| ffs.S (256281) | ffs.S (271337) |
|---|---|
| 1/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */ 2/* 3 * Copyright (c) 2001 Christopher Gilbert 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: --- 16 unchanged lines hidden (view full) --- 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31#include <machine/asm.h> 32 | 1/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */ 2/* 3 * Copyright (c) 2001 Christopher Gilbert 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: --- 16 unchanged lines hidden (view full) --- 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31#include <machine/asm.h> 32 |
| 33__FBSDID("$FreeBSD: stable/10/lib/libc/arm/string/ffs.S 172616 2007-10-13 12:06:31Z cognet $"); | 33__FBSDID("$FreeBSD: stable/10/lib/libc/arm/string/ffs.S 271337 2014-09-09 22:24:01Z ian $"); |
| 34 35/* 36 * ffs - find first set bit, this algorithm isolates the first set 37 * bit, then multiplies the number by 0x0450fbaf which leaves the top 38 * 6 bits as an index into the table. This algorithm should be a win 39 * over the checking each bit in turn as per the C compiled version. 40 * 41 * under ARMv5 there's an instruction called CLZ (count leading Zero's) that --- 33 unchanged lines hidden (view full) --- 75 .byte 10, 0, 0, 25, 0, 0, 21, 27 /* 40-47 */ 76 .byte 31, 0, 0, 0, 0, 24, 0, 20 /* 48-55 */ 77 .byte 30, 0, 23, 19, 29, 18, 17, 0 /* 56-63 */ 78#else 79 clzne r0, r0 80 rsbne r0, r0, #32 81 RET 82#endif | 34 35/* 36 * ffs - find first set bit, this algorithm isolates the first set 37 * bit, then multiplies the number by 0x0450fbaf which leaves the top 38 * 6 bits as an index into the table. This algorithm should be a win 39 * over the checking each bit in turn as per the C compiled version. 40 * 41 * under ARMv5 there's an instruction called CLZ (count leading Zero's) that --- 33 unchanged lines hidden (view full) --- 75 .byte 10, 0, 0, 25, 0, 0, 21, 27 /* 40-47 */ 76 .byte 31, 0, 0, 0, 0, 24, 0, 20 /* 48-55 */ 77 .byte 30, 0, 23, 19, 29, 18, 17, 0 /* 56-63 */ 78#else 79 clzne r0, r0 80 rsbne r0, r0, #32 81 RET 82#endif |
| 83END(ffs) |
|