Messages in this thread | | | Date | Wed, 15 Jun 2005 12:06:28 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: .../asm-i386/bitops.h performance improvements |
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On Wed, 15 Jun 2005, Maciej W. Rozycki wrote:
> On Wed, 15 Jun 2005, Bodo Eggert wrote: > >> lea is an 8086 instruction. All clones have it in it's basic form. However, >> the multiplicator is not documented for i486, therefore it will be a i586 >> extension. > > Huh? The SIB byte has been added in the original i386 with 32-bit > addressing. > > Maciej
Well the __documented__ '486 LEA instruction doesn't even allow the double-register indirect. It's just
LEA r16,m LEA r32,m
... repeated twice
Page 26-190, Intel486(tm) Microprocessor Programmer's Reference Manual. ISBN 1-55512-195-4. The instruction may have been one of those "immature features", read broken.
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