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Date: Thu, 16 Jun 2005 09:10:09 +0200
From: Mikael Pettersson <mikpe@csd.uu.se>
To: Bodo Eggert <7eggert@gmx.de>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>,
       "Richard B. Johnson" <linux-os@analogic.com>,
       Gene Heskett <gene.heskett@verizon.net>, cutaway@bellsouth.net,
       linux-kernel@vger.kernel.org
Subject: Re: .../asm-i386/bitops.h  performance improvements
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Bodo Eggert writes:
 > 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.

You're looking at the wrong parts of the documentation. The 16-bit
mode ModR/M doesn't have SIB, but the 32-bit mode does. The SIB includes
the scaled index. All IA32 processors have it. The only LEA-related
quirk is that its ModR/M must not describe a non-memory operand.