osfmk/ppc/bits.s

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