LibSoftGPU: Define a simple shader instruction set

This adds a simple instruction set with basic operations and adds an
instruction list to the shader class.

Userland/Libraries/LibSoftGPU/ISA.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2022, Stephan Unverwerth <s.unverwerth@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+
+namespace SoftGPU {
+
+constexpr u8 swizzle_pattern(u8 a, u8 b, u8 c, u8 d)
+{
+    return a | (b << 2) | (c << 4) | (d << 6);
+}
+
+constexpr u8 swizzle_index(u8 pattern, u8 element)
+{
+    return (pattern & (3 << (element * 2))) >> (element * 2);
+}
+
+enum class Opcode : u8 {
+    Input,
+    Output,
+    Sample2D,
+    Swizzle,
+    Add,
+    Sub,
+    Mul,
+    Div,
+};
+
+struct Instruction final {
+    union Arguments {
+        struct {
+            u16 target_register;
+            u8 input_index;
+        } input;
+        struct {
+            u16 source_register;
+            u8 output_index;
+        } output;
+        struct {
+            u16 target_register;
+            u16 coordinates_register;
+            u8 sampler_index;
+        } sample;
+        struct {
+            u16 target_register;
+            u16 source_register;
+            u8 pattern;
+        } swizzle;
+        struct {
+            u16 target_register;
+            u16 source_register1;
+            u16 source_register2;
+        } binop;
+    } arguments;
+    Opcode operation;
+};
+
+}