Re: [PATCH 3/4] rs6000: build constant via li/lis;rldicl/rldicr

[Jiufu Guo <guojiufu@linux.ibm.com>]

Hi,

David Edelsohn <dje.gcc@gmail.com> writes:
>  
> On Wed, Jun 7, 2023 at 9:56 PM Jiufu Guo <guojiufu@linux.ibm.com> wrote:
>
>  Hi,
>
>  This patch checks if a constant is possible left/right cleaned on a rotated
>  value from a negative value of "li/lis".  If so, we can build the constant
>  through "li/lis ; rldicl/rldicr".
>
>  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_lis_and_rldicl): New
>          function.
>          (can_be_built_by_li_lis_and_rldicr): New function.
>          (rs6000_emit_set_long_const): Call can_be_built_by_li_lis_and_rldicr and
>          can_be_built_by_li_lis_and_rldicl.
>
> This is okay.  See below.
>
> Thanks, David
>
>  
>  
>  gcc/testsuite/ChangeLog:
>
>          * gcc.target/powerpc/const-build.c: Add more tests.
>  ---
>   gcc/config/rs6000/rs6000.cc                   | 61 ++++++++++++++++++-
>   .../gcc.target/powerpc/const-build.c          | 44 +++++++++++++
>   2 files changed, 104 insertions(+), 1 deletion(-)
>
>  diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
>  index 03cd9d5e952..2a3fa733b45 100644
>  --- a/gcc/config/rs6000/rs6000.cc
>  +++ b/gcc/config/rs6000/rs6000.cc
>  @@ -10332,6 +10332,61 @@ can_be_built_by_li_lis_and_rotldi (HOST_WIDE_INT c, int *shift,
>     return false;
>   }
>
>  +/* Check if value C can be built by 2 instructions: one is 'li or lis',
>  +   another is rldicl.
>  +
>  +   If so, *SHIFT is set to the shift operand of rldicl, and *MASK is set to
>  +   the mask operand of rldicl, and return true.
>  +   Return false otherwise.  */
>  +
>  +static bool
>  +can_be_built_by_li_lis_and_rldicl (HOST_WIDE_INT c, int *shift,
>  +                                  HOST_WIDE_INT *mask)
>  +{
>  +  /* Leading zeros may be cleaned by rldicl with a mask.  Change leading zeros
>  +     to ones and then recheck it.  */
>  +  int lz = clz_hwi (c);
>  +  HOST_WIDE_INT unmask_c
>  +    = c | (HOST_WIDE_INT_M1U << (HOST_BITS_PER_WIDE_INT - lz));
>  +  int n;
>  +  if (can_be_rotated_to_negative_li (unmask_c, &n)
>
> using can_be_rotated_to_lowbits (~unmask_c, 15, &n)
>
> Maybe Segher would want the abstraction, but it seems more wasteful to
> me.

Thanks! I would update accordingly :)

