* [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW
@ 2019-08-27 1:14 Paul Clarke
2019-08-27 1:16 ` [Qemu-devel] [Bug 1841491] " Paul Clarke
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: Paul Clarke @ 2019-08-27 1:14 UTC (permalink / raw)
To: qemu-devel
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
--
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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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Qemu-devel] [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
@ 2019-08-27 1:16 ` Paul Clarke
2019-08-27 4:06 ` Paul Clarke
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Paul Clarke @ 2019-08-27 1:16 UTC (permalink / raw)
To: qemu-devel
** Attachment added: "2nd file of testcase"
https://bugs.launchpad.net/qemu/+bug/1841491/+attachment/5284809/+files/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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Qemu-devel] [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
2019-08-27 1:16 ` [Qemu-devel] [Bug 1841491] " Paul Clarke
@ 2019-08-27 4:06 ` Paul Clarke
2019-08-27 4:08 ` Paul Clarke
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Paul Clarke @ 2019-08-27 4:06 UTC (permalink / raw)
To: qemu-devel
Responding to the patch https://lists.nongnu.org/archive/html/qemu-
ppc/2019-08/msg00404.html, it seems to work for "double", but not for
"float". Test case attached.
** Attachment added: "float testcase"
https://bugs.launchpad.net/qemu/+bug/1841491/+attachment/5284810/+files/test-ffma.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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Qemu-devel] [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
2019-08-27 1:16 ` [Qemu-devel] [Bug 1841491] " Paul Clarke
2019-08-27 4:06 ` Paul Clarke
@ 2019-08-27 4:08 ` Paul Clarke
2019-08-27 4:29 ` Richard Henderson
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Paul Clarke @ 2019-08-27 4:08 UTC (permalink / raw)
To: qemu-devel
** Attachment added: "2nd file of float testcase"
https://bugs.launchpad.net/qemu/+bug/1841491/+attachment/5284821/+files/ffma.c
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Qemu-devel] [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
` (2 preceding siblings ...)
2019-08-27 4:08 ` Paul Clarke
@ 2019-08-27 4:29 ` Richard Henderson
2020-01-09 13:32 ` Thomas Huth
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: Richard Henderson @ 2019-08-27 4:29 UTC (permalink / raw)
To: qemu-devel
The float test failure is part of a larger problem for target/powerpc in
which all float routines are implemented incorrectly. They are all
implemented as double operations with rounding to float as a second
step. Which not only produces incorrect exceptions, as in this case,
but incorrect numerical results from the double rounding.
This should probably be split to a separate bug...
** Changed in: qemu
Status: New => Confirmed
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1841491
Title:
floating point emulation can fail to set FE_UNDERFLOW
Status in QEMU:
Confirmed
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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
` (3 preceding siblings ...)
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
6 siblings, 0 replies; 8+ messages in thread
From: Thomas Huth @ 2020-01-09 13:32 UTC (permalink / raw)
To: qemu-devel
A patch for this bug has been merged here:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=cbc65a8f22b29680f3
... can we close this ticket now or is there more to do?
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1841491
Title:
floating point emulation can fail to set FE_UNDERFLOW
Status in QEMU:
Confirmed
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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
` (4 preceding siblings ...)
2020-01-09 13:32 ` Thomas Huth
@ 2020-01-09 15:24 ` Paul Clarke
2020-01-10 8:38 ` Thomas Huth
6 siblings, 0 replies; 8+ messages in thread
From: Paul Clarke @ 2020-01-09 15:24 UTC (permalink / raw)
To: qemu-devel
Comment #5 suggested splitting the "float" issue to a separate bug,
which was done some time ago (bug #1841592).
I think this ticket can be closed.
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1841491
Title:
floating point emulation can fail to set FE_UNDERFLOW
Status in QEMU:
Confirmed
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
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug 1841491] Re: floating point emulation can fail to set FE_UNDERFLOW
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
` (5 preceding siblings ...)
2020-01-09 15:24 ` Paul Clarke
@ 2020-01-10 8:38 ` Thomas Huth
6 siblings, 0 replies; 8+ messages in thread
From: Thomas Huth @ 2020-01-10 8:38 UTC (permalink / raw)
To: qemu-devel
Ok, thanks for the pointer to the other bug! So I'm closing this one
now.
** Changed in: qemu
Status: Confirmed => Fix Released
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1841491
Title:
floating point emulation can fail to set FE_UNDERFLOW
Status in QEMU:
Fix Released
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
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-01-10 8:46 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-27 1:14 [Qemu-devel] [Bug 1841491] [NEW] floating point emulation can fail to set FE_UNDERFLOW Paul Clarke
2019-08-27 1:16 ` [Qemu-devel] [Bug 1841491] " 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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