projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 51533b61 MS |
1 | /* |
| 2 | * A fast checksum routine using movem | |
| 41f9412b | 3 | * Copyright (c) 1998-2007 Axis Communications AB |
| 51533b61 MS |
4 | * |
| 5 | * csum_partial(const unsigned char * buff, int len, unsigned int sum) | |
| 6 | */ | |
| 7 | ||
| 8 | .globl csum_partial | |
| 3a38125d | 9 | .type csum_partial,@function |
| 51533b61 MS |
10 | csum_partial: |
| 11 | ||
| 12 | ;; r10 - src | |
| 13 | ;; r11 - length | |
| 14 | ;; r12 - checksum | |
| 15 | ||
| 41f9412b JN |
16 | ;; Optimized for large packets |
| 17 | subq 10*4, $r11 | |
| 18 | blt _word_loop | |
| 19 | move.d $r11, $acr | |
| 51533b61 MS |
20 | |
| 21 | subq 9*4,$sp | |
| 41f9412b | 22 | clearf c |
| 51533b61 MS |
23 | movem $r8,[$sp] |
| 24 | ||
| 25 | ;; do a movem checksum | |
| 26 | ||
| 27 | _mloop: movem [$r10+],$r9 ; read 10 longwords | |
| 41f9412b JN |
28 | ;; Loop count without touching the c flag. |
| 29 | addoq -10*4, $acr, $acr | |
| 51533b61 MS |
30 | ;; perform dword checksumming on the 10 longwords |
| 31 | ||
| 41f9412b | 32 | addc $r0,$r12 |
| 51533b61 MS |
33 | addc $r1,$r12 |
| 34 | addc $r2,$r12 | |
| 35 | addc $r3,$r12 | |
| 36 | addc $r4,$r12 | |
| 37 | addc $r5,$r12 | |
| 38 | addc $r6,$r12 | |
| 39 | addc $r7,$r12 | |
| 40 | addc $r8,$r12 | |
| 41 | addc $r9,$r12 | |
| 42 | ||
| 41f9412b JN |
43 | ;; test $acr without trashing carry. |
| 44 | move.d $acr, $acr | |
| 45 | bpl _mloop | |
| 46 | ;; r11 <= acr is not really needed in the mloop, just using the dslot | |
| 47 | ;; to prepare for what is needed after mloop. | |
| 48 | move.d $acr, $r11 | |
| 51533b61 | 49 | |
| 41f9412b JN |
50 | ;; fold the last carry into r13 |
| 51 | addc 0, $r12 | |
| 51533b61 MS |
52 | movem [$sp+],$r8 ; restore regs |
| 53 | ||
| 54 | _word_loop: | |
| 41f9412b | 55 | addq 10*4,$r11 ; compensate for last loop underflowing length |
| 51533b61 MS |
56 | |
| 57 | moveq -1,$r9 ; put 0xffff in r9, faster than move.d 0xffff,r9 | |
| 58 | lsrq 16,$r9 | |
| 59 | ||
| 60 | move.d $r12,$r13 | |
| 61 | lsrq 16,$r13 ; r13 = checksum >> 16 | |
| 41f9412b | 62 | and.d $r9,$r12 ; checksum = checksum & 0xffff |
| 51533b61 MS |
63 | |
| 64 | _no_fold: | |
| 41f9412b | 65 | subq 2,$r11 |
| 51533b61 | 66 | blt _no_words |
| 41f9412b | 67 | add.d $r13,$r12 ; checksum += r13 |
| 51533b61 MS |
68 | |
| 69 | ;; checksum the rest of the words | |
| 51533b61 MS |
70 | _wloop: subq 2,$r11 |
| 71 | bge _wloop | |
| 72 | addu.w [$r10+],$r12 | |
| 73 | ||
| 51533b61 | 74 | _no_words: |
| 41f9412b | 75 | addq 2,$r11 |
| 51533b61 | 76 | ;; see if we have one odd byte more |
| 41f9412b | 77 | bne _do_byte |
| 51533b61 MS |
78 | nop |
| 79 | ret | |
| 80 | move.d $r12,$r10 | |
| 81 | ||
| 82 | _do_byte: | |
| 83 | ;; copy and checksum the last byte | |
| 84 | addu.b [$r10],$r12 | |
| 85 | ret | |
| 86 | move.d $r12,$r10 | |
| 3a38125d JN |
87 | |
| 88 | .size csum_partial, .-csum_partial |