BR,
Jeff (Jiufu) Guo

>  
>  +      || can_be_rotated_to_negative_lis (unmask_c, &n))
>  +    {
>  +      *mask = HOST_WIDE_INT_M1U >> lz;
>  +      *shift = n == 0 ? 0 : HOST_BITS_PER_WIDE_INT - n;
>  +      return true;
>  +    }
>  +
>  +  return false;
>  +}
>  +
>  +/* Check if value C can be built by 2 instructions: one is 'li or lis',
>  +   another is rldicr.
>  +
>  +   If so, *SHIFT is set to the shift operand of rldicr, and *MASK is set to
>  +   the mask operand of rldicr, and return true.
>  +   Return false otherwise.  */
>  +
>  +static bool
>  +can_be_built_by_li_lis_and_rldicr (HOST_WIDE_INT c, int *shift,
>  +                                  HOST_WIDE_INT *mask)
>  +{
>  +  /* Tailing zeros may be cleaned by rldicr with a mask.  Change tailing zeros
>  +     to ones and then recheck it.  */
>  +  int tz = ctz_hwi (c);
>  +  HOST_WIDE_INT unmask_c = c | ((HOST_WIDE_INT_1U << tz) - 1);
>  +  int n;
>  +  if (can_be_rotated_to_negative_li (unmask_c, &n)
>  +      || can_be_rotated_to_negative_lis (unmask_c, &n))
>  +    {
>  +      *mask = HOST_WIDE_INT_M1U << tz;
>  +      *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.  */
>  @@ -10378,7 +10433,9 @@ 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_lis_and_rotldi (c, &shift, &mask))
>  +  else if (can_be_built_by_li_lis_and_rotldi (c, &shift, &mask)
>  +          || can_be_built_by_li_lis_and_rldicl (c, &shift, &mask)
>  +          || can_be_built_by_li_lis_and_rldicr (c, &shift, &mask))
>       {
>         temp = !can_create_pseudo_p () ? dest : gen_reg_rtx (DImode);
>         unsigned HOST_WIDE_INT imm = (c | ~mask);
>  @@ -10387,6 +10444,8 @@ rs6000_emit_set_long_const (rtx dest, HOST_WIDE_INT c)
>         emit_move_insn (temp, GEN_INT (imm));
>         if (shift != 0)
>          temp = gen_rtx_ROTATE (DImode, temp, GEN_INT (shift));
>  +      if (mask != HOST_WIDE_INT_M1)
>  +       temp = gen_rtx_AND (DImode, temp, GEN_INT (mask));
>         emit_move_insn (dest, temp);
>       }
>     else if (ud3 == 0 && ud4 == 0)
>  diff --git a/gcc/testsuite/gcc.target/powerpc/const-build.c b/gcc/testsuite/gcc.target/powerpc/const-build.c
>  index c38a1dd91f2..8c209921d41 100644
>  --- a/gcc/testsuite/gcc.target/powerpc/const-build.c
>  +++ b/gcc/testsuite/gcc.target/powerpc/const-build.c
>  @@ -46,6 +46,42 @@ lis_rotldi_6 (void)
>     return 0x5310000ffffffff8LL;
>   }
>
>  +long long NOIPA
>  +li_rldicl_7 (void)
>  +{
>  +  return 0x3ffffffa1LL;
>  +}
>  +
>  +long long NOIPA
>  +li_rldicl_8 (void)
>  +{
>  +  return 0xff8531ffffffffLL;
>  +}
>  +
>  +long long NOIPA
>  +lis_rldicl_9 (void)
>  +{
>  +  return 0x00ff85310000ffffLL;
>  +}
>  +
>  +long long NOIPA
>  +li_rldicr_10 (void)
>  +{
>  +  return 0xffff8531fff00000LL;
>  +}
>  +
>  +long long NOIPA
>  +li_rldicr_11 (void)
>  +{
>  +  return 0x21fffffffff00000LL;
>  +}
>  +
>  +long long NOIPA
>  +lis_rldicr_12 (void)
>  +{
>  +  return 0x5310000ffffffff0LL;
>  +}
>  +
>   struct fun arr[] = {
>     {li_rotldi_1, 0x7531000000000LL},
>     {li_rotldi_2, 0x2100000000000064LL},
>  @@ -53,9 +89,17 @@ struct fun arr[] = {
>     {li_rotldi_4, 0x21ffffffffffff94LL},
>     {lis_rotldi_5, 0xffff85310000ffffLL},
>     {lis_rotldi_6, 0x5310000ffffffff8LL},
>  +  {li_rldicl_7, 0x3ffffffa1LL},
>  +  {li_rldicl_8, 0xff8531ffffffffLL},
>  +  {lis_rldicl_9, 0x00ff85310000ffffLL},
>  +  {li_rldicr_10, 0xffff8531fff00000LL},
>  +  {li_rldicr_11, 0x21fffffffff00000LL},
>  +  {lis_rldicr_12, 0x5310000ffffffff0LL},
>   };
>
>   /* { dg-final { scan-assembler-times {\mrotldi\M} 6 } } */
>  +/* { dg-final { scan-assembler-times {\mrldicl\M} 3 } } */
>  +/* { dg-final { scan-assembler-times {\mrldicr\M} 3 } } */
>
>   int
>   main ()
>  -- 
>  2.39.1