Make structs readonly when applicable (#4002)

* Make all structs readonly when applicable. It should reduce amount of needless defensive copies

* Make structs with trivial boilerplate equality code record structs

* Remove unnecessary readonly modifiers from TextureCreateInfo

* Make BitMap structs readonly too

Ryujinx.Graphics.Shader/Translation/AttributeInfo.cs

@@ -2,7 +2,7 @@
 
 namespace Ryujinx.Graphics.Shader.Translation
 {
-    struct AttributeInfo
+    readonly struct AttributeInfo
     {
         private static readonly Dictionary<int, AttributeInfo> _builtInAttributes = new Dictionary<int, AttributeInfo>()
         {

Ryujinx.Graphics.Shader/Translation/EmitterContext.cs

@@ -21,7 +21,7 @@ namespace Ryujinx.Graphics.Shader.Translation
 
         public int OperationsCount => _operations.Count;
 
-        private struct BrxTarget
+        private readonly struct BrxTarget
         {
             public readonly Operand Selector;
             public readonly int ExpectedValue;

Ryujinx.Graphics.Shader/Translation/FunctionMatch.cs

@@ -87,7 +87,7 @@ namespace Ryujinx.Graphics.Shader.Translation
             }
         }
 
-        private struct TreeNodeUse
+        private readonly struct TreeNodeUse
         {
             public TreeNode Node { get; }
             public int Index { get; }
@@ -345,7 +345,7 @@ namespace Ryujinx.Graphics.Shader.Translation
             bool Matches(in InstOp opInfo);
         }
 
-        private struct PatternTreeNodeUse
+        private readonly struct PatternTreeNodeUse
         {
             public IPatternTreeNode Node { get; }
             public int Index { get; }

Ryujinx.Graphics.Shader/Translation/RegisterUsage.cs

@@ -114,7 +114,7 @@ namespace Ryujinx.Graphics.Shader.Translation
             }
         }
 
-        public struct FunctionRegisterUsage
+        public readonly struct FunctionRegisterUsage
         {
             public Register[] InArguments { get; }
             public Register[] OutArguments { get; }

Ryujinx.Graphics.Shader/Translation/ShaderConfig.cs

@@ -69,36 +69,7 @@ namespace Ryujinx.Graphics.Shader.Translation
         private int _usedStorageBuffers;
         private int _usedStorageBuffersWrite;
 
-        private struct TextureInfo : IEquatable<TextureInfo>
-        {
-            public int CbufSlot { get; }
-            public int Handle { get; }
-            public bool Indexed { get; }
-            public TextureFormat Format { get; }
-
-            public TextureInfo(int cbufSlot, int handle, bool indexed, TextureFormat format)
-            {
-                CbufSlot = cbufSlot;
-                Handle = handle;
-                Indexed = indexed;
-                Format = format;
-            }
-
-            public override bool Equals(object obj)
-            {
-                return obj is TextureInfo other && Equals(other);
-            }
-
-            public bool Equals(TextureInfo other)
-            {
-                return CbufSlot == other.CbufSlot && Handle == other.Handle && Indexed == other.Indexed && Format == other.Format;
-            }
-
-            public override int GetHashCode()
-            {
-                return HashCode.Combine(CbufSlot, Handle, Indexed, Format);
-            }
-        }
+        private readonly record struct TextureInfo(int CbufSlot, int Handle, bool Indexed, TextureFormat Format);
 
         private struct TextureMeta
         {

Ryujinx.Graphics.Shader/Translation/ShaderHeader.cs

@@ -12,7 +12,7 @@ namespace Ryujinx.Graphics.Shader.Translation
         ScreenLinear = 3
     }
 
-    struct ImapPixelType
+    readonly struct ImapPixelType
     {
         public PixelImap X { get; }
         public PixelImap Y { get; }

Ryujinx.Graphics.Shader/Translation/Ssa.cs

@@ -108,7 +108,7 @@ namespace Ryujinx.Graphics.Shader.Translation
             }
         }
 
-        private struct Definition
+        private readonly struct Definition
         {
             public BasicBlock Block { get; }
             public Operand    Local { get; }

Ryujinx.Graphics.Shader/Translation/TranslationOptions.cs

@@ -1,6 +1,6 @@
 namespace Ryujinx.Graphics.Shader.Translation
 {
-    public struct TranslationOptions
+    public readonly struct TranslationOptions
     {
         public TargetLanguage TargetLanguage { get; }
         public TargetApi TargetApi { get; }

Ryujinx.Graphics.Shader/Translation/Translator.cs

@@ -14,7 +14,7 @@ namespace Ryujinx.Graphics.Shader.Translation
     {
         private const int HeaderSize = 0x50;
 
-        internal struct FunctionCode
+        internal readonly struct FunctionCode
         {
             public Operation[] Code { get; }