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      1 /* ----------------------------------------------------------------------- *
      2  *
      3  *   Copyright 2008 H. Peter Anvin - All Rights Reserved
      4  *
      5  *   Permission is hereby granted, free of charge, to any person
      6  *   obtaining a copy of this software and associated documentation
      7  *   files (the "Software"), to deal in the Software without
      8  *   restriction, including without limitation the rights to use,
      9  *   copy, modify, merge, publish, distribute, sublicense, and/or
     10  *   sell copies of the Software, and to permit persons to whom
     11  *   the Software is furnished to do so, subject to the following
     12  *   conditions:
     13  *
     14  *   The above copyright notice and this permission notice shall
     15  *   be included in all copies or substantial portions of the Software.
     16  *
     17  *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     18  *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
     19  *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     20  *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
     21  *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
     22  *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     23  *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
     24  *   OTHER DEALINGS IN THE SOFTWARE.
     25  *
     26  * ----------------------------------------------------------------------- */
     27 
     28 /*
     29  * memset.S
     30  *
     31  * Reasonably efficient memset, using aligned transfers at least
     32  * for the destination operand.
     33  */
     34 
     35 	.globl	memset
     36 	.type	memset,@function
     37 	.text
     38 memset:
     39 	jecxz	6f
     40 
     41 	pushl	%edi
     42 	pushl	%ebx
     43 	pushl	%eax		/* Return value */
     44 
     45 	movl	%eax,%edi
     46 	movb	%dl,%dh
     47 	movzwl	%dx,%eax
     48 	shll	$16,%edx
     49 	orl	%edx,%eax
     50 
     51 	/* Initial alignment */
     52 	movl	%edi,%edx
     53 	shrl	$1,%edx
     54 	jnc	1f
     55 	stosb
     56 	decl	%ecx
     57 1:
     58 	movb	%cl,%bl
     59 	cmpl	$2,%ecx
     60 	jb	3f
     61 	shrl	$1,%edx
     62 	jnc	2f
     63 	stosw
     64 	subl	$2,%ecx
     65 2:
     66 	/* Bulk transfer */
     67 	movb	%cl,%bl
     68 	shrl	$2,%ecx
     69 	rep; stosl
     70 
     71 	testb	$2,%bl
     72 	jz	4f
     73 	stosw
     74 3:
     75 4:
     76 	testb	$1,%bl
     77 	jz	5f
     78 	stosb
     79 5:
     80 	popl	%eax		/* Return value */
     81 	popl	%ebx
     82 	popl	%edi
     83 6:
     84 	ret
     85 
     86 	.size	memset, .-memset
     87