[Vulkan] Honor guest depth clear state (#290)

src/SharpEmu.Libs/Agc/AgcExports.cs

@@ -121,6 +121,7 @@ public static partial class AgcExports
     private const uint CbBlend0Control = 0x1E0;
     private const uint PaScModeCntl0 = 0x292;
     // GFX10 DB context registers (register byte address minus 0x28000, / 4).
+    private const uint DbRenderControl = 0x000;
     private const uint DbDepthView = 0x002;
     private const uint DbDepthSizeXy = 0x007;
     private const uint DbDepthClear = 0x00B;
@@ -5291,7 +5292,7 @@ public static partial class AgcExports
         var hasDepthOnlyCandidate = hasExportShader &&
             !hasPixelShader &&
             depthTarget is not null &&
-            (depthState.TestEnable || depthState.WriteEnable);
+            (depthState.TestEnable || depthState.WriteEnable || depthState.ClearEnable);
         if (hasDepthOnlyCandidate &&
             TryCreateTranslatedDepthOnlyGuestDraw(
                 ctx,
@@ -6652,27 +6653,30 @@ public static partial class AgcExports
 
     // DB_DEPTH_CONTROL (context register 0x200): Z_ENABLE bit1, Z_WRITE_ENABLE
     // bit2, ZFUNC bits[6:4] (GCN compare, matches Vulkan CompareOp ordering).
+    // DB_RENDER_CONTROL (context register 0x000): DEPTH_CLEAR_ENABLE bit0.
     private const uint DbDepthControl = 0x200;
 
-    private static GuestDepthState DecodeDepthState(
+    internal static GuestDepthState DecodeDepthState(
         IReadOnlyDictionary<uint, uint> registers)
     {
-        if (!registers.TryGetValue(DbDepthControl, out var control))
+        var hasDepthControl = registers.TryGetValue(DbDepthControl, out var control);
-        {
+        registers.TryGetValue(DbRenderControl, out var renderControl);
-            return GuestDepthState.Default;
-        }
-
         var testEnable = (control & 0x2u) != 0;
         var writeEnable = (control & 0x4u) != 0;
-        var compareOp = (control >> 4) & 0x7u;
+        var compareOp = hasDepthControl
-        return new GuestDepthState(testEnable, writeEnable, compareOp);
+            ? (control >> 4) & 0x7u
+            : GuestDepthState.Default.CompareOp;
+        var clearEnable = (renderControl & 0x1u) != 0;
+        return new GuestDepthState(testEnable, writeEnable, compareOp, clearEnable);
     }
 
     private static GuestDepthTarget? DecodeDepthTarget(
         IReadOnlyDictionary<uint, uint> registers)
     {
         var depthState = DecodeDepthState(registers);
-        if (!depthState.TestEnable && !depthState.WriteEnable)
+        if (!depthState.TestEnable &&
+            !depthState.WriteEnable &&
+            !depthState.ClearEnable)
         {
             return null;
         }

src/SharpEmu.Libs/Gpu/GuestGpuTypes.cs

@@ -91,9 +91,10 @@ internal readonly record struct GuestRasterState(
 internal readonly record struct GuestDepthState(
     bool TestEnable,
     bool WriteEnable,
-    uint CompareOp)
+    uint CompareOp,
+    bool ClearEnable = false)
 {
-    public static GuestDepthState Default { get; } = new(false, false, 7);
+    public static GuestDepthState Default { get; } = new(false, false, 7, false);
 }
 
 /// <summary>Factors/funcs are raw guest CB_BLEND*_CONTROL register bitfields; the

src/SharpEmu.Libs/VideoOut/VulkanVideoPresenter.cs

@@ -2213,6 +2213,12 @@ internal static unsafe class VulkanVideoPresenter
         return keys;
     }
 
+    internal static bool ShouldAttachGuestDepth(
+        GuestDepthTarget? target,
+        GuestDepthState state) =>
+        target is not null &&
+        (state.TestEnable || state.WriteEnable || state.ClearEnable);
+
     private readonly record struct Presentation(
         byte[]? Pixels,
         uint Width,
@@ -9440,6 +9446,7 @@ internal static unsafe class VulkanVideoPresenter
             {
                 var extent = new Extent2D(firstTarget.Width, firstTarget.Height);
                 var draw = work.Draw;
+                var clearDepthForDraw = draw.RenderState.Depth.ClearEnable;
                 if (work.DepthTarget?.ReadOnly == true && draw.RenderState.Depth.WriteEnable)
                 {
                     draw = draw with
@@ -9452,9 +9459,10 @@ internal static unsafe class VulkanVideoPresenter
                 }
                 GuestDepthResource? depth = null;
                 DepthFramebufferResource? depthFramebuffer = null;
-                if (work.DepthTarget is { } depthTarget &&
+                if (ShouldAttachGuestDepth(
-                    (draw.RenderState.Depth.TestEnable ||
+                        work.DepthTarget,
-                     draw.RenderState.Depth.WriteEnable))
+                        draw.RenderState.Depth) &&
+                    work.DepthTarget is { } depthTarget)
                 {
                     var effectiveDepthTarget = depthTarget;
                     if (depthTarget.Width < firstTarget.Width || depthTarget.Height < firstTarget.Height)
@@ -9501,21 +9509,45 @@ internal static unsafe class VulkanVideoPresenter
 
                     depth = GetOrCreateGuestDepth(effectiveDepthTarget);
                     PrepareFirstUseDepth(depth, draw.RenderState.Depth);
+                    if (clearDepthForDraw)
+                    {
+                        depth.GuestClearDepth = effectiveDepthTarget.ClearDepth;
+                        depth.ClearDepth = effectiveDepthTarget.ClearDepth;
+                    }
                     if (targets.Length == 1)
                     {
                         depthFramebuffer = GetOrCreateDepthFramebuffer(firstTarget, depth);
                     }
                 }
 
