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