Re: [PATCH] Modify combine pattern by anding a pseudo with its nonzero bits

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

On Tue, Nov 30, 2021 at 3:46 AM HAO CHEN GUI <guihaoc@linux.ibm.com> wrote:
>
> Hi,
>
>     This patch modifies the combine pattern with a helper - change_pseudo_and_mask when recog fails. The helper converts a single pseudo to the pseudo and with a mask if the outer operator is IOR/XOR/PLUS and the inner operator is ASHIFT/LSHIFTRT/AND. The conversion helps match shift + ior pattern.
>
>     Bootstrapped and tested on powerpc64-linux BE and LE with no regressions. Is this okay for trunk? Any recommendations? Thanks a lot.
>
> ChangeLog
>
> 2021-11-30 Haochen Gui <guihaoc@linux.ibm.com>
>
> gcc/
>         * combine.c (change_pseudo_and_mask): New.
>         (recog_for_combine): If recog fails, try again with the pattern
>         modified by change_pseudo_and_mask.
>
> gcc/testsuite/
>         * gcc.target/powerpc/20050603-3.c: Modify the dump check conditions.
>         * gcc.target/powerpc/rlwimi-2.c: Likewise.
>
> patch.diff
>
> diff --git a/gcc/combine.c b/gcc/combine.c
> index 03e9a780919..c83c0aceb57 100644
> --- a/gcc/combine.c
> +++ b/gcc/combine.c
> @@ -11539,6 +11539,42 @@ change_zero_ext (rtx pat)
>    return changed;
>  }
>
> +/* When the outer code of set_src is IOR/XOR/PLUS and the inner code is
> +   ASHIFT/LSHIFTRT/AND, convert a psuedo to psuedo AND with a mask if its

^^^ spelling mistake in comment: pseudo not psuedo

Thanks, David

> +   nonzero_bits is less than its mode mask.  */
> +static bool
> +change_pseudo_and_mask (rtx pat)
> +{
> +  bool changed = false;
> +
> +  rtx src = SET_SRC (pat);
> +  if ((GET_CODE (src) == IOR
> +       || GET_CODE (src) == XOR
> +       || GET_CODE (src) == PLUS)
> +      && (((GET_CODE (XEXP (src, 0)) == ASHIFT
> +           || GET_CODE (XEXP (src, 0)) == LSHIFTRT
> +           || GET_CODE (XEXP (src, 0)) == AND)
> +          && REG_P (XEXP (src, 1)))
> +         || ((GET_CODE (XEXP (src, 1)) == ASHIFT
> +              || GET_CODE (XEXP (src, 1)) == LSHIFTRT
> +              || GET_CODE (XEXP (src, 1)) == AND)
> +             && REG_P (XEXP (src, 0)))))
> +    {
> +      rtx *reg = REG_P (XEXP (src, 0))
> +                ? &XEXP (SET_SRC (pat), 0)
> +                : &XEXP (SET_SRC (pat), 1);
> +      machine_mode mode = GET_MODE (*reg);
> +      unsigned HOST_WIDE_INT nonzero = nonzero_bits (*reg, mode);
> +      if (nonzero < GET_MODE_MASK (mode))
> +       {
> +         rtx x = gen_rtx_AND (mode, *reg, GEN_INT (nonzero));
> +         SUBST (*reg, x);
> +         changed = true;
> +       }
> +     }
> +  return changed;
> +}
> +
>  /* Like recog, but we receive the address of a pointer to a new pattern.
>     We try to match the rtx that the pointer points to.
>     If that fails, we may try to modify or replace the pattern,
> @@ -11586,7 +11622,14 @@ recog_for_combine (rtx *pnewpat, rtx_insn *insn, rtx *pnotes)
>             }
>         }
>        else
> -       changed = change_zero_ext (pat);
> +       {
> +         if (change_pseudo_and_mask (pat))
> +           {
> +             maybe_swap_commutative_operands (SET_SRC (pat));
> +             changed = true;
> +           }
> +         changed |= change_zero_ext (pat);
> +       }
>      }
>    else if (GET_CODE (pat) == PARALLEL)
>      {
> diff --git a/gcc/testsuite/gcc.target/powerpc/20050603-3.c b/gcc/testsuite/gcc.target/powerpc/20050603-3.c
> index 4017d34f429..e628be11532 100644
> --- a/gcc/testsuite/gcc.target/powerpc/20050603-3.c
> +++ b/gcc/testsuite/gcc.target/powerpc/20050603-3.c
> @@ -12,7 +12,7 @@ void rotins (unsigned int x)
>    b.y = (x<<12) | (x>>20);
>  }
>
> -/* { dg-final { scan-assembler-not {\mrlwinm} } } */
> +/* { dg-final { scan-assembler-not {\mrlwinm} { target ilp32 } } } */
>  /* { dg-final { scan-assembler-not {\mrldic} } } */
>  /* { dg-final { scan-assembler-not {\mrot[lr]} } } */
>  /* { dg-final { scan-assembler-not {\ms[lr][wd]} } } */
> diff --git a/gcc/testsuite/gcc.target/powerpc/rlwimi-2.c b/gcc/testsuite/gcc.target/powerpc/rlwimi-2.c
> index bafa371db73..ffb5f9e450f 100644
> --- a/gcc/testsuite/gcc.target/powerpc/rlwimi-2.c
> +++ b/gcc/testsuite/gcc.target/powerpc/rlwimi-2.c
> @@ -2,14 +2,14 @@
>  /* { dg-options "-O2" } */
>
>  /* { dg-final { scan-assembler-times {(?n)^\s+[a-z]} 14121 { target ilp32 } } } */
> -/* { dg-final { scan-assembler-times {(?n)^\s+[a-z]} 20217 { target lp64 } } } */
> +/* { dg-final { scan-assembler-times {(?n)^\s+[a-z]} 21279 { target lp64 } } } */
>  /* { dg-final { scan-assembler-times {(?n)^\s+blr} 6750 } } */
>  /* { dg-final { scan-assembler-times {(?n)^\s+mr} 643 { target ilp32 } } } */
>  /* { dg-final { scan-assembler-times {(?n)^\s+mr} 11 { target lp64 } } } */
>  /* { dg-final { scan-assembler-times {(?n)^\s+rldicl} 7790 { target lp64 } } } */
>
>  /* { dg-final { scan-assembler-times {(?n)^\s+rlwimi} 1692 { target ilp32 } } } */
> -/* { dg-final { scan-assembler-times {(?n)^\s+rlwimi} 1666 { target lp64 } } } */
> +/* { dg-final { scan-assembler-times {(?n)^\s+rlwimi} 1692 { target lp64 } } } */
>
>  /* { dg-final { scan-assembler-times {(?n)^\s+mulli} 5036 } } */
>
>