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x86 long double: Consider pseudo numbers as signaling

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Add support to treat pseudo-numbers specially and implement x86
version to consider all of them as signaling.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This commit is contained in:
Siddhesh Poyarekar 2020-12-24 07:57:25 +05:30
parent 99468ed45f
commit 7525c1c71d
3 changed files with 69 additions and 3 deletions
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31
sysdeps/generic/nan-pseudo-number.h Normal file
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@ -0,0 +1,31 @@
/* Pseudo-normal number handling. Generic version.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef NAN_PSEUDO_NUMBER_H
#define NAN_PSEUDO_NUMBER_H 1
/* Set this macro and override the definition of IS_PSEUDO_SIGNALING if pseudo
numbers need special handling. */
#define HANDLE_PSEUDO_NUMBERS 0
static inline int
is_pseudo_signaling (uint32_t exi, uint32_t hxi)
{
return 0;
}
#endif /* nan-pseudo-number.h */

11
sysdeps/ieee754/ldbl-96/s_issignalingl.c
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@ -19,12 +19,19 @@
#include <math.h>
#include <math_private.h>
#include <nan-high-order-bit.h>
#include <nan-pseudo-number.h>
int
__issignalingl (long double x)
{
uint32_t exi, hxi, lxi;
GET_LDOUBLE_WORDS (exi, hxi, lxi, x);
/* By default we do not recognize a pseudo NaN as sNaN. However on 80387 and
later all pseudo numbers including pseudo NaNs result in a signal and are
hence recognized as signaling. */
int ret = is_pseudo_signaling (exi, hxi);
#if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
# error not implemented
#else
@ -34,11 +41,9 @@ __issignalingl (long double x)
hxi ^= 0x40000000;
/* If lxi != 0, then set any suitable bit of the significand in hxi. */
hxi |= (lxi | -lxi) >> 31;
/* We do not recognize a pseudo NaN as sNaN; they're invalid on 80387 and
later. */
/* We have to compare for greater (instead of greater or equal), because x's
significand being all-zero designates infinity not NaN. */
return ((exi & 0x7fff) == 0x7fff) && (hxi > 0xc0000000);
return ret || (((exi & 0x7fff) == 0x7fff) && (hxi > 0xc0000000));
#endif
}
libm_hidden_def (__issignalingl)

30
sysdeps/x86/fpu/nan-pseudo-number.h Normal file
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@ -0,0 +1,30 @@
/* Pseudo-normal number handling. x86 version.
Copyright (C) 2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef NAN_PSEUDO_NUMBER_H
#define NAN_PSEUDO_NUMBER_H 1
#define HANDLE_PSEUDO_NUMBERS 1
/* Pseudo numbers on x86 are always signaling. */
static inline int
is_pseudo_signaling (uint32_t exi, uint32_t hxi)
{
return ((exi & 0x7fff) && ((hxi & 0x80000000) == 0));
}
#endif /* nan-pseudo-number.h */