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swab.S revision 1.14 
      1   1.1       cgd /*
      2  1.11      salo  * Written by J.T. Conklin <jtc (at) NetBSD.org>.
      3   1.8       jtc  * Public domain.
      4   1.1       cgd  */
      5   1.1       cgd 
      6   1.7       jtc #include <machine/asm.h>
      7   1.7       jtc 
      8   1.2       jtc #if defined(LIBC_SCCS)
      9  1.14  uebayasi 	RCSID("$NetBSD: swab.S,v 1.14 2014/05/23 02:34:19 uebayasi Exp $")
     10   1.1       cgd #endif
     11   1.1       cgd 
     12   1.1       cgd /*
     13   1.1       cgd  * On the i486, this code is negligibly faster than the code generated
     14   1.3       jtc  * by gcc at about half the size.  If my i386 databook is correct, it
     15   1.1       cgd  * should be considerably faster than the gcc code on a i386.
     16   1.1       cgd  */
     17   1.1       cgd 
     18   1.1       cgd ENTRY(swab)
     19   1.1       cgd 	pushl	%esi
     20   1.1       cgd 	pushl	%edi
     21   1.1       cgd 	movl	12(%esp),%esi
     22   1.1       cgd 	movl	16(%esp),%edi
     23   1.1       cgd 	movl	20(%esp),%ecx
     24   1.1       cgd 
     25   1.4       jtc 	shrl	$1,%ecx
     26   1.1       cgd 	testl	$7,%ecx			# copy first group of 1 to 7 words
     27  1.12    rpaulo 	jz	L2			# while swapping alternate bytes.
     28  1.10    kleink 	_ALIGN_TEXT,0x90
     29   1.1       cgd L1:	lodsw
     30   1.6       jtc 	rorw	$8,%ax
     31   1.1       cgd 	stosw
     32   1.1       cgd 	decl	%ecx
     33   1.1       cgd 	testl	$7,%ecx
     34   1.4       jtc 	jnz	L1
     35   1.3       jtc 
     36   1.1       cgd L2:	shrl	$3,%ecx			# copy remainder 8 words at a time
     37   1.1       cgd 	jz	L4			# while swapping alternate bytes.
     38  1.10    kleink 	_ALIGN_TEXT,0x90
     39   1.1       cgd L3:	lodsw
     40   1.6       jtc 	rorw	$8,%ax
     41   1.1       cgd 	stosw
     42   1.1       cgd 	lodsw
     43   1.6       jtc 	rorw	$8,%ax
     44   1.1       cgd 	stosw
     45   1.1       cgd 	lodsw
     46   1.6       jtc 	rorw	$8,%ax
     47   1.1       cgd 	stosw
     48   1.1       cgd 	lodsw
     49   1.6       jtc 	rorw	$8,%ax
     50   1.1       cgd 	stosw
     51   1.1       cgd 	lodsw
     52   1.6       jtc 	rorw	$8,%ax
     53   1.1       cgd 	stosw
     54   1.1       cgd 	lodsw
     55   1.6       jtc 	rorw	$8,%ax
     56   1.1       cgd 	stosw
     57   1.1       cgd 	lodsw
     58   1.6       jtc 	rorw	$8,%ax
     59   1.1       cgd 	stosw
     60   1.1       cgd 	lodsw
     61   1.6       jtc 	rorw	$8,%ax
     62   1.1       cgd 	stosw
     63   1.1       cgd 	decl	%ecx
     64   1.1       cgd 	jnz	L3
     65   1.1       cgd 
     66   1.6       jtc L4:	popl	%edi
     67   1.1       cgd 	popl	%esi
     68   1.1       cgd 	ret
     69  1.14  uebayasi END(swab)
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