| 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 |
|---|
