about summary refs log tree commit diff
path: root/sysdeps/i386
diff options
context:
space:
mode:
authorJoseph Myers <joseph@codesourcery.com>2015-05-19 23:05:22 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-05-19 23:05:22 +0000
commit526af54142db14c1edcd2d80dc1b56d33ff4e8ce (patch)
tree04991e58f9d8c05a94a492eda37747bdcc8a4740 /sysdeps/i386
parent88ed594f5d431d855256edbe7e886c8cf4b575dc (diff)
downloadglibc-526af54142db14c1edcd2d80dc1b56d33ff4e8ce.tar.gz
glibc-526af54142db14c1edcd2d80dc1b56d33ff4e8ce.tar.xz
glibc-526af54142db14c1edcd2d80dc1b56d33ff4e8ce.zip
Fix i386 atanhl spurious underflows (bug 18049).
The i386 implementation of atanhl, for small arguments, does a
calculation that involves computing twice the square of the argument,
resulting in spurious underflows for some arguments.  This patch fixes
this by just returning the argument when its exponent is below -32,
with underflow being forced as needed for subnormal arguments.

Tested for x86 and x86_64.

	[BZ #18049]
	* sysdeps/i386/fpu/e_atanhl.S (__ieee754_atanhl): For exponents
	below -32, return the argument, with underflow if subnormal.
	* math/auto-libm-test-in: Add more tests of atanh.
	* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/i386')
-rw-r--r--sysdeps/i386/fpu/e_atanhl.S10
1 files changed, 10 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu/e_atanhl.S b/sysdeps/i386/fpu/e_atanhl.S
index 88a970378d..1ad6851058 100644
--- a/sysdeps/i386/fpu/e_atanhl.S
+++ b/sysdeps/i386/fpu/e_atanhl.S
@@ -56,6 +56,16 @@ ENTRY(__ieee754_atanhl)
 	andl	$0x7fff, %eax
 	cmpl	$0x7fff, %eax
 	je	5f
+	cmpl	$0x3fdf, %eax
+	jge	7f
+	// Exponent below -32; return x, with underflow if subnormal.
+	fldt	4(%esp)
+	cmpl	$0, %eax
+	jne	8f
+	fld	%st(0)
+	fmul	%st(0)
+	fstp	%st(0)
+8:	ret
 7:
 
 #ifdef PIC