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
2026-07-31 06:59:45 +08:00 · 2026-07-31 01:39:56 +03:00
parent 5864328e35
commit e7149bf41f
8 changed files with 1379 additions and 5 deletions
@@ -0,0 +1,142 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Collections.Generic;
+using SharpEmu.ShaderCompiler;
+using SharpEmu.ShaderCompiler.Ir;
+using Xunit;
+
+namespace SharpEmu.ShaderCompiler.Tests;
+
+public sealed class Gen5ReachingDefinitionTests
+{
+    private static Gen5ShaderInstruction Load(uint pc, uint destination) =>
+        new(
+            pc,
+            Gen5ShaderEncoding.Smem,
+            "SLoadDwordx4",
+            [0u, 0u],
+            [Gen5Operand.Scalar(0)],
+            [Gen5Operand.Scalar(destination)],
+            null);
+
+    private static Gen5ShaderInstruction Nop(uint pc) =>
+        new(pc, Gen5ShaderEncoding.Sop1, "SNop", [0u], [], [], null);
+
+    private static Gen5ShaderInstruction Branch(uint pc, string opcode, short wordOffset) =>
+        new(
+            pc,
+            Gen5ShaderEncoding.Sopp,
+            opcode,
+            [unchecked((uint)(ushort)wordOffset)],
+            [],
+            [],
+            null);
+
+    [Fact]
+    public void SingleDefinitionIsTracked()
+    {
+        List<Gen5ShaderInstruction> program = [Load(0, 16), Nop(4)];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: []);
+        var reaching = ssa.GetReachingDefinitionAt(4, 16);
+
+        Assert.Equal(IrReachingState.Single, reaching.State);
+        Assert.Equal(0u, reaching.DefinitionPc);
+    }
+
+    [Fact]
+    public void TwoDefinitionsOnDifferentPathsBecomeMultiple()
+    {
+        // The case that produced garbage descriptors: the same register is
+        // written on both sides of a branch and read after the join.
+        List<Gen5ShaderInstruction> program =
+        [
+            Branch(0, "SCbranchScc0", 2),
+            Load(4, 16),
+            Branch(8, "SBranch", 1),
+            Load(12, 16),
+            Nop(16),
+        ];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: []);
+
+        Assert.Equal(IrReachingState.Multiple, ssa.GetReachingDefinitionAt(16, 16).State);
+    }
+
+    [Fact]
+    public void DefinitionOnOnlyOnePathIsAlsoMultipleAtTheJoin()
+    {
+        List<Gen5ShaderInstruction> program =
+        [
+            Load(0, 16),
+            Branch(4, "SCbranchScc0", 1),
+            Load(8, 16),
+            Nop(12),
+        ];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: []);
+
+        Assert.Equal(IrReachingState.Multiple, ssa.GetReachingDefinitionAt(12, 16).State);
+    }
+
+    [Fact]
+    public void DefinitionBeforeTheBranchStaysSingle()
+    {
+        List<Gen5ShaderInstruction> program =
+        [
+            Load(0, 16),
+            Branch(4, "SCbranchScc0", 1),
+            Load(8, 16),
+            Nop(12),
+        ];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: []);
+        var reaching = ssa.GetReachingDefinitionAt(4, 16);
+
+        Assert.Equal(IrReachingState.Single, reaching.State);
+        Assert.Equal(0u, reaching.DefinitionPc);
+    }
+
+    [Fact]
+    public void UserDataCountsAsADefinition()
+    {
+        List<Gen5ShaderInstruction> program = [Nop(0)];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: [0x1111, 0x2222]);
+
+        Assert.Equal(IrReachingState.Single, ssa.GetReachingDefinitionAt(0, 0).State);
+        Assert.Equal(IrReachingState.None, ssa.GetReachingDefinitionAt(0, 64).State);
+    }
+
+    [Fact]
+    public void UnwrittenRegisterHasNoDefinition()
+    {
+        List<Gen5ShaderInstruction> program = [Load(0, 16), Nop(4)];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: []);
+
+        Assert.Equal(IrReachingState.None, ssa.GetReachingDefinitionAt(4, 32).State);
+    }
+
+    [Fact]
+    public void ReachingDefinitionSeesLoadsThatConstantPropagationCannot()
+    {
+        // The whole point of the second analysis: SLoadDwordx4 has no compile-time
+        // value, so constant propagation reports Unknown and never Merged. Reaching
+        // definitions still proves the register has two possible writers.
+        List<Gen5ShaderInstruction> program =
+        [
+            Branch(0, "SCbranchScc0", 2),
+            Load(4, 16),
+            Branch(8, "SBranch", 1),
+            Load(12, 16),
+            Nop(16),
+        ];
+
+        var ssa = Gen5ScalarSsa.Build(program, userData: []);
+
+        Assert.Equal(IrScalarState.Unknown, ssa.GetScalarAt(16, 16).State);
+        Assert.Equal(IrReachingState.Multiple, ssa.GetReachingDefinitionAt(16, 16).State);
+    }
+}