shader: add compact f16 arithmetic and compare lowering (#840)

Co-authored-by: Foued Attar <attar.foued@gmail.com>

tests/SharpEmu.ShaderCompiler.Tests/Gen5Float16ArithmeticTests.cs

@@ -0,0 +1,153 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Buffers.Binary;
+using SharpEmu.HLE;
+using SharpEmu.ShaderCompiler.Vulkan;
+using Xunit;
+
+namespace SharpEmu.ShaderCompiler.Tests;
+
+public sealed class Gen5Float16ArithmeticTests
+{
+    private const ulong ShaderAddress = 0x1_0000_0000;
+    private const uint SEndpgm = 0xBF810000;
+
+    [Fact]
+    public void CompactFloat16ArithmeticDecodesAndCompilesWithoutNativeFloat16()
+    {
+        var program = Decode(
+        [
+            0x64000501, // v_add_f16 v0, v1, v2
+            0x66060B04, // v_sub_f16 v3, v4, v5
+            0x680C1107, // v_subrev_f16 v6, v7, v8
+            0x6A12170A, // v_mul_f16 v9, v10, v11
+            0x72181D0D, // v_max_f16 v12, v13, v14
+            0x741E2310, // v_min_f16 v15, v16, v17
+            SEndpgm,
+        ]);
+
+        Assert.Equal(
+            ["VAddF16", "VSubF16", "VSubrevF16", "VMulF16", "VMaxF16", "VMinF16", "SEndpgm"],
+            program.Instructions.Select(instruction => instruction.Opcode));
+
+        var state = new Gen5ShaderState(program, [], null);
+        var scalarRegisters = new uint[256];
+        var evaluation = new Gen5ShaderEvaluation(
+            scalarRegisters,
+            scalarRegisters,
+            [],
+            []);
+
+        Assert.True(
+            Gen5SpirvTranslator.TryCompileComputeShader(
+                state,
+                evaluation,
+                1,
+                1,
+                1,
+                out var shader,
+                out var error),
+            error);
+
+        var opcodes = ReadOpcodes(shader.Spirv);
+        Assert.Contains((ushort)SpirvOp.FAdd, opcodes);
+        Assert.Contains((ushort)SpirvOp.FSub, opcodes);
+        Assert.Contains((ushort)SpirvOp.FMul, opcodes);
+        Assert.True(opcodes.Count(opcode => opcode == (ushort)SpirvOp.ExtInst) >= 2);
+        Assert.DoesNotContain((ushort)SpirvCapability.Float16, ReadCapabilities(shader.Spirv));
+    }
+
+    private static Gen5ShaderProgram Decode(IReadOnlyList<uint> words)
+    {
+        var memory = new TestCpuMemory(ShaderAddress, words.Count * sizeof(uint));
+        var bytes = new byte[words.Count * sizeof(uint)];
+        for (var index = 0; index < words.Count; index++)
+        {
+            BinaryPrimitives.WriteUInt32LittleEndian(
+                bytes.AsSpan(index * sizeof(uint)),
+                words[index]);
+        }
+
+        Assert.True(memory.TryWrite(ShaderAddress, bytes));
+        var context = new CpuContext(memory, Generation.Gen5);
+        Assert.True(
+            Gen5ShaderTranslator.TryDecodeProgram(
+                context,
+                ShaderAddress,
+                out var program,
+                out var error),
+            error);
+        return program;
+    }
+
+    private static IReadOnlyList<ushort> ReadOpcodes(byte[] spirv) =>
+        ReadInstructions(spirv)
+            .Select(instruction => instruction.Opcode)
+            .ToArray();
+
+    private static IReadOnlyList<ushort> ReadCapabilities(byte[] spirv) =>
+        ReadInstructions(spirv)
+            .Where(instruction => instruction.Opcode == (ushort)SpirvOp.Capability)
+            .Select(instruction => (ushort)instruction.FirstOperand)
+            .ToArray();
+
+    private static IReadOnlyList<(ushort Opcode, uint FirstOperand)> ReadInstructions(
+        byte[] spirv)
+    {
+        Assert.Equal(0x07230203u, BinaryPrimitives.ReadUInt32LittleEndian(spirv));
+        var instructions = new List<(ushort Opcode, uint FirstOperand)>();
+        for (var offset = 5 * sizeof(uint); offset < spirv.Length;)
+        {
+            var header = BinaryPrimitives.ReadUInt32LittleEndian(spirv.AsSpan(offset));
+            var wordCount = checked((int)(header >> 16));
+            Assert.InRange(wordCount, 1, (spirv.Length - offset) / sizeof(uint));
+            var firstOperand = wordCount > 1
+                ? BinaryPrimitives.ReadUInt32LittleEndian(spirv.AsSpan(offset + sizeof(uint)))
+                : 0;
+            instructions.Add(((ushort)header, firstOperand));
+            offset += wordCount * sizeof(uint);
+        }
+
+        return instructions;
+    }
+
+    private sealed class TestCpuMemory(ulong baseAddress, int size) : ICpuMemory
+    {
+        private readonly byte[] _storage = new byte[size];
+
+        public bool TryRead(ulong virtualAddress, Span<byte> destination)
+        {
+            if (!TryResolve(virtualAddress, destination.Length, out var offset))
+            {
+                return false;
+            }
+
+            _storage.AsSpan(offset, destination.Length).CopyTo(destination);
+            return true;
+        }
+
+        public bool TryWrite(ulong virtualAddress, ReadOnlySpan<byte> source)
+        {
+            if (!TryResolve(virtualAddress, source.Length, out var offset))
+            {
+                return false;
+            }
+
+            source.CopyTo(_storage.AsSpan(offset, source.Length));
+            return true;
+        }
+
+        private bool TryResolve(ulong address, int length, out int offset)
+        {
+            offset = 0;
+            if (address < baseAddress || address - baseAddress > int.MaxValue)
+            {
+                return false;
+            }
+
+            offset = (int)(address - baseAddress);
+            return offset <= _storage.Length - length;
+        }
+    }
+}