ports/sysdeps/alpha/ffs.S

   1 /* Copyright (C) 1996-2013 Free Software Foundation, Inc.
   2    Contributed by David Mosberger (davidm@cs.arizona.edu).
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library.  If not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 /* Finds the first bit set in an integer.  Optimized for the Alpha
  20    architecture.  */
  21
  22 #include <sysdep.h>
  23
  24         .set noreorder
  25         .set noat
  26
  27
  28 ENTRY(__ffs)
  29 #ifdef PROF
  30         ldgp    gp, 0(pv)
  31         lda     AT, _mcount
  32         jsr     AT, (AT), _mcount
  33         .prologue 1
  34         zap     $16, 0xF0, $16
  35         br      $ffsl..ng
  36 #else
  37         .prologue 0
  38         zap     $16, 0xF0, $16
  39         # FALLTHRU
  40 #endif
  41 END(__ffs)
  42
  43         .align 4
  44 ENTRY(ffsl)
  45 #ifdef PROF
  46         ldgp    gp, 0(pv)
  47         lda     AT, _mcount
  48         jsr     AT, (AT), _mcount
  49         .prologue 1
  50 $ffsl..ng:
  51 #else
  52         .prologue 0
  53 #endif
  54         not     $16, $1         # e0    :
  55         ldi     $2, -1          # .. e1 :
  56         cmpbge  $1, $2, $3      # e0    : bit N == 1 for byte N == 0
  57         clr     $0              # .. e1 :
  58         addq    $3, 1, $4       # e0    :
  59         bic     $4, $3, $3      # e1    : bit N == 1 for first byte N != 0
  60         and     $3, 0xF0, $4    # e0    :
  61         and     $3, 0xCC, $5    # .. e1 :
  62         and     $3, 0xAA, $6    # e0    :
  63         cmovne  $4, 4, $0       # .. e1 :
  64         cmovne  $5, 2, $5       # e0    :
  65         cmovne  $6, 1, $6       # .. e1 :
  66         addl    $0, $5, $0      # e0    :
  67         addl    $0, $6, $0      # e1    : $0 == N
  68         extbl   $16, $0, $1     # e0    : $1 == byte N
  69         ldi     $2, 1           # .. e1 :
  70         negq    $1, $3          # e0    :
  71         and     $3, $1, $3      # e1    : bit N == least bit set of byte N
  72         and     $3, 0xF0, $4    # e0    :
  73         and     $3, 0xCC, $5    # .. e1 :
  74         and     $3, 0xAA, $6    # e0    :
  75         cmovne  $4, 5, $2       # .. e1 :
  76         cmovne  $5, 2, $5       # e0    :
  77         cmovne  $6, 1, $6       # .. e1 :
  78         s8addl  $0, $2, $0      # e0    : mult byte ofs by 8 and sum
  79         addl    $5, $6, $5      # .. e1 :
  80         addl    $0, $5, $0      # e0    :
  81         nop                     # .. e1 :
  82         cmoveq  $16, 0, $0      # e0    : trap input == 0 case.
  83         ret                     # .. e1 : 18
  84
  85 END(ffsl)
  86
  87 weak_alias (__ffs, ffs)
  88 libc_hidden_builtin_def (ffs)
  89 weak_extern (ffsl)
  90 weak_alias (ffsl, ffsll)