+                if (clearDepthForDraw)
+                {
+                    // DB_RENDER_CONTROL.DEPTH_CLEAR_ENABLE makes this a DB
+                    // clear operation. The draw still produces color, but its
+                    // interpolated vertex Z is not the guest clear value.
+                    draw = draw with
+                    {
+                        RenderState = draw.RenderState with
+                        {
+                            Depth = draw.RenderState.Depth with
+                            {
+                                TestEnable = false,
+                                WriteEnable = false,
+                                ClearEnable = false,
+                            },
+                        },
+                    };
+                }
+
                 var renderPass = depthFramebuffer is null
                     ? firstTarget.Initialized
                         ? firstTarget.RenderPass
                         : firstTarget.InitialRenderPass
                     : firstTarget.Initialized
-                        ? depth!.Initialized
+                        ? depth!.Initialized && !clearDepthForDraw
                             ? depthFramebuffer.LoadRenderPass
                             : depthFramebuffer.DepthClearRenderPass
-                        : depth!.Initialized
+                        : depth!.Initialized && !clearDepthForDraw
                             ? depthFramebuffer.ColorClearRenderPass
                             : depthFramebuffer.BothClearRenderPass;
                 var framebuffer = depthFramebuffer?.Framebuffer ?? firstTarget.Framebuffer;
@@ -9531,7 +9563,7 @@ internal static unsafe class VulkanVideoPresenter
                         targets.Select(target =>
                             target.Initialized || target.InitialUploadPending).ToArray(),
                         depth,
-                        depth?.Initialized == true);
+                        depth?.Initialized == true && !clearDepthForDraw);
                     transientRenderPass = renderPass;
                     transientFramebuffer = framebuffer;
                 }
@@ -9719,7 +9751,12 @@ internal static unsafe class VulkanVideoPresenter
                 if (depth is not null)
                 {
                     depth.Initialized = true;
-                    if (draw.RenderState.Depth.WriteEnable)
+                    depth.Layout = ImageLayout.DepthStencilAttachmentOptimal;
+                    if (clearDepthForDraw)
+                    {
+                        depth.InitializationSource = "guest-depth-clear";
+                    }
+                    else if (draw.RenderState.Depth.WriteEnable)
                     {
                         depth.InitializationSource = "translated-depth-write";
                     }

tests/SharpEmu.Libs.Tests/VideoOut/VulkanDepthAttachmentTests.cs

@@ -0,0 +1,89 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.Libs.Agc;
+using SharpEmu.Libs.Gpu;
+using SharpEmu.Libs.VideoOut;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.VideoOut;
+
+public sealed class VulkanDepthAttachmentTests
+{
+    private static readonly GuestDepthTarget Target = new(
+        ReadAddress: 0x1000,
+        WriteAddress: 0x1000,
+        Width: 1920,
+        Height: 1080,
+        GuestFormat: 1,
+        SwizzleMode: 0,
+        ClearDepth: 1f,
+        ReadOnly: false);
+
+    [Fact]
+    public void GuestDepthTarget_AttachesForDepthWork()
+    {
+        var state = new GuestDepthState(
+            TestEnable: true,
+            WriteEnable: true,
+            CompareOp: 3);
+
+        Assert.True(VulkanVideoPresenter.ShouldAttachGuestDepth(Target, state));
+    }
+
+    [Theory]
+    [InlineData(true, false)]
+    [InlineData(false, true)]
+    public void GuestDepthTarget_AttachesForEitherDepthOperation(
+        bool testEnable,
+        bool writeEnable)
+    {
+        var state = new GuestDepthState(testEnable, writeEnable, CompareOp: 3);
+
+        Assert.True(VulkanVideoPresenter.ShouldAttachGuestDepth(Target, state));
+    }
+
+    [Fact]
+    public void GuestDepthTarget_RequiresTargetAndDepthWork()
+    {
+        var state = GuestDepthState.Default;
+
+        Assert.False(VulkanVideoPresenter.ShouldAttachGuestDepth(Target, state));
+        Assert.False(VulkanVideoPresenter.ShouldAttachGuestDepth(
+            target: null,
+            new GuestDepthState(true, false, CompareOp: 3)));
+    }
+
+    [Fact]
+    public void GuestDepthTarget_AttachesForDepthClear()
+    {
+        var state = new GuestDepthState(
+            TestEnable: false,
+            WriteEnable: false,
+            CompareOp: 7,
+            ClearEnable: true);
+
+        Assert.True(VulkanVideoPresenter.ShouldAttachGuestDepth(Target, state));
+    }
+
+    [Theory]
+    [InlineData(0x41u, true)]
+    [InlineData(0x40u, false)]
+    public void DepthState_DecodesRenderControlClearBit(
+        uint renderControl,
+        bool clearEnable)
+    {
+        var registers = new Dictionary<uint, uint>
+        {
+            [0x000] = renderControl,
+            [0x200] = 0x776,
+        };
+
+        var state = AgcExports.DecodeDepthState(registers);
+
+        Assert.True(state.TestEnable);
+        Assert.True(state.WriteEnable);
+        Assert.Equal(7u, state.CompareOp);
+        Assert.Equal(clearEnable, state.ClearEnable);
+    }
+}