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From: bimandre@kulcs.uucp (Andre Marien)
Newsgroups: comp.arch
Subject: Re: Endian reversing MOVEs
Message-ID: <1586@kulcs.kulcs.uucp>
Date: 8 Feb 89 11:14:21 GMT
References: <759@atanasoff.cs.iastate.edu,MXvZBhy00W428s8WI0@andrew.cmu.edu>
Reply-To: bimandre@kulcs.UUCP ()
Organization: B.I.M., Belgium
Lines: 46

> John Hascall writes:
> > ;
> > ;     Move and Reverse Endian-ness Longword
> > ;
> >       .macro  MREL    src,dst
> >       PUSHL   src                     ; stack source operand
> >       MOVB    0(SP),-(SP)             ; re-stack HI byte
> >       MOVB    2(SP),-(SP)             ; re-stack HI-MID byte
> >       MOVB    4(SP),-(SP)             ; re-stack LO-MID byte
> >       MOVB    6(SP),-(SP)             ; re-stack LO byte
> >       MOVL    (SP)+,dst               ; pop it into destination operand
> >       TSTL    (SP)+                   ; clear stack, set cond code
> >       .endm

> That's 11 memory references for something which has nothing to do with memory.
> It only takes 6 instructions (0 memory references) on the RT.

This can be done on the VAX too :
*/
int g,cg;

conv()
{
  asm("	movl	_g,r0");
  asm("	rotl	$8,r0,r1");
  asm("	rotl	$24,r0,r2");
  asm("	bicl2	$0xff00ff00,r1");
  asm("	bicl2	  $0xff00ff,r2");
  asm("	addl3	r1,r2,_cg");
}

main()
{ while(1)
  { scanf("%d",&g);
    conv();
    printf("src = %x dst = %x\n",g,cg);
  }
}

/*
Andre' Marien
B.I.M.
Belgium
bimandre@cs.kuleuven.ac.be
sun!sunuk!sunbim!kulcs!bimandre
*/