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#
#
# Nimrod's Runtime Library
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## Atomic operations for Nimrod.
when (defined(gcc) or defined(llvm_gcc)) and hasThreadSupport:
type
AtomMemModel* = enum
ATOMIC_RELAXED, ## No barriers or synchronization.
ATOMIC_CONSUME, ## Data dependency only for both barrier and
## synchronization with another thread.
ATOMIC_ACQUIRE, ## Barrier to hoisting of code and synchronizes with
## release (or stronger)
## semantic stores from another thread.
ATOMIC_RELEASE, ## Barrier to sinking of code and synchronizes with
## acquire (or stronger)
## semantic loads from another thread.
ATOMIC_ACQ_REL, ## Full barrier in both directions and synchronizes
## with acquire loads
## and release stores in another thread.
ATOMIC_SEQ_CST ## Full barrier in both directions and synchronizes
## with acquire loads
## and release stores in all threads.
TAtomType* = TNumber|pointer|ptr|char
## Type Class representing valid types for use with atomic procs
proc atomicLoadN*[T: TAtomType](p: ptr T, mem: AtomMemModel): T {.
importc: "__atomic_load_n", nodecl.}
## This proc implements an atomic load operation. It returns the contents at p.
## ATOMIC_RELAXED, ATOMIC_SEQ_CST, ATOMIC_ACQUIRE, ATOMIC_CONSUME.
proc atomicLoad*[T: TAtomType](p, ret: ptr T, mem: AtomMemModel) {.
importc: "__atomic_load", nodecl.}
## This is the generic version of an atomic load. It returns the contents at p in ret.
proc atomicStoreN*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel) {.
importc: "__atomic_store_n", nodecl.}
## This proc implements an atomic store operation. It writes val at p.
## ATOMIC_RELAXED, ATOMIC_SEQ_CST, and ATOMIC_RELEASE.
proc atomicStore*[T: TAtomType](p, val: ptr T, mem: AtomMemModel) {.
importc: "__atomic_store", nodecl.}
## This is the generic version of an atomic store. It stores the value of val at p
proc atomicExchangeN*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_exchange_n", nodecl.}
## This proc implements an atomic exchange operation. It writes val at p,
## and returns the previous contents at p.
## ATOMIC_RELAXED, ATOMIC_SEQ_CST, ATOMIC_ACQUIRE, ATOMIC_RELEASE, ATOMIC_ACQ_REL
proc atomicExchange*[T: TAtomType](p, val, ret: ptr T, mem: AtomMemModel) {.
importc: "__atomic_exchange", nodecl.}
## This is the generic version of an atomic exchange. It stores the contents at val at p.
## The original value at p is copied into ret.
proc atomicCompareExchangeN*[T: TAtomType](p, expected: ptr T, desired: T,
weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool {.
importc: "__atomic_compare_exchange_n ", nodecl.}
## This proc implements an atomic compare and exchange operation. This compares the
## contents at p with the contents at expected and if equal, writes desired at p.
## If they are not equal, the current contents at p is written into expected.
## Weak is true for weak compare_exchange, and false for the strong variation.
## Many targets only offer the strong variation and ignore the parameter.
## When in doubt, use the strong variation.
## True is returned if desired is written at p and the execution is considered
## to conform to the memory model specified by success_memmodel. There are no
## restrictions on what memory model can be used here. False is returned otherwise,
## and the execution is considered to conform to failure_memmodel. This memory model
## cannot be __ATOMIC_RELEASE nor __ATOMIC_ACQ_REL. It also cannot be a stronger model
## than that specified by success_memmodel.
proc atomicCompareExchange*[T: TAtomType](p, expected, desired: ptr T,
weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool {.
importc: "__atomic_compare_exchange_n ", nodecl.}
## This proc implements the generic version of atomic_compare_exchange.
## The proc is virtually identical to atomic_compare_exchange_n, except the desired
## value is also a pointer.
## Perform the operation return the new value, all memory models are valid
proc atomicAddFetch*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_add_fetch", nodecl.}
proc atomicSubFetch*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_sub_fetch", nodecl.}
proc atomicOrFetch*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_or_fetch ", nodecl.}
proc atomicAndFetch*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_and_fetch", nodecl.}
proc atomicXorFetch*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_xor_fetch", nodecl.}
proc atomicNandFetch*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_nand_fetch ", nodecl.}
## Perform the operation return the old value, all memory models are valid
proc atomicFetchAdd*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_fetch_add", nodecl.}
proc atomicFetchSub*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_fetch_sub", nodecl.}
proc atomicFetchOr*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_fetch_or", nodecl.}
proc atomicFetchAnd*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_fetch_and", nodecl.}
proc atomicFetchXor*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_fetch_xor", nodecl.}
proc atomicFetchNand*[T: TAtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
importc: "__atomic_fetch_nand", nodecl.}
proc atomicTestAndSet*(p: pointer, mem: AtomMemModel): bool {.
