michael@0: ! -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
michael@0: ! 
michael@0: ! This Source Code Form is subject to the terms of the Mozilla Public
michael@0: ! License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0: ! file, You can obtain one at http://mozilla.org/MPL/2.0/.
michael@0: 
michael@0: !
michael@0: !  atomic increment, decrement and swap routines for V8+ sparc (ultrasparc)
michael@0: !  using CAS (compare-and-swap) atomic instructions
michael@0: !
michael@0: !  this MUST be compiled with an ultrasparc-aware assembler
michael@0: !
michael@0: !  standard asm linkage macros; this module must be compiled
michael@0: !  with the -P option (use C preprocessor)
michael@0: 
michael@0: #include <sys/asm_linkage.h>
michael@0: 
michael@0: !  ======================================================================
michael@0: !
michael@0: !  Perform the sequence a = a + 1 atomically with respect to other
michael@0: !  fetch-and-adds to location a in a wait-free fashion.
michael@0: !
michael@0: !  usage : val = PR_AtomicIncrement(address)
michael@0: !  return: current value (you'd think this would be old val)
michael@0: !
michael@0: !  -----------------------
michael@0: !  Note on REGISTER USAGE:
michael@0: !  as this is a LEAF procedure, a new stack frame is not created;
michael@0: !  we use the caller's stack frame so what would normally be %i (input)
michael@0: !  registers are actually %o (output registers).  Also, we must not
michael@0: !  overwrite the contents of %l (local) registers as they are not
michael@0: !  assumed to be volatile during calls.
michael@0: !
michael@0: !  So, the registers used are:
michael@0: !     %o0  [input]   - the address of the value to increment
michael@0: !     %o1  [local]   - work register
michael@0: !     %o2  [local]   - work register
michael@0: !     %o3  [local]   - work register
michael@0: !  -----------------------
michael@0: 
michael@0:         ENTRY(PR_AtomicIncrement)       ! standard assembler/ELF prologue
michael@0: 
michael@0: retryAI:
michael@0:         ld      [%o0], %o2              ! set o2 to the current value
michael@0:         add     %o2, 0x1, %o3           ! calc the new value
michael@0:         mov     %o3, %o1                ! save the return value
michael@0:         cas     [%o0], %o2, %o3         ! atomically set if o0 hasn't changed
michael@0:         cmp     %o2, %o3                ! see if we set the value
michael@0:         bne     retryAI                 ! if not, try again
michael@0:         nop                             ! empty out the branch pipeline
michael@0:         retl                            ! return back to the caller
michael@0:         mov     %o1, %o0                ! set the return code to the new value
michael@0: 
michael@0:         SET_SIZE(PR_AtomicIncrement)    ! standard assembler/ELF epilogue
michael@0: 
michael@0: !
michael@0: !  end
michael@0: !
michael@0: !  ======================================================================
michael@0: !
michael@0: 
michael@0: !  ======================================================================
michael@0: !
michael@0: !  Perform the sequence a = a - 1 atomically with respect to other
michael@0: !  fetch-and-decs to location a in a wait-free fashion.
michael@0: !
michael@0: !  usage : val = PR_AtomicDecrement(address)
michael@0: !  return: current value (you'd think this would be old val)
michael@0: !
michael@0: !  -----------------------
michael@0: !  Note on REGISTER USAGE:
michael@0: !  as this is a LEAF procedure, a new stack frame is not created;
michael@0: !  we use the caller's stack frame so what would normally be %i (input)
michael@0: !  registers are actually %o (output registers).  Also, we must not
michael@0: !  overwrite the contents of %l (local) registers as they are not
michael@0: !  assumed to be volatile during calls.
michael@0: !
