[AArch64] Improve SVE dup intrinsics codegen

  Hi,

This patch teaches the aarch64 backend to improve codegen when using dup 
with NEON vectors with repeating patterns. It will attempt to use a 
smaller NEON vector (or element) to limit the number of instructions 
needed to construct the input vector.

Bootstrapped and regression tested  aarch64-none-linux-gnu.

Is his OK for trunk?

gcc/ChangeLog:

         * config/aarch64/aarch64.cc (aarch64_simd_container_mode): Make 
it global.
         * config/aarch64/aarch64-protos.h 
(aarch64_simd_container_mode): Declare it.
         * config/aarch64/aarch64-sve.md (*vec_duplicate<mode>_reg): 
Rename this to ...
         (@aarch64_vec_duplicae_reg_<mode>): ... this.
         * gcc/config/aarch64-sve-builtins-base.cc 
(svdup_lane_impl::expand): Improve codegen when inputs form a repeating 
pattern.

gcc/testsuite/ChangeLog:

         * gcc.target/aarch64/sve/dup_opt.c: New test.
  

"Andre Vieira (lists)" <andre.simoesdiasvieira@arm.com> writes:
> Hi,
>
> This patch teaches the aarch64 backend to improve codegen when using dup 
> with NEON vectors with repeating patterns. It will attempt to use a 
> smaller NEON vector (or element) to limit the number of instructions 
> needed to construct the input vector.

The new sequences definitely look like an improvement.  However, this
change overlaps a bit with what Prathamesh is doing for PR96463.

Stepping back and thinking about how we handle this kind of thing
in general, it might make sense to do the following:

(1) Extend VEC_PERM_EXPR so that it can handle Advanced SIMD inputs
    and SVE outputs (for constant permute indices).  This is part of
    what Prathamesh is doing.

(2a) Add a way for targets to expand such VEC_PERM_EXPRs when the
     arguments are CONSTRUCTORs.  This would only be useful for
     variable-length vectors, since VEC_PERM_EXPRs of CONSTRUCTORs
     should be folded to new CONSTRUCTORs for fixed-length vectors.

(2b) Generalise the SVE handling in aarch64_expand_vector_init
     to cope with general rtx_vector_builders, rather than just
     fixed-length ones, and use it to implement the new hook
     added in (2a).

(3a) Use VEC_PERM_EXPRs of CONSTRUCTORs to simplify or replace the
     duplicate_and_interleave stuff in SLP (think Richi would be glad
     to see this go :-)).

(3b) Make svdupq_impl::fold() lower non-constant inputs to VEC_PERM_EXPRs
     of CONSTRUCTORs.

with (3a) and (3b) being independent from each other.

The advantages of doing things this way are:

* autovectorised SLP code will benefit from the same tricks as svdupq.

* gimple optimisers get to work with the simplified svdupq form.

If you don't want to do that, or wait for it to happen, perhaps
we could short-circuit the process by doing (2b) on its own.
That is, create an interface like:

   void aarch64_expand_vector_init (rtx target, rtx_vector_builder &builder);

Then have svdupq_impl::expand stuff the elements into an
rtx_vector_builder (a bit like svdupq_impl::fold does with a
tree_vector_builder when the elements are constant) and pass the
rtx_vector_builder to this new routine.  Then aarch64_expand_vector_init
would be a home for all the optimisations, using the npatterns/
nelts_per_pattern information where useful.  It would be good if
possible to integrate it with the existing SVE aarch64_expand_vector_init
code.

This would also make it easier to optimise:

svint8_t int8_2(int8_t a, int8_t b)
{
    return svdupq_n_s8(a, b, a, b, a, b, a, b, a, b, a, b, a, b, a, b);
}

to the expected 16-bit dup, even without V2QI being defined.