importc: "__atomic_test_and_set", nodecl.}
## This built-in function performs an atomic test-and-set operation on the byte at p.
## The byte is set to some implementation defined nonzero “set” value and the return
## value is true if and only if the previous contents were “set”.
## All memory models are valid.
proc atomicClear*(p: pointer, mem: AtomMemModel) {.
importc: "__atomic_clear", nodecl.}
## This built-in function performs an atomic clear operation at p.
## After the operation, at p contains 0.
## ATOMIC_RELAXED, ATOMIC_SEQ_CST, ATOMIC_RELEASE
proc atomicThreadFence*(mem: AtomMemModel) {.
importc: "__atomic_thread_fence", nodecl.}
## This built-in function acts as a synchronization fence between threads based
## on the specified memory model. All memory orders are valid.
proc atomicSignalFence*(mem: AtomMemModel) {.
importc: "__atomic_signal_fence", nodecl.}
## This built-in function acts as a synchronization fence between a thread and
## signal handlers based in the same thread. All memory orders are valid.
proc atomicAlwaysLockFree*(size: int, p: pointer): bool {.
importc: "__atomic_always_lock_free", nodecl.}
## This built-in function returns true if objects of size bytes always generate
## lock free atomic instructions for the target architecture. size must resolve
## to a compile-time constant and the result also resolves to a compile-time constant.
## ptr is an optional pointer to the object that may be used to determine alignment.
## A value of 0 indicates typical alignment should be used. The compiler may also
## ignore this parameter.
proc atomicIsLockFree*(size: int, p: pointer): bool {.
importc: "__atomic_is_lock_free", nodecl.}
## This built-in function returns true if objects of size bytes always generate
## lock free atomic instructions for the target architecture. If it is not known
## to be lock free a call is made to a runtime routine named __atomic_is_lock_free.
## ptr is an optional pointer to the object that may be used to determine alignment.
## A value of 0 indicates typical alignment should be used. The compiler may also
## ignore this parameter.
elif defined(vcc) and hasThreadSupport:
proc addAndFetch*(p: ptr int, val: int): int {.
importc: "NimXadd", nodecl.}
else:
proc addAndFetch*(p: ptr int, val: int): int {.inline.} =
inc(p[], val)
result = p[]
# atomic compare and swap (CAS) funcitons to implement lock-free algorithms
#if defined(windows) and not defined(gcc) and hasThreadSupport:
# proc InterlockedCompareExchangePointer(mem: ptr pointer,
# newValue: pointer, comparand: pointer) : pointer {.nodecl,
# importc: "InterlockedCompareExchangePointer", header:"windows.h".}
# proc compareAndSwap*[T](mem: ptr T,
# expected: T, newValue: T): bool {.inline.}=
# ## Returns true if successfully set value at mem to newValue when value
# ## at mem == expected
# return InterlockedCompareExchangePointer(addr(mem),
# addr(newValue), addr(expected))[] == expected
#elif not hasThreadSupport:
# proc compareAndSwap*[T](mem: ptr T,
# expected: T, newValue: T): bool {.inline.} =
# ## Returns true if successfully set value at mem to newValue when value
# ## at mem == expected
# var oldval = mem[]
# if oldval == expected:
# mem[] = newValue
# return true
# return false
# Some convenient functions
proc atomicInc*(memLoc: var int, x: int = 1): int =
when defined(gcc) and hasThreadSupport:
result = atomic_add_fetch(memLoc.addr, x, ATOMIC_RELAXED)
else:
inc(memLoc, x)
result = memLoc
proc atomicDec*(memLoc: var int, x: int = 1): int =
when defined(gcc) and hasThreadSupport:
when defined(atomic_sub_fetch):
result = atomic_sub_fetch(memLoc.addr, x, ATOMIC_RELAXED)
else:
result = atomic_add_fetch(memLoc.addr, -x, ATOMIC_RELAXED)
else:
dec(memLoc, x)
result = memLoc
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