Re: [aarch64] Code-gen for vector initialization involving constants

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

On Wed, 31 May 2023 at 00:23, Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org> writes:
> > Hi Richard,
> > The s32 case for single constant patch doesn't regress now after the
> > above commit.
> > Bootstrapped+tested on aarch64-linux-gnu, and verified that the new
> > tests pass for aarch64_be-linux-gnu.
> > Is it OK to commit ?
> >
> > Thanks,
> > Prathamesh
> >
> > [aarch64] Improve code-gen for vector initialization with single constant element.
> >
> > gcc/ChangeLog:
> >       * config/aarch64/aarc64.cc (aarch64_expand_vector_init): Tweak condition
> >       if (n_var == n_elts && n_elts <= 16) to allow a single constant,
> >       and if maxv == 1, use constant element for duplicating into register.
> >
> > gcc/testsuite/ChangeLog:
> >       * gcc.target/aarch64/vec-init-single-const.c: New test.
> >       * gcc.target/aarch64/vec-init-single-const-be.c: Likewise.
> >       * gcc.target/aarch64/vec-init-single-const-2.c: Likewise.
>
> OK, thanks.
Hi Richard,
Sorry for the delay, I was away on vacation. Committed the patch after
rebasing on ToT, and verifying bootstrap+test passes on
aarch64-linux-gnu:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=9eb757d11746c006c044ff45538b956be7f5859c

