1 /* Copyright (C) 1996-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library. If not, see
16 <https://www.gnu.org/licenses/>. */
18 /* Finds the first bit set in an integer. Optimized for the Alpha
55 cmpbge $1, $2, $3 # e0 : bit N == 1 for byte N == 0
58 bic $4, $3, $3 # e1 : bit N == 1 for first byte N != 0
59 and $3, 0xF0, $4 # e0 :
60 and $3, 0xCC, $5 # .. e1 :
61 and $3, 0xAA, $6 # e0 :
62 cmovne $4, 4, $0 # .. e1 :
63 cmovne $5, 2, $5 # e0 :
64 cmovne $6, 1, $6 # .. e1 :
65 addl $0, $5, $0 # e0 :
66 addl $0, $6, $0 # e1 : $0 == N
67 extbl $16, $0, $1 # e0 : $1 == byte N
70 and $3, $1, $3 # e1 : bit N == least bit set of byte N
71 and $3, 0xF0, $4 # e0 :
72 and $3, 0xCC, $5 # .. e1 :
73 and $3, 0xAA, $6 # e0 :
74 cmovne $4, 5, $2 # .. e1 :
75 cmovne $5, 2, $5 # e0 :
76 cmovne $6, 1, $6 # .. e1 :
77 s8addl $0, $2, $0 # e0 : mult byte ofs by 8 and sum
78 addl $5, $6, $5 # .. e1 :
79 addl $0, $5, $0 # e0 :
81 cmoveq $16, 0, $0 # e0 : trap input == 0 case.
86 weak_alias (__ffs, ffs)
87 libc_hidden_def (__ffs)
88 libc_hidden_builtin_def (ffs)
90 weak_alias (ffsl, ffsll)