Re: bootsect.S changes

Andrzej Krzysztofowicz (ankry@pg.gda.pl)
Sat, 16 Oct 1999 17:05:55 +447403448 (MET DST)

Hi,
> The patch attempted to emulate the original bytecodes that as86/ld86
> output wherever possible. In an instruction by instruction disassembly,
> the new boot code differs only by a few bytes (or less with a recent
> binutils). Each 32 bit instruction in the original code was replaced by
> a 32 bitter in mine, and I don't recall adding or removing any: it was
> simply meant to be a "transcription" more than a cleanup (at least at
> this point).

I'm afraid there is some misunderstanding here...
16 -> 32-bit code migration started before the bin86->GAS migration.
You can see it in 2.3.19 as well as in 2.3.21.
I don't see any advantages of using the 32-bit code in bootsect.S.
So it was the reason of my first question:

are there *any* advantages of using it there ?

> What are the advantages of the following code:
> movw $128, %cx
> subw %si, %si
> subw %di, %di
> cld
> rep
> movsl <------- 32 bit
> instead of
> movw $256, %cx
> subw %si, %si
> subw %di, %di
> cld
> rep
> movsw <------- 16 bit
> (which is shorter), etc.
> I hope, nobody will joke saying it is faster ...

--
=======================================================================
  Andrzej M. Krzysztofowicz               ankry@mif.pg.gda.pl
  phone (48)(58) 347 14 61
Faculty of Applied Phys. & Math.,   Technical University of Gdansk




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