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To: <7eggert@gmx.de>, "Gene Heskett" <gene.heskett@verizon.net>,
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References: <4fB8l-73q-9@gated-at.bofh.it> <4fF2j-1Lo-19@gated-at.bofh.it> <E1DiZKe-0000em-58@be1.7eggert.dyndns.org>
Subject: Re: .../asm-i386/bitops.h  performance improvements
Date: Wed, 15 Jun 2005 19:53:27 -0400
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Ummm, in simple terms - this statement is flat out 100% wrong.

LEA with the SIB byte has been around since 386 and is included on every CPU
Linux is capable of running on.

Compile this using -m386 and look at the ASM listing file and convince
yourself.

unsigned int foo(int bar)
{
return ((bar<<3)+bar);
}

GCC is going to generate a MOV of parm to EAX, then a LEA EAX,[EAX+EAX*8]

Don't trust me - compile this and prove it to yourself.


----- Original Message ----- 
From: "Bodo Eggert" <harvested.in.lkml@posting.7eggert.dyndns.org>
To: "Gene Heskett" <gene.heskett@verizon.net>; <cutaway@bellsouth.net>;
<linux->
>
> However, the multiplicator is not documented for i486, therefore it will
be a i586
> extension.