Re: Ping^2 [PATCH V5 1/4] rs6000: build constant via li;rotldi

[David Edelsohn <dje.gcc@gmail.com>]

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On Mon, Sep 25, 2023 at 10:52 PM Jiufu Guo <guojiufu@linux.ibm.com> wrote:

> Hi,
>
> Gentle ping...
>
> BR,
> Jeff (Jiufu Guo)
>

This is okay.

Thanks, David


>
> Jiufu Guo via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>
> > Hi,
> >
> > Gentle ping...
> >
> > BR,
> > Jeff (Jiufu Guo)
> >
> > Jiufu Guo <guojiufu@linux.ibm.com> writes:
> >
> >> Hi,
> >>
> >> If a constant is possible to be rotated to/from a positive or negative
> >> value which "li" can generated, then "li;rotldi" can be used to build
> >> the constant.
> >>
> >> Compare with the previous version:
> >> https://gcc.gnu.org/pipermail/gcc-patches/2023-July/623528.html
> >> This patch just did minor changes to the comments according to previous
> >> review.
> >>
> >> Bootstrap and regtest pass on ppc64{,le}.
> >>
> >> Is this ok for trunk?
> >>
> >>
> >> BR,
> >> Jeff (Jiufu)
> >>
> >> gcc/ChangeLog:
> >>
> >>      * config/rs6000/rs6000.cc (can_be_built_by_li_and_rotldi): New
> function.
> >>      (rs6000_emit_set_long_const): Call can_be_built_by_li_and_rotldi.
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >>      * gcc.target/powerpc/const-build.c: New test.
> >> ---
> >>  gcc/config/rs6000/rs6000.cc                   | 47 +++++++++++++--
> >>  .../gcc.target/powerpc/const-build.c          | 57 +++++++++++++++++++
> >>  2 files changed, 98 insertions(+), 6 deletions(-)
> >>  create mode 100644 gcc/testsuite/gcc.target/powerpc/const-build.c
> >>
> >> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> >> index 42f49e4a56b..acc332acc05 100644
> >> --- a/gcc/config/rs6000/rs6000.cc
> >> +++ b/gcc/config/rs6000/rs6000.cc
> >> @@ -10258,6 +10258,31 @@ rs6000_emit_set_const (rtx dest, rtx source)
> >>    return true;
> >>  }
> >>
> >> +/* Check if value C can be built by 2 instructions: one is 'li',
> another is
> >> +   'rotldi'.
> >> +
> >> +   If so, *SHIFT is set to the shift operand of rotldi(rldicl), and
> *MASK
> >> +   is set to the mask operand of rotldi(rldicl), and return true.
> >> +   Return false otherwise.  */
> >> +
> >> +static bool
> >> +can_be_built_by_li_and_rotldi (HOST_WIDE_INT c, int *shift,
> >> +                               HOST_WIDE_INT *mask)
> >> +{
> >> +  /* If C or ~C contains at least 49 successive zeros, then C can be
> rotated
> >> +     to/from a positive or negative value that 'li' is able to load.
> */
> >> +  int n;
> >> +  if (can_be_rotated_to_lowbits (c, 15, &n)
> >> +      || can_be_rotated_to_lowbits (~c, 15, &n))
> >> +    {
> >> +      *mask = HOST_WIDE_INT_M1;
> >> +      *shift = HOST_BITS_PER_WIDE_INT - n;
> >> +      return true;
> >> +    }
> >> +
> >> +  return false;
> >> +}
> >> +
> >>  /* Subroutine of rs6000_emit_set_const, handling PowerPC64 DImode.
> >>     Output insns to set DEST equal to the constant C as a series of
> >>     lis, ori and shl instructions.  */
> >> @@ -10266,15 +10291,14 @@ static void
