Add backward derivatives for functions in diff.meta.slang (#2633)

* WIP: start adding backward derivatives

* Overhaul `transposeParameterBlock` to support `inout` params.

* Small bug fixes.

* Bug fix on differentiable intrinsic specialization.

* Fixes.

* Run autodiff tests on CPU.

* Clean up.

* Overhaul `transposeParameterBlock` to support `inout` params.

* Small bug fixes.

* Bug fix on differentiable intrinsic specialization.

* Fixes.

* Run autodiff tests on CPU.

* Clean up.

* More bug fixes.,

* WIP: working on detach

* Arithmetic simplifications and more IR clean up logic.

* WIP: adding detach and abs

* Fix detach and abs

* Fix.

* Add IR transform pass for cleaner code emit.

* Fix test cases.

* Fix type system logic for reference type.

* Add backward derivatives for functions that already have forward derivatives

* Fix changes

---------

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

1 files changed, 37 insertions, 0 deletions

diff --git a/tests/autodiff-dstdlib/dstdlib-log.slang b/tests/autodiff-dstdlib/dstdlib-log.slang
new file mode 100644
index 000000000..6961d2f09
--- /dev/null
+++ b/tests/autodiff-dstdlib/dstdlib-log.slang
@@ -0,0 +1,37 @@
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typedef DifferentialPair<float> dpfloat;
+typedef DifferentialPair<float2> dpfloat2;
+
+[BackwardDifferentiable]
+float diffLog(float x)
+{
+    return log(x);
+}
+
+[BackwardDifferentiable]
+float2 diffLog(float2 x)
+{
+    return log(x);
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    {
+        dpfloat dpa = dpfloat(10.0, 0.0);
+        __bwd_diff(diffLog)(dpa, 3.0);
+        outputBuffer[0] = dpa.d; // Expect: 0.300000
+    }
+
+    {
+        dpfloat2 dpx = dpfloat2(float2(2.0, 5.0), float2(0.0, 0.0));
+        __bwd_diff(diffLog)(dpx, float2(1.0, 1.0));
+        outputBuffer[1] = dpx.d[0]; // Expect: 0.500000
+        outputBuffer[2] = dpx.d[1]; // Expect: 0.200000
+    }
+}