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SubjectRe: .../asm-i386/bitops.h performance improvements
On Wed, 15 Jun 2005, Maciej W. Rozycki wrote:
> On Wed, 15 Jun 2005, Richard B. Johnson wrote:

> > 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.
>
> And "m" is presumably described in details elsewhere as the semantics is
> common for all instructions involving address calculation.

My documentation says:

lea reg16, mem
Available on 8086, 80186, 80286, 80386, 80486
32-bit-extension available
Opcode: 8D mod reg r/m

reg will be the target register (AX .. DI), and mod and r/m will select
something like a direct address, a register or a combination like
BP+DI+ofs (I won't copy the table). A multiplier is not mentioned there.
--
Microwave: Signal from a friendly micro...
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