Support `no_diff` on existential typed params. (#2540)

Co-authored-by: Yong He <yhe@nvidia.com>

2 files changed, 43 insertions, 0 deletions

diff --git a/tests/autodiff/no-diff-param-2.slang b/tests/autodiff/no-diff-param-2.slang
new file mode 100644
index 000000000..d29928d69
--- /dev/null
+++ b/tests/autodiff/no-diff-param-2.slang
@@ -0,0 +1,38 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typedef DifferentialPair<float> dpfloat;
+
+interface IFoo : IDifferentiable
+{
+    [ForwardDifferentiable]
+    float getVal();
+}
+
+struct A : IFoo
+{
+    float x;
+    [ForwardDifferentiable]
+    float getVal(){return x;}
+}
+
+[ForwardDifferentiable]
+float f(float x, no_diff IFoo y)
+{
+    return x * x + y.getVal();
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    {
+        A a;
+        a.x = 2.0;
+        let rs = __fwd_diff(f)(dpfloat(1.5, 1.0), a);
+        outputBuffer[0] = rs.p; // Expect: 6.25
+        outputBuffer[1] = rs.d; // Expect: 3.0
+    }
+}
diff --git a/tests/autodiff/no-diff-param-2.slang.expected.txt b/tests/autodiff/no-diff-param-2.slang.expected.txt
new file mode 100644
index 000000000..18066089d
--- /dev/null
+++ b/tests/autodiff/no-diff-param-2.slang.expected.txt
@@ -0,0 +1,5 @@
+type: float
+4.250000
+3.000000
+0.000000
+0.000000
\ No newline at end of file