michael@0: !  So, the registers used are:
michael@0: !     %o0  [input]   - the address of the value to increment
michael@0: !     %o1  [local]   - work register
michael@0: !     %o2  [local]   - work register
michael@0: !     %o3  [local]   - work register
michael@0: !  -----------------------
michael@0: 
michael@0:         ENTRY(PR_AtomicDecrement)       ! standard assembler/ELF prologue
michael@0: 
michael@0: retryAD:
michael@0:         ld      [%o0], %o2              ! set o2 to the current value
michael@0:         sub     %o2, 0x1, %o3           ! calc the new value
michael@0:         mov     %o3, %o1                ! save the return value
michael@0:         cas     [%o0], %o2, %o3         ! atomically set if o0 hasn't changed
michael@0:         cmp     %o2, %o3                ! see if we set the value
michael@0:         bne     retryAD                 ! if not, try again
michael@0:         nop                             ! empty out the branch pipeline
michael@0:         retl                            ! return back to the caller
michael@0:         mov     %o1, %o0                ! set the return code to the new value
michael@0: 
michael@0:         SET_SIZE(PR_AtomicDecrement)    ! standard assembler/ELF epilogue
michael@0: 
michael@0: !
michael@0: !  end
michael@0: !
michael@0: !  ======================================================================
michael@0: !
michael@0: 
michael@0: !  ======================================================================
michael@0: !
michael@0: !  Perform the sequence a = b atomically with respect to other
michael@0: !  fetch-and-stores to location a in a wait-free fashion.
michael@0: !
michael@0: !  usage : old_val = PR_AtomicSet(address, newval)
michael@0: !
michael@0: !  -----------------------
michael@0: !  Note on REGISTER USAGE:
michael@0: !  as this is a LEAF procedure, a new stack frame is not created;
michael@0: !  we use the caller's stack frame so what would normally be %i (input)
michael@0: !  registers are actually %o (output registers).  Also, we must not
michael@0: !  overwrite the contents of %l (local) registers as they are not
michael@0: !  assumed to be volatile during calls.
michael@0: !
michael@0: !  So, the registers used are:
michael@0: !     %o0  [input]   - the address of the value to increment
michael@0: !     %o1  [input]   - the new value to set for [%o0]
michael@0: !     %o2  [local]   - work register
michael@0: !     %o3  [local]   - work register
michael@0: !  -----------------------
michael@0: 
michael@0:         ENTRY(PR_AtomicSet)             ! standard assembler/ELF prologue
michael@0: 
michael@0: retryAS:
michael@0:         ld      [%o0], %o2              ! set o2 to the current value
michael@0:         mov     %o1, %o3                ! set up the new value
michael@0:         cas     [%o0], %o2, %o3         ! atomically set if o0 hasn't changed
michael@0:         cmp     %o2, %o3                ! see if we set the value
michael@0:         bne     retryAS                 ! if not, try again
michael@0:         nop                             ! empty out the branch pipeline
michael@0:         retl                            ! return back to the caller
michael@0:         mov     %o3, %o0                ! set the return code to the prev value
michael@0: 
michael@0:         SET_SIZE(PR_AtomicSet)          ! standard assembler/ELF epilogue
michael@0: 
michael@0: !
michael@0: !  end
michael@0: !
michael@0: !  ======================================================================
michael@0: !
michael@0: 
michael@0: !  ======================================================================
michael@0: !
michael@0: !  Perform the sequence a = a + b atomically with respect to other
michael@0: !  fetch-and-adds to location a in a wait-free fashion.
michael@0: !
michael@0: !  usage : newval = PR_AtomicAdd(address, val)
michael@0: !  return: the value after addition
michael@0: !
michael@0:         ENTRY(PR_AtomicAdd)       ! standard assembler/ELF prologue
michael@0: 
michael@0: retryAA:
michael@0:         ld      [%o0], %o2              ! set o2 to the current value
michael@0:         add     %o2, %o1, %o3           ! calc the new value
michael@0:         mov     %o3, %o4                ! save the return value
michael@0:         cas     [%o0], %o2, %o3         ! atomically set if o0 hasn't changed
michael@0:         cmp     %o2, %o3                ! see if we set the value
michael@0:         bne     retryAA                 ! if not, try again
michael@0:         nop                             ! empty out the branch pipeline
michael@0:         retl                            ! return back to the caller
michael@0:         mov     %o4, %o0                ! set the return code to the new value
michael@0: 
michael@0:         SET_SIZE(PR_AtomicAdd)    		! standard assembler/ELF epilogue
michael@0: 
michael@0: !
michael@0: !  end
michael@0: !