[v3,1/2] x86 long double: Consider pseudo numbers as signaling
Commit Message
Add support to treat pseudo-numbers specially and implement x86
version to consider all of them as signaling.
---
sysdeps/generic/nan-pseudo-number.h | 32 ++++++++++++++++++++++++
sysdeps/ieee754/ldbl-96/s_issignalingl.c | 11 +++++---
sysdeps/x86/fpu/nan-pseudo-number.h | 30 ++++++++++++++++++++++
3 files changed, 70 insertions(+), 3 deletions(-)
create mode 100644 sysdeps/generic/nan-pseudo-number.h
create mode 100644 sysdeps/x86/fpu/nan-pseudo-number.h
Comments
On 23/12/2020 23:45, Siddhesh Poyarekar wrote:
> Add support to treat pseudo-numbers specially and implement x86
> version to consider all of them as signaling.
Ok with the above changes.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> sysdeps/generic/nan-pseudo-number.h | 32 ++++++++++++++++++++++++
> sysdeps/ieee754/ldbl-96/s_issignalingl.c | 11 +++++---
> sysdeps/x86/fpu/nan-pseudo-number.h | 30 ++++++++++++++++++++++
> 3 files changed, 70 insertions(+), 3 deletions(-)
> create mode 100644 sysdeps/generic/nan-pseudo-number.h
> create mode 100644 sysdeps/x86/fpu/nan-pseudo-number.h
>
> diff --git a/sysdeps/generic/nan-pseudo-number.h b/sysdeps/generic/nan-pseudo-number.h
> new file mode 100644
> index 0000000000..1562e06e4b
> --- /dev/null
> +++ b/sysdeps/generic/nan-pseudo-number.h
> @@ -0,0 +1,32 @@
> +/* 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 __attribute__ ((unused)),
> + uint32_t hxi __attribute__ ((unused)))
> +{
> + return 0;
> +}
> +
> +#endif /* nan-pseudo-number.h */
Afaik, there is no need to __attribute__ ((unused)) on arguments for static
inline functions.
> diff --git a/sysdeps/ieee754/ldbl-96/s_issignalingl.c b/sysdeps/ieee754/ldbl-96/s_issignalingl.c
> index ec542ad468..37e05aa259 100644
> --- a/sysdeps/ieee754/ldbl-96/s_issignalingl.c
> +++ b/sysdeps/ieee754/ldbl-96/s_issignalingl.c
> @@ -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)
Ok.
> diff --git a/sysdeps/x86/fpu/nan-pseudo-number.h b/sysdeps/x86/fpu/nan-pseudo-number.h
> new file mode 100644
> index 0000000000..ea43b175a1
> --- /dev/null
> +++ b/sysdeps/x86/fpu/nan-pseudo-number.h
> @@ -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 */
>
Ok.
On Thu, 24 Dec 2020, Siddhesh Poyarekar via Libc-alpha wrote:
> diff --git a/sysdeps/generic/nan-pseudo-number.h b/sysdeps/generic/nan-pseudo-number.h
I don't think this belongs in sysdeps/generic/. The "pseudo-number"
concept is specific to the ldbl-96 format; a "generic" header is really
something specific to ldbl-96 and so should go in sysdeps/ieee754/ldbl-96/
instead. (x86 and m68k have different rules regarding what encodings are
valid. ia64 manuals seem to suggest that only a subset of the encodings
that are invalid on x86 are also invalid on ia64 but I don't have access
to hardware to test.)
On Dez 31 2020, Joseph Myers wrote:
> On Thu, 24 Dec 2020, Siddhesh Poyarekar via Libc-alpha wrote:
>
>> diff --git a/sysdeps/generic/nan-pseudo-number.h b/sysdeps/generic/nan-pseudo-number.h
>
> I don't think this belongs in sysdeps/generic/. The "pseudo-number"
> concept is specific to the ldbl-96 format; a "generic" header is really
> something specific to ldbl-96 and so should go in sysdeps/ieee754/ldbl-96/
> instead. (x86 and m68k have different rules regarding what encodings are
> valid.
m68k doesn't have the concept of pseudo-nan and pseudo-inf, as it treats
the explicit integer bit in those formats as don't-care.
Andreas.
new file mode 100644
@@ -0,0 +1,32 @@
+/* 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 __attribute__ ((unused)),
+ uint32_t hxi __attribute__ ((unused)))
+{
+ return 0;
+}
+
+#endif /* nan-pseudo-number.h */
@@ -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)
new file mode 100644
@@ -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 */