PEXT returns wrong values, seemingly switches arguments

[Lenard Szolnoki]

Hi,

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 GNU/Linux

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

[Thomas Huth (th-huth)]

Paolo sent a patch here:
https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg05700.html

[Thomas Huth (th-huth)]

Fix has been committed:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=75b208c28316095c4685