diff options
Diffstat (limited to 'lib/libc/alpha/string/ffs.S')
| -rw-r--r-- | lib/libc/alpha/string/ffs.S | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/lib/libc/alpha/string/ffs.S b/lib/libc/alpha/string/ffs.S new file mode 100644 index 0000000..4c30a16 --- /dev/null +++ b/lib/libc/alpha/string/ffs.S @@ -0,0 +1,91 @@ +/* $NetBSD: ffs.S,v 1.3 1996/10/17 03:08:13 cgd Exp $ */ + +/* + * Copyright (c) 1995 Christopher G. Demetriou + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by Christopher G. Demetriou + * for the NetBSD Project. + * 4. The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include <machine/asm.h> + +LEAF(ffs, 1) + addl a0, 0, t0 + beq t0, Lallzero + + /* + * Initialize return value (v0), and set up t1 so that it + * contains the mask with only the lowest bit set. + */ + subl zero, t0, t1 + ldil v0, 1 + and t0, t1, t1 + + and t1, 0xff, t2 + bne t2, Ldo8 + + /* + * If lower 16 bits empty, add 16 to result and use upper 16. + */ + zapnot t1, 0x03, t3 + bne t3, Ldo16 + sra t1, 16, t1 + addl v0, 16, v0 + +Ldo16: + /* + * If lower 8 bits empty, add 8 to result and use upper 8. + */ + and t1, 0xff, t4 + bne t4, Ldo8 + sra t1, 8, t1 + addl v0, 8, v0 + +Ldo8: + and t1, 0x0f, t5 /* lower 4 of 8 empty? */ + and t1, 0x33, t6 /* lower 2 of each 4 empty? */ + and t1, 0x55, t7 /* lower 1 of each 2 empty? */ + + /* If lower 4 bits empty, add 4 to result. */ + bne t5, Ldo4 + addl v0, 4, v0 + +Ldo4: /* If lower 2 bits of each 4 empty, add 2 to result. */ + bne t6, Ldo2 + addl v0, 2, v0 + +Ldo2: /* If lower bit of each 2 empty, add 1 to result. */ + bne t7, Ldone + addl v0, 1, v0 + +Ldone: + RET + +Lallzero: + bis zero, zero, v0 + RET +END(ffs) |
