Newsgroups:	comp.os.msdos.djgpp
From:	Peter Berdeklis <peter AT atmosp DOT physics DOT utoronto DOT ca>
Subject:	Re: SHRD & SHLD instructions
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Date:	Wed, 22 Jan 1997 16:35:38 GMT
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On 20 Jan 1997, Wayne Ross wrote:
> Are you sure about that? SHLD & SHRD shift a register's bits left/right and
> move bits from another register into the positions left behind., i.e,
> 
> For a SHLD reg1, count, reg2
> 
> 	reg1	reg2
> <----------	0110<---	1001
> 
> As the bits from reg1 are shifted left, bits are shifted in from reg2 to
> occupy the space.
> 
> For two 16 bit numbers SHLD would perform the same function as SHLL, but
> for two 32 bit numbers (one 64 bit number :-) ) it would not.

Sorry about that.  The correct name is shldl (or shldw for 16 bit 
registers).  The syntax is as follows:

shldl count,source,dest

where count is an immed. or %cl, giving the shift count, source is the
source of the shifted in bits and dest is the shifted reg.  This is the
exact backwards of the Intel syntax, as usual.  Note that only the dest 
is altered.

---------------
Peter Berdeklis
Dept. of Physics, Univ. of Toronto

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