[glibc] x86 long double: Support pseudo numbers in isnanl

[glibc] x86 long double: Support pseudo numbers in isnanl

[Siddhesh Poyarekar]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=94547d9209db483c17285599a0c22085067361f0

commit 94547d9209db483c17285599a0c22085067361f0
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date:   Wed Dec 23 14:02:02 2020 +0530

    x86 long double: Support pseudo numbers in isnanl
    
    This syncs up isnanl behaviour with gcc.  Also move the isnanl
    implementation to sysdeps/x86 and remove the sysdeps/x86_64 version.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 sysdeps/{i386 => x86}/fpu/s_isnanl.c | 12 +++++++-----
 sysdeps/x86_64/fpu/s_isnanl.c        |  1 -
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/sysdeps/i386/fpu/s_isnanl.c b/sysdeps/x86/fpu/s_isnanl.c
similarity index 76%
rename from sysdeps/i386/fpu/s_isnanl.c
rename to sysdeps/x86/fpu/s_isnanl.c
index fb97317bc9..45541df08a 100644
--- a/sysdeps/i386/fpu/s_isnanl.c
+++ b/sysdeps/x86/fpu/s_isnanl.c
@@ -28,16 +28,18 @@ static char rcsid[] = "$NetBSD: $";
 
 int __isnanl(long double x)
 {
-	int32_t se,hx,lx;
+	int32_t se,hx,lx,pn;
 	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!  */
+	/* Detect pseudo-normal numbers, i.e. exponent is non-zero and the top
+	   bit of the significand is not set.   */
+	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;
+
+	return (int)(((uint32_t)(se)) >> 16) | pn;
 }
 hidden_def (__isnanl)
 weak_alias (__isnanl, isnanl)
diff --git a/sysdeps/x86_64/fpu/s_isnanl.c b/sysdeps/x86_64/fpu/s_isnanl.c
deleted file mode 100644
index 06e69c3aeb..0000000000
--- a/sysdeps/x86_64/fpu/s_isnanl.c
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/i386/fpu/s_isnanl.c>