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From: | Paolo Bonzini |
Subject: | Re: [Qemu-ppc] [RFC] target-ppc/fpu_helper.c: Use C99 code to speed up floating point unit |
Date: | Sat, 3 Dec 2016 09:44:46 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 03/12/2016 06:59, Programmingkid wrote: > The floating point code used in fpu_helper.c can be sped up by using > the IEEE 754 support added to the C99 standard. To test this code out > simply set and unset the I_NEED_SPEED macro. The program to test out > each version of the helper_fmadd() function is below the patch. It > needs to be ran in the guest. The emulator to use is qemu-system-ppc. > I used a Mac OS X guest, but the test program would compile on a > Linux guest. > > This patch does make the fused multiply-add instruction fmadd work > faster and still give a correct result. > > This documentation might be of help to those who want to learn more > about C99's IEEE 754 support: > http://grouper.ieee.org/groups/754/meeting-materials/2001-07-18-c99.pdf You're undoing what was done in 2007: commit 76a66253e5e48f1744f689041c1c21cedcaff630 Author: j_mayer <address@hidden> Date: Wed Mar 7 08:32:30 2007 +0000 Great PowerPC emulation code resynchronisation and improvments: ... - Micro-operation fixes: ... * use softfloat routines for all floating-point operations Paolo
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