Shader cfg ssa (#707)

* [shader] add scalar control flow graph
* [shader] add gen5 branch resolver
* [shader] add scalar reaching definitions
* [shader] add cfg and dataflow tests
* [shader] guard descriptors from unresolved registers

src/SharpEmu.ShaderCompiler/Ir/Gen5IrBranchResolver.cs

@@ -0,0 +1,67 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System;
+
+namespace SharpEmu.ShaderCompiler.Ir;
+
+public sealed class Gen5IrBranchResolver : IIrBranchResolver
+{
+    public static Gen5IrBranchResolver Instance { get; } = new();
+
+    public bool IsBranch(Gen5ShaderInstruction instruction) =>
+        IsUnconditionalBranch(instruction) ||
+        IsConditional(instruction) ||
+        IsTerminator(instruction);
+
+    public bool IsConditional(Gen5ShaderInstruction instruction) => instruction.Opcode switch
+    {
+        "SCbranchScc0" or
+        "SCbranchScc1" or
+        "SCbranchVccz" or
+        "SCbranchVccnz" or
+        "SCbranchExecz" or
+        "SCbranchExecnz" or
+        "SCbranchCdbgsys" or
+        "SCbranchCdbguser" or
+        "SCbranchCdbgsysOrUser" or
+        "SCbranchCdbgsysAndUser" => true,
+        _ => false,
+    };
+
+    public bool TryGetBranchTarget(Gen5ShaderInstruction instruction, out uint targetPc)
+    {
+        targetPc = 0;
+        if (IsTerminator(instruction))
+        {
+            return false;
+        }
+
+        if (!IsUnconditionalBranch(instruction) && !IsConditional(instruction))
+        {
+            return false;
+        }
+
+        if (instruction.Encoding != Gen5ShaderEncoding.Sopp || instruction.Words.Count == 0)
+        {
+            return false;
+        }
+
+        var offset = unchecked((short)(instruction.Words[0] & 0xFFFF));
+        var nextPc = (long)instruction.Pc + instruction.Words.Count * sizeof(uint);
+        var target = nextPc + offset * sizeof(uint);
+        if (target < 0 || target > uint.MaxValue)
+        {
+            return false;
+        }
+
+        targetPc = (uint)target;
+        return true;
+    }
+
+    public static bool IsUnconditionalBranch(Gen5ShaderInstruction instruction) =>
+        string.Equals(instruction.Opcode, "SBranch", StringComparison.Ordinal);
+
+    public static bool IsTerminator(Gen5ShaderInstruction instruction) =>
+        instruction.Opcode is "SEndpgm" or "SEndpgmSaved";
+}