Make tuple types work in autodiff. (#4923)

1 files changed, 49 insertions, 0 deletions

diff --git a/tests/language-feature/tuple/tuple-autodiff.slang b/tests/language-feature/tuple/tuple-autodiff.slang
new file mode 100644
index 000000000..d42cc0159
--- /dev/null
+++ b/tests/language-feature/tuple/tuple-autodiff.slang
@@ -0,0 +1,49 @@
+
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-cpu -compute -output-using-type -shaderobj
+
+// This is a test modified from autodiff/reverse-struct-multi-write.slang to test that
+// tuple types can be autodiff'ed the same way as struct types.
+
+//TEST_INPUT:ubuffer(data=[1 2], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typealias A = Tuple<float, Tuple<float, float>>;
+
+[Differentiable]
+A f(A a)
+{
+    // Read/writes to local struct variables won't be SSA'd out by default.
+    // The backward diff preparation pass will kick in to create temp vars for them.
+    A aout;
+    aout._1._1 = 2 * a._1._0;
+    aout._1._1 = aout._1._1 + 2 * a._1._0;
+    aout._1._0 = aout._1._1 + 5 * a._1._0;
+
+    // The result should be equivalent to:
+    /*
+    A aout;
+    var tmp = 2 * a.x;
+    tmp = tmp + 2 * a.x;
+    aout.y = tmp;
+    aout.x = tmp + 5 * a.x;
+    */
+    return aout;
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    A a = makeTuple(1.0, makeTuple(1.0, 2.0));
+
+    var dpa = diffPair(a);
+
+    A.Differential dout = makeTuple(1.0, makeTuple(1.0, 1.0));
+    
+    bwd_diff(f)(dpa, dout);
+    // CHECK: 13
+    outputBuffer[0] = dpa.d._1._0; // Expect: 13
+    // CHECK: 0
+    outputBuffer[1] = dpa.d._1._1; // Expect: 0
+}