
>> >> > (set (reg:V4SI 95 [ v ])
>> >> > (vec_merge:V4SI (const_vector:V4SI [
>> >> > (const_int 0 [0]) repeated x4
>> >> > ])
>> >> > (reg:V4SI 97)
>> >> > (const_int 8 [0x8])))
>> >> >
>> >> > So, I wrote the following pattern to match the above insn:
>> >> > (define_insn "aarch64_simd_vec_set_zero<mode>"
>> >> > [(set (match_operand:VALL_F16 0 "register_operand" "=w")
>> >> > (vec_merge:VALL_F16
>> >> > (match_operand:VALL_F16 1 "const_dup0_operand" "w")
>> >> > (match_operand:VALL_F16 3 "register_operand" "0")
>> >> > (match_operand:SI 2 "immediate_operand" "i")))]
>> >> > "TARGET_SIMD"
>> >> > {
>> >> > int elt = ENDIAN_LANE_N (<nunits>, exact_log2 (INTVAL
>> >> > (operands[2])));
>> >> > operands[2] = GEN_INT ((HOST_WIDE_INT) 1 << elt);
>> >> > return "ins\\t%0.<Vetype>[%p2], wzr";
>> >> > }
>> >> > )
>> >> >
>> >> > which now matches the above insn produced by combine.
>> >> > However, in reload dump, it creates a new insn for assigning
>> >> > register to (const_vector (const_int 0)),
>> >> > which results in:
>> >> > (insn 19 8 13 2 (set (reg:V4SI 33 v1 [99])
>> >> > (const_vector:V4SI [
>> >> > (const_int 0 [0]) repeated x4
>> >> > ])) "wzr-test.c":8:1 1269 {*aarch64_simd_movv4si}
>> >> > (nil))
>> >> > (insn 13 19 14 2 (set (reg/i:V4SI 32 v0)
>> >> > (vec_merge:V4SI (reg:V4SI 33 v1 [99])
>> >> > (reg:V4SI 32 v0 [97])
>> >> > (const_int 8 [0x8]))) "wzr-test.c":8:1 1808
>> >> > {aarch64_simd_vec_set_zerov4si}
>> >> > (nil))
>> >> >
>> >> > and eventually the code-gen:
>> >> > foo:
>> >> > movi v1.4s, 0
>> >> > ins v0.s[3], wzr
>> >> > ret
>> >> >
>> >> > To get rid of redundant assignment of 0 to v1, I tried to split the
>> >> > above pattern
>> >> > as in the attached patch. This works to emit code-gen:
>> >> > foo:
>> >> > ins v0.s[3], wzr
>> >> > ret
>> >> >
>> >> > However, I am not sure if this is the right approach. Could you suggest,
>> >> > if it'd be possible to get rid of UNSPEC_SETZERO in the patch ?
>> >>
>> >> The problem is with the "w" constraint on operand 1, which tells LRA
>> >> to force the zero into an FPR. It should work if you remove the
>> >> constraint.
>> > Ah indeed, sorry about that, changing the constrained works.
>>
>> "i" isn't right though, because that's for scalar integers.
>> There's no need for any constraint here -- the predicate does
>> all of the work.
>>
>> > Does the attached patch look OK after bootstrap+test ?
>> > Since we're in stage-4, shall it be OK to commit now, or queue it for
>> > stage-1 ?
>>
>> It needs tests as well. :-)
>>
>> Also:
>>
>> > Thanks,
>> > Prathamesh
>> >
>> >
>> >>
>> >> Also, I think you'll need to use <vwcore>zr for the zero, so that
>> >> it uses xzr for 64-bit elements.
>> >>
>> >> I think this and the existing patterns ought to test
>> >> exact_log2 (INTVAL (operands[2])) >= 0 in the insn condition,
>> >> since there's no guarantee that RTL optimisations won't form
>> >> vec_merges that have other masks.
>> >>
>> >> Thanks,
>> >> Richard
>> >
>> > [aarch64] Use wzr/xzr for assigning 0 to vector element.
>> >
>> > gcc/ChangeLog:
>> > * config/aaarch64/aarch64-simd.md (aarch64_simd_vec_set_zero<mode>):
>> > New pattern.
>> > * config/aarch64/predicates.md (const_dup0_operand): New.
