From: "Alex Bennée" <alex.bennee@linaro.org>
To: Bug 1841442 <1841442@bugs.launchpad.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [Bug 1841442] Re: floating point emulation can fail to set FE_INEXACT
Date: Mon, 26 Aug 2019 17:11:35 +0100 [thread overview]
Message-ID: <87imqjzz2g.fsf@linaro.org> (raw)
In-Reply-To: <156683348223.2485.3705708265196858485.malone@chaenomeles.canonical.com>
Richard Henderson <rth@twiddle.net> writes:
> Well, maybe yes and maybe no. What you've done is choose two targets
> whose floating point emulation have not been well maintained.
So this is a failure on the x86_64 and ppc64 frontends to correctly set
the softfloat modes when their appropriate registers are set?
>
> If I try this same test on aarch64, it passes:
>
> $ ~/a.out 0x0000000000000001
> 0x0000000000000001 0.000000
> 0x0
>
> 0x18
> FE_INEXACT FE_UNDERFLOW
> 0x0000000000000000 0.000000
>
> $ ./aarch64-linux-user/qemu-aarch64 ~/a.out 0x0000000000000001
> 0x0000000000000001 0.000000
> 0x0
>
> 0x18
> FE_INEXACT FE_UNDERFLOW
> 0x0000000000000000 0.000000
--
Alex Bennée
WARNING: multiple messages have this Message-ID (diff)
From: "Alex Bennée" <alex.bennee@linaro.org>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [Bug 1841442] Re: floating point emulation can fail to set FE_INEXACT
Date: Mon, 26 Aug 2019 16:11:35 -0000 [thread overview]
Message-ID: <87imqjzz2g.fsf@linaro.org> (raw)
Message-ID: <20190826161135.bGvmDUwj6tYI9duua0YTSXqDY6xLm_j6vCDBRlhsrBk@z> (raw)
In-Reply-To: 156683348223.2485.3705708265196858485.malone@chaenomeles.canonical.com
Richard Henderson <rth@twiddle.net> writes:
> Well, maybe yes and maybe no. What you've done is choose two targets
> whose floating point emulation have not been well maintained.
So this is a failure on the x86_64 and ppc64 frontends to correctly set
the softfloat modes when their appropriate registers are set?
>
> If I try this same test on aarch64, it passes:
>
> $ ~/a.out 0x0000000000000001
> 0x0000000000000001 0.000000
> 0x0
>
> 0x18
> FE_INEXACT FE_UNDERFLOW
> 0x0000000000000000 0.000000
>
> $ ./aarch64-linux-user/qemu-aarch64 ~/a.out 0x0000000000000001
> 0x0000000000000001 0.000000
> 0x0
>
> 0x18
> FE_INEXACT FE_UNDERFLOW
> 0x0000000000000000 0.000000
--
Alex Bennée
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1841442
Title:
floating point emulation can fail to set FE_INEXACT
Status in QEMU:
New
Bug description:
Floating point emulation can fail to set FE_INEXACT in some
circumstances. This shows up quite often in glibc's "math" tests. A
similar test is attached.
On ppc64le native:
--
$ gcc nextafter.c -o nextafter -lm
$ ./nextafter $(./nextafter)
0x0000000000000001 0.000000
0x0
0xa000000
FE_INEXACT FE_UNDERFLOW
0x0000000000000000 0.000000
--
On x86_64:
--
$ gcc nextafter.c -o nextafter -lm
$ ./nextafter $(./nextafter)
0x0000000000000001 0.000000
0x0
0x30
FE_INEXACT FE_UNDERFLOW
0x0000000000000000 0.000000
--
Using qemu-system-ppc64
--
$ ./nextafter $(./nextafter)
0x0000000000000001 0.000000
0x0
0x8000000
FE_UNDERFLOW
0x0000000000000000 0.000000
--
Using qemu-x86_64:
--
$ ./nextafter $(./nextafter)
0x0000000000000001 0.000000
0x0
0x0
0x0000000000000000 0.000000
--
QEMU versions vary, but not too much, and are pretty close to git HEAD:
- 586f3dced9 (HEAD -> master, origin/master, origin/HEAD) Merge remote-tracking branch 'remotes/cohuck/tags/s390x-20190822' into staging
- 864ab31 Update version for v4.1.0-rc4 release
Since the issue happens nearly identically on different targets, I
suspect the issue lies somewhere in fpu/softfloat.c.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1841442/+subscriptions
next prev parent reply other threads:[~2019-08-26 16:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 15:00 [Qemu-devel] [Bug 1841442] [NEW] floating point emulation can fail to set FE_INEXACT Paul Clarke
2019-08-26 15:31 ` [Qemu-devel] [Bug 1841442] " Richard Henderson
2019-08-26 16:11 ` Alex Bennée [this message]
2019-08-26 16:11 ` Alex Bennée
2019-08-26 15:57 ` Paul Clarke
2019-08-26 17:06 ` Richard Henderson
2019-08-26 17:09 ` Richard Henderson
2020-03-10 8:47 ` Laurent Vivier
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