From c6c90d4cbcdd77e4a2b799ebcc6c0a0cb020136c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Thu, 9 Nov 2017 12:21:20 +0100
Subject: [PATCH] Improve Vulkan device selection mechanism to prefer discrete
 GPUs

---
 Common/Vulkan/VulkanContext.cpp | 51 +++++++++++++++++++++++++++------
 Common/Vulkan/VulkanContext.h   | 12 ++++++--
 android/jni/app-android.cpp     | 10 ++++++-
 3 files changed, 61 insertions(+), 12 deletions(-)

diff --git a/Common/Vulkan/VulkanContext.cpp b/Common/Vulkan/VulkanContext.cpp
index 6c1ce1eb5c..ae695251a1 100644
--- a/Common/Vulkan/VulkanContext.cpp
+++ b/Common/Vulkan/VulkanContext.cpp
@@ -120,6 +120,11 @@ VkResult VulkanContext::CreateInstance(const char *app_name, int app_ver, uint32
 	}
 
 	VulkanLoadInstanceFunctions(instance_);
+	if (!CheckLayers(instance_layer_properties_, instance_layer_names_)) {
+		WLOG("CheckLayers for instance failed");
+		// init_error_ = "Failed to validate instance layers";
+		// return;
+	}
 
 	uint32_t gpu_count = 1;
 	res = vkEnumeratePhysicalDevices(instance_, &gpu_count, nullptr);
@@ -141,11 +146,6 @@ VkResult VulkanContext::CreateInstance(const char *app_name, int app_ver, uint32
 		return res;
 	}
 
-	if (!CheckLayers(instance_layer_properties_, instance_layer_names_)) {
-		WLOG("CheckLayers failed");
-		// init_error_ = "Failed to validate instance layers";
-		// return;
-	}
 	return VK_SUCCESS;
 }
 
@@ -333,14 +333,47 @@ bool VulkanContext::CheckLayers(const std::vector<LayerProperties> &layer_props,
 	return true;
 }
 
+int VulkanContext::GetBestPhysicalDevice() {
+	// Rules: Prefer discrete over embedded.
+	// Prefer nVidia over Intel.
+
+	int maxScore = -1;
+	int best = -1;
+
+	for (size_t i = 0; i < physical_devices_.size(); i++) {
+		int score = 0;
+		VkPhysicalDeviceProperties props;
+		vkGetPhysicalDeviceProperties(physical_devices_[i], &props);
+		switch (props.deviceType) {
+		case VK_PHYSICAL_DEVICE_TYPE_CPU:
+			score += 1;
+			break;
+		case VK_PHYSICAL_DEVICE_TYPE_DISCRETE_GPU:
+			score += 20;
+			break;
+		case VK_PHYSICAL_DEVICE_TYPE_INTEGRATED_GPU:
+			score += 10;
+			break;
+		}
+		if (props.vendorID == VULKAN_VENDOR_AMD) {
+			score += 5;
+		} else if (props.vendorID == VULKAN_VENDOR_NVIDIA) {
+			score += 5;
+		}
+		if (score > maxScore) {
+			best = i;
+			maxScore = score;
+		}
+	}
+	return best;
+}
+
 void VulkanContext::ChooseDevice(int physical_device) {
 	physical_device_ = physical_device;
 
 	GetDeviceLayerProperties();
 	if (!CheckLayers(device_layer_properties_, device_layer_names_)) {
-		WLOG("CheckLayers failed (2)");
-		// init_error_ = "Failed to validate device layers";
-		// return;
+		WLOG("CheckLayers for device %d failed", physical_device);
 	}
 
 	vkGetPhysicalDeviceQueueFamilyProperties(physical_devices_[physical_device_], &queue_count, nullptr);
@@ -913,4 +946,4 @@ const char *VulkanResultToString(VkResult res) {
 	default:
 		return "VK_ERROR_...(unknown)";
 	}
-}
\ No newline at end of file
+}
diff --git a/Common/Vulkan/VulkanContext.h b/Common/Vulkan/VulkanContext.h
index 8c40442197..bf48a1460e 100644
--- a/Common/Vulkan/VulkanContext.h
+++ b/Common/Vulkan/VulkanContext.h
@@ -43,6 +43,15 @@ enum {
 	VULKAN_FLAG_PRESENT_FIFO_RELAXED = 8,
 };
 
+enum {
+	VULKAN_VENDOR_NVIDIA = 0x000010de,
+	VULKAN_VENDOR_INTEL = 0x00008086,   // Haha!
+	VULKAN_VENDOR_AMD = 0x00001002,
+	VULKAN_VENDOR_ARM = 0x000013B5,  // Mali
+	VULKAN_VENDOR_QUALCOMM = 0x00005143,
+	VULKAN_VENDOR_IMGTEC = 0x00001010,  // PowerVR
+};
+
 struct VulkanPhysicalDeviceInfo {
 	VkFormat preferredDepthStencilFormat;
 };
@@ -203,8 +212,7 @@ public:
 
 	VkResult CreateInstance(const char *app_name, int app_ver, uint32_t flags);
 	
-	// TODO: Actually do some checks?
-	int GetBestPhysicalDevice() const { return 0; }
+	int GetBestPhysicalDevice();
 	void ChooseDevice(int physical_device);
 	bool EnableDeviceExtension(const char *extension);
 	VkResult CreateDevice();
diff --git a/android/jni/app-android.cpp b/android/jni/app-android.cpp
index 19a133502f..2d16e1b0e7 100644
--- a/android/jni/app-android.cpp
+++ b/android/jni/app-android.cpp
@@ -290,7 +290,15 @@ bool AndroidVulkanContext::Init(ANativeWindow *wnd, int desiredBackbufferSizeX,
 		return false;
 	}
 
-	g_Vulkan->ChooseDevice(g_Vulkan->GetBestPhysicalDevice());
+	int physicalDevice = g_Vulkan->GetBestPhysicalDevice();
+	if (physicalDevice < 0) {
+		ELOG("No usable Vulkan device found.");
+		delete g_Vulkan;
+		g_Vulkan = nullptr;
+		return false;
+	}
+
+	g_Vulkan->ChooseDevice(physicalDevice);
 	// Here we can enable device extensions if we like.
 
 	ILOG("Creating vulkan device");