Created
April 23, 2014 04:23
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ARM is pretty, slightly faster edition
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| .global crc_asm02 /* uint32_t crc_asm02(void *buf, uint32_t len); */ | |
| .extern tab_asm02 /* uint32_t tab_asm02[256]; */ | |
| crc_asm02: | |
| push {r4, r5, r6} | |
| /* prepare table */ | |
| mov r4, #0x00 | |
| ldr r5, =tab_asm02 | |
| ldr r3, =0xEDB88320 | |
| .L2A: | |
| mov r2, r4 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| lsrs r2, #1 | |
| eorcs r2, r3 | |
| str r2, [r5] | |
| add r4, #1 | |
| add r5, #4 | |
| cmp r4, #0x100 | |
| bne .L2A | |
| /* perform CRC */ | |
| mvn r2, #0 | |
| ldr r6, =tab_asm02 | |
| .L2: | |
| ldrb r4, [r0] | |
| add r0, #1 | |
| eor r2, r4 | |
| and r5, r2, #0x000000FF | |
| ldr r4, [r6, r5, lsl #2] | |
| eor r2, r4, r2, lsr #8 | |
| subs r1, #1 | |
| bne .L2 | |
| mvn r0, r2 | |
| pop {r4, r5, r6} | |
| bx lr |
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