[PATCH v2 4/5] x86 long double: Consider pseudo numbers as signaling

[Siddhesh Poyarekar]

Add support to treat pseudo-numbers specially and implement x86
version to consider all of them as signaling.
---
 sysdeps/generic/nan-pseudo-number.h      | 27 ++++++++++++++++++++
 sysdeps/ieee754/ldbl-96/s_issignalingl.c |  7 +++++-
 sysdeps/x86/fpu/nan-pseudo-number.h      | 32 ++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 1 deletion(-)
 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..ce1176a208
--- /dev/null
+++ b/sysdeps/generic/nan-pseudo-number.h
@@ -0,0 +1,27 @@
+/* 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
+
+/* Define this macro to 1 and provide an definition for IS_PSEUDO_SIGNALING if
+   pseudo-normal numbers need special handling.  */
+#define HANDLE_PSEUDO_NUMBERS 0
+#define IS_PSEUDO_SIGNALING(x) 0
+
+#endif /* nan-pseudo-number.h */
diff --git a/sysdeps/ieee754/ldbl-96/s_issignalingl.c b/sysdeps/ieee754/ldbl-96/s_issignalingl.c
index ec542ad468..fff6a85932 100644
--- a/sysdeps/ieee754/ldbl-96/s_issignalingl.c
+++ b/sysdeps/ieee754/ldbl-96/s_issignalingl.c
@@ -19,12 +19,14 @@
 #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);
+  int ret = 0;
 #if HIGH_ORDER_BIT_IS_SET_FOR_SNAN
 # error not implemented
 #else
@@ -36,9 +38,12 @@ __issignalingl (long double x)
   hxi |= (lxi | -lxi) >> 31;
   /* We do not recognize a pseudo NaN as sNaN; they're invalid on 80387 and
      later.  */
+#if HANDLE_PSEUDO_NUMBERS
+  ret = IS_PSEUDO_SIGNALING(x);
+#endif
   /* 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)
diff --git a/sysdeps/x86/fpu/nan-pseudo-number.h b/sysdeps/x86/fpu/nan-pseudo-number.h
new file mode 100644
index 0000000000..9cc37a3eee
--- /dev/null
+++ b/sysdeps/x86/fpu/nan-pseudo-number.h
@@ -0,0 +1,32 @@
+/* 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
+/* A pseudo-normal number (that is not pseudo-denormal) has a non-zero exponent
+   and the MSB of significand is clear.  All pseudo-normal numbers are deemed
+   signaling.  */
+#define IS_PSEUDO_SIGNALING(x) ({					      \
+  uint32_t exi, hxi, lxi __attribute__ ((unused));			      \
+  GET_LDOUBLE_WORDS (exi, hxi, lxi, x);					      \
+  ((exi & 0x7fff) && ((hxi & 0x80000000) == 0));			      \
+})
+
+#endif /* nan-pseudo-number.h */
-- 
2.29.2