On Fri, 18 Oct 2024, Richard Sandiford wrote:
> There are a limited number of existing rules that benefit from
> knowing that a division is exact. Later patches will add more.
OK.
Thanks,
Richard.
> gcc/
> * match.pd: Simplify X / (1 << C) to X /[ex] (1 << C) if the
> low C bits of X are clear
>
> gcc/testsuite/
> * gcc.dg/tree-ssa/cmpexactdiv-6.c: New test.
> ---
> gcc/match.pd | 9 ++++++
> gcc/testsuite/gcc.dg/tree-ssa/cmpexactdiv-6.c | 29 +++++++++++++++++++
> 2 files changed, 38 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/cmpexactdiv-6.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 4aea028a866..b952225b08c 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -5431,6 +5431,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> TYPE_PRECISION (type)), 0))
> (convert @0)))
>
> +#if GIMPLE
> +/* X / (1 << C) -> X /[ex] (1 << C) if the low C bits of X are clear. */
> +(simplify
> + (trunc_div (with_possible_nonzero_bits2 @0) integer_pow2p@1)
> + (if (INTEGRAL_TYPE_P (type)
> + && !TYPE_UNSIGNED (type)
> + && wi::multiple_of_p (get_nonzero_bits (@0), wi::to_wide (@1), SIGNED))
> + (exact_div @0 @1)))
> +#endif
>
> /* (X /[ex] A) * A -> X. */
> (simplify
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/cmpexactdiv-6.c
> b/gcc/testsuite/gcc.dg/tree-ssa/cmpexactdiv-6.c
> new file mode 100644
> index 00000000000..82d517b05ab
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/cmpexactdiv-6.c
> @@ -0,0 +1,29 @@
> +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */
> +
> +typedef __INTPTR_TYPE__ intptr_t;
> +
> +int
> +f1 (int x, int y)
> +{
> + if ((x & 1) || (y & 1))
> + __builtin_unreachable ();
> + x /= 2;
> + y /= 2;
> + return x < y;
> +}
> +
> +int
> +f2 (void *ptr1, void *ptr2, void *ptr3)
> +{
> + ptr1 = __builtin_assume_aligned (ptr1, 4);
> + ptr2 = __builtin_assume_aligned (ptr2, 4);
> + ptr3 = __builtin_assume_aligned (ptr3, 4);
> + intptr_t diff1 = (intptr_t) ptr1 - (intptr_t) ptr2;
> + intptr_t diff2 = (intptr_t) ptr1 - (intptr_t) ptr3;
> + diff1 /= 2;
> + diff2 /= 2;
> + return diff1 < diff2;
> +}
> +
> +/* { dg-final { scan-tree-dump-not {<[a-z]*_div_expr,} "optimized" } } */
> +/* { dg-final { scan-tree-dump-not {<rshift_expr,} "optimized" } } */
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
