[shader] add scalar memory fallback

src/SharpEmu.Libs/Agc/AgcShaderCompilerHooks.cs

@@ -27,7 +27,7 @@ internal static class AgcShaderCompilerHooks
     internal static void Install()
     {
         Gen5ShaderScalarEvaluator.FallbackMemoryReader =
-            KernelMemoryCompatExports.TryReadTrackedLibcHeap;
+            KernelMemoryCompatExports.TryReadShaderGuestMemory;
         Gen5ShaderScalarEvaluator.GlobalMemoryPool =
             GuestDataPool.Shared;
     }

src/SharpEmu.ShaderCompiler/Gen5ShaderScalarEvaluator.cs

@@ -2350,7 +2350,8 @@ public static class Gen5ShaderScalarEvaluator
     private static bool TryReadUInt32(CpuContext ctx, ulong address, out uint value)
     {
         Span<byte> bytes = stackalloc byte[sizeof(uint)];
-        if (!ctx.Memory.TryRead(address, bytes))
+        if (!ctx.Memory.TryRead(address, bytes) &&
+            FallbackMemoryReader?.Invoke(address, bytes) != true)
         {
             value = 0;
             return false;

tests/SharpEmu.Libs.Tests/Agc/Gen5ScalarMemoryFallbackTests.cs

@@ -0,0 +1,99 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Buffers.Binary;
+using SharpEmu.HLE;
+using SharpEmu.ShaderCompiler;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.Agc;
+
+public sealed class Gen5ScalarMemoryFallbackTests
+{
+    private const ulong ScalarTableAddress = 0x4_4665_4FD0;
+    private static readonly object FallbackReaderGate = new();
+
+    [Fact]
+    public void ScalarLoadReadsTrackedFallbackMemory()
+    {
+        var expected = new uint[]
+        {
+            0x4665_4F70,
+            0x0000_0004,
+            0x4EA7_FCE0,
+            0x0000_0004,
+        };
+        var table = new byte[expected.Length * sizeof(uint)];
+        for (var index = 0; index < expected.Length; index++)
+        {
+            BinaryPrimitives.WriteUInt32LittleEndian(
+                table.AsSpan(index * sizeof(uint), sizeof(uint)),
+                expected[index]);
+        }
+
+        var load = new Gen5ShaderInstruction(
+            0,
+            Gen5ShaderEncoding.Smem,
+            "SLoadDwordx4",
+            [],
+            [Gen5Operand.Scalar(0)],
+            [
+                Gen5Operand.Scalar(16),
+                Gen5Operand.Scalar(17),
+                Gen5Operand.Scalar(18),
+                Gen5Operand.Scalar(19),
+            ],
+            new Gen5ScalarMemoryControl(4, 0, null));
+        var end = new Gen5ShaderInstruction(
+            8,
+            Gen5ShaderEncoding.Sopp,
+            "SEndpgm",
+            [],
+            [],
+            [],
+            null);
+        var state = new Gen5ShaderState(
+            new Gen5ShaderProgram(0, [load, end]),
+            [unchecked((uint)ScalarTableAddress), (uint)(ScalarTableAddress >> 32)],
+            null);
+        var ctx = new CpuContext(new FakeCpuMemory(0x1000, 0x100), Generation.Gen5);
+
+        lock (FallbackReaderGate)
+        {
+            var previousReader = Gen5ShaderScalarEvaluator.FallbackMemoryReader;
+            try
+            {
+                Gen5ShaderScalarEvaluator.FallbackMemoryReader = ReadFallback;
+                Assert.True(
+                    Gen5ShaderScalarEvaluator.TryEvaluate(
+                        ctx,
+                        state,
+                        out var evaluation,
+                        out var error),
+                    error);
+                Assert.Equal(expected, evaluation.ScalarRegisters.Skip(16).Take(4));
+            }
+            finally
+            {
+                Gen5ShaderScalarEvaluator.FallbackMemoryReader = previousReader;
+            }
+        }
+
+        bool ReadFallback(ulong address, Span<byte> destination)
+        {
+            if (address < ScalarTableAddress)
+            {
+                return false;
+            }
+
+            var offset = address - ScalarTableAddress;
+            if (offset + (ulong)destination.Length > (ulong)table.Length)
+            {
+                return false;
+            }
+
+            table.AsSpan((int)offset, destination.Length).CopyTo(destination);
+            return true;
+        }
+    }
+}