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Re: [PATCH 2.19] BZ16427: Fix ldbl-128 exp overflows
- From: Siddhesh Poyarekar <siddhesh at redhat dot com>
- To: Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 14 Jan 2014 14:54:01 +0530
- Subject: Re: [PATCH 2.19] BZ16427: Fix ldbl-128 exp overflows
- Authentication-results: sourceware.org; auth=none
- References: <20140114082948 dot GA6210 at bart>
On Tue, Jan 14, 2014 at 09:29:48AM +0100, Andreas Krebbel wrote:
> 2014-01-14 Andreas Krebbel <Andreas.Krebbel@de.ibm.com>
>
> [BZ #16427]
> * sysdeps/ieee754/ldbl-128/w_expl.c (__expl): Invoke the non-IEEE
> handling only for numbers special also in the IEEE case.
>
> commit 1e74b6daed6c95628a4710f64d140880457c9c44
> Author: Andreas Krebbel <krebbel@linux.vnet.ibm.com>
> Date: Mon Jan 13 14:41:47 2014 +0000
>
> S/390: Fix ldbl-128 exp overflows.
Please put in a more descriptive commit message and mention the bz# in
the subject line of the message so that the post-hook adds a comment
to the bug report.
>
> diff --git a/sysdeps/ieee754/ldbl-128/w_expl.c b/sysdeps/ieee754/ldbl-128/w_expl.c
> index 10193be..af37aba 100644
> --- a/sysdeps/ieee754/ldbl-128/w_expl.c
> +++ b/sysdeps/ieee754/ldbl-128/w_expl.c
> @@ -25,24 +25,16 @@ static char rcsid[] = "$NetBSD: $";
> #include <math.h>
> #include <math_private.h>
>
> -static const long double
> -o_threshold= 1.1356523406294143949491931077970763428449E4L,
> -u_threshold= -1.1433462743336297878837243843452621503410E4;
> -
> long double __expl(long double x) /* wrapper exp */
> {
> #ifdef _IEEE_LIBM
> return __ieee754_expl(x);
> #else
> - long double z;
> - z = __ieee754_expl(x);
> - if(_LIB_VERSION == _IEEE_) return z;
> - if(__finitel(x)) {
> - if(x>o_threshold)
> - return __kernel_standard_l(x,x,206); /* exp overflow */
> - else if(x<u_threshold)
> - return __kernel_standard_l(x,x,207); /* exp underflow */
> - }
> + long double z = __ieee754_expl (x);
> + if (__builtin_expect (!__finitel (z) || z == 0, 0)
Use __glibc_unlikely.
> + && __finitel (x) && _LIB_VERSION != _IEEE_)
> + return __kernel_standard_l (x, x, 206 + !!__signbitl (x));
> +
> return z;
> #endif
> }
>
Siddhesh