On Thu, 23 Oct 2025, zhaozhou wrote:
> In the 538.imagick_r benchmark of Spec2017, I find these pattern from
> MagickRound function. This patch implements these pattern in match.pd
> for 4 rules:
> 1) (x-floor(x)) < (ceil(x)-x) ? floor(x) : ceil(x) -> floor(x+0.5)
> 2) (x-floor(x)) >= (ceil(x)-x) ? ceil(x) : floor(x) -> floor(x+0.5)
> 3) (ceil(x)-x) > (x-floor(x)) ? floor(x) : ceil(x) -> floor(x+0.5)
> 4) (ceil(x)-x) <= (x-floor(x)) ? ceil(x) : floor(x) -> floor(x+0.5)
>
> The patch implements floor(x+0.5) operation to replace these pattern
> that semantics of round(x) function.
>
> The patch was regtested on aarch64-linux-gnu and x86_64-linux-gnu,
> SPEC 2017 and SPEC 2006 were run:
> As for SPEC 2017, 538.imagick_r benchmark performance increased by 3%+
> in base test of ratio mode.
> As for SPEC 2006, while the transform does not seem to be triggered,
> we also see no non-noise impact on performance.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
Richard.
> gcc/ChangeLog:
>
> * match.pd: Add new pattern for round.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/fold-round-1.c: New test.
> ---
> gcc/match.pd | 21 +++++++++++
> gcc/testsuite/gcc.dg/fold-round-1.c | 56 +++++++++++++++++++++++++++++
> 2 files changed, 77 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/fold-round-1.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index a4248a521cf..f7e074eaa56 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -794,6 +794,27 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (rdiv @0 (negate @1))
> (rdiv (negate @0) @1))
>
> +/* convert semantics of round(x) function to floor(x+0.5). */
> +/* (x-floor(x)) < (ceil(x)-x) ? floor(x) : ceil(x) --> floor(x+0.5). */
> +/* (x-floor(x)) >= (ceil(x)-x) ? ceil(x) : floor(x) --> floor(x+0.5). */
> +/* (ceil(x)-x) > (x-floor(x)) ? floor(x) : ceil(x) --> floor(x+0.5). */
> +/* (ceil(x)-x) <= (x-floor(x)) ? ceil(x) : floor(x) --> floor(x+0.5). */
> +(for op (lt lt lt lt ge ge ge ge)
> + bt (BUILT_IN_FLOORF BUILT_IN_FLOOR BUILT_IN_FLOORL IFN_FLOOR
> + BUILT_IN_CEILF BUILT_IN_CEIL BUILT_IN_CEILL IFN_CEIL)
> + bf (BUILT_IN_CEILF BUILT_IN_CEIL BUILT_IN_CEILL IFN_CEIL
> + BUILT_IN_FLOORF BUILT_IN_FLOOR BUILT_IN_FLOORL IFN_FLOOR)
> + floor (BUILT_IN_FLOORF BUILT_IN_FLOOR BUILT_IN_FLOORL IFN_FLOOR
> + BUILT_IN_FLOORF BUILT_IN_FLOOR BUILT_IN_FLOORL IFN_FLOOR)
> + ceil (BUILT_IN_CEILF BUILT_IN_CEIL BUILT_IN_CEILL IFN_CEIL
> + BUILT_IN_CEILF BUILT_IN_CEIL BUILT_IN_CEILL IFN_CEIL)
> + (simplify
> + (cond (op:c (minus:s SSA_NAME@0 (floor SSA_NAME@0))
> + (minus:s (ceil SSA_NAME@0) SSA_NAME@0))
> + (bt SSA_NAME@0) (bf SSA_NAME@0))
> + (if (!HONOR_SIGNED_ZEROS (type) && !HONOR_SIGN_DEPENDENT_ROUNDING (type))
> + (floor (plus @0 { build_real (type, dconsthalf); })))))
> +
> (if (flag_unsafe_math_optimizations)
> /* Simplify (C / x op 0.0) to x op 0.0 for C != 0, C != Inf/Nan.
> Since C / x may underflow to zero, do this only for unsafe math. */
> diff --git a/gcc/testsuite/gcc.dg/fold-round-1.c
> b/gcc/testsuite/gcc.dg/fold-round-1.c
> new file mode 100644
> index 00000000000..0d7f95429ac
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/fold-round-1.c
> @@ -0,0 +1,56 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast" } */
> +
> +extern void link_error (void);
> +
> +#define TEST_ROUND(TYPE, FFLOOR, FCEIL)
> \
> + void round_##FFLOOR##_1 (TYPE x)
> \
> + {
> \
> + TYPE t1 = 0;
> \
> + TYPE t2 = __builtin_##FFLOOR (x + 0.5);
> \
> + if ((x - __builtin_##FFLOOR (x)) < (__builtin_##FCEIL (x) - x))
> \
> + t1 = __builtin_##FFLOOR (x);
> \
> + else
> \
> + t1 = __builtin_##FCEIL (x);
> \
> + if (t1 != t2)
> \
> + link_error ();
> \
> + }
> \
> + void round_##FFLOOR##_2 (TYPE x)
> \
> + {
> \
> + TYPE t1 = 0;
> \
> + TYPE t2 = __builtin_##FFLOOR (x + 0.5);
> \
> + if ((__builtin_##FCEIL (x) - x) > (x - __builtin_##FFLOOR (x)))
> \
> + t1 = __builtin_##FFLOOR (x);
> \
> + else
> \
> + t1 = __builtin_##FCEIL (x);
> \
> + if (t1 != t2)
> \
> + link_error ();
> \
> + }
> \
> + void round_##FFLOOR##_3 (TYPE x)
> \
> + {
> \
> + TYPE t1 = 0;
> \
> + TYPE t2 = __builtin_##FFLOOR (x + 0.5);
> \
> + if ((__builtin_##FCEIL (x) - x) <= (x - __builtin_##FFLOOR (x)))
> \
> + t1 = __builtin_##FCEIL (x);
> \
> + else
> \
> + t1 = __builtin_##FFLOOR (x);
> \
> + if (t1 != t2)
> \
> + link_error ();
> \
> + }
> \
> + void round_##FFLOOR##_4 (TYPE x)
> \
> + {
> \
> + TYPE t1 = 0;
> \
> + TYPE t2 = __builtin_##FFLOOR (x + 0.5);
> \
> + if ((x - __builtin_##FFLOOR (x)) >= (__builtin_##FCEIL (x) - x))
> \
> + t1 = __builtin_##FCEIL (x);
> \
> + else
> \
> + t1 = __builtin_##FFLOOR (x);
> \
> + if (t1 != t2)
> \
> + link_error ();
> \
> + }
> +
> +TEST_ROUND (float, floorf, ceilf)
> +TEST_ROUND (double, floor, ceil)
> +TEST_ROUND (long double, floorl, ceill)
> +
> +/* { dg-final { scan-assembler-not "link_error" } } */
>
--
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)
