Add assembly instruction to GCC

[Amir Ghanbari]

Hello all,

I'm trying to expand X86 ISA. So I have added some hardware to X86 (in
Gem5 Simulator) and I have updated X86 decoder to support those
instructions. In order to call those instructions I use GCC inline
assembly ".byte" directive. something like this : ".byte 0xF0, 0x0F,
0x23;"
The problem is when I compile my code using GCC, it changes the
instructions that i have created. For instance:
I intend to have something generated like this:

    48 89 eb               mov    %rbp,%rbx
    48 83 e3 fe           and    $0xfffffffffffffffe,%rbx
    48 8b 7c 24 08      mov    0x8(%rsp),%rdi
    f0 0f 23                lock (bad)
    48 89 04 24          mov    %rax,(%rsp)
    4c 8b 34 24          mov    (%rsp),%r14

but GCC generates something like this:

    48 89 eb               mov    %rbp,%rbx"
    48 83 e3 fe           and    $0xfffffffffffffffe,%rbx"
    48 8b 7c 24 08      mov    0x8(%rsp),%rdi"
    f0 0f                     lock mov (bad),%db1"
    23 48 89               and    -0x77(%rax),%ecx"
    04 24                    add    $0x24,%al"
    4c 8b 34 24           mov    (%rsp),%r14"

Is there a way to tell GCC that "F0 0F 23" is a unique instruction so
it wouldn't mix it with other instructions?
Thank you,
--
Amir