projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| b20e47cb RM |
1 | /* Copyright (C) 1996 Free Software Foundation, Inc. |
| 2 | Contributed by David Mosberger (davidm@cs.arizona.edu). | |
| 3 | ||
| 4 | This file is part of the GNU C Library. | |
| 5 | ||
| 6 | The GNU C Library is free software; you can redistribute it and/or | |
| 7 | modify it under the terms of the GNU Library General Public License as | |
| 8 | published by the Free Software Foundation; either version 2 of the | |
| 9 | License, or (at your option) any later version. | |
| 10 | ||
| 11 | The GNU C Library is distributed in the hope that it will be useful, | |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 14 | Library General Public License for more details. | |
| 15 | ||
| 16 | You should have received a copy of the GNU Library General Public | |
| 17 | License along with the GNU C Library; see the file COPYING.LIB. If | |
| 18 | not, write to the Free Software Foundation, Inc., 675 Mass Ave, | |
| 19 | Cambridge, MA 02139, USA. */ | |
| 20 | ||
| 21 | /* Finds the first bit set in an integer. Optimized for the Alpha | |
| 22 | architecture. */ | |
| 23 | ||
| 24 | #include <sysdep.h> | |
| b20e47cb RM |
25 | |
| 26 | .set noreorder | |
| 27 | .set noat | |
| 28 | ||
| 29 | ENTRY(ffs) | |
| 2c6fe0bd UD |
30 | #ifdef PROF |
| 31 | ldgp gp, 0(pv) | |
| 32 | lda AT, _mcount | |
| 33 | jsr AT, (AT), _mcount | |
| 34 | .prologue 1 | |
| 35 | #else | |
| b20e47cb | 36 | .prologue 0 |
| 2c6fe0bd | 37 | #endif |
| b20e47cb RM |
38 | |
| 39 | ldq_u zero, 0(sp) # on the 21064, this helps dual-issuing | |
| 40 | addl a0, zero, a0 # the last insn and reduces the stall | |
| 41 | negq a0, t0 # due to the srl instruction | |
| 42 | and a0, t0, t0 | |
| 43 | clr v0 | |
| a5113b14 | 44 | beq a0, $done |
| b20e47cb RM |
45 | |
| 46 | # now do binary search for first non-zero bit | |
| 47 | ||
| 48 | zapnot t0, 0x03, t2 | |
| 49 | addq v0, 16, t3 | |
| 50 | cmoveq t2, t3, v0 | |
| 51 | ||
| 52 | zapnot t0, 0x05, t2 | |
| 53 | addq v0, 8, t3 | |
| 54 | cmoveq t2, t3, v0 | |
| 55 | ||
| 56 | srl t0, v0, t0 | |
| 57 | addq v0, 1, v0 | |
| 58 | ||
| 59 | and t0, 0x0f, t2 | |
| 60 | addq v0, 4, t3 | |
| 61 | cmoveq t2, t3, v0 | |
| 62 | ||
| 63 | and t0, 0x33, t2 | |
| 64 | addq v0, 2, t3 | |
| 65 | cmoveq t2, t3, v0 | |
| 66 | ||
| 67 | and t0, 0x55, t2 | |
| 68 | addq v0, 1, t3 | |
| 69 | cmoveq t2, t3, v0 | |
| 70 | ||
| a5113b14 | 71 | $done: ret |
| b20e47cb | 72 | |
| 84724245 | 73 | END(ffs) |