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96 lines
3.0 KiB
TeX
96 lines
3.0 KiB
TeX
%
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% $Id$
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% This file is part of the FPC documentation.
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% Copyright (C) 1997, by Michael Van Canneyt
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%
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% The FPC documentation is free text; you can redistribute it and/or
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% modify it under the terms of the GNU Library General Public License as
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% published by the Free Software Foundation; either version 2 of the
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% License, or (at your option) any later version.
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%
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% The FPC Documentation is distributed in the hope that it will be useful,
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% but WITHOUT ANY WARRANTY; without even the implied warranty of
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% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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% Library General Public License for more details.
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%
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% You should have received a copy of the GNU Library General Public
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% License along with the FPC documentation; see the file COPYING.LIB. If not,
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% write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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% Boston, MA 02111-1307, USA.
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%
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\chapter{The MMX unit}
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This chapter describes the \file{MMX} unit. This unit allows you to use the
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\var{MMX} capabilities of the \fpc compiler. It was written by Florian
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Kl\"ampfl for the \var{I386} processor.
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\section{Variables, Types and constants}
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The following types are defined in the \var{MMX} unit:
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\begin{verbatim}
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tmmxshortint = array[0..7] of shortint;
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tmmxbyte = array[0..7] of byte;
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tmmxword = array[0..3] of word;
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tmmxinteger = array[0..3] of integer;
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tmmxfixed = array[0..3] of fixed16;
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tmmxlongint = array[0..1] of longint;
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tmmxcardinal = array[0..1] of cardinal;
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{ for the AMD 3D }
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tmmxsingle = array[0..1] of single;
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\end{verbatim}
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And the following pointers to the above types:
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\begin{verbatim}
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pmmxshortint = ^tmmxshortint;
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pmmxbyte = ^tmmxbyte;
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pmmxword = ^tmmxword;
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pmmxinteger = ^tmmxinteger;
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pmmxfixed = ^tmmxfixed;
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pmmxlongint = ^tmmxlongint;
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pmmxcardinal = ^tmmxcardinal;
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{ for the AMD 3D }
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pmmxsingle = ^tmmxsingle;
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\end{verbatim}
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The following initialized constants allow you to determine if the computer
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has \var{MMX} extensions. They are set correctly in the unit's
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initialization code.
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\begin{verbatim}
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is_mmx_cpu : boolean = false;
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is_amd_3d_cpu : boolean = false;
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\end{verbatim}
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\section{Functions and Procedures}
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\begin{procedure}{Emms}
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\Declaration
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Procedure Emms ;
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\Description
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\var{Emms} sets all floating point registers to empty. This procedure must
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be called after you have used any \var{MMX} instructions, if you want to use
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floating point arithmetic. If you just want to move floating point data
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around, it isn't necessary to call this function, the compiler doesn't use
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the FPU registers when moving data. Only when doing calculations, you should
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use this function.
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\Errors
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None.
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\SeeAlso
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\progref
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\end{procedure}
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\begin{FPCList}
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\item[Example:]
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\begin{verbatim}
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Program MMXDemo;
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uses mmx;
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var
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d1 : double;
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a : array[0..10000] of double;
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i : longint;
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begin
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d1:=1.0;
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{$mmx+}
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{ floating point data is used, but we do _no_ arithmetic }
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for i:=0 to 10000 do
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a[i]:=d2; { this is done with 64 bit moves }
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{$mmx-}
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emms; { clear fpu }
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{ now we can do floating point arithmetic again }
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end.
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\end{verbatim}
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\end{FPCList}
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