Thanks,
Prathamesh
>
> Richard
>
> > diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> > index 5b046d32b37..30d6e3e8d83 100644
> > --- a/gcc/config/aarch64/aarch64.cc
> > +++ b/gcc/config/aarch64/aarch64.cc
> > @@ -22192,7 +22192,7 @@ aarch64_expand_vector_init_fallback (rtx target, rtx vals)
> >       and matches[X][1] with the count of duplicate elements (if X is the
> >       earliest element which has duplicates).  */
> >
> > -  if (n_var == n_elts && n_elts <= 16)
> > +  if (n_var >= n_elts - 1 && n_elts <= 16)
> >      {
> >        int matches[16][2] = {0};
> >        for (int i = 0; i < n_elts; i++)
> > @@ -22209,12 +22209,23 @@ aarch64_expand_vector_init_fallback (rtx target, rtx vals)
> >       }
> >        int maxelement = 0;
> >        int maxv = 0;
> > +      rtx const_elem = NULL_RTX;
> > +      int const_elem_pos = 0;
> > +
> >        for (int i = 0; i < n_elts; i++)
> > -     if (matches[i][1] > maxv)
> > -       {
> > -         maxelement = i;
> > -         maxv = matches[i][1];
> > -       }
> > +     {
> > +       if (matches[i][1] > maxv)
> > +         {
> > +           maxelement = i;
> > +           maxv = matches[i][1];
> > +         }
> > +       if (CONST_INT_P (XVECEXP (vals, 0, i))
> > +           || CONST_DOUBLE_P (XVECEXP (vals, 0, i)))
> > +         {
> > +           const_elem_pos = i;
> > +           const_elem = XVECEXP (vals, 0, i);
> > +         }
> > +     }
> >
> >        /* Create a duplicate of the most common element, unless all elements
> >        are equally useless to us, in which case just immediately set the
> > @@ -22252,8 +22263,19 @@ aarch64_expand_vector_init_fallback (rtx target, rtx vals)
> >            vector register.  For big-endian we want that position to hold
> >            the last element of VALS.  */
> >         maxelement = BYTES_BIG_ENDIAN ? n_elts - 1 : 0;
> > -       rtx x = force_reg (inner_mode, XVECEXP (vals, 0, maxelement));
> > -       aarch64_emit_move (target, lowpart_subreg (mode, x, inner_mode));
> > +
> > +       /* If we have a single constant element, use that for duplicating
> > +          instead.  */
> > +       if (const_elem)
> > +         {
> > +           maxelement = const_elem_pos;
> > +           aarch64_emit_move (target, gen_vec_duplicate (mode, const_elem));
> > +         }
> > +       else
> > +         {
> > +           rtx x = force_reg (inner_mode, XVECEXP (vals, 0, maxelement));
> > +           aarch64_emit_move (target, lowpart_subreg (mode, x, inner_mode));
> > +         }
> >       }
> >        else
> >       {
> > diff --git a/gcc/testsuite/gcc.target/aarch64/vec-init-single-const-2.c b/gcc/testsuite/gcc.target/aarch64/vec-init-single-const-2.c
> > new file mode 100644
> > index 00000000000..f4dcab429c1
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/vec-init-single-const-2.c
> > @@ -0,0 +1,30 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2" } */
> > +
> > +#include <arm_neon.h>
> > +
> > +/* In case where there are no duplicate elements in vector initializer,
> > +   check that the constant is used for duplication.  */
> > +
> > +int8x16_t f_s8(int8_t a0, int8_t a1, int8_t a2, int8_t a3, int8_t a4,
> > +                int8_t a5, int8_t a6, int8_t a7, int8_t a8, int8_t a9,
> > +                int8_t a10, int8_t a11, int8_t a12, int8_t a13, int8_t a14)
> > +{
> > +  return (int8x16_t) { a0, a1, a2, a3, a4, a5, a6, a7,
> > +                       a8, a9, a10, a11, a12, a13, a14, 1 };
> > +}
> > +
> > +int16x8_t f_s16(int16_t a0, int16_t a1, int16_t a2, int16_t a3, int16_t a4,
> > +             int16_t a5, int16_t a6)
> > +{
> > +  return (int16x8_t) { a0, a1, a2, a3, a4, a5, a6, 1 };
> > +}
> > +
> > +int32x4_t f_s32(int32_t a0, int32_t a1, int32_t a2)
> > +{
> > +  return (int32x4_t) { a0, a1, a2, 1 };
> > +}
> > +
> > +/* { dg-final { scan-assembler {\tmovi\tv[0-9]+\.8b, 0x1} } } */
> > +/* { dg-final { scan-assembler {\tmovi\tv[0-9]+\.4h, 0x1} } } */
> > +/* { dg-final { scan-assembler {\tmovi\tv[0-9]+\.2s, 0x1} } } */
> > diff --git a/gcc/testsuite/gcc.target/aarch64/vec-init-single-const-be.c b/gcc/testsuite/gcc.target/aarch64/vec-init-single-const-be.c
> > new file mode 100644
> > index 00000000000..3140e007b5d
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/vec-init-single-const-be.c
> > @@ -0,0 +1,58 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fno-schedule-insns -fno-schedule-insns2" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { be } } } } */
> > +
> > +#include <arm_neon.h>
> > +
> > +/*
> > +** f_s8:
> > +**   dup     v0.16b, w0
> > +**   movi    (v[0-9]+)\.8b, 0x1
> > +**   ins     v0.b\[0\], \1\.b\[0\]
> > +**   ret
> > +*/
> > +
> > +int8x16_t f_s8(int8_t x)
> > +{
> > +  return (int8x16_t) { x, x, x, x, x, x, x, x,
> > +                       x, x, x, x, x, x, x, 1 };
> > +}
> > +
> > +/*
> > +** f_s16:
> > +**   dup     v0.8h, w0
> > +**   movi    (v[0-9]+)\.4h, 0x1
> > +**   ins     v0.h\[0\], \1\.h\[0\]
> > +**   ret
> > +*/
> > +
> > +int16x8_t f_s16(int16_t x)
> > +{
> > +  return (int16x8_t) { x, x, x, x, x, x, x, 1 };
> > +}
> > +
> > +/*
> > +** f_s32:
> > +**   dup     v0.4s, w0
> > +**   movi    (v[0-9]+)\.2s, 0x1
> > +**   ins     v0.s\[0\], \1\.s\[0\]
> > +**   ret
> > +*/
> > +
> > +int32x4_t f_s32(int32_t x)
> > +{
> > +  return (int32x4_t) { x, x, x, 1 };
> > +}
> > +
> > +/*
> > +** f_s64:
> > +**   adrp    x[0-9]+, .LC[0-9]+
> > +**   ldr     q0, \[x[0-9]+, #:lo12:.LC[0-9]+\]
> > +**   ins     v0\.d\[1\], x0
> > +**   ret
> > +*/
> > +
> > +int64x2_t f_s64(int64_t x)
> > +{
> > +  return (int64x2_t) { x, 1 };
> > +}
> > diff --git a/gcc/testsuite/gcc.target/aarch64/vec-init-single-const.c b/gcc/testsuite/gcc.target/aarch64/vec-init-single-const.c
> > new file mode 100644
> > index 00000000000..274b0b39ac4
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/vec-init-single-const.c
> > @@ -0,0 +1,58 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fno-schedule-insns -fno-schedule-insns2" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } } } */
> > +
> > +#include <arm_neon.h>
> > +
> > +/*
> > +** f_s8:
> > +**   dup     v0.16b, w0
> > +**   movi    (v[0-9]+)\.8b, 0x1
> > +**   ins     v0.b\[15\], \1\.b\[0\]
> > +**   ret
> > +*/
> > +
> > +int8x16_t f_s8(int8_t x)
> > +{
> > +  return (int8x16_t) { x, x, x, x, x, x, x, x,
> > +                       x, x, x, x, x, x, x, 1 };
> > +}
> > +
> > +/*
> > +** f_s16:
> > +**   dup     v0.8h, w0
> > +**   movi    (v[0-9]+)\.4h, 0x1
> > +**   ins     v0.h\[7\], \1\.h\[0\]
> > +**   ret
> > +*/
> > +
> > +int16x8_t f_s16(int16_t x)
> > +{
> > +  return (int16x8_t) { x, x, x, x, x, x, x, 1 };
> > +}
> > +
> > +/*
> > +** f_s32:
> > +**   dup     v0.4s, w0
> > +**   movi    (v[0-9]+)\.2s, 0x1
> > +**   ins     v0.s\[3\], \1\.s\[0\]
> > +**   ret
> > +*/
> > +
> > +int32x4_t f_s32(int32_t x)
> > +{
> > +  return (int32x4_t) { x, x, x, 1 };
> > +}
> > +
> > +/*
> > +** f_s64:
> > +**   adrp    x[0-9]+, .LC[0-9]+
> > +**   ldr     q0, \[x[0-9]+, #:lo12:.LC[0-9]+\]
> > +**   ins     v0\.d\[0\], x0
> > +**   ret
> > +*/
> > +
> > +int64x2_t f_s64(int64_t x)
> > +{
> > +  return (int64x2_t) { x, 1 };
> > +}