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[Bug 1912934] [NEW] QEMU emulation of fmadds instruction on powerpc64le
From: |
Bruno Haible |
Subject: |
[Bug 1912934] [NEW] QEMU emulation of fmadds instruction on powerpc64le is buggy |
Date: |
Sun, 24 Jan 2021 08:40:41 -0000 |
Public bug reported:
The attached program test-fmadds.c tests the fmadds instruction on
powerpc64le.
Result on real hardware (POWER8E processor):
$ ./a.out ; echo $?
0
Result in Alpine Linux 3.13/powerpcle, emulated by QEMU 5.0.0 on Ubuntu 16.04:
$ ./a.out ; echo $?
32
Result in Debian 8.6.0/ppc64el, emulated by QEMU 2.9.0 on Ubuntu 16.04:
$ ./a.out ; echo $?
32
Through 'nm --dynamic qemu-system-ppc64 | grep fma' I can see that QEMU
is NOT using the fmaf() or fma() function from the host system's libc;
this function is working fine in glibc of the host system (see
https://www.gnu.org/software/gnulib/manual/html_node/fmaf.html ).
** Affects: qemu
Importance: Undecided
Status: New
** Attachment added: "Test case"
https://bugs.launchpad.net/bugs/1912934/+attachment/5456225/+files/test-fmadds.c
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https://bugs.launchpad.net/bugs/1912934
Title:
QEMU emulation of fmadds instruction on powerpc64le is buggy
Status in QEMU:
New
Bug description:
The attached program test-fmadds.c tests the fmadds instruction on
powerpc64le.
Result on real hardware (POWER8E processor):
$ ./a.out ; echo $?
0
Result in Alpine Linux 3.13/powerpcle, emulated by QEMU 5.0.0 on Ubuntu 16.04:
$ ./a.out ; echo $?
32
Result in Debian 8.6.0/ppc64el, emulated by QEMU 2.9.0 on Ubuntu 16.04:
$ ./a.out ; echo $?
32
Through 'nm --dynamic qemu-system-ppc64 | grep fma' I can see that
QEMU is NOT using the fmaf() or fma() function from the host system's
libc; this function is working fine in glibc of the host system (see
https://www.gnu.org/software/gnulib/manual/html_node/fmaf.html ).
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- [Bug 1912934] [NEW] QEMU emulation of fmadds instruction on powerpc64le is buggy,
Bruno Haible <=