[PATCH 2/5] x86 long double: Support pseudo numbers in isnanl

[Siddhesh Poyarekar]

Sync up with gcc behaviour.  This change splits out the core isnanl
logic so that it can be reused.
---
 sysdeps/i386/fpu/s_isnanl.c     | 10 ++--------
 sysdeps/x86/fpu/isnanl_common.h | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 8 deletions(-)
 create mode 100644 sysdeps/x86/fpu/isnanl_common.h

diff --git a/sysdeps/i386/fpu/s_isnanl.c b/sysdeps/i386/fpu/s_isnanl.c
index fb97317bc9..6824f31d96 100644
--- a/sysdeps/i386/fpu/s_isnanl.c
+++ b/sysdeps/i386/fpu/s_isnanl.c
@@ -25,19 +25,13 @@ static char rcsid[] = "$NetBSD: $";
 
 #include <math.h>
 #include <math_private.h>
+#include "sysdeps/x86/fpu/isnanl_common.h"
 
 int __isnanl(long double x)
 {
 	int32_t se,hx,lx;
 	GET_LDOUBLE_WORDS(se,hx,lx,x);
-	se = (se & 0x7fff) << 1;
-	/* The additional & 0x7fffffff is required because Intel's
-	   extended format has the normally implicit 1 explicit
-	   present.  Sigh!  */
-	lx |= hx & 0x7fffffff;
-	se |= (uint32_t)(lx|(-lx))>>31;
-	se = 0xfffe - se;
-	return (int)((uint32_t)(se))>>16;
+	return x86_isnanl (se, hx, lx);
 }
 hidden_def (__isnanl)
 weak_alias (__isnanl, isnanl)
diff --git a/sysdeps/x86/fpu/isnanl_common.h b/sysdeps/x86/fpu/isnanl_common.h
new file mode 100644
index 0000000000..60a4af5b41
--- /dev/null
+++ b/sysdeps/x86/fpu/isnanl_common.h
@@ -0,0 +1,32 @@
+/* Common inline isnanl implementation for x86.
+   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/>.  */
+
+static inline __always_inline int
+x86_isnanl (int32_t se, int32_t hx, int32_t lx)
+{
+  se = (se & 0x7fff) << 1;
+  /* Detect pseudo-normal numbers, i.e. exponent is non-zero and the top
+     bit of the significand is not set.   */
+  int pn = (uint32_t)((~hx & 0x80000000) & (se | (-se))) >> 31;
+  /* Clear the significand bit when computing mantissa.  */
+  lx |= hx & 0x7fffffff;
+  se |= (uint32_t)(lx | (-lx)) >> 31;
+  se = 0xfffe - se;
+
+  return (int)(((uint32_t)(se)) >> 16) | pn;
+}
-- 
2.29.2