projects / dragonfly.git / blame
| Commit | Line | Data |
|---|---|---|
| f4a040fe PA |
1 | /* |
| 2 | * Written by J.T. Conklin <jtc@NetBSD.org>. | |
| 3 | * Public domain. | |
| 4 | * Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com> | |
| 5 | * | |
| 6 | * $NetBSD: bzero.S,v 1.2 2003/07/26 19:24:38 salo Exp $ | |
| 7 | * $FreeBSD: src/lib/libc/amd64/string/bzero.S,v 1.3 2008/11/02 01:10:54 peter Exp $ | |
| 8 | */ | |
| 9 | ||
| 10 | #include <machine/asm.h> | |
| 11 | ||
| 12 | ENTRY(bzero) | |
| 13 | cld /* set fill direction forward */ | |
| 14 | xorq %rax,%rax /* set fill data to 0 */ | |
| 15 | ||
| 16 | /* | |
| 17 | * if the string is too short, it's really not worth the overhead | |
| 18 | * of aligning to word boundries, etc. So we jump to a plain | |
| 19 | * unaligned set. | |
| 20 | */ | |
| 21 | cmpq $16,%rsi | |
| 22 | jb L1 | |
| 23 | ||
| 24 | movq %rdi,%rcx /* compute misalignment */ | |
| 25 | negq %rcx | |
| 26 | andq $7,%rcx | |
| 27 | subq %rcx,%rsi | |
| 28 | rep /* zero until word aligned */ | |
| 29 | stosb | |
| 30 | ||
| 31 | movq %rsi,%rcx /* zero by words */ | |
| 32 | shrq $3,%rcx | |
| 33 | andq $7,%rsi | |
| 34 | rep | |
| 35 | stosq | |
| 36 | ||
| 37 | L1: movq %rsi,%rcx /* zero remainder by bytes */ | |
| 38 | rep | |
| 39 | stosb | |
| 40 | ||
| 41 | ret | |
| 42 | END(bzero) |