Vulkan: Use atomics in SerialFactory.

This allows serials to be generated from multiple threads without locking for
very little/no cost.

BUG=angleproject:2464

Change-Id: Id61d170e7a985c3100da0057156859ffcb083dad
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1516514
Commit-Queue: Geoff Lang <[email protected]>
Reviewed-by: Shahbaz Youssefi <[email protected]>

Author: vonture

src/libANGLE/renderer/renderer_utils.h

@@ -12,6 +12,7 @@
 
 #include <cstdint>
 
+#include <atomic>
 #include <limits>
 #include <map>
 
@@ -61,8 +62,6 @@ class ResourceSerial
     uintptr_t mValue;
 };
 
-class SerialFactory;
-
 class Serial final
 {
   public:
@@ -93,27 +92,32 @@ class Serial final
     constexpr uint64_t getValue() const { return mValue; }
 
   private:
-    friend class SerialFactory;
+    template <typename T>
+    friend class SerialFactoryBase;
     constexpr explicit Serial(uint64_t value) : mValue(value) {}
     uint64_t mValue;
     static constexpr uint64_t kInvalid = 0;
 };
 
-class SerialFactory final : angle::NonCopyable
+template <typename SerialBaseType>
+class SerialFactoryBase final : angle::NonCopyable
 {
   public:
-    SerialFactory() : mSerial(1) {}
+    SerialFactoryBase() : mSerial(1) {}
 
     Serial generate()
     {
-        ASSERT(mSerial != std::numeric_limits<uint64_t>::max());
+        ASSERT(mSerial + 1 > mSerial);
         return Serial(mSerial++);
     }
 
   private:
-    uint64_t mSerial;
+    SerialBaseType mSerial;
 };
 
+using SerialFactory       = SerialFactoryBase<uint64_t>;
+using AtomicSerialFactory = SerialFactoryBase<std::atomic<uint64_t>>;
+
 using MipGenerationFunction = void (*)(size_t sourceWidth,
                                        size_t sourceHeight,
                                        size_t sourceDepth,

src/libANGLE/renderer/vulkan/RendererVk.h

@@ -187,8 +187,8 @@ class RendererVk : angle::NonCopyable
     uint32_t mCurrentQueueFamilyIndex;
     uint32_t mMaxVertexAttribDivisor;
     VkDevice mDevice;
-    SerialFactory mQueueSerialFactory;
-    SerialFactory mShaderSerialFactory;
+    AtomicSerialFactory mQueueSerialFactory;
+    AtomicSerialFactory mShaderSerialFactory;
     Serial mCurrentQueueSerial;
 
     bool mDeviceLost;