Miscellaneous backward autodiff fixes. (#2665)

* Fix differentiable type registration

* Fix use of non-differentiable return value in a differentiable func.

* Fix use of primal inst that does not dominate the diff block.

* Fix primal inst hoisting, and add missing type legalization logic.

* Make `detach` defined on all differentiable T.

---------

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

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/autodiff/bool-return-control-flow.slang b/tests/autodiff/bool-return-control-flow.slang
new file mode 100644
index 000000000..9dd398a89
--- /dev/null
+++ b/tests/autodiff/bool-return-control-flow.slang
@@ -0,0 +1,31 @@
+//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;
+
+[BackwardDifferentiable]
+bool conditionFunc(no_diff float a, inout float x)
+{
+    x = x * a;
+    return x > 100.f;
+}
+
+[BackwardDifferentiable]
+float outerFunc(no_diff float a, float x)
+{
+    if (conditionFunc(a, x))
+        return x;
+    else
+        return -x;
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    float a = 10.0;
+    DifferentialPair<float> dpx = DifferentialPair<float>(4.f, 1.f);
+    __bwd_diff(outerFunc)(a, dpx, 1.0);
+
+    outputBuffer[0] = dpx.d;
+}
\ No newline at end of file