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 movl 0xc(%esp),%ecx 40 movl 0x8(%esp),%edx 41 movl 0x4(%esp),%eax 42 43 jecxz 6f 44 45 pushl %edi 46 pushl %ebx 47 pushl %eax /* Return value */ 48 49 movl %eax,%edi 50 movb %dl,%dh 51 movzwl %dx,%eax 52 shll $16,%edx 53 orl %edx,%eax 54 55 /* Initial alignment */ 56 movl %edi,%edx 57 shrl $1,%edx 58 jnc 1f 59 stosb 60 decl %ecx 61 1: 62 movb %cl,%bl 63 cmpl $2,%ecx 64 jb 3f 65 shrl $1,%edx 66 jnc 2f 67 stosw 68 subl $2,%ecx 69 2: 70 /* Bulk transfer */ 71 movb %cl,%bl 72 shrl $2,%ecx 73 rep; stosl 74 75 testb $2,%bl 76 jz 4f 77 stosw 78 3: 79 4: 80 testb $1,%bl 81 jz 5f 82 stosb 83 5: 84 popl %eax /* Return value */ 85 popl %ebx 86 popl %edi 87 6: 88 ret 89 90 .size memset, .-memset 91
