The problem is that the binary being generated is not exactly what I want. when I simulate my code, I get an "invalid opcode" error and the address of the instruction is exactly where the disassembly get screwed up. So I believe that's what's happening. I need to make GCC treat that "F0 0F 23" as an instruction and put it in the binary intact and don't mix it with other instructions. I tried defining a machine instruction in GCC for ia64, but I couldn't figure out how to generate the assembly for that instruction. On Fri, Apr 13, 2012 at 1:15 AM, Ian Lance Taylor <iant@xxxxxxxxxx> wrote: > > Amir Ghanbari <a.ghanbari1990@xxxxxxxxx> writes: > > > 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? > > I don't understand what you are asking. GCC does not generate any > output that looks like the lines quoted above. It looks like you are > showing us the output of a disassembler, but GCC does not include a > disassembler. And it looks like the bytes that the disassembler is > showing are the bytes that you want, they just aren't being disassembled > the way you want them to be. It sounds like you need to change your > disassembler to support your instruction. > > Ian