Thanks,
Richard
    
> Bootstrapped and regression tested  aarch64-none-linux-gnu.
>
> Is his OK for trunk?
>
> gcc/ChangeLog:
>
>          * config/aarch64/aarch64.cc (aarch64_simd_container_mode): Make 
> it global.
>          * config/aarch64/aarch64-protos.h 
> (aarch64_simd_container_mode): Declare it.
>          * config/aarch64/aarch64-sve.md (*vec_duplicate<mode>_reg): 
> Rename this to ...
>          (@aarch64_vec_duplicae_reg_<mode>): ... this.
>          * gcc/config/aarch64-sve-builtins-base.cc 
> (svdup_lane_impl::expand): Improve codegen when inputs form a repeating 
> pattern.
>
> gcc/testsuite/ChangeLog:
>
>          * gcc.target/aarch64/sve/dup_opt.c: New test.
>
> diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
> index 2ac781dff4a93cbe0f0b091147b2521ed1a88750..cfc31b467cf1d3cd79b2dfe6a54e6910dd43b5d8 100644
> --- a/gcc/config/aarch64/aarch64-protos.h
> +++ b/gcc/config/aarch64/aarch64-protos.h
> @@ -771,6 +771,7 @@ int aarch64_branch_cost (bool, bool);
>  enum aarch64_symbol_type aarch64_classify_symbolic_expression (rtx);
>  bool aarch64_advsimd_struct_mode_p (machine_mode mode);
>  opt_machine_mode aarch64_vq_mode (scalar_mode);
> +machine_mode aarch64_simd_container_mode (scalar_mode, poly_int64);
>  opt_machine_mode aarch64_full_sve_mode (scalar_mode);
>  bool aarch64_can_const_movi_rtx_p (rtx x, machine_mode mode);
>  bool aarch64_const_vec_all_same_int_p (rtx, HOST_WIDE_INT);
> diff --git a/gcc/config/aarch64/aarch64-sve-builtins-base.cc b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> index c24c05487246f529f81867d6429e636fd6dc74d0..f8b755a83dc37578363270618323f87c95fa327f 100644
> --- a/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> +++ b/gcc/config/aarch64/aarch64-sve-builtins-base.cc
> @@ -875,13 +875,98 @@ public:
>         argument N to go into architectural lane N, whereas Advanced SIMD
>         vectors are loaded memory lsb to register lsb.  We therefore need
>         to reverse the elements for big-endian targets.  */
> -    rtx vq_reg = gen_reg_rtx (vq_mode);
>      rtvec vec = rtvec_alloc (elements_per_vq);
>      for (unsigned int i = 0; i < elements_per_vq; ++i)
>        {
>  	unsigned int argno = BYTES_BIG_ENDIAN ? elements_per_vq - i - 1 : i;
>  	RTVEC_ELT (vec, i) = e.args[argno];
>        }
> +
> +    /* Look for a repeating pattern in the 128-bit input as that potentially
> +       simplifies constructing the input vector.
> +       For example, codegen for svdupq_n_s32 (a, b, a, b), could be simplified
> +       from:
> +	dup     v0.4s, w0
> +	fmov    s1, w1
> +	ins     v0.s[1], v1.s[0]
> +	ins     v0.s[3], v1.s[0]
> +	dup     z0.q, z0.q[0]
> +       to:
> +	fmov	d0, x0
> +	ins	v0.s[1], w1
> +	mov	z0.d, d0
> +       where we can see it uses a [a, b] input vector reducing the number of
> +       needed instructions.  */
> +    if  (elements_per_vq > 1 && mode == e.vector_mode(0))
> +      {
> +	unsigned int new_elements_n = elements_per_vq;
> +	bool group = true;
> +	while (group && new_elements_n > 1)
> +	  {
> +	    for (unsigned int i = 0; i < new_elements_n / 2; ++i)
> +	      {
> +		if (rtx_equal_p (RTVEC_ELT (vec, i),
> +				 RTVEC_ELT (vec, new_elements_n / 2 + i)) == 0)
> +		  {
> +		    group = false;
> +		    break;
> +		  }
> +	      }
> +	    if (group)
> +	      new_elements_n /= 2;
> +	  }
> +	/* We have found a repeating pattern smaller than 128-bits, so use that
> +	   instead.  */
> +	if (new_elements_n < elements_per_vq)
> +	  {
> +	    unsigned int input_size = 128 / elements_per_vq * new_elements_n;
> +	    scalar_mode new_mode
> +	      = int_mode_for_size (input_size, 0).require ();
> +	    rtx input;
> +	    if (new_elements_n > 1)
