Make backward differentiation work with generics. (#2586)

* Make backward differentiation work with generics.

* Fix.

* Another fix.

* More fix.

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

2 files changed, 53 insertions, 0 deletions

diff --git a/tests/autodiff/dynamic-dispatch-reverse-1.slang b/tests/autodiff/dynamic-dispatch-reverse-1.slang
new file mode 100644
index 000000000..846004f95
--- /dev/null
+++ b/tests/autodiff/dynamic-dispatch-reverse-1.slang
@@ -0,0 +1,47 @@
+// Test calling differentiable function through dynamic dispatch.
+
+//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 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+[anyValueSize(16)]
+interface IInterface
+{
+    static float calc(float x);
+}
+
+struct A : IInterface
+{
+    static float calc(float x) { return 1.0; }
+};
+
+struct B : IInterface
+{
+    static float calc(float x) { return 2.0; }
+};
+
+[BackwardDifferentiable]
+float sqr<T:IInterface>(T obj, float x)
+{
+    return no_diff(obj.calc(x)) + x * x;
+}
+
+//TEST_INPUT: type_conformance A:IInterface = 0
+//TEST_INPUT: type_conformance B:IInterface = 1
+
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    var obj = createDynamicObject<IInterface>(dispatchThreadID.x, 0); // A
+    var p = DifferentialPair<float>(2.0, 1.0);
+    __bwd_diff(sqr)(obj, p, 1.0); // A.calc, expect 4
+    outputBuffer[0] = p.d;
+
+    obj = createDynamicObject<IInterface>(dispatchThreadID.x + 1, 0); // B
+    p = DifferentialPair<float>(1.5, 1.0);
+    __bwd_diff(sqr)(obj, p, 1.0);                                                     // A.calc, expect 4
+    outputBuffer[1] = p.d; // B.calc, expect 3
+}
diff --git a/tests/autodiff/dynamic-dispatch-reverse-1.slang.expected.txt b/tests/autodiff/dynamic-dispatch-reverse-1.slang.expected.txt
new file mode 100644
index 000000000..780ba6ed4
--- /dev/null
+++ b/tests/autodiff/dynamic-dispatch-reverse-1.slang.expected.txt
@@ -0,0 +1,6 @@
+type: float
+4.000000
+3.000000
+0.000000
+0.000000
+0.000000