summaryrefslogtreecommitdiff
path: root/js/src/jit/x86-shared/AtomicOperations-x86-shared.h
diff options
context:
space:
mode:
Diffstat (limited to 'js/src/jit/x86-shared/AtomicOperations-x86-shared.h')
-rw-r--r--js/src/jit/x86-shared/AtomicOperations-x86-shared.h108
1 files changed, 0 insertions, 108 deletions
diff --git a/js/src/jit/x86-shared/AtomicOperations-x86-shared.h b/js/src/jit/x86-shared/AtomicOperations-x86-shared.h
index 1230c7feb..4eee00a3d 100644
--- a/js/src/jit/x86-shared/AtomicOperations-x86-shared.h
+++ b/js/src/jit/x86-shared/AtomicOperations-x86-shared.h
@@ -45,18 +45,6 @@
#if defined(__clang__) || defined(__GNUC__)
-// The default implementation tactic for gcc/clang is to use the newer
-// __atomic intrinsics added for use in C++11 <atomic>. Where that
-// isn't available, we use GCC's older __sync functions instead.
-//
-// ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS is kept as a backward
-// compatible option for older compilers: enable this to use GCC's old
-// __sync functions instead of the newer __atomic functions. This
-// will be required for GCC 4.6.x and earlier, and probably for Clang
-// 3.1, should we need to use those versions.
-
-// #define ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
-
// Lock-free 8-byte atomics are assumed on x86 but must be disabled in
// corner cases, see comments below and in isLockfree8().
@@ -77,15 +65,11 @@
inline bool
js::jit::AtomicOperations::isLockfree8()
{
-# ifndef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int8_t), 0));
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int16_t), 0));
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int32_t), 0));
-# endif
# ifdef LOCKFREE8
-# ifndef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int64_t), 0));
-# endif
return true;
# else
return false;
@@ -95,11 +79,7 @@ js::jit::AtomicOperations::isLockfree8()
inline void
js::jit::AtomicOperations::fenceSeqCst()
{
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- __sync_synchronize();
-# else
__atomic_thread_fence(__ATOMIC_SEQ_CST);
-# endif
}
template<typename T>
@@ -107,16 +87,8 @@ inline T
js::jit::AtomicOperations::loadSeqCst(T* addr)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- // Inhibit compiler reordering with a volatile load. The x86 does
- // not reorder loads with respect to subsequent loads or stores
- // and no ordering barrier is required here. See more elaborate
- // comments in storeSeqCst.
- T v = *static_cast<T volatile*>(addr);
-# else
T v;
__atomic_load(addr, &v, __ATOMIC_SEQ_CST);
-# endif
return v;
}
@@ -141,43 +113,7 @@ inline void
js::jit::AtomicOperations::storeSeqCst(T* addr, T val)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- // Inhibit compiler reordering with a volatile store. The x86 may
- // reorder a store with respect to a subsequent load from a
- // different location, hence there is an ordering barrier here to
- // prevent that.
- //
- // By way of background, look to eg
- // http://bartoszmilewski.com/2008/11/05/who-ordered-memory-fences-on-an-x86/
- //
- // Consider:
- //
- // uint8_t x = 0, y = 0; // to start
- //
- // thread1:
- // sx: AtomicOperations::store(&x, 1);
- // gy: uint8_t obs1 = AtomicOperations::loadSeqCst(&y);
- //
- // thread2:
- // sy: AtomicOperations::store(&y, 1);
- // gx: uint8_t obs2 = AtomicOperations::loadSeqCst(&x);
- //
- // Sequential consistency requires a total global ordering of
- // operations: sx-gy-sy-gx, sx-sy-gx-gy, sx-sy-gy-gx, sy-gx-sx-gy,
- // sy-sx-gy-gx, or sy-sx-gx-gy. In every ordering at least one of
- // sx-before-gx or sy-before-gy happens, so *at least one* of
- // obs1/obs2 is 1.
