From: Paul Clarke <pc@us.ibm.com>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW
Date: Tue, 27 Aug 2019 01:14:57 -0000 [thread overview]
Message-ID: <156686849716.6431.16425651381928336460.malonedeb@gac.canonical.com> (raw)
Public bug reported:
Floating point emulation can fail to set FE_UNDERFLOW in some
circumstances. This shows up often in glibc's "math" tests. A similar
test is attached.
This is similar to bug #1841442, but not the same problem, and I don't
think the fix will be in the same code.
On ppc64le native:
--
$ gcc -c -O2 fma.c
$ gcc -O2 test-fma.c fma.o -lm -o test-fma
$ ./test-fma $(./test-fma)
fma(0x1.ffffffffffffcp-1022, 0x1.0000000000001p-1, 0x0.0000000000001p-1022)
0x0
0xa000000
FE_INEXACT FE_UNDERFLOW
0x1p-1022
--
On qemu-system-ppc64:
--
$ ./test-fma $(./test-fma)
fma(0x1.ffffffffffffcp-1022, 0x1.0000000000001p-1, 0x0.0000000000001p-1022)
0x0
0x2000000
FE_INEXACT
0x1p-1022
--
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
There are worse symptoms on qemu-x86_64, but this is apparently not
surprising per https://bugs.launchpad.net/qemu/+bug/1841442/comments/6.
** Affects: qemu
Importance: Undecided
Status: New
** Attachment added: "testcase reporting exceptions set by simple floating point multiply-add"
https://bugs.launchpad.net/bugs/1841491/+attachment/5284808/+files/test-fma.c
--
You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1841491
Title:
floating point emulation can fail to set FE_UNDERFLOW
Status in QEMU:
New
Bug description:
Floating point emulation can fail to set FE_UNDERFLOW in some
circumstances. This shows up often in glibc's "math" tests. A similar
test is attached.
This is similar to bug #1841442, but not the same problem, and I don't
think the fix will be in the same code.
On ppc64le native:
--
$ gcc -c -O2 fma.c
$ gcc -O2 test-fma.c fma.o -lm -o test-fma
$ ./test-fma $(./test-fma)
fma(0x1.ffffffffffffcp-1022, 0x1.0000000000001p-1, 0x0.0000000000001p-1022)
0x0
0xa000000
FE_INEXACT FE_UNDERFLOW
0x1p-1022
--
On qemu-system-ppc64:
--
$ ./test-fma $(./test-fma)
fma(0x1.ffffffffffffcp-1022, 0x1.0000000000001p-1, 0x0.0000000000001p-1022)
0x0
0x2000000
FE_INEXACT
0x1p-1022
--
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
There are worse symptoms on qemu-x86_64, but this is apparently not
surprising per
https://bugs.launchpad.net/qemu/+bug/1841442/comments/6.
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1841491/+subscriptions
next reply other threads:[~2019-08-27 1:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 1:14 Paul Clarke [this message]
2019-08-27 1:16 ` [Qemu-devel] [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
2019-08-27 4:06 ` Paul Clarke
2019-08-27 4:08 ` Paul Clarke
2019-08-27 4:29 ` Richard Henderson
2020-01-09 13:32 ` Thomas Huth
2020-01-09 15:24 ` Paul Clarke
2020-01-10 8:38 ` Thomas Huth
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