Re: add edi,0FFFFFFFFH

On 15 Aug, 09:19, "Rod Pemberton"
<do_not_h...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
It's important for assembly to produce exactly what it was told to do...
Not being able to generate a specific instruction encoding is an issue
I've seen with other assemblers

It's never been my opinion that an assembler should allow you to
generate any instruction encoding, only that it should generate an
encoding which performs the requested operation (ideally an
'optimised' encoding, when there is a choice). For example consider
those encodings which incorporate a 'direction' (d) bit; do you
suggest that an assembler should allow you to generate both these
encodings, and if so how (32-bit code, but the point remains the
same):

03 C3 add eax,ebx
01 D8 add eax,ebx

What about cases where there are dedicated encodings for the EAX
register. Would you expect an assembler to allow you to choose
between these alternatives:

83 C0 08 add eax,8
05 08 00 00 00 add eax,8
81 C0 08 00 00 00 add eax,8

Although I can see why you might want to choose between alternative
encodings in some specific cases, requiring that you can generate
*any* valid encoding seems somewhat unreasonable and I'm not aware of
any assembler that does (other than by using DBs).

Richard.
http://www.rtrussell.co.uk/
.

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