On Thu, 2 Jan 2025, 赵洲 wrote:
> Add Reviewer Richard Biener.
>
>
> > -----原始邮件-----
> > 发件人: "Zhou Zhao" <zhaoz...@loongson.cn>
> > 发送时间:2025-01-02 19:37:07 (星期四)
> > 收件人: gcc-patches@gcc.gnu.org
> > 抄送: xry...@xry111.site, i...@xen0n.name, chengl...@loongson.cn,
> > xucheng...@loongson.cn, zhaoz...@loongson.cn
> > 主题: [PATCH] match.pd: Fold pattern of round semantics.
> >
> > This patch implements 4 rules for semantics of round func in match.pd under
> > -funsafe-math-optimizations:
> > 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 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.
> > OK for mainline?
> >
> > gcc/ChangeLog:
> >
> > * match.pd: Add new pattern for round.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.dg/fold-round-1.c: New test.
> > ---
> > gcc/match.pd | 27 ++++++++++++++
> > gcc/testsuite/gcc.dg/fold-round-1.c | 56 +++++++++++++++++++++++++++++
> > 2 files changed, 83 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.dg/fold-round-1.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index 83eca8b2e0a..7b22b7913ac 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -777,6 +777,33 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > (rdiv @0 (negate @1))
> > (rdiv (negate @0) @1))
> >
> > +(if (flag_unsafe_math_optimizations)
> > +/* 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) */
I think you should be able to merge the cases for swapped compares
by just matching (cond (op:c (...)).
I do wonder about the compares itself though, (x-floor(x)) < (ceil(x)-x)
isn't that true exactly when x > 0? With flag_unsafe_optimizations
< vs. <= and thus x not having a fractional component would be
unimportant. That said, wouldn't we expect the compares to be
simplified?
I'm also curious where you got these expressions to be simplified from?
Note we're in stage3 so unless this fixes a bug it isn't appropriate
at this stage and should be re-posted/pinged when stage1 opens for
GCC 16.
Richard.
> > +(for op (lt ge)
> > + bt (FLOOR CEIL)
> > + bf (CEIL FLOOR)
> > + floor (FLOOR FLOOR)
> > + ceil (CEIL CEIL)
> > + (simplify
> > + (cond (op (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))
> > + (floor (plus @0 { build_real (type, dconsthalf); }))))
> > +(for op (gt le)
> > + bt (FLOOR CEIL)
> > + bf (CEIL FLOOR)
> > + floor (FLOOR FLOOR)
> > + ceil (CEIL CEIL)
> > + (simplify
> > + (cond (op (minus:s (ceil SSA_NAME@0) SSA_NAME@0)
> > + (minus:s SSA_NAME@0 (floor SSA_NAME@0)))
> > + (bt SSA_NAME@0) (bf SSA_NAME@0))
> > + (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..845d6d2e475
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/fold-round-1.c
> > @@ -0,0 +1,56 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-Ofast -funsafe-math-optimizations" } */
> > +
> > +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" } } */
> > --
> > 2.20.1
>
>
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--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
