SERVER-6018 Use gcc __sync primitives if they are available and useable

3 files changed, 114 insertions, 8 deletions

diff --git a/src/mongo/platform/atomic_intrinsics.h b/src/mongo/platform/atomic_intrinsics.h
index c67fa3495fb..d8a60ada361 100644
--- a/src/mongo/platform/atomic_intrinsics.h
+++ b/src/mongo/platform/atomic_intrinsics.h
@@ -54,14 +54,12 @@
 
 #if defined(_WIN32)
 #include "mongo/platform/atomic_intrinsics_win32.h"
-#elif defined(__GNUC__)
-#if defined(HAVE_GCC_ATOMIC_BUILTINS)
-#include "mongo/platform/atomic_intrinsics_gcc_generic.h"
+#elif defined(MONGO_HAVE_GCC_ATOMIC_BUILTINS)
+#include "mongo/platform/atomic_intrinsics_gcc_atomic.h"
+#elif defined(MONGO_HAVE_GCC_SYNC_BUILTINS)
+#include "mongo/platform/atomic_intrinsics_gcc_sync.h"
 #elif defined(__i386__) || defined(__x86_64__)
 #include "mongo/platform/atomic_intrinsics_gcc_intel.h"
 #else
-#error "Unsupported platform: no gcc atomic builtins or port available"
-#endif
-#else
 #error "Unsupported os/compiler family"
 #endif
diff --git a/src/mongo/platform/atomic_intrinsics_gcc_generic.h b/src/mongo/platform/atomic_intrinsics_gcc_atomic.h
index 0848585d312..5e2e7d24a14 100644
--- a/src/mongo/platform/atomic_intrinsics_gcc_generic.h
+++ b/src/mongo/platform/atomic_intrinsics_gcc_atomic.h
@@ -32,8 +32,6 @@
 
 #pragma once
 
-#include <boost/utility.hpp>
-
 namespace mongo {
 
     /**
diff --git a/src/mongo/platform/atomic_intrinsics_gcc_sync.h b/src/mongo/platform/atomic_intrinsics_gcc_sync.h
new file mode 100644
index 00000000000..2ff7b33f4be
--- /dev/null
+++ b/src/mongo/platform/atomic_intrinsics_gcc_sync.h
@@ -0,0 +1,110 @@
+/*    Copyright 2014 10gen Inc.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+/**
+ * Implementation of the AtomicIntrinsics<T>::* operations for systems on any
+ * architecture using a GCC 4.1+ compatible compiler toolchain.
+ */
+
+#pragma once
+
+#include <boost/utility.hpp>
+
+namespace mongo {
+
+    /**
+     * Instantiation of AtomicIntrinsics<> for all word types T.
+     */
+    template <typename T, typename IsTLarge=void>
+    class AtomicIntrinsics {
+    public:
+
+        static T compareAndSwap(volatile T* dest, T expected, T newValue) {
+            return __sync_val_compare_and_swap(dest, expected, newValue);
+        }
+
+        static T swap(volatile T* dest, T newValue) {
+            T currentValue = *dest;
+            while (true) {
+                const T result = compareAndSwap(dest, currentValue, newValue);
+                if (result == currentValue)
+                    return result;
+                currentValue = result;
+            }
+        }
+
+        static T load(volatile const T* value) {
+            __sync_synchronize();
+            T result = *value;
+            __sync_synchronize();
+            return result;
+        }
+
+        static T loadRelaxed(volatile const T* value) {
+            asm volatile("" ::: "memory");
+            return *value;
+        }
+
+        static void store(volatile T* dest, T newValue) {
+            __sync_synchronize();
+            *dest = newValue;
+            __sync_synchronize();
+        }
+
+        static T fetchAndAdd(volatile T* dest, T increment) {
+            return __sync_fetch_and_add(dest, increment);
+        }
+
+    private:
+        AtomicIntrinsics();
+        ~AtomicIntrinsics();
+    };
+
+    template <typename T>
+    class AtomicIntrinsics<T, typename boost::disable_if_c<sizeof(T) <= sizeof(void*)>::type> {
+    public:
+
+        static T compareAndSwap(volatile T* dest, T expected, T newValue) {
+            return __sync_val_compare_and_swap(dest, expected, newValue);
+        }
+
+        static T swap(volatile T* dest, T newValue) {
+            T currentValue = *dest;
+            while (true) {
+                const T result = compareAndSwap(dest, currentValue, newValue);
+                if (result == currentValue)
+                    return result;
+                currentValue = result;
+            }
+        }
+
+        static T load(volatile const T* value) {
+            return compareAndSwap(const_cast<volatile T*>(value), T(0), T(0));
+        }
+
+        static void store(volatile T* dest, T newValue) {
+            swap(dest, newValue);
+        }
+
+        static T fetchAndAdd(volatile T* dest, T increment) {
+            return __sync_fetch_and_add(dest, increment);
+        }
+
+    private:
+        AtomicIntrinsics();
+        ~AtomicIntrinsics();
+    };
+
+}  // namespace mongo