From: Richard Henderson <rth@twiddle.net>
To: Aurelien Jarno <aurelien@aurel32.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 11/11] target-i386: use floatx80_log2() to implement helper_fyl2x*()
Date: Tue, 17 May 2011 08:41:57 -0700 [thread overview]
Message-ID: <4DD29745.5060002@twiddle.net> (raw)
In-Reply-To: <1305468801-6015-12-git-send-email-aurelien@aurel32.net>
On 05/15/2011 07:13 AM, Aurelien Jarno wrote:
> + temp = floatx80_add(ST0, floatx80_one, &env->fp_status);
> + if (!floatx80_is_neg(temp)) {
> + temp = floatx80_add(ST0, floatx80_one, &env->fp_status);
> + temp = floatx80_log2(temp, &env->fp_status);
> + ST1 = floatx80_mul(ST1, temp, &env->fp_status);
While this is probably better than the existing code, you really
should be using a different series expansion than for log2. This
expansion will be wildly inaccurate for inputs near zero.
r~
prev parent reply other threads:[~2011-05-17 15:42 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-15 14:13 [Qemu-devel] [PATCH 00/11] softfloat-native removal and i386 improvements Aurelien Jarno
2011-05-15 14:13 ` [Qemu-devel] [PATCH 01/11] target-ppc: remove old CONFIG_SOFTFLOAT #ifdef Aurelien Jarno
2011-05-20 10:01 ` Peter Maydell
2011-05-15 14:13 ` [Qemu-devel] [PATCH 02/11] target-mips/gdbstub: " Aurelien Jarno
2011-05-15 14:29 ` Peter Maydell
2011-05-15 15:46 ` Aurelien Jarno
2011-05-15 14:13 ` [Qemu-devel] [PATCH 03/11] softfloat-native: remove Aurelien Jarno
2011-05-20 10:06 ` Peter Maydell
2011-05-15 14:13 ` [Qemu-devel] [PATCH 04/11] softfloat: always enable floatx80 and float128 support Aurelien Jarno
2011-05-20 10:09 ` Peter Maydell
2011-05-15 14:13 ` [Qemu-devel] [PATCH 05/11] target-i386: remove old code handling float64 Aurelien Jarno
2011-05-20 10:21 ` Peter Maydell
2011-05-15 14:13 ` [Qemu-devel] [PATCH 06/11] target-i386: use floatx80 constants in helper_fld*_ST0() Aurelien Jarno
2011-05-15 21:17 ` Andreas Färber
2011-05-20 10:32 ` Peter Maydell
2011-05-21 9:35 ` Andreas Färber
2011-05-29 11:43 ` Andreas Färber
2011-05-15 14:13 ` [Qemu-devel] [PATCH 07/11] softfloat: add float*_is_zero_or_denormal() Aurelien Jarno
2011-05-20 10:34 ` Peter Maydell
2011-05-15 14:13 ` [Qemu-devel] [PATCH 08/11] target-i386: cleanup helper_fxam_ST0() Aurelien Jarno
2011-05-15 14:13 ` [Qemu-devel] [PATCH 09/11] target-i386: add support for FPU exceptions Aurelien Jarno
2011-05-15 14:13 ` [Qemu-devel] [PATCH 10/11] softfloat: add floatx80_log2() function Aurelien Jarno
2011-05-15 14:13 ` [Qemu-devel] [PATCH 11/11] target-i386: use floatx80_log2() to implement helper_fyl2x*() Aurelien Jarno
2011-05-17 15:41 ` Richard Henderson [this message]
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