Reinstated experimental DXC pragmas, Metal texture atomics hack, and HDRP overrides for texture array declarations and sampling.

Assets/Resources/FSR3/ffx_fsr3upscaler_unity_common.cginc

@@ -24,3 +24,59 @@
 
 #define FFX_GPU         // Compiling for GPU
 #define FFX_HLSL        // Compile for plain HLSL
+
+// Use the DXC shader compiler on modern graphics APIs to enable a few advanced features
+// The DXC-related pragmas are disabled by default, as DXC doesn't support all platforms yet and will break on some platforms when enabled.
+// Consider this to be an experimental feature. If you want to benefit from 16-bit floating point and wave operations, and don't care about supporting older graphics APIs, then it's worth a try. 
+//#if defined(SHADER_API_D3D12) || defined(SHADER_API_VULKAN) || defined(SHADER_API_METAL)
+//#pragma use_dxc   // Using DXC will currently break DX11 support since DX11 and DX12 share the same shader bytecode in Unity.
+//#endif
+
+// Enable half precision data types on platforms that support it
+//#if defined(UNITY_COMPILER_DXC) && defined(FFX_HALF)
+//#pragma require Native16Bit
+//#endif
+
+// Hack to work around the lack of texture atomics on Metal
+#if defined(SHADER_API_METAL)
+#define InterlockedAdd(dest, val, orig)     { (orig) = (dest); (dest) += (val); }
+#define InterlockedMin(dest, val)           { (dest) = min((dest), (val)); }
+#define InterlockedMax(dest, val)           { (dest) = max((dest), (val)); }
+#endif
+
+// Workaround for HDRP using texture arrays for its camera buffers on some platforms
+// The below defines are copied from: Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/TextureXR.hlsl
+#if defined(UNITY_FSR3UPSCALER_HDRP)
+    // Must be in sync with C# with property useTexArray in TextureXR.cs
+    #if ((defined(SHADER_API_D3D11) || defined(SHADER_API_D3D12)) && !defined(SHADER_API_XBOXONE) && !defined(SHADER_API_GAMECORE)) || defined(SHADER_API_PSSL) || defined(SHADER_API_VULKAN)
+        #define UNITY_TEXTURE2D_X_ARRAY_SUPPORTED
+    #endif
+
+    // Control if TEXTURE2D_X macros will expand to texture arrays
+    #if defined(UNITY_TEXTURE2D_X_ARRAY_SUPPORTED) && !defined(DISABLE_TEXTURE2D_X_ARRAY)
+        #define USE_TEXTURE2D_X_AS_ARRAY
+    #endif
+
+    // Early defines for single-pass instancing
+    #if defined(STEREO_INSTANCING_ON) && defined(UNITY_TEXTURE2D_X_ARRAY_SUPPORTED)
+        #define UNITY_STEREO_INSTANCING_ENABLED
+    #endif
+
+    // Helper macros to handle XR single-pass with Texture2DArray
+    #if defined(USE_TEXTURE2D_X_AS_ARRAY)
+
+        // Only single-pass stereo instancing used array indexing
+        #if defined(UNITY_STEREO_INSTANCING_ENABLED)
+            #define SLICE_ARRAY_INDEX   unity_StereoEyeIndex
+        #else
+            #define SLICE_ARRAY_INDEX  0
+        #endif
+
+        // Declare and sample camera buffers as texture arrays
+        #define UNITY_FSR3_TEX2D(type)      Texture2DArray<type>
+        #define UNITY_FSR3_RWTEX2D(type)    RWTexture2DArray<type>
+        #define UNITY_FSR3_POS(pxPos)       FfxUInt32x3(pxPos, SLICE_ARRAY_INDEX)
+        #define UNITY_FSR3_UV(uv)           FfxFloat32x3(uv, SLICE_ARRAY_INDEX)
+        
+    #endif
+#endif