SkAtomic: always use std::atomic

include/private/SkAtomics.h

Index: include/private/SkAtomics.h
diff --git a/include/private/SkAtomics.h b/include/private/SkAtomics.h
index 56eace4447e2b9f90f2036381eab97b1cca0026f..249723d785865610fb46a00bd3d259e0a22c1d1d 100644
--- a/include/private/SkAtomics.h
+++ b/include/private/SkAtomics.h
@@ -10,6 +10,9 @@
 
 // This file is not part of the public Skia API.
 #include "SkTypes.h"
+#include <atomic>
+
+// ~~~~~~~~ APIs ~~~~~~~~~
 
 enum sk_memory_order {
     sk_memory_order_relaxed,
@@ -86,15 +89,65 @@ private:
     T fVal;
 };
 
-// IWYU pragma: begin_exports
-#if defined(_MSC_VER)
-    #include "../ports/SkAtomics_std.h"
-#elif !defined(SK_BUILD_FOR_IOS) && defined(__ATOMIC_RELAXED)
-    #include "../ports/SkAtomics_atomic.h"
-#else
-    #include "../ports/SkAtomics_sync.h"
-#endif
-// IWYU pragma: end_exports
+// ~~~~~~~~ Implementations ~~~~~~~~~
+
+template <typename T>
+T sk_atomic_load(const T* ptr, sk_memory_order mo) {
+    SkASSERT(mo == sk_memory_order_relaxed ||
+             mo == sk_memory_order_seq_cst ||
+             mo == sk_memory_order_acquire ||
+             mo == sk_memory_order_consume);
+    const std::atomic<T>* ap = reinterpret_cast<const std::atomic<T>*>(ptr);
+    return std::atomic_load_explicit(ap, (std::memory_order)mo);
+}
+
+template <typename T>
+void sk_atomic_store(T* ptr, T val, sk_memory_order mo) {
+    SkASSERT(mo == sk_memory_order_relaxed ||
+             mo == sk_memory_order_seq_cst ||
+             mo == sk_memory_order_release);
+    std::atomic<T>* ap = reinterpret_cast<std::atomic<T>*>(ptr);
+    return std::atomic_store_explicit(ap, val, (std::memory_order)mo);
+}
+
+template <typename T>
+T sk_atomic_fetch_add(T* ptr, T val, sk_memory_order mo) {
+    // All values of mo are valid.
+    std::atomic<T>* ap = reinterpret_cast<std::atomic<T>*>(ptr);
+    return std::atomic_fetch_add_explicit(ap, val, (std::memory_order)mo);
+}
+
+template <typename T>
+T sk_atomic_fetch_sub(T* ptr, T val, sk_memory_order mo) {
+    // All values of mo are valid.
+    std::atomic<T>* ap = reinterpret_cast<std::atomic<T>*>(ptr);
+    return std::atomic_fetch_sub_explicit(ap, val, (std::memory_order)mo);
+}
+
+template <typename T>
+bool sk_atomic_compare_exchange(T* ptr, T* expected, T desired,
+                                sk_memory_order success,
+                                sk_memory_order failure) {
+    // All values of success are valid.
+    SkASSERT(failure == sk_memory_order_relaxed ||
+             failure == sk_memory_order_seq_cst ||
+             failure == sk_memory_order_acquire ||
+             failure == sk_memory_order_consume);
+    SkASSERT(failure <= success);
+    std::atomic<T>* ap = reinterpret_cast<std::atomic<T>*>(ptr);
+    return std::atomic_compare_exchange_strong_explicit(ap, expected, desired,
+                                                        (std::memory_order)success,
+                                                        (std::memory_order)failure);
+}
+
+template <typename T>
+T sk_atomic_exchange(T* ptr, T val, sk_memory_order mo) {
+    // All values of mo are valid.
+    std::atomic<T>* ap = reinterpret_cast<std::atomic<T>*>(ptr);
+    return std::atomic_exchange_explicit(ap, val, (std::memory_order)mo);
+}
+
+// ~~~~~~~~ Legacy APIs ~~~~~~~~~
 
 // From here down we have shims for our old atomics API, to be weaned off of.
 // We use the default sequentially-consistent memory order to make things simple