gdb prints only 128 bits of a YMM register (AVX)

gdb prints only 128 bits of a YMM register (AVX)

[Laurent ML]

Hello,

I have created a small C program that uses AVX extensions, and I have
compiled it with options -03 -mavx.
Next I used GDB to print the content of YMM registers, but each time I
print the content of one of the YMM register, gdb prints only the
highest 128 bits of the registers:

Breakpoint 1, 0x0000000000400a70 in func2_compare_32bitsPack ()
$1 = ">"
$2 = {0xffffffffffff00000000000000000000, 0x00000000000000000000000000000000}
$3 = {0x0000000000006e6f73697261706d6f43, 0x00000000000000000000000000000000}
$4 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$5 = {0x000000000000ff000000000000ffffff, 0x00000000000000000000000000000000}
$6 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$7 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$8 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$9 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$10 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$11 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$12 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$13 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$14 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$15 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$16 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$17 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}

Is there a way to get the last part of the register ?

I used gdb on EL7 :
$ gdb -v
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-64.el7

Thanks for your help.

RE: gdb prints only 128 bits of a YMM register (AVX)

[Tedeschi, Walfred]

Hello Laurent,

I did not understand how you are trying to see register values from the example bellow.

Have you used print $ymm0 or info register?

Thanks and regards,
-Fred

-----Original Message-----
From: gdb-owner@sourceware.org [mailto:gdb-owner@sourceware.org] On Behalf Of Laurent ML
Sent: Monday, July 27, 2015 2:48 PM
To: gdb@gnu.org
Subject: gdb prints only 128 bits of a YMM register (AVX)

Hello,

I have created a small C program that uses AVX extensions, and I have compiled it with options -03 -mavx.
Next I used GDB to print the content of YMM registers, but each time I print the content of one of the YMM register, gdb prints only the highest 128 bits of the registers:

Breakpoint 1, 0x0000000000400a70 in func2_compare_32bitsPack ()
$1 = ">"
$2 = {0xffffffffffff00000000000000000000, 0x00000000000000000000000000000000}
$3 = {0x0000000000006e6f73697261706d6f43, 0x00000000000000000000000000000000}
$4 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$5 = {0x000000000000ff000000000000ffffff, 0x00000000000000000000000000000000}
$6 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$7 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$8 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$9 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$10 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$11 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$12 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$13 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$14 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$15 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$16 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
$17 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}

Is there a way to get the last part of the register ?

I used gdb on EL7 :
$ gdb -v
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-64.el7

Thanks for your help.
Intel Deutschland GmbH
Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de
Managing Directors: Christin Eisenschmid, Prof. Dr. Hermann Eul
Chairperson of the Supervisory Board: Tiffany Doon Silva
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928

Re: gdb prints only 128 bits of a YMM register (AVX)

[Laurent ML]

Hi,

I ran this set like below in gdb:

b func2_compare_32bitsPack
commands 1
print $ymm1.v2_int128
print $ymm2.v2_int128
print $ymm3.v2_int128
print $ymm4.v2_int128
print $ymm5.v2_int128
print $ymm6.v2_int128
print $ymm7.v2_int128
print $ymm8.v2_int128
print $ymm9.v2_int128
print $ymm10.v2_int128
print $ymm11.v2_int128
print $ymm12.v2_int128
print $ymm13.v2_int128
print $ymm14.v2_int128
print $ymm15.v2_int128
continue
end

Concerning my problem, I found the reason: it's because of the
compiler optimization. If I compile my program without using any
optimization switch, the AVX register is completely set.

Thanks,
Laurent


On Wed, Jul 29, 2015 at 1:48 PM, Tedeschi, Walfred
<walfred.tedeschi@intel.com> wrote:
> Hello Laurent,
>
> I did not understand how you are trying to see register values from the example bellow.
>
> Have you used print $ymm0 or info register?
>
> Thanks and regards,
> -Fred
>
> -----Original Message-----
> From: gdb-owner@sourceware.org [mailto:gdb-owner@sourceware.org] On Behalf Of Laurent ML
> Sent: Monday, July 27, 2015 2:48 PM
> To: gdb@gnu.org
> Subject: gdb prints only 128 bits of a YMM register (AVX)
>
> Hello,
>
> I have created a small C program that uses AVX extensions, and I have compiled it with options -03 -mavx.
> Next I used GDB to print the content of YMM registers, but each time I print the content of one of the YMM register, gdb prints only the highest 128 bits of the registers:
>
> Breakpoint 1, 0x0000000000400a70 in func2_compare_32bitsPack ()
> $1 = ">"
> $2 = {0xffffffffffff00000000000000000000, 0x00000000000000000000000000000000}
> $3 = {0x0000000000006e6f73697261706d6f43, 0x00000000000000000000000000000000}
> $4 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $5 = {0x000000000000ff000000000000ffffff, 0x00000000000000000000000000000000}
> $6 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $7 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $8 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $9 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $10 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $11 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $12 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $13 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $14 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $15 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $16 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
> $17 = {0x00000000000000000000000000000000, 0x00000000000000000000000000000000}
>
> Is there a way to get the last part of the register ?
>
> I used gdb on EL7 :
> $ gdb -v
> GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-64.el7
>
> Thanks for your help.
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de
> Managing Directors: Christin Eisenschmid, Prof. Dr. Hermann Eul
> Chairperson of the Supervisory Board: Tiffany Doon Silva
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928