On Thu, May 5, 2022 at 10:07 AM HAO CHEN GUI via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi,
> This patch skips constant folding for fmin/max when either argument
> is sNaN. According to C standard,
> fmin(sNaN, sNaN）= qNaN, fmin(sNaN, NaN) = qNaN
> So signaling NaN should be tested and skipped for fmin/max in match.pd.
>
> Bootstrapped and tested on ppc64 Linux BE and LE with no regressions.
> Is this okay for trunk? Any recommendations? Thanks a lot.
OK.
Thanks,
Richard.
> ChangeLog
>
> 2022-05-05 Haochen Gui <guih...@linux.ibm.com>
>
> gcc/
> PR target/105414
> * match.pd (minmax): Skip constant folding for fmin/fmax when both
> arguments are sNaN or one is sNaN and another is NaN.
>
> gcc/testsuite/
> PR target/105414
> * gcc.dg/pr105414.c: New.
>
> patch.diff
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index cad61848daa..f256bcbb483 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3093,7 +3093,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (for minmax (min max FMIN_ALL FMAX_ALL)
> (simplify
> (minmax @0 @0)
> - @0))
> + /* if both are sNaN, it should return qNaN. */
> + (if (!tree_expr_maybe_signaling_nan_p (@0))
> + @0)))
> /* min(max(x,y),y) -> y. */
> (simplify
> (min:c (max:c @0 @1) @1)
> @@ -3193,12 +3195,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (minmax @1 (convert @2)))))
>
> (for minmax (FMIN_ALL FMAX_ALL)
> - /* If either argument is NaN, return the other one. Avoid the
> - transformation if we get (and honor) a signalling NaN. */
> + /* If either argument is NaN and other one is not sNaN, return the other
> + one. Avoid the transformation if we get (and honor) a signalling NaN.
> */
> (simplify
> (minmax:c @0 REAL_CST@1)
> - (if (real_isnan (TREE_REAL_CST_PTR (@1))
> - && (!HONOR_SNANS (@1) || !TREE_REAL_CST (@1).signalling))
> + (if (real_isnan (TREE_REAL_CST_PTR (@1))
> + && (!HONOR_SNANS (@1) || !TREE_REAL_CST (@1).signalling)
> + && !tree_expr_maybe_signaling_nan_p (@0))
> @0)))
> /* Convert fmin/fmax to MIN_EXPR/MAX_EXPR. C99 requires these
> functions to return the numeric arg if the other one is NaN.
> diff --git a/gcc/testsuite/gcc.dg/pr105414.c b/gcc/testsuite/gcc.dg/pr105414.c
> new file mode 100644
> index 00000000000..78772700acf
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr105414.c
> @@ -0,0 +1,30 @@
> +/* { dg-do run { target { *-*-linux* *-*-gnu* } } } */
> +/* { dg-options "-O1 -fsignaling-nans -lm" } */
> +/* { dg-add-options ieee } */
> +/* { dg-require-effective-target issignaling } */
> +
> +
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <math.h>
> +
> +int main()
> +{
> + double a = __builtin_nans ("");
> +
> + if (issignaling (fmin (a, a)))
> + __builtin_abort ();
> +
> + if (issignaling (fmax (a, a)))
> + __builtin_abort ();
> +
> + double b = __builtin_nan ("");
> +
> + if (issignaling (fmin (a, b)))
> + __builtin_abort ();
> +
> + if (issignaling (fmax (a, b)))
> + __builtin_abort ();
> +
> + return 0;
> +}
