Re: [ros-dev] MASM using longer opcode sequences than GAS

[David Quintana (gigaherz)]

No idea about the encoding length, but I wonder why we don't just use NASM
everywhere, instead of having two separate assemblers.

On 17 January 2017 at 10:23, Colin Finck <colin(a)reactos.org> wrote:

>   Hi all,
>
>  In order to make our ISOs flashable to USB drives and bootable from them
>  (cf. CORE-12648), I'm currently overhauling our ISO boot sector
>  "isoboot.S". This adds a lot of code and while I stay in the 2K size
>  limit when assembling it with GAS, I break it with MASM.
>
>  Disassembling the assembled files shows the difference.
>  A line like:
>
>     mov word ptr ds:[GetlinsecPtr], ax
>
>  is assembled by GAS to:
>
>     A35B50            mov [0x505b],ax
>
>  while MASM does this:
>
>     67A35B500000      mov [dword 0x505b],ax
>
>
>  Is there any option to enforce the shorter opcode sequence for MASM too?
>  The code uses a lot of similar MOVs and this seems to be the only reason
>  why I break the 2K size limit with MASM.
>
>  If there is no such option, what are the advantages of using MASM for
>  our MSVC build anyway? Can't we just use GAS for both or decide on a
>  common third-party assembler (NASM) for our assembly files?
>
>
>  Cheers,
>
>  Colin
>
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