>> >
>> > diff --git a/gcc/config/aarch64/aarch64-simd.md
>> > b/gcc/config/aarch64/aarch64-simd.md
>> > index 104088f67d2..8e54ee4e886 100644
>> > --- a/gcc/config/aarch64/aarch64-simd.md
>> > +++ b/gcc/config/aarch64/aarch64-simd.md
>> > @@ -1083,6 +1083,20 @@
>> > [(set_attr "type" "neon_ins<q>, neon_from_gp<q>,
>> > neon_load1_one_lane<q>")]
>> > )
>> >
>> > +(define_insn "aarch64_simd_vec_set_zero<mode>"
>> > + [(set (match_operand:VALL_F16 0 "register_operand" "=w")
>> > + (vec_merge:VALL_F16
>> > + (match_operand:VALL_F16 1 "const_dup0_operand" "i")
>> > + (match_operand:VALL_F16 3 "register_operand" "0")
>> > + (match_operand:SI 2 "immediate_operand" "i")))]
>> > + "TARGET_SIMD && exact_log2 (INTVAL (operands[2])) >= 0"
>> > + {
>> > + int elt = ENDIAN_LANE_N (<nunits>, exact_log2 (INTVAL (operands[2])));
>> > + operands[2] = GEN_INT ((HOST_WIDE_INT) 1 << elt);
>> > + return "ins\\t%0.<Vetype>[%p2], <vwcore>zr";
>> > + }
>> > +)
>> > +
>> > (define_insn "@aarch64_simd_vec_copy_lane<mode>"
>> > [(set (match_operand:VALL_F16 0 "register_operand" "=w")
>> > (vec_merge:VALL_F16
>> > diff --git a/gcc/config/aarch64/predicates.md
>> > b/gcc/config/aarch64/predicates.md
>> > index ff7f73d3f30..901fa1bd7f9 100644
>> > --- a/gcc/config/aarch64/predicates.md
>> > +++ b/gcc/config/aarch64/predicates.md
>> > @@ -49,6 +49,13 @@
>> > return CONST_INT_P (op) && IN_RANGE (INTVAL (op), 1, 3);
>> > })
>> >
>> > +(define_predicate "const_dup0_operand"
>> > + (match_code "const_vector")
>> > +{
>> > + op = unwrap_const_vec_duplicate (op);
>> > + return CONST_INT_P (op) && rtx_equal_p (op, const0_rtx);
>> > +})
>> > +
>>
>> We already have aarch64_simd_imm_zero for this. aarch64_simd_imm_zero
>> is actually more general, because it works for floating-point modes too.
>>
>> I think the tests should cover all modes included in VALL_F16, since
>> that should have picked up this and the xzr thing.
> Hi Richard,
> Thanks for the suggestions. Does the attached patch look OK ?
> I am not sure how to test for v4bf and v8bf since it seems the compiler
> refuses conversions to/from bfloat16_t ?
>
> Thanks,
> Prathamesh
>
>>
>> Thanks,
>> Richard
>>
>> > (define_predicate "subreg_lowpart_operator"
>> > (ior (match_code "truncate")
>> > (and (match_code "subreg")
>
> [aarch64] Use wzr/xzr for assigning 0 to vector element.
>
> gcc/ChangeLog:
> * config/aaarch64/aarch64-simd.md (aarch64_simd_vec_set_zero<mode>):
> New pattern.
>
> gcc/testsuite/ChangeLog:
> * gcc.target/aarch64/vec-set-zero.c: New test.
>
> diff --git a/gcc/config/aarch64/aarch64-simd.md
> b/gcc/config/aarch64/aarch64-simd.md
> index 7f212bf37cd..7428e74beaf 100644
> --- a/gcc/config/aarch64/aarch64-simd.md
> +++ b/gcc/config/aarch64/aarch64-simd.md
> @@ -1083,6 +1083,20 @@
> [(set_attr "type" "neon_ins<q>, neon_from_gp<q>, neon_load1_one_lane<q>")]
> )
>
> +(define_insn "aarch64_simd_vec_set_zero<mode>"
> + [(set (match_operand:VALL_F16 0 "register_operand" "=w")
> + (vec_merge:VALL_F16
> + (match_operand:VALL_F16 1 "aarch64_simd_imm_zero" "")
> + (match_operand:VALL_F16 3 "register_operand" "0")
> + (match_operand:SI 2 "immediate_operand" "i")))]
> + "TARGET_SIMD && exact_log2 (INTVAL (operands[2])) >= 0"
> + {
> + int elt = ENDIAN_LANE_N (<nunits>, exact_log2 (INTVAL (operands[2])));
> + operands[2] = GEN_INT ((HOST_WIDE_INT) 1 << elt);
> + return "ins\\t%0.<Vetype>[%p2], <vwcore>zr";
> + }
> +)
> +
> (define_insn "@aarch64_simd_vec_copy_lane<mode>"
> [(set (match_operand:VALL_F16 0 "register_operand" "=w")
> (vec_merge:VALL_F16
> diff --git a/gcc/testsuite/gcc.target/aarch64/vec-set-zero.c
> b/gcc/testsuite/gcc.target/aarch64/vec-set-zero.c
> new file mode 100644
> index 00000000000..c260cc9e445
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/vec-set-zero.c
> @@ -0,0 +1,32 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +#include "arm_neon.h"
> +
> +#define FOO(type) \
> +type f_##type(type v) \
> +{ \
> + v[1] = 0; \
> + return v; \
> +}
> +
> +FOO(int8x8_t)
> +FOO(int16x4_t)
> +FOO(int32x2_t)
> +
> +FOO(int8x16_t)
> +FOO(int16x8_t)
> +FOO(int32x4_t)
> +FOO(int64x2_t)
> +
> +FOO(float16x4_t)
> +FOO(float32x2_t)
> +
> +FOO(float16x8_t)
> +FOO(float32x4_t)
> +FOO(float64x2_t)
> +
> +/* { dg-final { scan-assembler-times "ins\\tv\[0-9\]+\.b\\\[\[1\]\\\], wzr"
> 2 } } */
> +/* { dg-final { scan-assembler-times "ins\\tv\[0-9\]+\.h\\\[\[1\]\\\], wzr"
> 4 } } */
> +/* { dg-final { scan-assembler-times "ins\\tv\[0-9\]+\.s\\\[\[1\]\\\], wzr"
> 4 } } */
> +/* { dg-final { scan-assembler-times "ins\\tv\[0-9\]+\.d\\\[\[1\]\\\], xzr"
> 2 } } */
Can you test big-endian too? I'd expect it to use different INS indices.
It might be worth quoting the regexps with {...} rather than "...",
to reduce the number of backslashes needed.
Thanks,
Richard