- //
- // If AtomicOperations::{load,store}SeqCst were just volatile
- // {load,store}, x86 could reorder gx/gy before each thread's
- // prior load. That would permit gx-gy-sx-sy: both loads would be
- // 0! Thus after a volatile store we must synchronize to ensure
- // the store happens before the load.
- *static_cast<T volatile*>(addr) = val;
- __sync_synchronize();
-# else
__atomic_store(addr, &val, __ATOMIC_SEQ_CST);
-# endif
}
# ifndef LOCKFREE8
@@ -201,19 +137,9 @@ inline T
js::jit::AtomicOperations::exchangeSeqCst(T* addr, T val)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- T v;
- do {
- // Here I assume the compiler will not hoist the load. It
- // shouldn't, because the CAS could affect* addr.
- v = *addr;
- } while (!__sync_bool_compare_and_swap(addr, v, val));
- return v;
-# else
T v;
__atomic_exchange(addr, &val, &v, __ATOMIC_SEQ_CST);
return v;
-# endif
}
# ifndef LOCKFREE8
@@ -237,12 +163,8 @@ inline T
js::jit::AtomicOperations::compareExchangeSeqCst(T* addr, T oldval, T newval)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- return __sync_val_compare_and_swap(addr, oldval, newval);
-# else
__atomic_compare_exchange(addr, &oldval, &newval, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
return oldval;
-# endif
}
# ifndef LOCKFREE8
@@ -266,11 +188,7 @@ inline T
js::jit::AtomicOperations::fetchAddSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- return __sync_fetch_and_add(addr, val);
-# else
return __atomic_fetch_add(addr, val, __ATOMIC_SEQ_CST);
-# endif
}
template<typename T>
@@ -278,11 +196,7 @@ inline T
js::jit::AtomicOperations::fetchSubSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- return __sync_fetch_and_sub(addr, val);
-# else
return __atomic_fetch_sub(addr, val, __ATOMIC_SEQ_CST);
-# endif
}
template<typename T>
@@ -290,11 +204,7 @@ inline T
js::jit::AtomicOperations::fetchAndSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- return __sync_fetch_and_and(addr, val);
-# else
return __atomic_fetch_and(addr, val, __ATOMIC_SEQ_CST);
-# endif
}
template<typename T>
@@ -302,11 +212,7 @@ inline T
js::jit::AtomicOperations::fetchOrSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- return __sync_fetch_and_or(addr, val);
-# else
return __atomic_fetch_or(addr, val, __ATOMIC_SEQ_CST);
-# endif
}
template<typename T>
@@ -314,11 +220,7 @@ inline T
js::jit::AtomicOperations::fetchXorSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- return __sync_fetch_and_xor(addr, val);
-# else
return __atomic_fetch_xor(addr, val, __ATOMIC_SEQ_CST);
-# endif
}
template<typename T>
@@ -351,17 +253,12 @@ template<size_t nbytes>
inline void
js::jit::RegionLock::acquire(void* addr)
{
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- while (!__sync_bool_compare_and_swap(&spinlock, 0, 1))
- continue;
-# else
uint32_t zero = 0;
uint32_t one = 1;
while (!__atomic_compare_exchange(&spinlock, &zero, &one, false, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE)) {
zero = 0;
continue;
}
-# endif
}
template<size_t nbytes>
@@ -369,15 +266,10 @@ inline void
js::jit::RegionLock::release(void* addr)
{
MOZ_ASSERT(AtomicOperations::loadSeqCst(&spinlock) == 1, "releasing unlocked region lock");
-# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
- __sync_sub_and_fetch(&spinlock, 1); // Should turn into LOCK XADD
-# else
uint32_t zero = 0;
__atomic_store(&spinlock, &zero, __ATOMIC_SEQ_CST);
-# endif
}
-# undef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
# undef LOCKFREE8
#elif defined(_MSC_VER)
generated by cgit v1.2.3 (git 2.26.2) at 2024-06-02 06:02:42 +0000