Split atomic and mutex implementations and make inlinable.

src/ports/SkAtomics_sync.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkAtomics_sync_DEFINED
+#define SkAtomics_sync_DEFINED
+
+/** GCC/Clang __sync based atomics. */
+
+#include <stdint.h>
+
+static inline __attribute__((always_inline)) int32_t sk_atomic_inc(int32_t* addr) {
+    return __sync_fetch_and_add(addr, 1);
+}
+
+static inline __attribute__((always_inline)) int32_t sk_atomic_add(int32_t* addr, int32_t inc) {
+    return __sync_fetch_and_add(addr, inc);
+}
+
+static inline __attribute__((always_inline)) int32_t sk_atomic_dec(int32_t* addr) {
+    return __sync_fetch_and_add(addr, -1);
+}
+
+static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_dec() { }
+
+static inline __attribute__((always_inline)) int32_t sk_atomic_conditional_inc(int32_t* addr) {
+    int32_t value = *addr;
+
+    while (true) {
+        if (value == 0) {
+            return 0;
+        }
+
+        int32_t before = __sync_val_compare_and_swap(addr, value, value + 1);
+
+        if (before == value) {
+            return value;
+        } else {
+            value = before;
+        }
+    }
+}
+
+static inline __attribute__((always_inline)) void sk_membar_acquire__after_atomic_conditional_inc() { }
+
+#endif