Re: Compiler support for Intel-MMX?

Frank Peelo schrieb:
>
> {MMX} : MMX support
> As of version 0.9.8, Free Pascal supports optimization for the MMX
> Intel processor.


....


> Things that change are Data with a
> size that is a multiple of 8 bytes is moved using the movq assembler
> instruction, which moves 8 bytes at a time


This wasn't a clever idea, we removed it and future versions will use
fld/fst.


> FP
> [Sounds like they're using it for block moves, which is certainly a fine
> idea but doesn't use any of the DSP-like arithmetic goodies. -John]


The new versions (0.99.x) contain a better MMX support, but it's still
in beta state (you need to recompile the compiler with -dSUPPORT_MMX)


the compiler allows the "explicit" use of MMX instructions:


var
      a,b,c : array[0..4] of integer;


begin
{$mmx+} { switch mmx instructions on }
      a:=b+c; { does a vectorial add of b and c }
      ....
{$saturation+} { work with saturating mmx instructions }
      a:=b+c;


Though I'am implementing that features, I'am not sure, if there are
serious applications for it. If you need _real_ (which is mostly
important where MMX is used) speed you should use assembler.
--

Return to the comp.compilers page.
Search the comp.compilers archives again.