Implement clear buffer (fast path) (#1902)

* Implement clear buffer (fast path)

* Remove blank line

Ryujinx.Graphics.Gpu/Engine/MethodCopyBuffer.cs

@@ -200,8 +200,24 @@ namespace Ryujinx.Graphics.Gpu.Engine
             }
             else
             {
-                // Buffer to buffer copy.
-                BufferManager.CopyBuffer(cbp.SrcAddress, cbp.DstAddress, (uint)size);
+                if (remap &&
+                    swizzle.UnpackDstX() == BufferSwizzleComponent.ConstA &&
+                    swizzle.UnpackDstY() == BufferSwizzleComponent.ConstA &&
+                    swizzle.UnpackDstZ() == BufferSwizzleComponent.ConstA &&
+                    swizzle.UnpackDstW() == BufferSwizzleComponent.ConstA &&
+                    swizzle.UnpackSrcComponentsCount() == 1 &&
+                    swizzle.UnpackDstComponentsCount() == 1 &&
+                    swizzle.UnpackComponentSize() == 4)
+                {
+                    // Fast path for clears when remap is enabled.
+                    BufferManager.ClearBuffer(cbp.DstAddress, (uint)size * 4, state.Get<uint>(MethodOffset.CopyBufferConstA));
+                }
+                else
+                {
+                    // TODO: Implement remap functionality.
+                    // Buffer to buffer copy.
+                    BufferManager.CopyBuffer(cbp.SrcAddress, cbp.DstAddress, (uint)size);
+                }
             }
         }
     }

Ryujinx.Graphics.Gpu/Memory/BufferManager.cs

@@ -821,6 +821,28 @@ namespace Ryujinx.Graphics.Gpu.Memory
             dstBuffer.Flush(dstAddress, size);
         }
 
+        /// <summary>
+        /// Clears a buffer at a given address with the specified value.
+        /// </summary>
+        /// <remarks>
+        /// Both the address and size must be aligned to 4 bytes.
+        /// </remarks>
+        /// <param name="gpuVa">GPU virtual address of the region to clear</param>
+        /// <param name="size">Number of bytes to clear</param>
+        /// <param name="value">Value to be written into the buffer</param>
+        public void ClearBuffer(GpuVa gpuVa, ulong size, uint value)
+        {
+            ulong address = TranslateAndCreateBuffer(gpuVa.Pack(), size);
+
+            Buffer buffer = GetBuffer(address, size);
+
+            int offset = (int)(address - buffer.Address);
+
+            _context.Renderer.Pipeline.ClearBuffer(buffer.Handle, offset, (int)size, value);
+
+            buffer.Flush(address, size);
+        }
+
         /// <summary>
         /// Gets a buffer sub-range for a given memory range.
         /// </summary>

Ryujinx.Graphics.Gpu/State/BufferSwizzleComponent.cs

@@ -0,0 +1,16 @@
+namespace Ryujinx.Graphics.Gpu.State
+{
+    /// <summary>
+    /// Buffer swizzle component.
+    /// </summary>
+    enum BufferSwizzleComponent
+    {
+        SrcX,
+        SrcY,
+        SrcZ,
+        SrcW,
+        ConstA,
+        ConstB,
+        NoWrite
+    }
+}

Ryujinx.Graphics.Gpu/State/CopyBufferSwizzle.cs

@@ -9,6 +9,42 @@ namespace Ryujinx.Graphics.Gpu.State
         public uint Swizzle;
 #pragma warning restore CS0649
 
+        /// <summary>
+        /// Unpacks the source for the buffer destination vector X component.
+        /// </summary>
+        /// <returns>Destination component</returns>
+        public BufferSwizzleComponent UnpackDstX()
+        {
+            return (BufferSwizzleComponent)(Swizzle & 7);
+        }
+
+        /// <summary>
+        /// Unpacks the source for the buffer destination vector Y component.
+        /// </summary>
+        /// <returns>Destination component</returns>
+        public BufferSwizzleComponent UnpackDstY()
+        {
+            return (BufferSwizzleComponent)((Swizzle >> 4) & 7);
+        }
+
+        /// <summary>
+        /// Unpacks the source for the buffer destination vector Z component.
+        /// </summary>
+        /// <returns>Destination component</returns>
+        public BufferSwizzleComponent UnpackDstZ()
+        {
+            return (BufferSwizzleComponent)((Swizzle >> 8) & 7);
+        }
+
+        /// <summary>
+        /// Unpacks the source for the buffer destination vector W component.
+        /// </summary>
+        /// <returns>Destination component</returns>
+        public BufferSwizzleComponent UnpackDstW()
+        {
+            return (BufferSwizzleComponent)((Swizzle >> 12) & 7);
+        }
+
         /// <summary>
         /// Unpacks the size of each vector component of the copy.
         /// </summary>

Ryujinx.Graphics.Gpu/State/MethodOffset.cs

@@ -23,6 +23,8 @@ namespace Ryujinx.Graphics.Gpu.State
         TfBufferState                   = 0xe0,
         CopyBufferParams                = 0x100,
         TfState                         = 0x1c0,
+        CopyBufferConstA                = 0x1c0,
+        CopyBufferConstB                = 0x1c1,
         CopyBufferSwizzle               = 0x1c2,
         CopyBufferDstTexture            = 0x1c3,
         CopyBufferSrcTexture            = 0x1ca,