projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| a8cf7539 KB |
1 | /*- |
| 2 | * Copyright (c) 1990 The Regents of the University of California. | |
| 3 | * All rights reserved. | |
| 4 | * | |
| 5 | * %sccs.include.redist.c% | |
| 6 | */ | |
| 7 | ||
| 8 | #if defined(LIBC_SCCS) && !defined(lint) | |
| 9 | .asciz "@(#)memmove.s 5.1 (Berkeley) %G%" | |
| 10 | #endif /* LIBC_SCCS and not lint */ | |
| 11 | ||
| 12 | /* | |
| 13 | * void *memmove(dst, src, size) | |
| 14 | * returns dst | |
| 15 | * | |
| 16 | * This optimises the usual case (count < 65536) at the expense | |
| 17 | * of some extra memory references and branches when count >= 65536. | |
| 18 | */ | |
| 19 | ||
| 20 | #include "DEFS.h" | |
| 21 | ||
| 22 | ENTRY(memmove, 0) | |
| 23 | movzwl $65535,r0 /* r0 = 64K (needed below) */ | |
| 24 | movq 8(ap),r1 /* r1 = src, r2 = length */ | |
| 25 | movl 4(ap),r3 /* r3 = dst */ | |
| 26 | cmpl r1,r3 | |
| 27 | bgtru 1f /* normal forward case */ | |
| 28 | beql 2f /* equal, nothing to do */ | |
| 29 | addl2 r2,r1 /* overlaps iff src<dst but src+len>dst */ | |
| 30 | cmpl r1,r3 | |
| 31 | bgtru 4f /* overlapping, must move backwards */ | |
| 32 | subl2 r2,r1 | |
| 33 | ||
| 34 | 1: /* move forward */ | |
| 35 | cmpl r2,r0 | |
| 36 | bgtru 3f /* stupid movc3 limitation */ | |
| 37 | movc3 r2,(r1),(r3) /* move it all */ | |
| 38 | 2: | |
| 39 | movl 4(ap),r0 /* return original dst */ | |
| 40 | ret | |
| 41 | 3: | |
| 42 | subl2 r0,12(ap) /* adjust length by 64K */ | |
| 43 | movc3 r0,(r1),(r3) /* move 64K */ | |
| 44 | movl 12(ap),r2 | |
| 45 | decw r0 /* from 0 to 65535 */ | |
| 46 | brb 1b /* retry */ | |
| 47 | ||
| 48 | 4: /* move backward */ | |
| 49 | addl2 r2,r3 | |
| 50 | 5: | |
| 51 | cmpl r2,r0 | |
| 52 | bgtru 6f /* stupid movc3 limitation */ | |
| 53 | subl2 r2,r1 | |
| 54 | subl2 r2,r3 | |
| 55 | movc3 r2,(r1),(r3) /* move it all */ | |
| 56 | movl 4(ap),r0 /* return original dst */ | |
| 57 | ret | |
| 58 | 6: | |
| 59 | subl2 r0,12(ap) /* adjust length by 64K */ | |
| 60 | subl2 r0,r1 | |
| 61 | subl2 r0,r3 | |
| 62 | movc3 r0,(r1),(r3) /* move 64K */ | |
| 63 | movl 12(ap),r2 | |
| 64 | decw r0 | |
| 65 | subl2 r0,r1 | |
| 66 | subl2 r0,r3 | |
| 67 | brb 5b |