code_asm: expose rip/eip regs

[wtfsck]

It's possible to use rip-relative addressing if you reference a label. It should be possible to do the same thing if you want to use any address (assuming it's close enough to the generated code).

#209

[ancorehraq]

I just ran into this in my Rust project. Would it be difficult for a newcomer to implement? It looks like AsmMemoryOperand::displ and Instruction::mem_displ are overloaded to contain a displacement or a label ID and I'd have to separate them somehow.

[wtfsck]

It could be easy, I don't remember all the details. You can try this:

• Manually add rip to the generated code (registers.rs, no need to touch the C# generator yet)
• try to assemble: lea rax,[rip+0x123456789AB] assuming 0x123456789AB is within 2GB of your generated code.

[ancorehraq]

That doesn't work by itself, the displacement is interpreted as an instruction index if it's a valid index, and used as a literal displacement without adjustment otherwise:

displ -1
0000000010000000 488D05F8FFFFEF lea rax,[0FFFFFFFFFFFFFFFFh]
displ 0
0000000010000000 488D05F9FFFFFF lea rax,[10000000h]
displ 1
0000000010000000 488D05FAFFFFEF lea rax,[1]
displ 2
0000000010000000 488D05FBFFFFEF lea rax,[2]

[wtfsck]

Try updating to_memory_operand() in mem.rs and set displ_size to 8 if base is RIP, will that work?

If that doesn't work, I'd compare the Instructions that was created by the assembler and compare it against another instruction created by the decoder that also has an RIP relative operand.