Example reproducer:

$ tar xf gdb_avx_issue.tar
$ cd gdb_avx_issue/
$ ./build
$ ./run
Out 0: 0xdeadbeef
Out 1: 0xdeadbeef
Out 2: 0xdeadbeef
Out 3: 0xdeadbeef
Out 4: 0xdeadbeef
Out 5: 0xdeadbeef
Out 6: 0xdeadbeef
Out 7: 0xdeadbeef

Now in gdb:

$ gdb run
...
(gdb) b test_func
Breakpoint 1 at 0x401240: file /usr/lib/gcc/x86_64-redhat-linux/11/include/avxintrin.h, line 174.
(gdb) r
...
Breakpoint 1, test_func (x=...) at test.c:12
12 return _mm256_and_ps(x, constants[512]);
(gdb) c
Continuing.
Out 0: 0x00000000
Out 1: 0x00000000
Out 2: 0x00000000
Out 3: 0x00000000
Out 4: 0x00000000
Out 5: 0x00000000
Out 6: 0x00000000
Out 7: 0x00000000

This issue appears to happen not just in rhel8 but any other recent environment
tested with different gdb major versions.

For the reproducer, the issue appear to only happen if the breakpoint is in the
vandps instruction, but probably might trigger in other instructions or
conditions.

(gdb) p $ymm0
$1 = {..., v8_int32 = {-1, -1, -1, -1, -1, -1, -1, -1}, ... }
(gdb) watch $ymm0
Watchpoint 2: $ymm0
(gdb) disassemble
Dump of assembler code for function test_func:
=> 0x0000000000401240 <+0>: vandps 0x6e18(%rip),%ymm0,%ymm0 # 0x408060 <constants+16384>
0x0000000000401248 <+8>: ret
End of assembler dump.
(gdb) si

Watchpoint 2: $ymm0

Old value = {..., v8_int32 = {-1, -1, -1, -1, -1, -1, -1, -1}, ...}
New value = {..., v8_int32 =

, ...}
0x0000000000401248 in test_func (x=...) at test.c:18
18 }