From: Richard Henderson <richard.henderson@linaro.org>
To: Programmingkid <programmingkidx@gmail.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"BALATON Zoltan" <balaton@eik.bme.hu>
Cc: QEMU Developers <qemu-devel@nongnu.org>,
"qemu-ppc@nongnu.org" <qemu-ppc@nongnu.org>,
Howard Spoelstra <hsp.cat7@gmail.com>,
luigi burdo <intermediadc@hotmail.com>,
Dino Papararo <skizzato73@msn.com>,
Aleksandar Markovic <aleksandar.m.mail@gmail.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [RFC PATCH v2] target/ppc: Enable hardfloat for PPC
Date: Sun, 1 Mar 2020 20:28:55 -0800 [thread overview]
Message-ID: <2576fd41-8b01-91a0-ca56-792ce65b5092@linaro.org> (raw)
In-Reply-To: <FE03C155-E46D-4925-BA2B-FABBE2518C8C@gmail.com>
On 3/1/20 4:13 PM, Programmingkid wrote:
> Ok, I was just looking at Intel's x87 chip documentation. It supports IEEE 754 floating point operations and exception flags. This leads me to this question. Would simply taking the host exception flags and using them to set the PowerPC's FPU's flag be an acceptable solution to this problem?
No.
The primary issue is the FPSCR.FI flag. This is not an accumulative bit, per
ieee754, but per operation.
The "hardfloat" option works (with other targets) only with ieee745
accumulative exceptions, when the most common of those exceptions, inexact, has
already been raised. And thus need not be raised a second time.
Per the PowerPC architecture, inexact must be recognized afresh for every
operation. Which is cheap in hardware but expensive in software.
And once you're done with FI, FR has been and continues to be emulated incorrectly.
r~
next prev parent reply other threads:[~2020-03-02 4:29 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-18 17:10 [RFC PATCH v2] target/ppc: Enable hardfloat for PPC BALATON Zoltan
2020-02-18 17:38 ` BALATON Zoltan
2020-02-19 2:27 ` Programmingkid
2020-02-19 15:35 ` BALATON Zoltan
2020-02-19 18:28 ` Howard Spoelstra
2020-02-19 19:28 ` BALATON Zoltan
2020-02-20 5:43 ` Howard Spoelstra
2020-02-25 3:07 ` Programmingkid
2020-02-25 12:09 ` BALATON Zoltan
2020-02-26 10:46 ` Programmingkid
2020-02-26 11:28 ` BALATON Zoltan
2020-02-26 13:00 ` R: " luigi burdo
2020-02-26 13:08 ` Dino Papararo
2020-02-26 14:28 ` Alex Bennée
2020-02-26 15:50 ` Aleksandar Markovic
2020-02-26 17:04 ` G 3
2020-02-26 17:27 ` Aleksandar Markovic
2020-02-26 18:14 ` R: " Dino Papararo
2020-02-26 18:51 ` Aleksandar Markovic
2020-02-27 2:43 ` Programmingkid
2020-02-27 7:16 ` Aleksandar Markovic
2020-02-27 11:54 ` BALATON Zoltan
2020-02-26 18:09 ` R: " Alex Bennée
2020-03-02 0:13 ` Programmingkid
2020-03-02 4:28 ` Richard Henderson [this message]
2020-03-02 11:42 ` BALATON Zoltan
2020-03-02 16:55 ` Richard Henderson
2020-03-02 23:16 ` BALATON Zoltan
2020-03-03 0:11 ` Richard Henderson
[not found] ` <CAKyx-3Pt2qLPXWQjBwrHn-nxR-9e++TioGp4cKFC3adMN3rtiw@mail.gmail.com>
2020-03-04 18:43 ` Fwd: " G 3
2020-03-05 19:25 ` Richard Henderson
2020-03-02 17:10 ` Alex Bennée
2020-03-02 23:01 ` BALATON Zoltan
2020-02-26 22:51 ` R: " BALATON Zoltan
2020-02-20 20:13 ` Richard Henderson
2020-02-21 16:04 ` BALATON Zoltan
2020-02-21 16:11 ` Peter Maydell
2020-02-21 16:51 ` Aleksandar Markovic
2020-02-21 18:04 ` BALATON Zoltan
2020-02-21 18:26 ` Peter Maydell
2020-02-21 19:52 ` BALATON Zoltan
2020-02-26 12:28 ` Alex Bennée
2020-02-26 13:07 ` BALATON Zoltan
2020-04-10 13:50 ` 罗勇刚(Yonggang Luo)
2020-04-10 18:04 ` BALATON Zoltan
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