--- a/js/src/jit/AtomicOperations.h
+++ b/js/src/jit/AtomicOperations.h
@@ -337,7 +337,9 @@ AtomicOperations::isLockfree(int32_t size)
   // C++ realizations of atomics.  These operations cannot be written
   // in portable C++, hence the default here is to crash.  See the
   // top of the file for more guidance.
-# if defined(__ppc64__) || defined(__PPC64__) || defined(__ppc64le__) || defined(__PPC64LE__)
+# if defined(__ia64__)
+#  include "jit/none/AtomicOperations-ia64.h"
+# elif defined(__ppc64__) || defined(__PPC64__) || defined(__ppc64le__) || defined(__PPC64LE__)
 #  include "jit/none/AtomicOperations-ppc.h"
 # elif defined(__aarch64__)
 #  include "jit/arm64/AtomicOperations-arm64.h"
--- /dev/null
+++ b/js/src/jit/none/AtomicOperations-ia64.h
@@ -0,0 +1,239 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * 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/. */
+
+/* For documentation, see jit/AtomicOperations.h */
+
+#ifndef jit_ia64_AtomicOperations_ia64_h
+#define jit_ia64_AtomicOperations_ia64_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Types.h"
+
+#if defined(__GNUC__)
+
+// The default implementation tactic for gcc 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, should we need to use
+// those versions.
+
+//#define ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
+
+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));
+    MOZ_ASSERT(__atomic_always_lock_free(sizeof(int64_t), 0));
+#  endif
+    return true;
+# else
+    return false;
+# endif
+}
+
+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>
+inline T
+js::jit::AtomicOperations::loadSeqCst(T* addr)
+{
+    MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
+# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
+    __sync_synchronize();
+    T v = *addr;
+    __sync_synchronize();
+# else
+    T v;
+    __atomic_load(addr, &v, __ATOMIC_SEQ_CST);
+# endif
+    return v;
+}
+
+template<typename T>
+inline void
+js::jit::AtomicOperations::storeSeqCst(T* addr, T val)
+{
+    MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
+# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
+    __sync_synchronize();
+    *addr = val;
+    __sync_synchronize();
+# else
+    __atomic_store(addr, &val, __ATOMIC_SEQ_CST);
+# endif
+}
+
+template<typename T>
+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
+}
+
+template<typename T>
+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>
+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>
+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>
+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>
+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>
+inline T
+js::jit::AtomicOperations::loadSafeWhenRacy(T* addr)
+{
+    return *addr;               // FIXME (1208663): not yet safe
+}
+
+template<typename T>
+inline void
+js::jit::AtomicOperations::storeSafeWhenRacy(T* addr, T val)
+{
+    *addr = val;                // FIXME (1208663): not yet safe
+}
+
+inline void
+js::jit::AtomicOperations::memcpySafeWhenRacy(void* dest, const void* src, size_t nbytes)
+{
+    ::memcpy(dest, src, nbytes); // FIXME (1208663): not yet safe
+}
+
+inline void
+js::jit::AtomicOperations::memmoveSafeWhenRacy(void* dest, const void* src, size_t nbytes)
+{
+    ::memmove(dest, src, nbytes); // FIXME (1208663): not yet safe
+}
+
+template<typename T>
+inline T
+js::jit::AtomicOperations::exchangeSeqCst(T* addr, T val)
+{
+    MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
+# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
+    T v;
+    __sync_synchronize();
+    do {
+	v = *addr;
+    } while (__sync_val_compare_and_swap(addr, v, val) != v);
+    return v;
+# else
+    T v;
+    __atomic_exchange(addr, &val, &v, __ATOMIC_SEQ_CST);
+    return v;
+# endif
+}
+
+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))
+        ;
+# 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>
+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);
+# else
+    uint32_t zero = 0;
+    __atomic_store(&spinlock, &zero, __ATOMIC_SEQ_CST);
+# endif
+}
+
+# undef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
+
+#elif defined(ENABLE_SHARED_ARRAY_BUFFER)
+
+# error "Either disable JS shared memory, use GCC, or add code here"
+
+#endif
+
+#endif // jit_ia64_AtomicOperations_ia64_h