Fix derivative signature bug in checkDerivativeAttribute. (#2905)

2 files changed, 30 insertions, 0 deletions

diff --git a/tests/autodiff/reverse-inout-param-custom-derivative.slang b/tests/autodiff/reverse-inout-param-custom-derivative.slang
new file mode 100644
index 000000000..8769a33c7
--- /dev/null
+++ b/tests/autodiff/reverse-inout-param-custom-derivative.slang
@@ -0,0 +1,28 @@
+//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], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+float rng(inout int state, float x)
+{
+    return state + x;
+}
+
+[BackwardDerivativeOf(rng)]
+void rng_bwd(int inState, inout DifferentialPair<float> x, float dOut)
+{
+    x = diffPair(x.p, (float)inState + dOut - 1.0);
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    var x = diffPair(2.0, 1.0);
+
+    __bwd_diff(rng)(4, x, 3.0);
+
+    outputBuffer[0] = x.d; // should be 6
+
+}
diff --git a/tests/autodiff/reverse-inout-param-custom-derivative.slang.expected.txt b/tests/autodiff/reverse-inout-param-custom-derivative.slang.expected.txt
new file mode 100644
index 000000000..bb8f4137d
--- /dev/null
+++ b/tests/autodiff/reverse-inout-param-custom-derivative.slang.expected.txt
@@ -0,0 +1,2 @@
+type: float
+6.000000