> +	      {
> +		if (input_size < 64)
> +		  {
> +		    /* TODO: Remove this when support for 32- and 16-bit vectors
> +		       is added.
> +		       */
> +		    new_elements_n *= 64/input_size;
> +		    input_size = 64;
> +		    new_mode = int_mode_for_size (input_size, 0).require ();
> +		  }
> +		input = gen_reg_rtx (new_mode);
> +		rtvec new_vec = rtvec_alloc (new_elements_n);
> +		for (unsigned int i = 0; i < new_elements_n; ++i)
> +		  RTVEC_ELT (new_vec, i) = RTVEC_ELT (vec, i);
> +
> +		machine_mode merge_mode
> +		  = aarch64_simd_container_mode (element_mode, input_size);
> +
> +		rtx merge_subreg = simplify_gen_subreg (merge_mode, input,
> +							new_mode, 0);
> +		aarch64_expand_vector_init (merge_subreg,
> +					    gen_rtx_PARALLEL (merge_mode,
> +							      new_vec));
> +	      }
> +	    else
> +	      input = simplify_gen_subreg (new_mode, RTVEC_ELT (vec, 0),
> +					   element_mode, 0);
> +	    machine_mode sve_mode
> +	      = aarch64_full_sve_mode (new_mode).require ();
> +
> +	    rtx target = simplify_gen_subreg (sve_mode, e.possible_target,
> +					      mode, 0);
> +
> +	    expand_operand ops[2];
> +	    create_output_operand (&ops[0], target, sve_mode);
> +	    create_fixed_operand (&ops[1], input);
> +	    expand_insn (code_for_aarch64_vec_duplicate_reg (sve_mode), 2,
> +			 ops);
> +	    return e.possible_target;
> +	  }
> +      }
> +
> +    rtx vq_reg = gen_reg_rtx (vq_mode);
>      aarch64_expand_vector_init (vq_reg, gen_rtx_PARALLEL (vq_mode, vec));
>  
>      /* If the result is a boolean, compare the data vector against zero.  */
> diff --git a/gcc/config/aarch64/aarch64-sve.md b/gcc/config/aarch64/aarch64-sve.md
> index bd60e65b0c3f05f1c931f03807170f3b9d699de5..a7d6041bcda03318ff10f6d425889801b9a8fa63 100644
> --- a/gcc/config/aarch64/aarch64-sve.md
> +++ b/gcc/config/aarch64/aarch64-sve.md
> @@ -2508,7 +2508,7 @@ (define_expand "vec_duplicate<mode>"
>  ;; the scalar input gets spilled to memory during RA.  We want to split
>  ;; the load at the first opportunity in order to allow the PTRUE to be
>  ;; optimized with surrounding code.
> -(define_insn_and_split "*vec_duplicate<mode>_reg"
> +(define_insn_and_split "@aarch64_vec_duplicate_reg_<mode>"
>    [(set (match_operand:SVE_ALL 0 "register_operand" "=w, w, w")
>  	(vec_duplicate:SVE_ALL
>  	  (match_operand:<VEL> 1 "aarch64_sve_dup_operand" "r, w, Uty")))
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index f650abbc4ce49cf0947049931f86bad1130c3428..f5e66a43ec5d47e6f5d5540cb41fba0e0e9f92d6 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -301,7 +301,6 @@ static bool aarch64_builtin_support_vector_misalignment (machine_mode mode,
>  							 const_tree type,
>  							 int misalignment,
>  							 bool is_packed);
> -static machine_mode aarch64_simd_container_mode (scalar_mode, poly_int64);
>  static bool aarch64_print_address_internal (FILE*, machine_mode, rtx,
>  					    aarch64_addr_query_type);
>  static HOST_WIDE_INT aarch64_clamp_to_uimm12_shift (HOST_WIDE_INT val);
> @@ -20502,7 +20501,7 @@ aarch64_vq_mode (scalar_mode mode)
>  
>  /* Return appropriate SIMD container
>     for MODE within a vector of WIDTH bits.  */
> -static machine_mode
> +machine_mode
>  aarch64_simd_container_mode (scalar_mode mode, poly_int64 width)
>  {
>    if (TARGET_SVE
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/dup_opt.c b/gcc/testsuite/gcc.target/aarch64/sve/dup_opt.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..66a1fcfb585b2c2b36a1344d4a33811257188dee
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/dup_opt.c
> @@ -0,0 +1,203 @@
> +/* { dg-options { "-O2" } } */
> +/* { dg-final { check-function-bodies "**" "" "" } } */
