Add SkBarriers to ports.
This completes a TODO we've had to move our memory-barrier code out of
SkOnce. I also want to start using sk_acquire_load elsewhere.
BUG=skia:
R=bungeman@google.com, mtklein@google.com, reed@google.com
Author: mtklein@chromium.org
Review URL: https://codereview.chromium.org/304593003
git-svn-id: http://skia.googlecode.com/svn/trunk@14970 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/ports/SkBarriers_x86.h b/src/ports/SkBarriers_x86.h
new file mode 100644
index 0000000..fc57615
--- /dev/null
+++ b/src/ports/SkBarriers_x86.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkBarriers_x86_DEFINED
+#define SkBarriers_x86_DEFINED
+
+#ifdef SK_BUILD_FOR_WIN
+# include <intrin.h>
+static inline void sk_compiler_barrier() { _ReadWriteBarrier(); }
+#else
+static inline void sk_compiler_barrier() { asm volatile("" : : : "memory"); }
+#endif
+
+template <typename T>
+T sk_acquire_load(T* ptr) {
+ T val = *ptr;
+ // On x86, all loads are acquire loads, so we only need a compiler barrier.
+ sk_compiler_barrier();
+ return val;
+}
+
+template <typename T>
+void sk_release_store(T* ptr, T val) {
+ // On x86, all stores are release stores, so we only need a compiler barrier.
+ sk_compiler_barrier();
+ *ptr = val;
+}
+
+#endif//SkBarriers_x86_DEFINED