js/src/lock_SunOS.s

   1 !
   2 ! ***** BEGIN LICENSE BLOCK *****
   3 ! Version: MPL 1.1/GPL 2.0/LGPL 2.1
   4 !
   5 ! The contents of this file are subject to the Mozilla Public License Version
   6 ! 1.1 (the "License"); you may not use this file except in compliance with
   7 ! the License. You may obtain a copy of the License at
   8 ! http://www.mozilla.org/MPL/
   9 !
  10 ! Software distributed under the License is distributed on an "AS IS" basis,
  11 ! WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  12 ! for the specific language governing rights and limitations under the
  13 ! License.
  14 !
  15 ! The Original Code is Mozilla Communicator client code, released
  16 ! March 31, 1998.
  17 !
  18 ! The Initial Developer of the Original Code is
  19 ! Netscape Communications Corporation.
  20 ! Portions created by the Initial Developer are Copyright (C) 1998-1999
  21 ! the Initial Developer. All Rights Reserved.
  22 !
  23 ! Contributor(s):
  24 !
  25 ! Alternatively, the contents of this file may be used under the terms of
  26 ! either the GNU General Public License Version 2 or later (the "GPL"), or
  27 ! the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28 ! in which case the provisions of the GPL or the LGPL are applicable instead
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  34 ! the provisions above, a recipient may use your version of this file under
  35 ! the terms of any one of the MPL, the GPL or the LGPL.
  36 !
  37 ! ***** END LICENSE BLOCK *****
  38
  39 !
  40 !  atomic compare-and-swap routines for V8 sparc
  41 !  and for V8+ (ultrasparc)
  42 !
  43 !
  44 !  standard asm linkage macros; this module must be compiled
  45 !  with the -P option (use C preprocessor)
  46
  47 #include <sys/asm_linkage.h>
  48
  49 !  ======================================================================
  50 !
  51 !  Perform the sequence *a = b atomically with respect to previous value
  52 !  of a (a0). If *a==a0 then assign *a to b, all in one atomic operation.
  53 !  Returns 1 if assignment happened, and 0 otherwise.
  54 !
  55 !  usage : old_val = compare_and_swap(address, oldval, newval)
  56 !
  57 !  -----------------------
  58 !  Note on REGISTER USAGE:
  59 !  as this is a LEAF procedure, a new stack frame is not created;
  60 !  we use the caller stack frame so what would normally be %i (input)
  61 !  registers are actually %o (output registers).  Also, we must not
  62 !  overwrite the contents of %l (local) registers as they are not
  63 !  assumed to be volatile during calls.
  64 !
  65 !  So, the registers used are:
  66 !     %o0  [input]   - the address of the value to increment
  67 !     %o1  [input]   - the old value to compare with
  68 !     %o2  [input]   - the new value to set for [%o0]
  69 !     %o3  [local]   - work register
  70 !  -----------------------
  71 #ifndef ULTRA_SPARC
  72 !  v8
  73
  74         ENTRY(compare_and_swap)         ! standard assembler/ELF prologue
  75
  76         stbar
  77         mov -1,%o3                      ! busy flag
  78         swap [%o0],%o3                  ! get current value
  79 l1:     cmp %o3,-1                      ! busy?
  80         be,a l1                         ! if so, spin
  81         swap [%o0],%o3                  ! using branch-delay to swap back value
  82         cmp %o1,%o3                     ! compare old with current
  83         be,a l2                         ! if equal then swap in new value
  84         swap [%o0],%o2                  ! done.
  85         swap [%o0],%o3                  ! otherwise, swap back current value
  86         retl
  87         mov 0,%o0                       ! return false
  88 l2:     retl
  89         mov 1,%o0                       ! return true
  90
  91         SET_SIZE(compare_and_swap)      ! standard assembler/ELF epilogue
  92
  93 !
  94 !  end
  95 !
  96 #else /* ULTRA_SPARC */
  97 !  ======================================================================
  98 !
  99 !  v9
 100
 101         ENTRY(compare_and_swap)         ! standard assembler/ELF prologue
 102
 103         stbar
 104         cas [%o0],%o1,%o2               ! compare *w with old value and set to new if equal
 105         cmp %o1,%o2                     ! did we succeed?
 106         be,a m1                         ! yes
 107         mov 1,%o0                       ! return true (annulled when no jump)
 108         mov 0,%o0                       ! return false
 109 m1:     retl
 110         nop
 111
 112         SET_SIZE(compare_and_swap)      ! standard assembler/ELF epilogue
 113
 114 !
 115 !  end
 116 !
 117 !  ======================================================================
 118 !
 119 #endif