> >>  rs6000_emit_set_long_const (rtx dest, HOST_WIDE_INT c)
> >>  {
> >>    rtx temp;
> >> +  int shift;
> >> +  HOST_WIDE_INT mask;
> >>    HOST_WIDE_INT ud1, ud2, ud3, ud4;
> >>
> >>    ud1 = c & 0xffff;
> >> -  c = c >> 16;
> >> -  ud2 = c & 0xffff;
> >> -  c = c >> 16;
> >> -  ud3 = c & 0xffff;
> >> -  c = c >> 16;
> >> -  ud4 = c & 0xffff;
> >> +  ud2 = (c >> 16) & 0xffff;
> >> +  ud3 = (c >> 32) & 0xffff;
> >> +  ud4 = (c >> 48) & 0xffff;
> >>
> >>    if ((ud4 == 0xffff && ud3 == 0xffff && ud2 == 0xffff && (ud1 &
> 0x8000))
> >>        || (ud4 == 0 && ud3 == 0 && ud2 == 0 && ! (ud1 & 0x8000)))
> >> @@ -10305,6 +10329,17 @@ rs6000_emit_set_long_const (rtx dest,
> HOST_WIDE_INT c)
> >>        emit_move_insn (dest, gen_rtx_XOR (DImode, temp,
> >>                                       GEN_INT ((ud2 ^ 0xffff) << 16)));
> >>      }
> >> +  else if (can_be_built_by_li_and_rotldi (c, &shift, &mask))
> >> +    {
> >> +      temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
> >> +      unsigned HOST_WIDE_INT imm = (c | ~mask);
> >> +      imm = (imm >> shift) | (imm << (HOST_BITS_PER_WIDE_INT - shift));
> >> +
> >> +      emit_move_insn (temp, GEN_INT (imm));
> >> +      if (shift != 0)
> >> +    temp = gen_rtx_ROTATE (DImode, temp, GEN_INT (shift));
> >> +      emit_move_insn (dest, temp);
> >> +    }
> >>    else if (ud3 == 0 && ud4 == 0)
> >>      {
> >>        temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
> >> diff --git a/gcc/testsuite/gcc.target/powerpc/const-build.c
> b/gcc/testsuite/gcc.target/powerpc/const-build.c
> >> new file mode 100644
> >> index 00000000000..69b37e2bb53
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.target/powerpc/const-build.c
> >> @@ -0,1 +1,57 @@
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -save-temps" } */
> >> +/* { dg-require-effective-target has_arch_ppc64 } */
> >> +
> >> +/* Verify that two instructions are successfully used to build
> constants.
> >> +   One insn is li, another is rotate: rldicl.  */
> >> +
> >> +#define NOIPA __attribute__ ((noipa))
> >> +
> >> +struct fun
> >> +{
> >> +  long long (*f) (void);
> >> +  long long val;
> >> +};
> >> +
> >> +long long NOIPA
> >> +li_rotldi_1 (void)
> >> +{
> >> +  return 0x7531000000000LL;
> >> +}
> >> +
> >> +long long NOIPA
> >> +li_rotldi_2 (void)
> >> +{
> >> +  return 0x2100000000000064LL;
> >> +}
> >> +
> >> +long long NOIPA
> >> +li_rotldi_3 (void)
> >> +{
> >> +  return 0xffff8531ffffffffLL;
> >> +}
> >> +
> >> +long long NOIPA
> >> +li_rotldi_4 (void)
> >> +{
> >> +  return 0x21ffffffffffff94LL;
> >> +}
> >> +
> >> +struct fun arr[] = {
> >> +  {li_rotldi_1, 0x7531000000000LL},
> >> +  {li_rotldi_2, 0x2100000000000064LL},
> >> +  {li_rotldi_3, 0xffff8531ffffffffLL},
> >> +  {li_rotldi_4, 0x21ffffffffffff94LL},
> >> +};
> >> +
> >> +/* { dg-final { scan-assembler-times {\mrotldi\M} 4 } } */
> >> +
> >> +int
> >> +main ()
> >> +{
> >> +  for (int i = 0; i < sizeof (arr) / sizeof (arr[0]); i++)
> >> +    if ((*arr[i].f) () != arr[i].val)
> >> +      __builtin_abort ();
> >> +
> >> +  return 0;
> >> +}
>