Make VkNonDispatchableHandle POD

Modified VkNonDispatchableHandle so that it's a plain old data type.
By making sure VkNonDispatchableHandle is POD, it may benefit from
the same rules and register usage as the default object handles.

Bug b/129979580

Change-Id: I8aea419df8a6ee2ff95717424f3344e1c317fb28
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/32989
Tested-by: Alexis Hétu <sugoi@google.com>
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Vulkan/VulkanPlatform.h

diff --git a/src/Vulkan/VulkanPlatform.h b/src/Vulkan/VulkanPlatform.h
index 519cfd1..4659d77 100644
--- a/src/Vulkan/VulkanPlatform.h
+++ b/src/Vulkan/VulkanPlatform.h
@@ -17,26 +17,29 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <type_traits>

 
 template<typename T> class VkNonDispatchableHandle
 {
 public:
-	VkNonDispatchableHandle(uint64_t h) : handle(h)
+	operator void*() const
 	{
 		static_assert(sizeof(VkNonDispatchableHandle) == sizeof(uint64_t), "Size is not 64 bits!");
-	}
 
-	void* get() const
-	{
+		// VkNonDispatchabbleHandle must be POD to ensure it gets passed by value the same way as a uint64_t,
+		// which is the upstream header's handle type when compiled for 32b architectures. On 64b architectures,
+		// the upstream header's handle type is a pointer type.
+		static_assert(std::is_trivial<VkNonDispatchableHandle<T>>::value, "VkNonDispatchableHandle<T> is not trivial!");
+		static_assert(std::is_standard_layout<VkNonDispatchableHandle<T>>::value, "VkNonDispatchableHandle<T> is not standard layout!");
+
 		return reinterpret_cast<void*>(static_cast<uintptr_t>(handle));
 	}
 
-	operator void*() const
+	void operator=(uint64_t h)
 	{
-		return get();
+		handle = h;
 	}
 
-private:
 	uint64_t handle;
 };