Re: Assembly codes in jitinterfacex86.cpp

Thanks a lot, it is quite clear now

On Thu, 19 Jun 2003, Barry Bond wrote:

> Emit32/16/8 just copies the 32/16/8-bit argument directly into the
> output buffer with no mapping.
>
> In your example, 0xfb83 is little-endian for bytes 0x83 0xfb, where 0x83
> is the x86 opcode "CMP r/m32, imm8" (which Intel documents as opcode "83
> /7 ib", and 0xfb is the mod/rm byte, encoding "mod=3", the 7 from the
> CMP opcode, and "rm=3", where the mod/rm bits mean "register ebx".  The
> Emit8(0) that follows copies  the value of the imm8 field in the opcode.
>
> The code could have also been written as:
>         Emit8(0x83);
>         Emit8(0xfb);
>         Emit8(0x00);
> But the C compiler won't produce as efficient code as it will for
> Emit16(0xfb83).
>
> Barry
> This posting is provided "AS IS" with no warranties, and confers no
> rights.
>
> -----Original Message-----
> From: Discussion of the Rotor Shared Source CLI implementation
> [mailto:[email protected]] On Behalf Of Archana
> Sent: Thursday, June 19, 2003 3:24 AM
> To: [email protected]
> Subject: [DOTNET-ROTOR] Assembly codes in jitinterfacex86.cpp
>
> Hi,
>  Is there any documentation regarding the opcodes used in the file
> jitinterfacex86.cpp and how the intel opcodes are mapped onto these
> codes
>   for example this is a piece of code from vm/i386/cgencpu.cpp,
>
>       // cmp ebx,0
>       Emit16(0xfb83);
>       Emit8(0);
> if one needs to write
>      // cmp edx,0
>
> what parameter should be passed to Emit16 etc..
>
> Thanks,
> archana
>