From bbea352e3b9dc07bb97519e1af75fedf3a138b9c Mon Sep 17 00:00:00 2001
From: Wunkolo <Wunkolo@gmail.com>
Date: Tue, 8 Oct 2024 20:13:16 -0700
Subject: [PATCH] vk: Optimize redundant `QuadBuffer` uploads

Hashes the contents of the `QuadBuffer` vertex-data such that data is only uploaded when the vertices actually change rather than every frame.
---
 core/rend/vulkan/quad.cpp           | 25 ++++++++++++++++++++++++-
 core/rend/vulkan/quad.h             | 21 ++++++++++++++++++---
 core/rend/vulkan/vk_context_lr.cpp  |  2 +-
 core/rend/vulkan/vulkan_context.cpp |  4 ++--
 4 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/core/rend/vulkan/quad.cpp b/core/rend/vulkan/quad.cpp
index 3458075cba..c82868f530 100644
--- a/core/rend/vulkan/quad.cpp
+++ b/core/rend/vulkan/quad.cpp
@@ -23,6 +23,19 @@
 
 #include <memory>
 
+namespace {
+	size_t hashQuadVertex(const QuadVertex& vertex)
+	{
+		size_t seed = 0;
+		seed ^= std::hash<float>{}(vertex.x) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+		seed ^= std::hash<float>{}(vertex.y) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+		seed ^= std::hash<float>{}(vertex.z) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+		seed ^= std::hash<float>{}(vertex.u) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+		seed ^= std::hash<float>{}(vertex.v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+		return seed;
+	}
+}
+
 static VulkanContext *GetContext()
 {
 	return VulkanContext::Instance();
@@ -169,7 +182,7 @@ void QuadDrawer::Init(QuadPipeline *pipeline)
 		descSet.reset();
 }
 
-void QuadDrawer::Draw(vk::CommandBuffer commandBuffer, vk::ImageView imageView, QuadVertex vertices[], bool nearestFilter, const float *color)
+void QuadDrawer::Draw(vk::CommandBuffer commandBuffer, vk::ImageView imageView, QuadVertex vertices[4], bool nearestFilter, const float *color)
 {
 	VulkanContext *context = GetContext();
 	auto &descSet = descriptorSets[context->GetCurrentImageIndex()];
@@ -198,3 +211,13 @@ void QuadDrawer::Draw(vk::CommandBuffer commandBuffer, vk::ImageView imageView,
 	commandBuffer.pushConstants(pipeline->GetPipelineLayout(), vk::ShaderStageFlagBits::eFragment, 0, sizeof(float) * 4, color);
 	buffer->Draw(commandBuffer);
 }
+
+size_t QuadBuffer::hashQuadVertexData(QuadVertex vertices[4]) const
+{
+	size_t seed = 0;
+	seed ^= hashQuadVertex(vertices[0]) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+	seed ^= hashQuadVertex(vertices[1]) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+	seed ^= hashQuadVertex(vertices[2]) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+	seed ^= hashQuadVertex(vertices[3]) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+	return seed;
+}
diff --git a/core/rend/vulkan/quad.h b/core/rend/vulkan/quad.h
index cc36bef081..d3e060e641 100644
--- a/core/rend/vulkan/quad.h
+++ b/core/rend/vulkan/quad.h
@@ -50,11 +50,12 @@ class QuadBuffer
 		commandBuffer.draw(4, 1, 0, 0);
 	}
 
-	void Update(QuadVertex vertices[] = nullptr)
+	void Update(QuadVertex vertices[4] = nullptr)
 	{
 		if (vertices == nullptr)
 		{
-			static QuadVertex defaultVtx[] {
+			static QuadVertex defaultVtx[4]
+			{
 				{ -1.f, -1.f, 0.f, 0.f, 0.f },
 				{  1.f, -1.f, 0.f, 1.f, 0.f },
 				{ -1.f,  1.f, 0.f, 0.f, 1.f },
@@ -62,10 +63,24 @@ class QuadBuffer
 			};
 			vertices = defaultVtx;
 		};
+
+		const size_t quadVerticesHash = hashQuadVertexData(vertices);;
+		if (quadVerticesHash == lastUploadHash)
+		{
+			// data already uploaded
+			return;
+		}
+
+		// new data to upload, update hash
+		lastUploadHash = quadVerticesHash;
 		buffer->upload(sizeof(QuadVertex) * 4, vertices);
+
 	}
 private:
 	std::unique_ptr<BufferData> buffer;
+
+	size_t hashQuadVertexData(QuadVertex vertices[4]) const;
+	size_t lastUploadHash = 0;
 };
 
 class QuadPipeline
@@ -119,7 +134,7 @@ class QuadDrawer
 	QuadDrawer& operator=(const QuadDrawer &) = delete;
 
 	void Init(QuadPipeline *pipeline);
-	void Draw(vk::CommandBuffer commandBuffer, vk::ImageView imageView, QuadVertex vertices[] = nullptr, bool nearestFilter = false, const float *color = nullptr);
+	void Draw(vk::CommandBuffer commandBuffer, vk::ImageView imageView, QuadVertex vertices[4] = nullptr, bool nearestFilter = false, const float *color = nullptr);
 private:
 	QuadPipeline *pipeline = nullptr;
 	std::unique_ptr<QuadBuffer> buffer;
diff --git a/core/rend/vulkan/vk_context_lr.cpp b/core/rend/vulkan/vk_context_lr.cpp
index 4f999de65c..5f0db5c724 100644
--- a/core/rend/vulkan/vk_context_lr.cpp
+++ b/core/rend/vulkan/vk_context_lr.cpp
@@ -329,7 +329,7 @@ void VulkanContext::PresentFrame(vk::Image image, vk::ImageView imageView, const
 	getVideoShift(shiftX, shiftY);
 
 	beginFrame(extent);
-	QuadVertex vtx[] {
+	QuadVertex vtx[4] {
 		{ -1, -1, 0, 0, 0 },
 		{  1, -1, 0, 1, 0 },
 		{ -1,  1, 0, 0, 1 },
diff --git a/core/rend/vulkan/vulkan_context.cpp b/core/rend/vulkan/vulkan_context.cpp
index 6761420571..c3b7d153c8 100644
--- a/core/rend/vulkan/vulkan_context.cpp
+++ b/core/rend/vulkan/vulkan_context.cpp
@@ -924,7 +924,7 @@ void VulkanContext::Present() noexcept
 
 void VulkanContext::DrawFrame(vk::ImageView imageView, const vk::Extent2D& extent, float aspectRatio)
 {
-	QuadVertex vtx[] {
+	QuadVertex vtx[4] {
 		{ -1, -1, 0, 0, 0 },
 		{  1, -1, 0, 1, 0 },
 		{ -1,  1, 0, 0, 1 },
@@ -1314,7 +1314,7 @@ bool VulkanContext::GetLastFrame(std::vector<u8>& data, int& width, int& height)
 	pipeline.BindPipeline(*commandBuffer);
 
 	// Draw
-	QuadVertex vtx[] {
+	QuadVertex vtx[4] {
 		{ -1, -1, 0, 0, 0 },
 		{  1, -1, 0, 1, 0 },
 		{ -1,  1, 0, 0, 1 },