Support for segment registers about xbyak

[AlexAltea]

I was thinking about having a class SegmentReg : class Reg type for the members cs,ds,ss,es,fs,gs and extending RegExp to allow following expressions:

(ptr|dword|word|byte) [(cs|ds|ss|es|fs|gs) | base + index * (1|2|4|8) + displacement]

Such that, for example, following expressions were possible:

mov(ecx, ptr[rax]);
mov(ecx, ptr[fs | rax]);
mov(ebx, ptr[gs | rax + rcx*4]);
mov(fs, rax);

This matches more or less the Intel syntax.

[herumi]

Thank you for your suggestion, but it is difficult to extend Addressing to support segment registers.

How about the following extension?

add method cs(), ds(), ... to Xbyak::CodeGenerator;

cs() { db(0x2e); }
ds() { db(0x3e); }
...

mov(ecx, ptr[rax]);
fs(); mov(ecx, ptr[rax]);
gs(); mov(ebx, ptr[rax + rcx*4]);

It is necessary for mov to support segment registers.

[AlexAltea]

True, that's a simpler workaround. I guess I will do that (for now). Thanks for the tip! :-)

[herumi]

https://github.com/herumi/xbyak/releases/tag/v4.87 supports the following codes.

putSeg(fs); mov(eax, ptr [ecx]);
mov(cs, ax);
push(ds);

Could you try it?

[AlexAltea]

I've tried it and it works perfectly. Thank you very much for your support and congratulations for this great library. I'm closing this issue. :-)