Re: 387 emulator hack - mutant AAD trick - any objections?

[Mikael Pettersson]

cutaway@xxxxxxxxxxxxx writes:
 > Will there be any objections to using a quasi-documented mutation of the
 > x86's AAD instruction in the 387 emulator? Every CPU around has to do this
 > mutation correctly or a LOT of existing code will break...
 > 
 > The performance of storing to user space of BCD numbers in the 387 emulator
 > code could be improved significantly by using the mutant AAD instruction
 > trick (i.e. alter its implicit base from 10 to 16).  See reg_ld_str.c, in
 > function FPU_store_bcd()

What do you mean by "quasi-documented" and "mutant"?
Intel certainly documents the "D5 ib" form as being a
valid way to change the base from the default 10.

The only issue AFAIK is that assemblers may only
recognise the plain base-10 AAD syntax. No biggie.

/Mikael
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