Overhaul `transposeParameterBlock` to support `inout` params. (#2621)

* 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.,

* Add test coverage on inout param.

* Fix language server hinting for transcribed mutable params.

---------

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

1 files changed, 72 insertions, 0 deletions

diff --git a/tests/autodiff/reverse-inout-param-2.slang b/tests/autodiff/reverse-inout-param-2.slang
new file mode 100644
index 000000000..1fa64751b
--- /dev/null
+++ b/tests/autodiff/reverse-inout-param-2.slang
@@ -0,0 +1,72 @@
+//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 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+struct D : IDifferentiable
+{
+    float m;
+    float n;
+}
+
+struct ND
+{
+    float nd;
+}
+
+[BackwardDifferentiable]
+void g(
+    inout no_diff D p,
+    out no_diff D po,
+    out ND v1,
+    inout ND v2,
+    float x,
+    out float y)
+{
+    v1 = v2;
+    v2.nd = v2.nd + 1.0;
+    p.n = v1.nd + 1.0;
+    p.m = v2.nd + 1.0 + x; // == v2.nd + 2 + x == 1 + 2 + x == 3+x
+    po = p;
+    po.m += 1.0; // == 4+x
+    y = p.m * x; // == (3+x)*x
+}
+
+[BackwardDifferentiable]
+void f(inout no_diff D p, out no_diff D p0, out ND v1, inout ND v2, float x, out float y)
+{
+    // v2.nd is 3.
+    g(p, p0, v1, v2, x, y);
+    // v2.nd is now 4, now g is equivalent to (4+x)*x.
+    g(p, p0, v1, v2, x, y);
+}
+
+[ForwardDifferentiable]
+float f_ref(float x)
+{
+    return (3 + 3 * x + x * x) * (3 * x + x * x);
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    D p;
+    p.m = 1.0;
+    p.n = 2.0;
+
+    ND v2 = { 1.0 };
+
+    var x = diffPair(5.0);
+    float yDiffOut = 1.0;
+
+    __bwd_diff(f)(p, v2, x, yDiffOut);
+
+    // (3+((3+x)*x))*((3+x)*x) = (3+3x+x^2)*(3x+x^2)
+    outputBuffer[0] = x.p; // should be 5, since bwd_diff does not write back new primal val.
+    outputBuffer[1] = x.d; // 14
+    outputBuffer[2] = p.m; // 1.0
+    outputBuffer[3] = p.n; // 2.0
+    outputBuffer[4] = v2.nd; // 1.0
+}
\ No newline at end of file