Always run AD cleanup pass. (#5157)

4 files changed, 57 insertions, 6 deletions

diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index 71ef7ee33..a29142ba1 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -834,12 +834,10 @@ Result linkAndOptimizeIR(
     if (codeGenContext->shouldReportCheckpointIntermediates())
         reportCheckpointIntermediates(codeGenContext, sink, irModule);
 
-    if (requiredLoweringPassSet.autodiff)
-        finalizeAutoDiffPass(targetProgram, irModule);
-
-    // Remove auto-diff related decorations.
-    // We may have an autodiff decoration regardless of if autodiff is being used.
-    stripAutoDiffDecorations(irModule);
+    // Finalization is always run so AD-related instructions can be removed,
+    // even the AD pass itself is not run.
+    // 
+    finalizeAutoDiffPass(targetProgram, irModule);
 
     finalizeSpecialization(irModule);
 
diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index 94a605a68..6c729ea63 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -2559,6 +2559,8 @@ bool finalizeAutoDiffPass(TargetProgram* target, IRModule* module)
 
     stripNoDiffTypeAttribute(module);
 
+    stripAutoDiffDecorations(module);
+
     return modified;
 }
 
diff --git a/tests/autodiff/no-diff-strip.slang b/tests/autodiff/no-diff-strip.slang
new file mode 100644
index 000000000..ebcdd7972
--- /dev/null
+++ b/tests/autodiff/no-diff-strip.slang
@@ -0,0 +1,45 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX:-cpu -compute -output-using-type -shaderobj
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+// This test just checks that we compile and run successfully.
+// "NDBuffer<float, 2>" & "no_diff NDBuffer<float, 2>" should resolve to the same code-gen type.
+// 
+
+struct NDBuffer<T, let N : int>
+{
+    RWStructuredBuffer<T> buffer;
+    int[N] strides;
+    int[N] transform;
+
+    T get(int[N] index) { return buffer[index[0]]; }
+}
+
+float _read_slice(int2 index, NDBuffer<float, 2> texture) 
+{ 
+    return texture.get({index.x, index.y}); 
+}
+
+[Differentiable]
+void _trampoline(no_diff in vector<int,2> index, in no_diff NDBuffer<float, 2> texture, no_diff out float _result)
+{
+    _result = _read_slice(index, texture);
+}
+
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    NDBuffer<float, 2> texture;
+    texture.buffer = outputBuffer;
+    texture.strides = {1, 1};
+
+    float result;
+    _trampoline({dispatchThreadID.x, dispatchThreadID.y}, texture, result);
+    outputBuffer[dispatchThreadID.x] = result;
+}
+
diff --git a/tests/autodiff/no-diff-strip.slang.expected.txt b/tests/autodiff/no-diff-strip.slang.expected.txt
new file mode 100644
index 000000000..e070cf84d
--- /dev/null
+++ b/tests/autodiff/no-diff-strip.slang.expected.txt
@@ -0,0 +1,6 @@
+type: float
+0.000000
+0.000000
+0.000000
+0.000000
+0.000000