qemu doesn't seem to support lxvwsx for POWER9 target

[Sergey Evlashev]

When running a simple program built for POWER9 on QEMU 3.0.0 in linux-user mode, it crashes with a message: "illegal instruction". It turns out that lxvwsx instruction "Load Word and Splat Indexed" is not supported. If workaround is implemented by issuing two separate instructions (first load then splat) then all tests pass correctly.

Operating system: Ubuntu Mate 16.04.2 64-bit (or Linux Mint 18 64-bit).
Cross-compiler for gcc-powerpc64le-linux-gnu is installed (gcc-5 series).
QEMU 3.0.0 is built from source and installed with: sudo make install

The program in question: https://github.com/VectorChief/UniSIMD-assembler
Turn off the workaround: RT_ELEM_COMPAT_PW9 should be set to 1 in the following file:
https://github.com/VectorChief/UniSIMD-assembler/blob/master/core/config/rtarch_p32_128x1v2.h

Change to the "test" directory and type "make -f simd_make_p64.mk".
powerpc64le-linux-gnu-objdump -d simd_test.p64_32Lp9 > simd_test_p64_32Lp9.txt
Open newly created text file simd_test_p64_32Lp9.txt and search for lxvwsx (in s_test01, ...)
The instruction shows up in objdump correctly.

[Sergey Evlashev (vectorchiefrocks)]

Small clarification to the bug description above.

Host architecture: x86_64 (AMD64)
Instructions used for building QEMU 3.0.0 from source are here:
https://github.com/VectorChief/UniSIMD-assembler/blob/master/INSTALL

The command line for emulating POWER9 target is below:
qemu-ppc64le -cpu POWER9 simd_test.p64_32Lp9 -c 1

With the workaround for lxvwsx instruction turned off (as described above)
QEMU crashes in s_test08 function of the following common SIMD test file:
https://github.com/VectorChief/UniSIMD-assembler/blob/master/test/simd_test.cpp

[Thomas Huth (th-huth)]

A patch has been posted here:
https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg02218.html
("ppc/translate: Implement lxvwsx opcode")

[Thomas Huth (th-huth)]

Released with QEMU v5.2.0.