VK: Add a new platform method to check UMA (#8704)

* VK: Add a new context method to check UMA

This heuristic should work on almost all devices,
can be extended later as needed.

* Addressing PR comments

---------

Co-authored-by: Powei Feng <powei@google.com>
Co-authored-by: Serge Metral <sergemetral@google.com>

filament/backend/src/vulkan/VulkanContext.h

@@ -142,6 +142,10 @@ public:
         return mPortabilitySubsetFeatures.imageView2DOn3DImage == VK_TRUE;
     }
 
+    inline bool isUnifiedMemoryArchitecture() const noexcept {
+        return mIsUnifiedMemoryArchitecture;
+    }
+
 private:
     VkPhysicalDeviceMemoryProperties mMemoryProperties = {};
     VkPhysicalDeviceProperties2 mPhysicalDeviceProperties = {
@@ -164,6 +168,7 @@ private:
     bool mDebugUtilsSupported = false;
     bool mLazilyAllocatedMemorySupported = false;
     bool mProtectedMemorySupported = false;
+    bool mIsUnifiedMemoryArchitecture = false;
 
     fvkutils::VkFormatList mDepthStencilFormats;
     fvkutils::VkFormatList mBlittableDepthStencilFormats;

filament/backend/src/vulkan/platform/VulkanPlatform.cpp

@@ -631,6 +631,21 @@ fvkutils::VkFormatList findBlittableDepthStencilFormats(VkPhysicalDevice device)
     return ret;
 }
 
+/**
+ *  Check if the GPU has a unified memory architecture.
+ */
+bool hasUnifiedMemoryArchitecture(VkPhysicalDeviceMemoryProperties memoryProperties) noexcept {
+    // Try to identify if the platform is running on a Unified Memory Architecture by inspecting the
+    // memory heap flags, if they are all VK_MEMORY_HEAP_DEVICE_LOCAL_BIT it's UMA, otherwise not
+    // enough information to make a decision, so default to false.
+    for (uint32_t i = 0; i < memoryProperties.memoryHeapCount; ++i) {
+        if ((memoryProperties.memoryHeaps[i].flags & VK_MEMORY_HEAP_DEVICE_LOCAL_BIT) == 0) {
+            return false;
+        }
+    }
+    return true;
+}
+
 }// anonymous namespace
 
 using SwapChainPtr = VulkanPlatform::SwapChainPtr;
@@ -864,6 +879,8 @@ Driver* VulkanPlatform::createDriver(void* sharedContext,
         }
     }
 
+    context.mIsUnifiedMemoryArchitecture = hasUnifiedMemoryArchitecture(context.mMemoryProperties);
+
 #ifdef NDEBUG
     // If we are in release build, we should not have turned on debug extensions
     FILAMENT_CHECK_POSTCONDITION(!context.mDebugUtilsSupported && !context.mDebugMarkersSupported)