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[Qemu-devel] [Bug 1793608] Re: qemu doesn't seem to support lxvwsx for P

From: Sergey Evlashev
Subject: [Qemu-devel] [Bug 1793608] Re: qemu doesn't seem to support lxvwsx for POWER9 target
Date: Sat, 22 Sep 2018 13:53:13 -0000

Small clarification to the bug description above.

Host architecture: x86_64 (AMD64)
Instructions used for building QEMU 3.0.0 from source are here:

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:

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  qemu doesn't seem to support lxvwsx for POWER9 target

Status in QEMU:

Bug description:
  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:

  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.

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