osfmk/ppc/bits.s

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * @OSF_COPYRIGHT@
  24  *
  25  */
  26
  27 #include <ppc/asm.h>
  28 #include <ppc/proc_reg.h>
  29
  30 #
  31 # void setbit(int bitno, int *s)
  32 #
  33 # Set indicated bit in bit string.
  34 #     Note:     being big-endian, bit 0 is 0x80000000.
  35
  36 ENTRY(setbit,TAG_NO_FRAME_USED)
  37
  38         rlwinm          r8,r3,29,3,31           /* Get byte displacement */
  39         rlwinm          r9,r3,0,29,31           /* Get bit within byte */
  40         li                      r6,0x80                         /* Start with bit 0 */
  41         lbzx            r5,r4,r8                        /* Grab target byte */
  42         srw                     r6,r6,r9                        /* Get the right bit (fits right into the load cycle) */
  43         or                      r5,r5,r6                        /* Turn on the right bit */
  44         stbx            r5,r4,r8                        /* Save the byte back */
  45         blr
  46
  47 #
  48 # void clrbit(int bitno, int *s)
  49 #
  50 # Clear indicated bit in bit string.
  51 #     Note:     being big-endian, bit 0 is 0x80000000.
  52
  53 ENTRY(clrbit,TAG_NO_FRAME_USED)
  54
  55         rlwinm          r8,r3,29,3,31           /* Get byte displacement */
  56         rlwinm          r9,r3,0,29,31           /* Get bit within byte */
  57         li                      r6,0x80                         /* Start with bit 0 */
  58         lbzx            r5,r4,r8                        /* Grab target byte */
  59         srw                     r6,r6,r9                        /* Get the right bit (fits right into the load cycle) */
  60         andc            r5,r5,r6                        /* Turn off the right bit */
  61         stbx            r5,r4,r8                        /* Save the byte back */
  62         blr
  63
  64
  65 # /*
  66 #  * Find first bit set in bit string.
  67 #  */
  68 # int
  69 # ffsbit(int *s)
  70 #
  71 # Returns the bit index of the first bit set (starting from 0)
  72 # Assumes pointer is word-aligned
  73
  74 ENTRY(ffsbit, TAG_NO_FRAME_USED)
  75         lwz     r0,     0(ARG0)
  76                 mr      ARG1,   ARG0    /* Free up ARG0 for result */
  77
  78         cmpwi   r0,     0               /* Check against zero... */
  79                 cntlzw  ARG0,   r0      /* Free inst... find the set bit... */
  80         bnelr+                          /* Return if bit in first word */
  81
  82 .L_ffsbit_lp:
  83         lwz     r0,     4(ARG1)
  84         addi    ARG1,   ARG1,   4
  85         cmpwi   r0,     0               /* Check against zero... */
  86                 cntlzw  r12,    r0
  87                 add     ARG0,   ARG0,   r12     /* ARG0 keeps bit count */
  88         beq+    .L_ffsbit_lp
  89         blr
  90
  91 /*
  92  * int tstbit(int bitno, int *s)
  93  *
  94  * Test indicated bit in bit string.
  95  *      Note:    being big-endian, bit 0 is 0x80000000.
  96  */
  97
  98 ENTRY2(tstbit, testbit, TAG_NO_FRAME_USED)
  99
 100         rlwinm          r8,r3,29,3,31           /* Get byte displacement */
 101         rlwinm          r9,r3,0,29,31           /* Get bit within byte */
 102         lbzx            r5,r4,r8                        /* Grab target byte */
 103         addi            r9,r9,25                        /* Get actual shift value */
 104         rlwnm           r3,r5,r9,31,31          /* Pass the bit back */
 105         blr