GPU: Swap bindings array instead of copying (#4003)

* GPU: Swap bindings array instead of copying

Reduces work on UpdateShaderState. Now the cost is a few reference moves for arrays, rather than copying data.

Downside: bindings arrays are no longer readonly.

* Micro optimisation

* Add missing docs

* Address Feedback

2 files changed, 109 insertions, 0 deletions

diff --git a/Ryujinx.Graphics.Gpu/Shader/CachedShaderBindings.cs b/Ryujinx.Graphics.Gpu/Shader/CachedShaderBindings.cs
new file mode 100644
index 00000000..1734f08a
--- /dev/null
+++ b/Ryujinx.Graphics.Gpu/Shader/CachedShaderBindings.cs
@@ -0,0 +1,103 @@
+using Ryujinx.Graphics.GAL;
+using Ryujinx.Graphics.Gpu.Engine;
+using Ryujinx.Graphics.Gpu.Image;
+using Ryujinx.Graphics.Shader;
+using System;
+using System.Linq;
+
+namespace Ryujinx.Graphics.Gpu.Shader
+{
+    /// <summary>
+    /// A collection of shader bindings ready for insertion into the buffer and texture managers.
+    /// </summary>
+    internal class CachedShaderBindings
+    {
+        public TextureBindingInfo[][] TextureBindings { get; }
+        public TextureBindingInfo[][] ImageBindings { get; }
+        public BufferDescriptor[][] ConstantBufferBindings { get; }
+        public BufferDescriptor[][] StorageBufferBindings { get; }
+
+        public int MaxTextureBinding { get; }
+        public int MaxImageBinding { get; }
+
+        /// <summary>
+        /// Create a new cached shader bindings collection.
+        /// </summary>
+        /// <param name="isCompute">Whether the shader is for compute</param>
+        /// <param name="stages">The stages used by the shader</param>
+        public CachedShaderBindings(bool isCompute, CachedShaderStage[] stages)
+        {
+            int stageCount = isCompute ? 1 : Constants.ShaderStages;
+
+            TextureBindings = new TextureBindingInfo[stageCount][];
+            ImageBindings = new TextureBindingInfo[stageCount][];
+            ConstantBufferBindings = new BufferDescriptor[stageCount][];
+            StorageBufferBindings = new BufferDescriptor[stageCount][];
+
+            int maxTextureBinding = -1;
+            int maxImageBinding = -1;
+            int offset = isCompute ? 0 : 1;
+
+            for (int i = 0; i < stageCount; i++)
+            {
+                CachedShaderStage stage = stages[i + offset];
+
+                if (stage == null)
+                {
+                    TextureBindings[i] = Array.Empty<TextureBindingInfo>();
+                    ImageBindings[i] = Array.Empty<TextureBindingInfo>();
+                    ConstantBufferBindings[i] = Array.Empty<BufferDescriptor>();
+                    StorageBufferBindings[i] = Array.Empty<BufferDescriptor>();
+
+                    continue;
+                }
+
+                TextureBindings[i] = stage.Info.Textures.Select(descriptor =>
+                {
+                    Target target = ShaderTexture.GetTarget(descriptor.Type);
+
+                    var result = new TextureBindingInfo(
+                        target,
+                        descriptor.Binding,
+                        descriptor.CbufSlot,
+                        descriptor.HandleIndex,
+                        descriptor.Flags);
+
+                    if (descriptor.Binding > maxTextureBinding)
+                    {
+                        maxTextureBinding = descriptor.Binding;
+                    }
+
+                    return result;
+                }).ToArray();
+
+                ImageBindings[i] = stage.Info.Images.Select(descriptor =>
+                {
+                    Target target = ShaderTexture.GetTarget(descriptor.Type);
+                    Format format = ShaderTexture.GetFormat(descriptor.Format);
+
+                    var result = new TextureBindingInfo(
+                        target,
+                        format,
+                        descriptor.Binding,
+                        descriptor.CbufSlot,
+                        descriptor.HandleIndex,
+                        descriptor.Flags);
+
+                    if (descriptor.Binding > maxImageBinding)
+                    {
+                        maxImageBinding = descriptor.Binding;
+                    }
+
+                    return result;
+                }).ToArray();
+
+                ConstantBufferBindings[i] = stage.Info.CBuffers.ToArray();
+                StorageBufferBindings[i] = stage.Info.SBuffers.ToArray();
+            }
+
+            MaxTextureBinding = maxTextureBinding;
+            MaxImageBinding = maxImageBinding;
+        }
+    }
+}
diff --git a/Ryujinx.Graphics.Gpu/Shader/CachedShaderProgram.cs b/Ryujinx.Graphics.Gpu/Shader/CachedShaderProgram.cs
index 69fcb278..ff9c39a1 100644
--- a/Ryujinx.Graphics.Gpu/Shader/CachedShaderProgram.cs
+++ b/Ryujinx.Graphics.Gpu/Shader/CachedShaderProgram.cs
@@ -25,6 +25,11 @@ namespace Ryujinx.Graphics.Gpu.Shader
         public CachedShaderStage[] Shaders { get; }
 
         /// <summary>
+        /// Cached shader bindings, ready for placing into the bindings manager.
+        /// </summary>
+        public CachedShaderBindings Bindings { get; }
+
+        /// <summary>
         /// Creates a new instance of the shader bundle.
         /// </summary>
         /// <param name="hostProgram">Host program with all the shader stages</param>
@@ -37,6 +42,7 @@ namespace Ryujinx.Graphics.Gpu.Shader
             Shaders = shaders;
 
             SpecializationState.Prepare(shaders);
+            Bindings = new CachedShaderBindings(shaders.Length == 1, shaders);
         }
 
         /// <summary>