osfmk/ppc/bits.s

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * @OSF_COPYRIGHT@
  27  *
  28  */
  29
  30 #include <ppc/asm.h>
  31 #include <ppc/proc_reg.h>
  32
  33 #
  34 # void setbit(int bitno, int *s)
  35 #
  36 # Set indicated bit in bit string.
  37 #     Note:     being big-endian, bit 0 is 0x80000000.
  38
  39 ENTRY(setbit,TAG_NO_FRAME_USED)
  40
  41         rlwinm          r8,r3,29,3,31           /* Get byte displacement */
  42         rlwinm          r9,r3,0,29,31           /* Get bit within byte */
  43         li                      r6,0x80                         /* Start with bit 0 */
  44         lbzx            r5,r4,r8                        /* Grab target byte */
  45         srw                     r6,r6,r9                        /* Get the right bit (fits right into the load cycle) */
  46         or                      r5,r5,r6                        /* Turn on the right bit */
  47         stbx            r5,r4,r8                        /* Save the byte back */
  48         blr
  49
  50 #
  51 # void clrbit(int bitno, int *s)
  52 #
  53 # Clear indicated bit in bit string.
  54 #     Note:     being big-endian, bit 0 is 0x80000000.
  55
  56 ENTRY(clrbit,TAG_NO_FRAME_USED)
  57
  58         rlwinm          r8,r3,29,3,31           /* Get byte displacement */
  59         rlwinm          r9,r3,0,29,31           /* Get bit within byte */
  60         li                      r6,0x80                         /* Start with bit 0 */
  61         lbzx            r5,r4,r8                        /* Grab target byte */
  62         srw                     r6,r6,r9                        /* Get the right bit (fits right into the load cycle) */
  63         andc            r5,r5,r6                        /* Turn off the right bit */
  64         stbx            r5,r4,r8                        /* Save the byte back */
  65         blr
  66
  67
  68 # /*
  69 #  * Find first bit set in bit string.
  70 #  */
  71 # int
  72 # ffsbit(int *s)
  73 #
  74 # Returns the bit index of the first bit set (starting from 0)
  75 # Assumes pointer is word-aligned
  76
  77 ENTRY(ffsbit, TAG_NO_FRAME_USED)
  78         lwz     r0,     0(ARG0)
  79                 mr      ARG1,   ARG0    /* Free up ARG0 for result */
  80
  81         cmpwi   r0,     0               /* Check against zero... */
  82                 cntlzw  ARG0,   r0      /* Free inst... find the set bit... */
  83         bnelr+                          /* Return if bit in first word */
  84
  85 .L_ffsbit_lp:
  86         lwz     r0,     4(ARG1)
  87         addi    ARG1,   ARG1,   4
  88         cmpwi   r0,     0               /* Check against zero... */
  89                 cntlzw  r12,    r0
  90                 add     ARG0,   ARG0,   r12     /* ARG0 keeps bit count */
  91         beq+    .L_ffsbit_lp
  92         blr
  93
  94 /*
  95  * int tstbit(int bitno, int *s)
  96  *
  97  * Test indicated bit in bit string.
  98  *      Note:    being big-endian, bit 0 is 0x80000000.
  99  */
 100
 101 ENTRY2(tstbit, testbit, TAG_NO_FRAME_USED)
 102
 103         rlwinm          r8,r3,29,3,31           /* Get byte displacement */
 104         rlwinm          r9,r3,0,29,31           /* Get bit within byte */
 105         lbzx            r5,r4,r8                        /* Grab target byte */
 106         addi            r9,r9,25                        /* Get actual shift value */
 107         rlwnm           r3,r5,r9,31,31          /* Pass the bit back */
 108         blr