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[Bug 1605123] Re: PEXT returns wrong values, seemingly switches argument

From: Thomas Huth
Subject: [Bug 1605123] Re: PEXT returns wrong values, seemingly switches arguments
Date: Tue, 19 Jan 2021 06:35:40 -0000

Fix has been committed:

** Changed in: qemu
       Status: New => Fix Committed

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  PEXT returns wrong values, seemingly switches arguments

Status in QEMU:
  Fix Committed

Bug description:

  I fiddled with BMI2 instructions and discovered that pext instructions
  emulated with "qemu-x86_64 -cpu Haswell" return the wrong value. It
  seemingly switches up its arguments. I suspect that the error is around the
  gen_helper_pext(...) call in target-i386/translate.c. I checked helper_pext
  in target-i386/int_helper.c and it works fine.

  I ran my program on a CPU with BMI2 instruction set too, and it indeed
  returns different values.

  I didn't check pdep, it could have the same problem.

  $ qemu-x86_64 --version
  qemu-x86_64 version 2.6.50 (v2.6.0-2095-ge66b05e-dirty), Copyright (c) 
2003-2008 Fabrice Bellard

  $ uname -a
  Linux lenard-hp 4.3.0-1-amd64 #1 SMP Debian 4.3.5-1 (2016-02-06) x86_64 

  I compiled the attached file with the command line "gcc -o main -g
  -mbmi2 main.c".

  $ gcc --version
  gcc (Debian 5.4.0-6) 5.4.0 20160609

  Best regards,
  Lénárd Szolnoki

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