> +#include <arm_sve.h>
> +
> +/*
> +** float32_0:
> +**	ins	v0.s\[1\], v1.s\[0\]
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +svfloat32_t float32_0(float x, float y)
> +{
> +    return svdupq_n_f32(x, y, x, y);
> +}
> +
> +/*
> +** float32_1:
> +**	mov	z0.s, s0
> +**	ret
> +*/
> +
> +svfloat32_t float32_1(float x)
> +{
> +    return svdupq_n_f32(x, x, x, x);
> +}
> +
> +/*
> +** float16_0:
> +**	ins	v0.h\[1\], v1.h\[0\]
> +**	ins	v0.h\[2\], v2.h\[0\]
> +**	ins	v0.h\[3\], v3.h\[0\]
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svfloat16_t float16_0 (float16_t a, float16_t b, float16_t c, float16_t d)
> +{
> +  return svdupq_n_f16 (a, b, c, d, a, b, c, d);
> +}
> +
> +/*
> +** float16_1:
> +**	dup	v0.4h, v0.h\[0\]
> +**	ins	v0.h\[1\], v1.h\[0\]
> +**	ins	v0.h\[3\], v1.h\[0\]
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svfloat16_t float16_1 (float16_t a, float16_t b)
> +{
> +  return svdupq_n_f16 (a, b, a, b, a, b, a, b);
> +}
> +
> +/*
> +** float16_2:
> +**	mov	z0.h, h0
> +**	ret
> +*/
> +
> +svfloat16_t float16_2 (float16_t a)
> +{
> +  return svdupq_n_f16 (a, a, a, a, a, a, a, a);
> +}
> +
> +/*
> +** int64_0:
> +**	mov	z0.d, x0
> +**	ret
> +*/
> +
> +svint64_t int64_0 (int64_t a)
> +{
> +    return svdupq_n_s64 (a, a);
> +}
> +
> +/*
> +** int32_0:
> +**	fmov	d0, x0
> +**	ins	v0.s\[1\], w1
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svuint32_t int32_0(uint32_t a, uint32_t b) {
> +    return svdupq_n_u32(a, b, a, b);
> +}
> +
> +/*
> +** int32_1:
> +**	mov	z0.s, w0
> +**	ret
> +*/
> +
> +svint32_t int32_1(int32_t a)
> +{
> +    return svdupq_n_s32(a, a, a, a);
> +}
> +
> +/*
> +** int16_0:
> +**	...
> +**	fmov	d0, x0
> +**	ins	v0.h\[1\], w1
> +**	ins	v0.h\[2\], w2
> +**	ins	v0.h\[3\], w3
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svint16_t int16_0(int16_t a, int16_t b, int16_t c, int16_t d)
> +{
> +    return svdupq_n_s16(a, b, c, d, a, b, c, d);
> +}
> +
> +/*
> +** int16_1:
> +**	dup	v0.4h, w0
> +**	ins	v0.h\[1\], w1
> +**	ins	v0.h\[3\], w1
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svuint16_t int16_1(uint16_t a, uint16_t b)
> +{
> +    return svdupq_n_u16(a, b, a, b, a, b, a, b);
> +}
> +
> +/*
> +** int16_2:
> +**	mov	z0.h, w0
> +**	ret
> +*/
> +
> +svint16_t int16_2(int16_t a)
> +{
> +    return svdupq_n_s16(a, a, a, a, a, a, a, a);
> +}
> +/*
> +** int8_0:
> +**	...
> +**	fmov	d0, x0
> +**	ins	v0.b\[1\], w1
> +**	ins	v0.b\[2\], w2
> +**	ins	v0.b\[3\], w3
> +**	ins	v0.b\[4\], w4
> +**	ins	v0.b\[5\], w5
> +**	ins	v0.b\[6\], w6
> +**	ins	v0.b\[7\], w7
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svuint8_t int8_0(uint8_t a, uint8_t b, uint8_t c, uint8_t d, uint8_t e, uint8_t f, uint8_t g, uint8_t h)
> +{
> +    return svdupq_n_u8(a, b, c, d, e, f, g, h, a, b, c, d, e, f, g, h);
> +}
> +
> +/*
> +** int8_1:
> +**	dup	v0.8b, w0
> +**	ins	v0.b\[1\], w1
> +**	ins	v0.b\[2\], w2
> +**	ins	v0.b\[3\], w3
> +**	ins	v0.b\[5\], w1
> +**	ins	v0.b\[6\], w2
> +**	ins	v0.b\[7\], w3
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svint8_t int8_1(int8_t a, int8_t b, int8_t c, int8_t d)
> +{
> +    return svdupq_n_s8(a, b, c, d, a, b, c, d, a, b, c, d, a, b, c, d);
> +}
> +
> +/*
> +** int8_2:
> +**	dup	v0.8b, w0
> +**	ins	v0.b\[1\], w1
> +**	ins	v0.b\[3\], w1
> +**	ins	v0.b\[5\], w1
> +**	ins	v0.b\[7\], w1
> +**	mov	z0.d, d0
> +**	ret
> +*/
> +
> +svint8_t int8_2(int8_t a, int8_t b)
> +{
> +    return svdupq_n_s8(a, b, a, b, a, b, a, b, a, b, a, b, a, b, a, b);
> +}
> +
> +/*
> +** int8_3:
> +**	mov	z0.b, w0
> +**	ret
> +*/
> +
> +svint8_t int8_3(int8_t a)
> +{
> +    return svdupq_n_s8(a, a, a, a, a, a, a, a, a, a, a, a, a, a, a, a);
> +}