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Fix ldbl-128 expm1l spurious underflow (bug 16539).

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This patch fixes spurious underflows from ldbl-128 expm1l, as reported
in <https://sourceware.org/ml/libc-alpha/2014-06/msg00835.html> and
exposed by the tests added for such a bug in the x86 / x86-64
version.  The bug and fix are essentially the same, so no separate bug
is filed in Bugzilla.

Tested for mips64.

	[BZ #16539]
	* sysdeps/ieee754/ldbl-128/s_expm1l.c: Include <float.h>.
	(__expm1l): Return argument unchanged when small but not
	subnormal.
This commit is contained in:
Joseph Myers 2014-06-30 17:38:16 +00:00
parent 3a6e988706
commit ce9c5b3e95
2 changed files with 10 additions and 0 deletions
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5
ChangeLog
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@ -1,5 +1,10 @@
2014-06-30 Joseph Myers <joseph@codesourcery.com>
[BZ #16539]
* sysdeps/ieee754/ldbl-128/s_expm1l.c: Include <float.h>.
(__expm1l): Return argument unchanged when small but not
subnormal.
* soft-fp/op-1.h (_FP_UNPACK_RAW_1): Rename local variables to
include macro name.
(_FP_UNPACK_RAW_1_P): Likewise.

5
sysdeps/ieee754/ldbl-128/s_expm1l.c
View File

@ -54,6 +54,7 @@
#include <errno.h>
#include <float.h>
#include <math.h>
#include <math_private.h>
@ -136,6 +137,10 @@ __expm1l (long double x)
if (x < minarg)
return (4.0/big - 1.0L);
/* Avoid internal underflow when result does not underflow. */
if (fabsl (x) < 0x1p-113L && fabsl (x) >= LDBL_MIN)
return x;
/* Express x = ln 2 (k + remainder), remainder not exceeding 1/2. */
xx = C1 + C2; /* ln 2. */
px = __floorl (0.5 + x / xx);