[Port] [6000.0] RenderGraph - Fix "Cannot return local 'actualPasses'" error

Author: YohannVaastUnity

Packages/com.unity.render-pipelines.core/Runtime/RenderGraph/Compiler/NativePassCompiler.cs

@@ -656,7 +656,7 @@ void DetectMemoryLessResources()
                 foreach (ref readonly var nativePass in contextData.NativePasses)
                 {
                     // Loop over all created resources by this nrp
-                    var graphPasses = nativePass.GraphPasses(contextData);
+                    var graphPasses = nativePass.GraphPasses(contextData, out var actualPasses);
                     foreach (ref readonly var subPass in graphPasses)
                     {
                         foreach (ref readonly var createdRes in subPass.FirstUsedResources(contextData))
@@ -698,6 +698,8 @@ void DetectMemoryLessResources()
                             }
                         }
                     }
+                    if (actualPasses.IsCreated)
+                        actualPasses.Dispose();
                 }
             }
         }
@@ -742,7 +744,8 @@ private void ExecuteInitializeResource(InternalRenderGraphContext rgContext, Ren
                     if (pass.mergeState == PassMergeState.Begin || pass.mergeState == PassMergeState.None)
                     {
                         ref var nativePass = ref contextData.nativePassData.ElementAt(pass.nativePassIndex);
-                        foreach (ref readonly var subPass in nativePass.GraphPasses(contextData))
+                        var graphPasses = nativePass.GraphPasses(contextData, out var actualPasses);
+                        foreach (ref readonly var subPass in graphPasses)
                         {
                             foreach (ref readonly var res in subPass.FirstUsedResources(contextData))
                             {
@@ -770,6 +773,8 @@ private void ExecuteInitializeResource(InternalRenderGraphContext rgContext, Ren
                                 }
                             }
                         }
+                        if (actualPasses.IsCreated)
+                            actualPasses.Dispose();
                     }
                 }
                 // Other passes just create them at the beginning of the individual pass
@@ -1290,7 +1295,8 @@ private void ExecuteDestroyResource(InternalRenderGraphContext rgContext, Render
                     if (pass.mergeState == PassMergeState.End || pass.mergeState == PassMergeState.None)
                     {
                         ref var nativePass = ref contextData.nativePassData.ElementAt(pass.nativePassIndex);
-                        foreach (ref readonly var subPass in nativePass.GraphPasses(contextData))
+                        var graphPasses = nativePass.GraphPasses(contextData, out var actualPasses);
+                        foreach (ref readonly var subPass in graphPasses)
                         {
                             foreach (ref readonly var res in subPass.LastUsedResources(contextData))
                             {
@@ -1301,6 +1307,8 @@ private void ExecuteDestroyResource(InternalRenderGraphContext rgContext, Render
                                 }
                             }
                         }
+                        if (actualPasses.IsCreated)
+                            actualPasses.Dispose();
                     }
                 }
                 else

Packages/com.unity.render-pipelines.core/Runtime/RenderGraph/Compiler/PassesData.cs

@@ -615,15 +615,16 @@ public readonly bool IsValid()
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public readonly ReadOnlySpan<PassData> GraphPasses(CompilerContextData ctx)
+        public readonly ReadOnlySpan<PassData> GraphPasses(CompilerContextData ctx, out NativeArray<PassData> actualPasses)
         {
             // When there's no pass being culled, we can directly return a Span of the Native List
             if (lastGraphPass - firstGraphPass + 1 == numGraphPasses)
             {
+                actualPasses = default;
                 return ctx.passData.MakeReadOnlySpan(firstGraphPass, numGraphPasses);
             }
 
-            var actualPasses =
+            actualPasses =
                 new NativeArray<PassData>(numGraphPasses, Allocator.Temp,
                     NativeArrayOptions.UninitializedMemory);
 
@@ -642,10 +643,14 @@ public readonly ReadOnlySpan<PassData> GraphPasses(CompilerContextData ctx)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public readonly void GetGraphPassNames(CompilerContextData ctx, DynamicArray<Name> dest)
         {
-            foreach (ref readonly var pass in GraphPasses(ctx))
+            var span = GraphPasses(ctx, out var actualPasses);
+            foreach (ref readonly var pass in span)
             {
                 dest.Add(pass.GetName(ctx));
             }
+
+            if (actualPasses.IsCreated)
+                actualPasses.Dispose();
         }
 
         // This function does not modify the current render graph state, it only evaluates and returns the correct PassBreakAudit

Packages/com.unity.render-pipelines.core/Tests/Editor/NativePassCompilerRenderGraphTests.cs

@@ -1316,7 +1316,9 @@ public void GraphPassesDoesNotAlloc()
 
             ValidateNoGCAllocs(() =>
             {
-                passes[0].GraphPasses(result.contextData);
+                var graphPasses = passes[0].GraphPasses(result.contextData, out var actualPasses);
+                if (actualPasses.IsCreated)
+                    actualPasses.Dispose();
             });
 
             // From RenderPassCullingTests.cs